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Objective: To evaluate the propofol-sparing and hemodynamic effects of guaifenesin administered for co-induction of anesthesia in sheep., Study Design: Prospective, blinded, two-way crossover experimental study., Animals: Thirteen healthy adult female sheep., Methods: Anesthesia was induced without premedication with intravenous (IV) guaifenesin 5% at 100 mg kg -1 (GGE) or an equivalent volume of physiologic saline (SAL), followed by IV propofol at a controlled rate (1 mg kg -1 min -1 ). Heart rate (HR), respiratory rate and oscillometric noninvasive arterial blood pressure (NIBP) were recorded at baseline after co-induction administration, following endotracheal intubation and every 2 minutes thereafter for 10 minutes. Propofol doses required to achieve intubation after each co-induction treatment were compared by independent Student's t-test. Values of p < 0.05 were considered statistically significant., Results: The propofol dose required (mean ± standard deviation) to achieve intubation was significantly lower (p = 0.001) in the GGE treatment (3.40 ± 0.74 mg kg -1 ) than in the SAL treatment (5.94 ± 1.09 mg kg -1 ). HR was increased after anesthetic induction compared with baseline in both treatments. HR was generally lower in the GGE treatment than in the SAL treatment. NIBP did not vary between GGE and SAL treatments., Conclusions and Clinical Relevance: Guaifenesin, when administered as a co-induction agent with propofol in sheep, reduces propofol dose requirements and maintains hemodynamic variables within a clinically acceptable range., (Published by Elsevier Ltd.)

General anesthesia in calves is easier to perform under field conditions, total intravenous anesthesia (TIVA) than using inhalation anesthesia. In the present study, cardiopulmonary function, anesthetic effects, quality of arousal, hematology, and blood biochemistry were assessed during continuous infusion of a combination solution of 0.01% xylazine, 0.001% butorphanol, and 0.2% propofol (XBP) at doses of 6 (G6; 10 μg/kg/min xylazine, 1 μg/kg/min butorphanol, 200 μg/kg/min propofol) and 9 mL/kg/h (G9; 15 μg/kg/min xylazine, 1.5 μg/kg/min butorphanol 300 μg/kg/min propofol). For both groups, five castrated Holstein calves received intravenous injections of xylazine (0.2 mg/kg) and propofol (2 mg/kg), followed by a continuous infusion of XBP for 60 min to maintain anesthesia. Respiratory management consisted of tracheal intubation followed by spontaneous inhalation of pure oxygen. Cardiopulmonary, anesthesia, hematology, and blood biochemistry variables were assessed at rest (baseline) and every 5 or 15 min after the start of the XBP infusion. Quality of arousal was assessed based on the swallowing reflex recovery time from the stop of XBP infusion, and the sternal position time and standing time after atipamezole administration. XBP produced adequate sedation, analgesia, and muscle relaxation in all calves and maintained stable anesthesia for 60 min. As XBP infusion time passed, rectal temperature and heart rate became lower, and mean arterial blood pressure increased. In both groups, hematologic and blood biochemical effects were mild. The quality of arousal was not different, and all calves were standing. The results of the present study suggested that XBP is useful for TIVA in calves., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Background: When inhalant anesthetic equipment is not available or during upper airway surgery, intravenous infusion of one or more drugs are commonly used to induce and/or maintain general anesthesia. Total intravenous anesthesia (TIVA) does not require endotracheal intubation, which may be more difficult to achieve in rabbits. A range of different injectable drug combinations have been used as continuous infusion rate in animals. Recently, a combination of ketamine and propofol (ketofol) has been used for TIVA in both human patients and animals. The purpose of this prospective, blinded, randomized, crossover study was to evaluate anesthetic and cardiopulmonary effects of ketofol total intravenous anesthesia (TIVA) in combination with constant rate infusion (CRI) of midazolam, fentanyl or dexmedetomidine in eight New Zealand White rabbits. Following IV induction with ketofol and endotracheal intubation, anesthesia was maintained with ketofol infusion in combination with CRIs of midazolam (loading dose [LD]: 0.3 mg/kg; CRI: 0.3 mg/kg/hr; KPM), fentanyl (LD: 6 µg/kg; CRI: 6 µg/kg/hr; KPF) or dexmedetomidine (LD: 3 µg/kg; CRI: 3 µg/kg/hr; KPD). Rabbits in the control treatment (KPS) were administered the same volume of saline for LD and CRI. Ketofol infusion rate (initially 0.6 mg kg - 1 minute - 1 [0.3 mg kg - 1 minute - 1 of each drug]) was adjusted to suppress the pedal withdrawal reflex. Ketofol dose and physiologic variables were recorded every 5 min., Results: Ketofol induction doses were 14.9 ± 1.8 (KPM), 15.0 ± 1.9 (KPF), 15.5 ± 2.4 (KPD) and 14.7 ± 3.4 (KPS) mg kg - 1 and did not differ among treatments (p > 0.05). Ketofol infusion rate decreased significantly in rabbits in treatments KPM and KPD as compared with saline. Ketofol maintenance dose in rabbits in treatments KPM (1.0 ± 0.1 mg/kg/min) and KPD (1.0 ± 0.1 mg/kg/min) was significantly lower as compared to KPS (1.3 ± 0.1 mg/kg/min) treatment (p < 0.05). Ketofol maintenance dose did not differ significantly between treatments KPF (1.1 ± 0.3 mg/kg/min) and KPS (1.3 ± 0.1 mg/kg/min). Cardiovascular variables remained at clinically acceptable values but ketofol infusion in combination with fentanyl CRI was associated with severe respiratory depression., Conclusions: At the studied doses, CRIs of midazolam and dexmedetomidine, but not fentanyl, produced ketofol-sparing effect in rabbits. Mechanical ventilation should be considered during ketofol anesthesia, particularly when fentanyl CRI is used., (© 2024. The Author(s).)

Background: The anesthetic management of adrenalectomies for phaeochromocytoma excision, a catecholamine-secreting tumor, is challenging due to the potential for fatal complications following severe hemodynamic variations, including hypertensive crisis following tumor manipulation or sympathetic stimulation, but also severe hypotension and volume depletion post resection., Case Description: An 11 kg, 15-year-old male neutered Jack Russel Terrier, with mitral valve disease stage B2, was referred for adrenalectomy for phaeochromocytoma resection. The patient was administered per os prazosin 0.11 mg/kg twice a day and amlodipine 0.125 mg/kg once a day for preoperative stabilization. On the day of surgery, the dog received maropitant 1 mg/kg intravenously (IV) and was premedicated with 0.2 mg/kg methadone IV. Anesthesia was induced with alfaxalone 1 mg/kg IV and midazolam 0.2 mg/kg IV and maintained with partial intravenous anesthesia using sevoflurane in 70% oxygen and constant rate infusions of dexmedetomidine 0.5 μg/kg/hour and maropitant 100 μg/kg/hour. After induction of anesthesia, the dog was mechanically ventilated, and a transversus abdominal plane block was performed with ropivacaine 0.2%. The dog remained remarkably stable with a single, self-limiting, hypertension episode recorded intraoperatively. Postoperative rescue analgesia consisted of methadone and ketamine. The dog was discharged 48 hours after surgery, but persistent hypertension was reported at suture removal., Conclusion: The use of a low-dose dexmedetomidine CRI, a maropitant CRI, and a transversus abdominal plane block provided stable perioperative hemodynamic conditions for phaeochromocytoma excision in a dog., Competing Interests: The authors declare that there is no conflict of interest.

Propofol is a potential injectable anesthetic agent used in total intravenous anesthesia. However, the sparing effect of fentanyl and medetomidine on the required propofol dose in dogs remains unclear. We aimed to investigate the effect of fentanyl constant-rate infusion (CRI) with or without medetomidine on the minimum infusion rate of propofol required to prevent motor movement (MIR NM ) in dogs. Six healthy purpose-bred dogs were anesthetized on three occasions with propofol alone (loading dose [LD], 8 mg/kg to effect; initial infusion rate [IR], 0.70 mg/kg/min); propofol (LD, 6 mg/kg to effect; IR, 0.35 mg/kg/min) and fentanyl (LD, 2 µg/kg; IR, 0.10 µg/kg/min); or propofol (LD, 4 mg/kg to effect; IR, 0.25 mg/kg/min), fentanyl (LD, 2 µg/kg; IR, 0.10 µg/kg/min), and medetomidine (LD, 2 µg/kg; IR, 0.5 µg/kg/hr) under controlled ventilation. The MIR NM was determined by observing the response to a noxious electrical stimulus. Heart rate, blood pressure, and blood gas analyses were performed at 1, 2, 3, and 4 hr after initiating CRI. The MIR NM (mean [range]) was significantly lower in the propofol-fentanyl-medetomidine group (0.16 [0.10-0.27] mg/kg/min) than that in the propofol-alone group (0.63 [0.47-0.82] mg/kg/min) (P=0.0004). Fentanyl combined with medetomidine did not significantly decrease the mean arterial pressure in dogs receiving propofol CRI 1-3 hr after initiating CRI compared with propofol CRI alone (P>0.9999, P=0.1536, and P=0.0596, respectively), despite inducing a significantly lower heart rate.

Systemic anesthesia in penguins is often achieved using inhalation anesthetic agents alone, and information on injectable drugs for systemic anesthesia is limited. General anesthesia with a minimal effect on circulatory dynamics is necessary to perform noninvasive examinations and treatments in animals, including penguins. In this study, alfaxalone (ALFX), an injectable anesthetic agent, was examined to establish the optimal anesthetic method for gentoo penguins ( Pygoscelis papua ). Alfaxalone was administered intravenously through the metatarsal vein, and anesthesia was maintained by a constant rate infusion (CRI). A biological monitor was used to record numerous clinical indices, and the anesthetic depth was evaluated every 5 minutes during anesthesia; the CRI was adjusted until the optimal anesthetic depth was obtained. Anesthesia depth was assessed, and the CRI rate was adjusted. The CRI was stopped, and the time until recovery was recorded. Blood samples were collected to analyze plasma concentrations of ALFX. The mean total dose of ALFX required for anesthetic induction was 9 ± 1.9 mg/kg, the intubation time was 126 ± 21 seconds, and the maintenance infusion rate of ALFX was 0.3 ± 0.08 mg/kg/min. The time from discontinuation of anesthesia to extubation was 42 ± 23 minutes, and the time to recovery was 90 ± 33 minutes. Significant changes in the heart rate and blood pressure were not observed during the anesthetic events. The plasma concentration of ALFX under stable anesthesia was 6734 ± 4386 ng/mL (range, 3315-14 326 ng/mL). Although anesthesia using ALFX tended to result in a prolonged time to recovery in gentoo penguins, rapid induction of anesthesia and stable hemodynamics during anesthetic maintenance were achieved. Therefore, ALFX may be considered a suitable anesthetic method for noninvasive examinations and treatments in penguins.

Objective: To describe ketamine-propofol total intravenous anaesthesia (TIVA) following premedication with acepromazine and either medetomidine, midazolam or morphine in rabbits., Study Design: Randomized, crossover experimental study., Animals: A total of six healthy female New Zealand White rabbits (2.2 ± 0.3 kg)., Methods: Rabbits were anaesthetized on four occasions, each separated by 7 days: an intramuscular injection of saline alone (treatment Saline) or acepromazine (0.5 mg kg -1 ) in combination with medetomidine (0.1 mg kg -1 ), midazolam (1 mg kg -1 ) or morphine (1 mg kg -1 ), treatments AME, AMI or AMO, respectively, in random order. Anaesthesia was induced and maintained with a mixture containing ketamine (5 mg mL -1 ) and propofol (5 mg mL -1 ) (ketofol). Each trachea was intubated and the rabbit administered oxygen during spontaneous ventilation. Ketofol infusion rate was initially 0.4 mg kg -1 minute -1 (0.2 mg kg -1 minute -1 of each drug) and was adjusted to maintain adequate anaesthetic depth based on clinical assessment. Ketofol dose and physiological variables were recorded every 5 minutes. Quality of sedation, intubation and recovery times were recorded., Results: Ketofol induction doses decreased significantly in treatments AME (7.9 ± 2.3) and AMI (8.9 ± 4.0) compared with treatment Saline (16.8 ± 3.2 mg kg -1 ) (p < 0.05). The total ketofol dose to maintain anaesthesia was significantly lower in treatments AME, AMI and AMO (0.6 ± 0.1, 0.6 ± 0.2 and 0.6 ± 0.1 mg kg -1 minute -1 , respectively) than in treatment Saline (1.2 ± 0.2 mg kg -1 minute -1 ) (p < 0.05). Cardiovascular variables remained at clinically acceptable values, but all treatments caused some degree of hypoventilation., Conclusions and Clinical Relevance: Premedication with AME, AMI and AMO, at the doses studied, significantly decreased the maintenance dose of ketofol infusion in rabbits. Ketofol was determined to be a clinically acceptable combination for TIVA in premedicated rabbits., (Copyright © 2023 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To evaluate effects of repeated alfaxalone or propofol administration on haematological and serum biochemical variables in cats undergoing radiotherapy., Study Design: Prospective, block-randomized, clinical trial., Animals: A group of 39 client-owned cats., Methods: After butorphanol (0.2 mg kg -1 ) and midazolam (0.1 mg kg -1 ) sedation, cats were randomly assigned to receive either alfaxalone or propofol for induction of anaesthesia and sevoflurane maintenance. Cats were anaesthetized daily with the same induction agent for 10-12 days. Complete blood counts, reticulocytes, Heinz body score and serum biochemistry were performed before the first treatment (T1), at T6, T10 and 3 weeks after the final treatment (T21). Cumulative induction agent dose for each cat at each time point was evaluated for an effect on Heinz body score. Data are shown as mean ± standard deviation; p < 0.05., Results: At baseline there were no significant differences in signalment or blood variables between groups. A significant decrease in haematocrit of 2.3% ± 0.77 (p = 0.02) between T1-T6 and T1-T10 [mean 4.1% (± 0.78, p < 0.0001)] was detected, with a significant increase in haematocrit of 2.1% ± 0.80 (p = 0.046) between T6-T21 and 4.0% ± 0.8 (p < 0.001) between T10-T21. Heinz body score significantly increased by 1.86 ± 0.616 (p = 0.013) between T1-T10. In the propofol group, reticulocytes increased significantly between T1-T6 [mean 23,090 μL -1 ± 7670 (p = 0.02)] and T1-T10 [mean 27,440 μL -1 ± 7990 (p = 0.007)]. Mean cumulative dose at T10 was 19.65 mg kg -1 ± 5.3 and 43.4 mg kg -1 ± 14.4 for alfaxalone and propofol, respectively, with no significant effect on Heinz body formation at any time point., Conclusions and Clinical Relevance: Haematocrit decreased in both groups with recovery after 3 weeks. Repeated alfaxalone and propofol administration was not associated with marked haematological or serum biochemistry changes., (Copyright © 2022 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objectives: This study aimed to assess the effect of dexmedetomidine on the propofol-based anesthesia of cats subjected to ovariohysterectomy., Methods: Twenty-eight cats were randomly allocated to four groups (seven cats in each) and premedicated with either 5 µg/kg dexmedetomidine (groups Dex 1, Dex 3 and Dex 5) or 0.05 ml saline (Prop group) intramuscularly. After the induction of anesthesia with propofol, total intravenous anesthesia was initiated with 300 µg/kg/min propofol plus 3 ml/kg/h NaCl 0.9% (Prop), or 200 µg/kg/min propofol plus dexmedetomidine at the rates of 1 µg/kg/h (Dex 1), 3 µg/kg/h (Dex 3) or 5 µg/kg/h (Dex 5). Cardiorespiratory variables were assessed 5 mins after induction and every 10 mins thereafter, until the end of anesthesia. The propofol infusion rate was adjusted every 10 mins (± 50 µg/kg/min) to maintain anesthetic depth. The times to extubation, sternal recumbency, ambulation and total recovery were recorded. Pain scoring was performed 1, 2, 4, 8, 12 and 24 h after the end of anesthesia., Results: Dexmedetomidine produced a propofol-sparing effect of 72.8%, 71.1% and 74.6% in the Dex 1, Dex 3 and Dex 5 groups, respectively. Cats in the Prop group maintained higher heart rate values than the other groups, and the mean arterial pressure remained higher in the Dex 3 and Dex 5 groups. Rescue intraoperative analgesia (fentanyl bolus) was most frequent in the Prop group. There was no significant difference in the time of extubation. Cats in the Dex 1 and Dex 3 groups had a faster anesthetic recovery, with shorter times to achieving sternal recumbency, regaining ambulation and reaching full recovery. Cats in the Dex 1 and Dex 5 groups presented the best recovery quality scores, with 4 (range 4-5) and 4 (range 3-5), respectively, while the Prop group scored 1 (range 1-3), the worst anesthetic recovery score among the groups., Conclusions and Relevance: The use of dexmedetomidine as a total intravenous anesthesia adjuvant, especially at doses of 1 and 3 µg/kg/h, reduces propofol consumption and improves cardiorespiratory stability and intraoperative analgesia, while promoting a better and quicker recovery from anesthesia.

The objective of this study was to evaluate the clinical usefulness of the combination of tiletamine-zolazepam used in low doses as a continuous rate infusion in a partial intravenous anesthesia protocol. Fifteen clinically healthy, different breed bitches weighing 25.08 ± 10.39 kg was used in this study. After a food fast for at least 12 hours and water fast for 4 hours, the animals were premedicated with dexmedetomidine. After 15 minutes, the bolus of tiletamine-zolazepam combination was given as an. Induction of general anesthesia, immediately followed by continuous intravenous infusion. The following parameters were measured immediately after the induction of general anesthesia and lasted until the end of the surgery: electrocardiography, heart rate, systolic arterial blood pressure, diastolic arterial blood pressure, mean arterial blood pressure, body temperature respiratory rate end tidal of CO 2 . During the recovery period, pain level was evaluated as well as sedation assessment. Time for successful intubation after administration of the tiletamine-zolazepam combination was within 3 minutes. Heart rate was within reference values. Systolic, diastolic, and mean arterial blood pressure were also within the reference values. Internal body temperature showed a downward trend for a whole procedure time. During recovery, only 1 patient showed symptoms of pain and signs of dissociation. In summary, the partial intravenous protocol with the use of tiletamine-zolazepam combination and low anesthetic gases concentration is clinically useful because of ensuring the correct level of anesthesia and stability of intraoperative parameters as well as a good recovery period., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objective: To evaluate alfaxalone for total intravenous anesthesia (TIVA) in rabbits premedicated with dexmedetomidine or dexmedetomidine and buprenorphine., Study Design: Crossover study (part 1) with observational study (part 2)., Animals: A total of eight New Zealand White rabbits (Oryctolagus cuniculus), four female and four male, aged 12-16 weeks and weighing 2.8-3.5 kg in part 1. Separately, four additional rabbits in part 2., Methods: Crossover study design with eight rabbits per treatment. Rabbits were administered treatment D, dexmedetomidine (0.2 mg kg -1 ), or treatment DB, dexmedetomidine (0.1 mg kg -1 ) and buprenorphine (0.05 mg kg -1 ) intramuscularly. Anesthesia was induced with alfaxalone intravenously until a supraglottic airway device was placed to deliver 100% oxygen. Anesthesia was maintained with alfaxalone (TIVA). Infusion rates were adjusted to achieve an absent pedal withdrawal reflex. Heart rate, respiratory rate, noninvasive blood pressure, end-tidal carbon dioxide partial pressure and peripheral hemoglobin oxygen saturation (SpO 2 ) were recorded every 5 minutes. Subsequently, four rabbits underwent ovariohysterectomy using treatment DB and alfaxalone TIVA., Results: The mean ± standard deviation alfaxalone infusion rate was 9.6 ± 2.6 and 4.5 ± 1.3 mg kg -1 hour -1 for treatments D and DB, respectively. In both treatments, blood pressure remained within acceptable range and SpO 2 was > 95%. Postinduction apnea and respiratory depression were observed in both treatments and managed with manual positive pressure ventilation. Four separate rabbits underwent successful ovariohysterectomy with treatment DB and alfaxalone TIVA. One rabbit required supplementation with inhalant anesthesia; three rabbits were successfully maintained using alfaxalone TIVA alone., Conclusions and Clinical Relevance: Premedication with dexmedetomidine-buprenorphine combined with alfaxalone TIVA may be a viable alternative for performing abdominal surgery in the rabbit. The use of supplemental oxygen and ability to provide respiratory support are advised., (Copyright © 2022 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To determine the effects of intravenous ethyl pyruvate, an anti-inflammatory with putative benefits in horses with endotoxemia, on cardiopulmonary variables during anesthesia and the quality of anesthetic recovery., Study Design: Randomized, crossover, blinded experimental design., Animals: A total of six healthy Standardbred geldings, aged 13 ± 3 years and weighing 507 ± 66 kg (mean ± standard deviation)., Methods: Horses were anesthetized for approximately 90 minutes on two occasions with a minimum of 2 weeks apart using xylazine for sedation, ketamine and diazepam for induction, and isoflurane in oxygen for maintenance. Lactated Ringer's solution (LRS; 10 mL kg -1 hour -1 ) was administered during anesthesia. Treatments were randomized and administered starting approximately 30 minutes after induction of anesthesia and infused over 60 minutes: LRS (1 L) or ethyl pyruvate (150 mg kg -1 in 1 L LRS). Invasive arterial pressures, heart rate, respiratory rate and end-tidal carbon dioxide tensions were recorded every 5 minutes for the duration of anesthesia. Arterial blood gases, glucose and lactate concentrations were measured every 20 minutes. Anesthetic recovery was video recorded, stored, and subsequently rated by two individuals blinded to treatments. Total recovery time, time to extubation, number of attempts and time to sternal recumbency, number of attempts to stand and time to stand were recorded. Quality of recovery was analyzed. Data between treatments and within a treatment were assessed using two-way repeated-measures anova and a Pearson correlation coefficient, significant at p < 0.05., Results: All horses completed the study. No significant differences were detected between the ethyl pyruvate and LRS treatments for either the cardiopulmonary variables or quality of recovery from anesthesia., Conclusions and Clinical Relevance: The results suggest that intravenous ethyl pyruvate can be administered to healthy anesthetized horses with minimal impact on the cardiopulmonary variables studied or the quality of recovery from anesthesia., (Copyright © 2022 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Background: The present study aimed to investigate the effect of endotracheal intubation on nasal and tracheal endogenous NO concentrations, gas exchange and oxygenation in horses undergoing general anaesthesia. In many species a major part of physiological nitric oxide (NO) production takes place in the nasopharynx. Inhaled NO acts as a pulmonary vasodilator and regulates lung perfusion and endotracheal intubation bypasses the nasopharynx. Six horses were randomly assigned to either the "intubated" (INT) or the "non-intubated" (nINT) treatment group. Horses were premedicated with dexmedetomidine (5 μg/kg IV). Anaesthesia was induced with 2.5 mg/kg ketamine and 0.05 mg/kg diazepam IV, and it was maintained by administration of a triple-drip (100 mg/kg/h guaifenesin, 4 mg/kg/h ketamine, 7 μg/kg/h dexmedetomidine). The horses were spontaneously breathing room air. Heart rate, cardiac output, arterial blood pressure, pulmonary arterial blood pressures and respiratory rate were recorded during a 100-min anaesthesia period. Arterial, venous and mixed venous blood samples were taken every 10 minutes and analysed for partial pressure of oxygen (PO 2 ) and carbon dioxide (PCO 2 ), oxygen saturation and haemoglobin content. Standard oxygenation indices were calculated. Nasal and tracheal endogenous NO concentration was determined by chemiluminescence., Results: Cardiovascular variables, respiratory rate, PO 2 , PCO 2 , oxygen saturation, haemoglobin content, CaO 2 , O 2 ER, P (a-ET) CO 2 and Q s /Q t did not differ significantly between the two treatment groups. The P (A-a) O 2 was significantly higher in INT (6.1 ± 0.3 kPa) compared to nINT (4.9 ± 0.1 kPa) (p = 0.045), respectively. The nasal (8.0 ± 6.2 ppb) and tracheal (13.0 ± 6.3 ppb) endogenous NO concentration differed significantly in INT (p = 0.036), but not in nINT (nasal: 16.9 ± 9.0 ppb; tracheal: 18.5 ± 9.5 ppb) (p = 0.215)., Conclusion: Endotracheal intubation reduces the nasal and tracheal endogenous NO concentration. The influence on pulmonary gas exchange and oxygenation is negligible in horses breathing room air., (© 2022. The Author(s).)

The present study aimed to determine the effect of either ketamine or dexmedetomidine constant rate infusion (CRI) on intraoperative propofol anaesthetic requirements during total intravenous anaesthesia (TIVA) in healthy dogs undergoing hindlimbs orthopaedic procedures receiving epidural anaesthesia. In this randomised, blinded clinical study, thirty-nine healthy client-owned dogs were premedicated intramuscularly (dexmedetomidine 4 μg/kg and methadone 0.3 mg/kg). General anaesthesia was induced to effect with propofol administered as intravenous bolus, and maintained with propofol TIVA (18 mg/kg/h), adjusted to meet the suitable clinical anaesthetic depth (indicatively±20%) based on clinical judgement. Lumbosacral epidural anaesthesia was performed using bupivacaine (1 mg/kg) and morphine preservative free (0.1 mg/kg). Dogs randomly received either saline (SP; loading dose 1 mL/kg, CRI 1 mL/kg/h), or ketamine (KP; loading dose 1.5 mg/kg, CRI 1.5 mg/kg/h), or dexmedetomidine (DP; loading dose 1 μg/kg/, CRI 1 μg/kg/h). Physiological variables were recorded intraoperatively at 5-min intervals using standard-of-care monitoring. Recovery quality and duration were recorded. Treatment groups were compared with parametric and non-parametric tests as appropriate, p < 0.05. Propofol rates and recovery scores were similar between groups. Overall mean and diastolic blood pressures were higher in group DP compared to group KP (12-14 mmHg, p = 0.016 and p = 0.015, respectively). More dogs required mechanical ventilation in group KP (12 dogs) than in either group SP or DP (7 dogs per group, p = 0.037). Ketamine or dexmedetomidine CRIs, at the studied rates, did not reduce propofol TIVA requirements in dogs undergoing orthopaedic surgery with epidural anaesthesia., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Propofol is a widely used drug in veterinary medicine to induce anesthesia; as well as the chosen compound for protocols of intravenous anesthesia. The present study aimed to describe the hematological, biochemical and oxidative stress alterations in calves kept under anesthesia by propofol in different dosages. In order to achieve this, eight Holstein calves were induced using propofol in a 5 mg/kg dosage and maintained under continuous propofol infusion for 60 min, having being administered 0.6 mg/kg/h or 0.8 mg/kg/h in crossover design with seven days interval. Blood samples were collected immediately before the anesthesia induction (baseline), and 30 min, 1, 2, 3, 4 and 5 h after the procedure started. Statistically relevant propofol influence was observed both in blood and biochemical parameters, with differences between dosages according to the time of infusion. The drug action over oxidative stress was also observed, causing a raise of the total antioxidant capacity (TAC) with an uric acid increase. Additionally, the increase of triglycerides, induced by the anesthesia maintenance with propofol, caused lipemia in the samples, which was capable of interfering directly in the measurements made by refractometry and spectrophotometry. It was concluded that, in spite of propofol induced alterations in blood and biochemical parameters, such alterations are subtle. In addition to that, the drug presented an antioxidative effect, which reinstates the safety of anesthesia maintenance with propofol in calves., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Total intravenous anesthesia (TIVA) has been gaining ground in the routine of small animals. This study aimed to evaluate the hemodynamic effects produced by continuous infusion of propofol isolated or associated with ketamine, S-ketamine, or remifentanil in dogs submitted to video laparoscopic ovariectomy. Thirty-two female dogs were randomly assigned to 4 groups (n = 8): G,1 propofol (0.6 mg/kg/min); G2. ketamine (2 mg/kg followed by 100 µg/kg/min) and propofol (0.4 mg/kg/min); G3, S-ketamine (1 mg/kg followed by 50 µg/kg/min) and propofol (0.4 mg/kg/min); and G4, remifentanil (1 µg/kg followed by 0.2 µg/kg/min) and propofol (0.4 mg/kg/min). All dogs were submitted to the same pre-anesthetic protocol with acepromazine (0.1 mg/kg) and meperidine (4 mg/kg) intramuscularly, followed by anesthetic induction with propofol (4 mg/kg). All animals were mechanically ventilated. Heart rate (HR), respiratory rate (f), SpO 2 , systolic, diastolic and mean arterial blood pressures (SAP, DAP and MAP, respectively), EtCO 2 , cardiac output (CO), blood glucose and rectal temperature were evaluated in 7 time-points (M0-M7). HR increased throughout the anesthesia in all groups, except for G4, which showed inferior values. In all groups, EtCO 2 increased from M1 to M7. SAP was higher in G1 in relation to G2 in M2 and M3, and G4 in all time points. G4 also obtained the lower values for DAP and MAP, although not inferior to 60 mmHg. CO was unchanged through time and among groups. No groups had hyperglycemia, although glucose levels varied with time. It was concluded that all TIVA protocols showed satisfactory results and hemodynamic stability., (Copyright © 2021 Elsevier Inc. All rights reserved.)

The present study was designed to compare the effects of lidocaine and ropivacaine in intravenous regional anaesthesia (IVRA) in dogs. Twelve adult male dogs were used. Under isoflurane anaesthesia, exsanguination was performed in the target forelimb. Then, a blood pressure cuff was encircled around the limb proximal to the elbow joint with a pressure of approximately 150 mmHg above the mean arterial blood pressure. The animals then received one of the two treatments of lidocaine (3 mg/kg) or ropivacaine (1.5 mg/kg) with a final volume of 0.6 mL/kg into the cephalic vein. After 60 min, the anaesthesia was disrupted and the tourniquet was removed using intermittent opening (30 s) and closing (5 min) manner for three times. The results revealed that at 20 and 30 min after the initiation of IVRA, the dogs in ROP showed higher analgesia than LID. A leakage under the tourniquet during IVRA was detected. Tremor and hypersalivation were observed after tourniquet removal in some dogs. It was concluded that ropivacaine might provide a higher quality of anaesthesia than lidocaine in IVRA in dogs. The development of local anaesthetic toxicity is a major concern and should be considered at the time of tourniquet removal., (© 2021 The Authors. Veterinary Medicine and Science published by John Wiley & Sons Ltd.)

Objective: To compare effects of intravenous (IV) alfaxalone with ketamine-xylazine combination on anaesthetic induction, recovery and cardiopulmonary variables in mute swans., Study Design: Randomized, controlled, clinical study., Animals: A group of 58 mute swans., Methods: Swans were given either alfaxalone (10 mg kg -1 ; group A) or a combination of ketamine (12.5 mg kg -1 ) and xylazine (0.28 mg kg -1 ) (group KX) IV. Heart and respiratory rates, end-tidal carbon dioxide and peripheral haemoglobin oxygen saturation were recorded at 5 minute intervals during anaesthesia. Time from anaesthetic induction to intubation, from cessation of isoflurane to extubation, to lifting head, sternal recumbency and absence of head/neck ataxia were recorded. Anaesthetic and recovery quality were scored (1 = very poor; 5 = excellent). Data are presented as median (interquartile range). Significance was set at p < 0.05., Results: In group A, 44% (12/27) of swans required mechanical ventilation for 2-14 minutes versus 3.2% (1/31) of swans in group KX (p = 0.0002). Heart rate was higher in group A than in group KX [146 (127-168) versus 65.5 (56-78) beats minute -1 , respectively; p < 0.0001]. The isoflurane concentration required to maintain anaesthesia was higher in group A than in group KX [2.5% (2.0-3.0%) versus 1.5% (1.0-2.0%), respectively; p = 0.0001]. Time from cessation of isoflurane administration to lifting head was significantly longer in group A than in group KX [12 (9-17) versus 6 (4-7.75) minutes, respectively; p < 0.0001]. Anaesthesia quality scores were significantly better in group KX than in group A [4 (4-5) versus 4 (3-4), respectively; p = 0.0011], as were recovery scores [4 (3-5) versus 2 (2-3), respectively; p = 0.0005]., Conclusions and Clinical Relevance: Alfaxalone is a suitable anaesthetic induction agent for use in mute swans. There is a greater incidence of postinduction apnoea and a higher incidence of agitation on recovery with alfaxalone than with ketamine-xylazine., (Copyright © 2021 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objectives: To describe Spanish-speaking veterinary anaesthetists' attitudes towards use of total intravenous anaesthesia (TIVA) in dogs., Study Design: Prospective online voluntary survey., Population: Data from 300 answered surveys., Methods: An anonymous questionnaire was sent via e-mail to representatives of the four largest Spanish-speaking veterinary anaesthesia and analgesia associations. It was distributed through mailing lists (Spain, Argentina, Mexico) or social media (Spain, Chile) to gather information on the use, opinions and perceived advantages of TIVA, as well as on preferred alternatives to isoflurane for providing general anaesthesia. Logistic regression was used to test for response associations., Results: A total of 275 (92%) respondents had used TIVA (24% rarely, 36% sometimes, 40% very often or always). There was an association between a higher rate of TIVA usage and a low specialization level, less clinical experience and unavailability of anaesthetic gas scavenging systems. The main reasons for not using TIVA were lack of familiarity with the technique (92%), unavailability of infusion pumps (32%), established institutional anaesthetic protocol (32%), and technical difficulty (20%). Among frequent TIVA users, a higher proportion reported the greater ease of TIVA use (52%) compared to those that did not perceive such benefit (17%) [odds ratio (OR) = 5.2; 95% confidence interval (CI95), 1.7-16.6; p = 0.004). More respondents did not consider TIVA more expensive (60%) (OR = 2.1; CI95, 1.0-4.3; p = 0.034), more difficult to perform (59%) (OR = 2.5; CI95, 1.3-4.9; p = 0.006) or to manage the equipment (53%) (OR = 3.3; CI95, 1.4-7.8; p = 0.008), than inhalational anaesthetics. During isoflurane shortages, respondents reportedly preferred using an alternative inhalational agent (59%) rather than TIVA (47%)., Conclusions and Clinical Relevance: TIVA use is widespread among veterinarians within the surveyed associations. Frequent TIVA users reported greater perceived advantages. In situations of isoflurane shortage, an alternative inhalational anaesthetic was preferred over TIVA., (Copyright © 2021 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

The objectives of this study were (a) to establish a population pharmacokinetic model and (b) to investigate the clinical and physiological effects of a single bolus dose of propofol in common marmosets. In Study 1, pharmacokinetic analysis was performed in six marmosets under sevoflurane anaesthesia. 8 mg/kg of propofol was administrated at a rate of 4 mg kg -1  min -1 . Blood samples were collected 2, 5, 15, 30, 60, 90, 120 or 180 min after starting propofol administration. Plasma concentration was measured, and population pharmacokinetic modelling was performed. A two-compartment model was selected as the final model. The population pharmacokinetic parameters were as follows: V 1  = 1.14 L, V 2  = 77.6 L, CL 1  = 0.00182 L/min, CL 2  = 0.0461 L/min. In Study 2, clinical and physiological parameters were assessed and recorded every 2 min after 12 mg/kg of propofol was administrated at a rate of 4 mg kg -1  min -1 . Immobilization was sustained for 5 min following propofol administration without apparent bradycardia. While combination of propofol and sevoflurane caused apnoea in Study 1, apnoea was not observed following single administration of propofol in Study 2. These data provide bases for further investigation on intravenous anaesthesia using propofol in common marmosets., (© 2020 John Wiley & Sons Ltd.)

The practice of creating and maintaining general anesthesia using intravenous anesthetic drugs is defined as total intravenous anesthesia. Total intravenous anesthesia produces general anesthesia by selective drug properties that fulfill the 3 elements of anesthesia. Total intravenous anesthesia has potential application in veterinary emergency and critical care medicine. This article reviews the theory and application of total intravenous anesthesia and identifies possible application in emergency and critical care medicine., Competing Interests: Disclosure The author has no commercial or financial conflicts of interest related to the material contained in this article. The author has no research funding which may be a conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Sterilization clinics often occur in remote places where anesthesia machines and compressed oxygen are unavailable. This study describes the use of total injectable anesthesia in dogs and cats presented for sterilization in a remote location., Results: A total of 100 animals were sterilized; 26 female cats (CF), 22 male cats (CM), 28 female dogs (DF), and 24 male dogs (DM). CF were anesthetized with dexmedetomidine (20 mcg/kg), ketamine (8 mg/kg) and hydromorphone (0.1 mg/kg) IM. CM were anesthetized with dexmedetomidine (15 mcg/kg), ketamine (5 mg/kg) and hydromorphone (0.1 mg/kg) IM. Insufficient anesthesia in cats was treated with alfaxalone (1 mg/kg) IM. All cats were administered meloxicam at 0.3 mg/kg SQ. DF were anesthetized with dexmedetomidine (15 mcg/kg), ketamine (7-10 mg/kg) and hydromorphone (0.1 mg/kg) IM. DM were anesthetized with dexmedetomidine (15 mcg/kg), ketamine (5 mg/kg) and hydromorphone (0.1 mg/kg) IM. All dogs had IV catheter and endotracheal tube placed. If SpO 2  < 91%, ventilation was assisted with an Ambu bag. Insufficient anesthesia in dogs was treated with alfaxalone (1 mg/kg) IV. All dogs were administered meloxicam at 0.2 mg/kg SQ. Following surgery, atipamezole (0.05-0.1 mg/kg) IM was administered to any patient that did not have voluntary movement. All patients survived and were discharged. Less than 25% of cats and male dogs required supplemental anesthesia. Fifty seven percent of female dogs required supplemental anesthesia. More than 89% of patients (in any group) required atipamezole administration. One cat recovered with agitation and hyperthermia (41.1C/ 106F). Some dogs required ventilatory assistance to remain normoxemic while anesthetized., Conclusion: Total injectable anesthesia can be accomplished for remote location sterilization clinics with minimal morbidity.

The aim of the present study was to establish appropriate doses for both lidocaine hydrochloride (Hcl) and mepivacaine in intravenous regional analgesia (IVRA) and to assess their intraoperative and postoperative analgesic effects in horses with distal limb surgeries. A total of 55 draft horses were included in the present study. Six clinically healthy horses were selected randomly for establishing the doses of lidocaine Hcl and mepivacaine in IVRA in horse limbs. After selection, 32 horses suffered from various distal limb surgical affections were randomly allocated into three groups: thiopental group (n = 6), animals were operated under general anesthesia using thiopental sodium; IVRA-LID group (n = 12), animals were operated under both general anesthesia and IVRA using lidocaine Hcl; and IVRA-MEP group (n = 14), horses were operated under both general anesthesia and IVRA using mepivacaine. Postoperative pain was measured using both Horse Grimace Pain Scale and multifactorial numerical rating composite pain. The results showed that conjunction of IVRA along with thiopental general anesthesia using either lidocaine or mepivacaine significantly decreased the total required doses of thiopental sodium during the operations and significantly increased the duration of postoperative analgesia to 60 and 150 minutes using lidocaine and mepivacaine, respectively. In conclusion, the uses of local IVRA before distal limb surgery improve the depth of general anesthesia and reduced postoperative pain, despite thiopental anesthesia alone. Mepivacaine is superior to lidocaine in IVRA, with a longer duration of action., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: To determine the alfaxalone dose reduction during total intravenous anaesthesia (TIVA) when combined with ketamine or midazolam constant rate infusions and to assess recovery quality in healthy dogs., Study Design: Prospective, blinded clinical study., Animals: A group of 33 healthy, client-owned dogs subjected to dental procedures., Methods: After premedication with intramuscular acepromazine 0.05 mg kg -1 and methadone 0.3 mg kg -1 , anaesthetic induction started with intravenous alfaxalone 0.5 mg kg -1 followed by either lactated Ringer's solution (0.04 mL kg -1 , group A), ketamine (2 mg kg -1 , group AK) or midazolam (0.2 mg kg -1 , group AM) and completed with alfaxalone until endotracheal intubation was achieved. Anaesthesia was maintained with alfaxalone (6 mg kg -1 hour -1 ), adjusted (±20%) every 5 minutes to maintain a suitable level of anaesthesia. Ketamine (0.6 mg kg -1 hour -1 ) or midazolam (0.4 mg kg -1 hour -1 ) were employed for anaesthetic maintenance in groups AK and AM, respectively. Physiological variables were monitored during anaesthesia. Times from alfaxalone discontinuation to extubation, sternal recumbency and standing position were calculated. Recovery quality and incidence of adverse events were recorded. Groups were compared using parametric analysis of variance and nonparametric (Kruskal-Wallis, Chi-square, Fisher's exact) tests as appropriate, p < 0.05., Results: Midazolam significantly reduced alfaxalone induction and maintenance doses (46%; p = 0.034 and 32%, p = 0.012, respectively), whereas ketamine only reduced the alfaxalone induction dose (30%; p = 0.010). Recovery quality was unacceptable in nine dogs in group A, three dogs in group AK and three dogs in group AM., Conclusions and Clinical Relevance: Midazolam, but not ketamine, reduced the alfaxalone infusion rate, and both co-adjuvant drugs reduced the alfaxalone induction dose. Alfaxalone TIVA allowed anaesthetic maintenance for dental procedures in dogs, but the quality of anaesthetic recovery remained unacceptable irrespective of its combination with ketamine or midazolam., (Copyright © 2020 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To evaluate the effect of four recumbent body positions on intraocular pressure (IOP) in anesthetized normal horses., Animals Studied: Ten nonglaucomatous adult horses., Procedures: Intraocular pressure was measured with a rebound tonometer in both eyes of standing sedated horses (baseline), then under general anesthesia during four randomized recumbent body positions, including Trendelenburg (Tr; 15-degree head down), reverse Trendelenburg (RTr; 15-degree head up), dorsal, and lateral; only the superior eye was measured in lateral positions. The mean of 3 IOP readings was taken at each position, allowing a minimum of 2 minutes of acclimatization after each position change before obtaining measurements. Repeated Measures Analysis with Newman-Keuls Multiple Comparison Post hoc was used to compare IOPs in different positions, and linear regression was used to compare IOP with age and weight cofactors., Results: When compared to baseline, the greatest change in IOP occurred in Tr (increase of 25.63 ± 8.12 mm Hg). When comparing all recumbent positions to baseline, IOP significantly increased in 3 of 4 body positions (P < .001), with no significant difference identified between RTr and baseline. When comparing all body positions to each other, the greatest IOP difference occurred between the Tr and the RTr positions (increase of 26.95 ± 5.41 mm Hg). Age and weight were not correlated with IOP in any position., Conclusions: Recumbent body position significantly increases IOP in normal eyes of horses under injectable anesthesia., (© 2020 American College of Veterinary Ophthalmologists.)

Objective: To evaluate the anesthetic and cardiopulmonary effects of xylazine-alfaxalone anesthesia in donkey foals undergoing field castration., Study Design: Prospective clinical study., Animals: A group of seven standard donkeys aged [median (range)] 12 (10-26) weeks, weighing 47.3 (37.3-68.2) kg., Methods: Donkeys were anesthetized with xylazine (1 mg kg -1 ) intravenously (IV) followed 3 minutes later by alfaxalone (1 mg kg -1 ) IV. Additional doses of xylazine (0.5 mg kg -1 ) and alfaxalone (0.5 mg kg -1 ) IV were administered as needed to maintain surgical anesthesia. Intranasal oxygen was supplemented at 3 L minute -1 . Heart rate (HR), respiratory rate (f R ) and mean arterial pressure (MAP) by oscillometry were recorded before drug administration and every 5 minutes after induction of anesthesia. Peripheral oxygen saturation (SpO 2 ) was recorded every 5 minutes after induction. Time to recumbency after alfaxalone administration, time to anesthetic re-dose, time to first movement, sternal and standing after last anesthetic dose and surgery time were recorded. Induction and recovery quality were scored (1, very poor; 5, excellent)., Results: Median (range) induction score was 5 (1-5), and recovery score 4 (1-5). Overall, two donkeys were assigned a score of 1 (excitement) during induction or recovery. HR and MAP during the procedure did not differ from baseline. f R was decreased at 5 and 10 minutes but was not considered clinically significant. SpO 2 was <90% at one time point in two animals., Conclusions and Clinical Relevance: Xylazine-alfaxalone anesthesia resulted in adequate conditions for castration in 12 week old donkeys. While the majority of inductions and recoveries were good to excellent, significant excitement occurred in two animals and may limit the utility of this protocol for larger donkeys. Hypoxemia occurred despite intranasal oxygen supplementation., (Copyright © 2020 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To compare the propofol infusion rate and cardiopulmonary effects during total intravenous anesthesia with propofol alone and propofol combined with methadone, fentanyl or nalbuphine in domestic chickens undergoing ulna osteotomy., Study Design: Prospective, randomized, experiment trial., Animals: A total of 59 healthy Hissex Brown chickens weighing 1.5 ± 0.2 kg., Methods: Anesthesia was induced with propofol (9 mg kg -1 ) administered intravenously (IV) and maintained with propofol (1.2 mg kg -1 minute -1 ) for 30 minutes. Birds were intubated and supplemented with 100% oxygen through a nonrebreathing circuit under spontaneous ventilation. Thereafter, each animal was randomly assigned to one of four groups: group P, no treatment; group PM, methadone (6 mg kg -1 ) intramuscularly (IM); group PN, nalbuphine IM (12.5 mg kg -1 ); and group PF, fentanyl IV (30 μg kg -1 loading dose, 30 μg kg -1 hour -1 constant rate infusion). During the osteotomy surgery, the propofol infusion rate was adjusted to avoid movement of birds and provide adequate anesthesia. Pulse rate, invasive blood pressure, respiratory frequency, end-tidal carbon dioxide partial pressure (Pe'CO 2 ) and hemoglobin oxygen saturation (SpO 2 ) were recorded., Results: Data were available from 58 chickens. The mean ± standard deviation propofol infusion rate (mg kg -1 minute -1 ) for the duration of anesthesia was: group P, 0.81 ± 0.15; group PM, 0.66 ± 0.11; group PN, 0.60 ± 0.14; and group PF, 0.80 ± 0.07. Significant differences were P versus PM (p = 0.042), P versus PN (p = 0.002) and PF versus PN (p = 0.004). Pulse rate, blood pressure and SpO 2 remained acceptable for anesthetized birds with minor differences among groups. Values of Pe'CO 2 >60 mmHg (8 kPa) were observed in all groups., Conclusions and Clinical Relevance: Methadone and nalbuphine, but not fentanyl, decreased the propofol infusion rate required for anesthesia maintenance, but resulted in no obvious benefit in physiological variables., (Copyright © 2020 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

In this study, adult intact male and female ( n = 10) naked mole-rats ( Heterocephalus glaber ) were anesthetized using a combination of dexmedetomidine (0.06 mg/kg intramuscularly [IM]), ketamine (20 mg/kg IM), and midazolam (1.0 mg/kg IM). Atipamezole (1.0 mg/kg IM) and flumazenil (0.1 mg/kg IM) were administered 40 min after induction. Induction and recovery times were monitored and recorded. Vital parameters, including heart rate, respiratory rate, and SpO 2 , and reflexes were monitored every 5 min during the anesthetic period. Anesthetic induction was smooth and rapid. All monitored reflexes were lost within a median time of 60 sec (interquartile range, 15 sec). Heart rate and respiratory rate were significantly decreased from baseline, whereas there was no difference in SpO 2 over the anesthetic period. The mean time to recovery was 15 ± 7 min (mean ± SD). One animal was found dead 40 min after apparent recovery, which is suspected to be an anesthetic-related death. Based on these findings, dexmedetomidine-ketamine-midazolam anesthesia is an effective anesthetic protocol in naked mole rats that provides a consistent anesthetic plane but should be used with caution in animals with underlying conditions.

Objective: To qualitatively assess the co-induction of anaesthesia with midazolam and alfaxalone and to determine cardiovascular or respiratory alterations compared with alfaxalone alone., Study Design: A randomized, blinded, clinical trial., Animals: A total of 29 American Society of Anesthesiologists grade I or II, client-owned dogs undergoing elective orthopaedic or soft tissue surgery., Methods: All dogs received 0.02 mg kg -1 acepromazine and 0.3 mg kg -1 methadone intramuscularly 30 minutes prior to anaesthesia. Measurements of heart rate (HR), respiratory frequency and blood pressure (BP) were assessed pre-induction and at 0, 2 and 5 minutes post-induction. Anaesthesia was induced with 0.5 mg kg -1 alfaxalone followed by either 0.4 mg kg -1 midazolam intravenously (group M) or an equal volume of saline (group S). Conditions were assessed for intubation and further boluses of 0.25 mg kg -1 alfaxalone were given as required. Response to co-induction, ease of intubation and quality of induction were scored, and total dose of alfaxalone required for intubation was recorded. Repeated measures one-way analysis of variance with post hoc Tukey's test was used to assess within group changes over time and Student t tests were used to compare between groups. Incidence of apnoea was assessed using a Fisher's exact test. Data are shown as mean ± standard deviation., Results: Group M included 14 dogs and group S 15 dogs. There was a significant difference in the total dose of alfaxalone required for intubation, 0.65 ± 0.20 mg kg -1 group M and 0.94 ± 0.26 mg kg -1 group S (p = 0.002). Apnoea occurred significantly more frequently in group M (p = 0.007). There were no clinically significant differences in HR or BP at the measured time points between groups., Conclusions and Clinical Relevance: Co-induction with midazolam had significant alfaxalone-sparing effects with no clinically detectable cardiovascular changes. Apnoea is common after co-induction., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To characterize the hemodynamic effects of subclinical, clinical and supraclinical plasma alfaxalone concentrations in cats., Study Design: Experimental study., Animals: A group of six adult healthy male neutered cats., Methods: Cats were anesthetized with desflurane in oxygen for instrumentation. Catheters were placed in a medial saphenous vein for drug administration and in a carotid artery for arterial blood pressure measurement and blood collection. A thermodilution catheter was placed in the pulmonary artery via an introducer placed in a jugular vein for measurement of central venous pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, cardiac output and core body temperature, and for sampling mixed venous blood. A lead II electrocardiogram was connected. Desflurane administration was discontinued and a target-controlled infusion system was used to administer alfaxalone to reach six plasma alfaxalone concentrations ranging from 1.0 to 30.4 mg L -1 , with 7.6 mg L -1 considered a clinical concentration for anesthesia. Cardiovascular measurements were recorded, and arterial and mixed-venous blood samples were collected for blood-gas analysis and plasma alfaxalone concentration measurement at each target concentration. Data were analyzed using a repeated-measures analysis of variance and Dunnett's test for comparisons to the lowest target concentration. Significance was set at p < 0.05., Results: Mean ± standard deviation plasma alfaxalone concentrations were 0.73 ± 0.32, 1.42 ± 0.41, 3.44 ± 0.40, 6.56 ± 0.43, 18.88 ± 6.81 and 49.47 ± 5.50 mg L -1 for the 1, 1.9, 3.8, 7.6, 15.2, and 30.4 mg L -1 target concentrations, respectively. PaCO 2 increased with increasing target plasma alfaxalone concentrations and was 69.4 ± 14.2 mmHg (9.3 ± 1.9 kPa) at the 30.4 mg L -1 target. Some cardiovascular variables were statistically significantly affected by increasing target plasma alfaxalone concentrations., Conclusion and Clinical Relevance: Within the plasma concentration range studied, alfaxalone caused hypoventilation, but the cardiovascular effects were of small clinical significance., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To evaluate the cardiovascular effects, pharmacokinetic (PK) data and recovery characteristics of an alfaxalone constant rate infusion (CRI) of different duration in dogs at manufacturer's recommended dose rate., Study Design: Experimental, prospective, randomized, crossover study., Animals: Six intact female Beagles., Methods: Following an intravenous alfaxalone bolus (3 mg kg -1 ), anaesthesia was maintained using an alfaxalone CRI at 0.15 mg kg -1 minute -1 for 90 (short CRI) or 180 minutes (long CRI). Venous blood samples were collected to determine the PK profile. Cardiovascular variables and recovery characteristics were evaluated. Recovery was scored on a scale ranging from 0, excellent to 4, bad. A mixed-model statistical approach was used to compare the cardiovascular parameters (global α = 0.05). An analysis of variance was performed to compare PK parameters and recovery times between treatments., Results: No significant difference was noted between protocols for any PK parameter. Volume of distribution at steady state (935.74 ± 170.25 versus 1119.15 ± 190.65 mL kg -1 ), elimination half-life (12 ± 2 versus 13 ± 3 minutes), clearance from the central compartment (26.02 ± 4.41 versus 27.74 ± 5.65 mL kg -1 minute -1 ) and intercompartmental clearance (8.47 ± 4.06 versus 12.58 ± 7.03 mL kg -1 minute -1 ) were comparable for short CRI and long CRI. Cardiovascular variables remained within physiological limits. Mechanical ventilation was necessary (short CRI: n = 1, long CRI: n = 4). The manufacturer's recommended dose rate resulted in a light plane of anaesthesia. No significant differences in recovery times and scores were observed between treatments. The quality of recovery was scored as very poor with both protocols., Conclusions and Clinical Relevance: PK data were similar between long and short infusions of alfaxalone at the manufacturer's recommended dose, with acceptable cardiovascular conditions. Nevertheless, both protocols resulted in a superficial plane of general anaesthesia with poor recovery characteristics., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To compare IV doses of alfaxalone and ketamine needed to facilitate orotracheal intubation and assess effects of each treatment on selected physiologic variables in goats undergoing orthopedic surgery with isoflurane anesthesia., Animals: 18 healthy adult goats., Procedures: Behavior was assessed before and after sedation with midazolam (0.1 mg/kg, IV) for IV catheter placement. Anesthesia was induced with additional midazolam (0.1 mg/kg, IV) and alfaxalone (n = 9) or ketamine (9) at 2 mg/kg, IV, over 30 seconds. An additional dose of alfaxalone or ketamine (1 mg/kg) was given IV if needed for intubation; anesthesia was maintained with isoflurane in oxygen and IV fluids with ketamine (0.5 to 1 mg/kg/h). Direct systolic (SAP), diastolic (DAP), and mean (MAP) arterial blood pressures; heart rate; and respiratory rate were recorded before induction, immediately after intubation, and during surgery. Qualitative anesthetic induction and recovery characteristics were assessed. Variables were compared within and between groups by statistical methods., Results: No preinduction variables differed significantly between groups. Postintubation and 30-minute intraoperative SAP, DAP, and MAP were higher for the ketamine group than for the alfaxalone group; within the alfaxalone group, postintubation SAP, MAP, and respiratory rate prior to mechanical ventilation were lower than respective preinduction values. All alfaxalone-group goats were intubated after 1 dose of the induction agent; 5 of 9 ketamine-group goats required an additional (1-mg/kg) dose. Postoperative recovery was good to excellent for all animals., Conclusions and Clinical Relevance: Both drugs were suitable for induction of anesthesia after sedation with midazolam, but most goats required higher doses of ketamine to allow intubation. For situations in which alfaxalone administration is appropriate, the potential for decreased arterial blood pressures and respiratory rate should be considered.

Objective: To describe clinically relevant, physiological measurements collected during a 3 hour duration of alfaxalone total intravenous anaesthesia., Study Design: Case series., Animals: A total of 112 client-owned middle-aged or older dogs., Methods: Dogs were premedicated with intramuscular acepromazine (0.03 mg kg -1 ). Anaesthesia was induced and subsequently maintained for up to 3 hours with alfaxalone administered intravenously. Dogs breathed 100% oxygen via an endotracheal tube. Heart rate, respiratory rate and blood pressure were evaluated 30 minutes after administration of acepromazine and used as baseline values for comparisons of intra-anaesthetic data. Blood glucose was measured 1 week prior to anaesthesia and every hour during alfaxalone anaesthesia. Quality and duration of recovery were recorded. Mean data for physiological variables were compared over three time points-before induction of anaesthesia, for the first hour of anaesthesia and from 60 minutes to discontinuation of anaesthesia., Results: Mean induction dose of alfaxalone was 1.4 mg kg -1 [95% confidence interval (CI) 1.3-1.5). Post induction apnoea for >60 seconds occurred in 13 (11.6%) dogs. Mean alfaxalone infusion rate during the first 60 minutes of anaesthesia was 0.099 mg kg -1 minute -1 ; mean infusion rate was 0.092 mg kg -1 minute -1 from 60 minutes until discontinuation of anaesthesia. Heart rate was well maintained; hypotension (mean arterial blood pressure < 60 mmHg) was encountered in 23 (21%) dogs. Blood glucose levels did not alter during anaesthesia. Median time between discontinuation of alfaxalone infusion and extubation was 17 (7-35 minutes), time to assuming sternal recumbency was 75 (58-110 minutes), and time to standing was 109 (88-140 minutes)., Conclusions and Clinical Relevance: Alfaxalone infusion provided effective anaesthesia in this population. In a minority of cases, respiratory and haemodynamic support of the patient was required., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. All rights reserved.)

Background: There is no information directly comparing midazolam with guaifenesin when used in combination with an alpha-2 agonist and ketamine to maintain anaesthesia via i.v. infusion in horses., Objectives: To compare ketamine-medetomidine-guaifenesin with ketamine-medetomidine-midazolam for total intravenous anaesthesia (TIVA) in young horses anaesthetised for computerised tomography., Study Design: Prospective, randomised, blinded, crossover trial., Methods: Fourteen weanlings received medetomidine 7 μg/kg bwt i.v. and anaesthesia was induced with ketamine 2.2 mg/kg bwt i.v. On two separate occasions horses each received infusions of ketamine 3 mg/kg bwt/h, medetomidine 5 μg/kg bwt/h, guaifenesin 100 mg/kg bwt/h (KMG) or ketamine 3 mg/kg bwt/h, medetomidine 5 μg/kg bwt/h, midazolam 0.1 mg/kg bwt/h (KMM) for 50 min. Cardiorespiratory variables and anaesthetic depth were assessed every 5-10 min. Recovery times after the infusions ceased were recorded and recovery quality was assessed using a composite score system (CSS), simple descriptive scale (SDS) and visual analogue scale (VAS). Multivariable models were used to generate mean recovery scores for each treatment and each recovery score system and provide P-values comparing treatment groups., Results: Anaesthesia was uneventful with no difference in additional anaesthetic requirements and little clinically relevant differences in cardiopulmonary variables between groups. All horses recovered without incident with no significant difference in recovery times. Quality of the anaesthetic recovery was significantly better for the KMM group compared with the KMG group using the CSS (P<0.001), SDS (P<0.001) and VAS (P<0.001)., Main Limitations: No surgical stimulus was applied and study animals may not represent general horse population., Conclusion: Midazolam is a suitable alternative to guaifenesin when co-infused with ketamine and medetomidine for anaesthesia in young horses undergoing noninvasive procedures. Both infusions produce a clinically comparable quality of anaesthesia; however, recovery from anaesthesia is of a better quality following an infusion of ketamine-medetomidine-midazolam., (© 2018 EVJ Ltd.)

Objective: To evaluate effects of anesthesia induced with alfaxalone and maintained with alfaxalone, dexmedetomidine and remifentanil infusions in foals., Study Design: Prospective, experimental study., Animals: A group of six healthy foals [median (range) 11 (8-33) days] undergoing abdominal surgery., Methods: Intravenous (IV) dexmedetomidine (3-7μgkg -1 ) provided sedation for insertion of a pulmonary artery catheter. IV anesthesia was induced with alfaxalone (2mgkg -1 ) and maintained with alfaxalone (6mgkg -1 hour -1 ), dexmedetomidine (1μgkg -1 hour -1 ) and remifentanil (3μgkg -1 hour -1 ). Foals were endotracheally intubated and lungs were mechanically ventilated with oxygen. Cardiac output (thermodilution), heart rate and systemic arterial pressure were measured. Arterial and mixed venous blood was analyzed for PO 2 and PCO 2 , and glucose, lactate and electrolyte concentrations. Anesthetic depth was subjectively assessed. Systemic vascular resistance (SVR), oxygen utilization and intrapulmonary shunt were calculated. Preinduction (PB) or 10 minutes postinduction (+10B) data were used as baselines with one-way analysis of variance for repeated measures. Data are mean ± standard deviation; significance was p ≤ 0.05., Results: Duration of anesthesia was 129 ± 22minutes. One foal was administered additional alfaxalone (0.5mgkg -1 ) following induction. Cardiac index decreased to 107 ± 31 and 87 ± 21mLkg -1 minute -1 at 60 and 80minutes, respectively, compared with PB (157 ± 33mLkg -1 minute -1 ). SVR increased to 1223 ± 166dynessecond -1 cm -5 at 80minutes compared with +10B (704 ± 247dynessecond -1 cm -5 ). Mean arterial pressures were 63-128mmHg. Time from stopping infusions to standing was 46-106minutes. All foals were hypothermic (<36°C) and three foals were administered atipamezole (0.05mgkg -1 ) intramuscularly during recovery., Conclusion: and clinical relevance Combined alfaxalone-dexmedetomidine-remifentanil provided suitable anesthesia to permit laparotomy in foals. At the doses evaluated, prolonged recovery may occur., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Alfaxalone, a synthetic neuroactive steroid, has been attributed with properties including sedation, anaesthesia and analgesia. The clinical relevance of any analgesic properties of alfaxalone has not been demonstrated. This study was a prospective, blinded, randomized, negative control clinical trial in 65 healthy dogs presented for ovariohysterectomy. Anaesthesia was induced and maintained, for Group 1 (TIVA) dogs (n = 30) with intravenous alfaxalone alone and for Group 2 dogs (n = 35) with thiopental followed by isoflurane in 100% oxygen inhalation. After ovariohysterectomy, quantitative measures of pain or nociception were recorded at 15 min intervals for 4 hr using three independent scoring systems, a composite measure pain scale (CMPS), von Frey threshold testing and measures of fentanyl rescue analgesia. The mean CMPS scores of Group 2 (THIO/ISO) dogs remained higher than Group 1 (TIVA) dogs from 15 to 135 min post-surgery but this difference was not statistically significant. There were no significant differences between groups in the proportions of dogs requiring rescue fentanyl analgesia, the total fentanyl dose used or the time to first fentanyl dose. The Von Frey threshold testing was found to be unsuitable for measurement of pain in this experimental model. When administered as total intravenous anaesthesia, alfaxalone did not provide analgesia in the postoperative period., (© 2019 John Wiley & Sons Ltd.)

To investigate the clinical pharmacokinetics and pharmacodynamics of intravenous alfaxalone in young Thoroughbred horses, seven Thoroughbred horses were randomly anaesthetised twice with either 1 or 2 mg/kg of intravenous alfaxalone after premedication with medetomidine (6 µg/kg intravenous) and midazolam (20 µg/kg intravenous). Blood samples were collected at predetermined time points up to two hours after administration. Plasma alfaxalone concentrations were quantified by a liquid chromatography tandem-mass spectrometry method and analysed by non-compartmental pharmacokinetic analysis. Induction and recovery qualities were good to excellent for both doses. Recovery time for the 2 mg/kg (median 90 minutes) was significantly longer than that for the 1 mg/kg (median 50 minutes). Respiratory rate for the 2 mg/kg was significantly lower than that for the 1 mg/kg, resulting in hypoxaemia. The median (range) elimination half-life, total clearance and volume of distribution were 58.2 (42.3-70.7) minutes, 11.6 (10.3-14.5) ml/minute/kg and 0.8 (0.7-0.9) l/kg for the 1 mg/kg and 59.8 (47.5-68.0) minutes, 14.7 (12.1-16.0) ml/minute/kg and 0.9 (0.9-1.2) l/kg for the 2 mg/kg, respectively. Alfaxalone is rapidly eliminated from the plasma in young Thoroughbred horses. Respiratory depression should be especially noted when alfaxalone is used in clinical practice., Competing Interests: Competing interests: None declared., (© British Veterinary Association 2018. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: To determine the effect of fentanyl on the induction dose and minimum infusion rate of alfaxalone required to prevent movement in response to a noxious stimulus (MIR NM ) in dogs., Study Design: Experimental crossover design., Animals: A group of six healthy, adult, intact female mixed-breed dogs, weighing 19.7 ± 1.3 kg., Methods: Dogs were randomly administered one of three treatments at weekly intervals: premedication with 0.9% saline (treatment A), fentanyl 5 μg kg -1 (treatment ALF) or fentanyl 10 μg kg -1 (treatment AHF), administered intravenously over 5 minutes. Anesthesia was induced 5 minutes later with incremental doses of alfaxalone to achieve intubation and was maintained for 90 minutes in A with alfaxalone (0.12 mg kg -1 minute -1 ), in ALF with alfaxalone (0.09 mg kg -1 minute -1 ) and fentanyl (0.1 μg kg -1 minute -1 ) and in AHF with alfaxalone (0.06 mg kg -1 minute -1 ) and fentanyl (0.2 μg kg -1 minute -1 ). The alfaxalone infusion was increased or decreased by 0.006 mg kg -1 minute -1 based on positive or negative response to antebrachium stimulation (50 V, 50 Hz, 10 ms). Data were analyzed using a mixed-model anova and presented as least squares means ± standard error., Results: Alfaxalone induction doses were 3.50 ± 0.13 (A), 2.17 ± 0.10 (ALF) and 1.67 ± 0.10 mg kg -1 (AHF) and differed among treatments (p < 0.05). Alfaxalone MIR NM was 0.17 ± 0.01 (A), 0.10 ± 0.01 (ALF) and 0.07 ± 0.01 mg kg -1 minute -1 (AHF) and differed among treatments. ALF and AHF decreased the MIR NM by 44 ± 8% and 62 ± 5%, respectively (p < 0.05). Plasma alfaxalone concentrations at MIR NM were 5.82 ± 0.48 (A), 4.40 ± 0.34 (ALF) and 2.28 ± 0.09 μg mL -1 (AHF)., Conclusions and Clinical Relevance: Fentanyl, at the doses studied, significantly decreased the alfaxalone induction dose and MIR NM ., (Published by Elsevier Ltd.)

Objective: To determine the suitability of alfaxalone total intravenous (IV) anaesthesia in horses and concurrently evaluate infusion rates, cardiovascular effects, pharmacokinetics and the quality of the anaesthetic recovery period., Study Design: Prospective, experimental study., Animals: Eight Standardbred horses., Methods: Horses were premedicated with IV acepromazine (0.03 mg kg -1 ) and xylazine (1 mg kg -1 ) and anaesthesia was induced with guaifenesin (35 mg kg -1 ) and alfaxalone (1 mg kg -1 ). Anaesthesia was maintained for 180 minutes using an IV infusion of alfaxalone at a rate determined by a horse's response to a supramaximal electrical noxious stimulus. Venous blood samples were regularly collected to determine alfaxalone plasma concentrations and for pharmacokinetic analysis. Cardiopulmonary variables were monitored and the quality of the anaesthetic recovery period scored., Results: The median (range) alfaxalone infusion rate was 3.1 (2.4-4.3) mg kg -1 hour -1 . The mean ± standard deviation plasma elimination half-life, plasma clearance and volume of distribution for alfaxalone were 41 minutes, 25 ± 6.3 mL minute -1 kg -1 and 1.6 ± 0.5 L kg -1 , respectively. During anaesthesia, mean arterial blood pressure was maintained above 70 mmHg in all horses. Cardiac index reached a minimum value (68% of baseline values) immediately after induction of anaesthesia and was maintained between 74% and 90% of baseline values for the remainder of the anaesthetic protocol. Following the cessation of the alfaxalone infusion, six of eight horses exhibited muscle tremors and paddling. All horses stood without incident on the first or second attempt with a median recovery score of 4.5 (good to excellent)., Conclusions and Clinical Relevance: Anaesthesia in horses can be maintained with an infusion of alfaxalone at approximately 3 mg kg -1 hour -1 . The alfaxalone infusion rates used resulted in minimal haemodynamic changes and good recovery quality. Mean alfaxalone plasma concentration was stable over the infusion period and clearance rates were similar to previously published single-dose alfaxalone studies in horses., (Copyright © 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

The commonly used sedative α 2 -adrenoceptor agonist dexmedetomidine has adverse cardiovascular effects in dogs that can be prevented by concomitant administration of the peripherally acting α 2 -adrenoceptor antagonist MK-467. An ancillary effect of dexmedetomidine is to decrease insulin release from the pancreas, whereas MK-467 stimulates insulin release. This study assessed the effects of co-administered dexmedetomidine and MK-467 in a canine glibenclamide-induced hypoglycaemia model. In a randomised, cross-over experiment, eight beagle dogs received five intravenous treatments, comprising two administrations of saline, with dexmedetomidine or dexmedetomidine and MK-467, and three administrations of glibenclamide, with saline, dexmedetomidine or dexmedetomidine and MK-467. Plasma concentrations of glucose, lactate, insulin, glucagon and the test drugs were monitored. Administration of glibenclamide significantly increased insulin secretion and decreased blood glucose concentrations. Dexmedetomidine counteracted glibenclamide-evoked hypoglycaemia. This was opposed by the α 2 -adrenoceptor antagonist MK-467, but the glibenclamide-evoked hypoglycaemia was not potentiated by co-administration of dexmedetomidine and MK-467. None of the dogs developed uncontrolled hypoglycaemia. Thus, the combination of dexmedetomidine and MK-467 appeared to be safe in this canine hypoglycaemia model. Nevertheless, when MK-467 is used to alleviate the undesired cardiovascular effects of α 2 -adrenoceptor agonists in dogs, it should be used with caution in animals at risk for hypoglycaemia because of its insulin-releasing and hypoglycaemic effects., (Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: The aim of the present study was to evaluate clinical efficacy of constant rate infusions (CRIs) of medetomidine-propofol combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery. Thirty horses were sedated intravenously (IV) with medetomidine (6.0 μg/kg) and midazolam (0.02 mg/kg) and induced IV with ketamine (1.0 mg/kg) and propofol (1.0 mg/kg). These horses were randomly allocated to three groups and maintained with sevoflurane and CRI of either medetomidine (3.0 μg/kg/h) (Group M; n = 10); or medetomidine (3.0 μg/kg/h) and propofol (3.0 mg/kg/h) (Group MP3; n = 10); or medetomidine (3.0 μg/kg/h) and propofol (6.0 mg/kg/h) (Group MP6; n = 10). End-tidal sevoflurane concentration (ET SEVO ), cardiovascular parameters, plasma propofol concentration, and recovery time and quality were compared among groups. Data were analyzed by using ANOVA with Tukey's multiple comparison test, considering P < 0.05 significant., Results: ET SEVO (%) was 2.4 ± 0.1 in Group M, 1.7 ± 0.2 in Group MP3, and 1.4 ± 0.2 in Group MP6; ET SEVO declined significantly in a propofol-dose-dependent manner. The rates of dobutamine infusion (μg/kg/min) required to keep the mean arterial blood pressure over 70 mmHg were significantly lower in Group MP3 (0.20 ± 0.10) and Group MP6 (0.15 ± 0.06) than in Group M (0.37 ± 0.18). Recovery time and quality did not differ among groups. All horses in Group MP3 required only one attempt to stand, and recovery quality was excellent. Plasma propofol concentrations were stable throughout maintenance of anesthesia in Group MP3, whereas those in Group MP6 increased significantly with increasing duration of maintenance., Conclusions: CRIs of medetomidine-propofol reduced the sevoflurane requirement for surgical anesthesia as the propofol dose increased, compared with a CRI of medetomidine alone. Additionally, the two propofol protocols provided good maintenance of cardiovascular function. CRIs of medetomidine (3.0 μg/kg/h) and propofol (3.0 mg/kg/h) resulted in excellent-quality recovery. This protocol could therefore be an especially useful additive to sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery.

Objective: To evaluate cardiopulmonary and recovery characteristics of horses administered total intravenous anesthesia (TIVA) with xylazine and ketamine combined with midazolam or propofol., Study Design: Randomized crossover study., Animals: A group of eight adult horses, aged 7-22 years, weighing 493-740 kg., Methods: Horses were administered xylazine (1 mg kg -1 ) intravenously (IV), and anesthesia was induced with ketamine (2.2 mg kg -1 ) IV. Anesthesia was maintained for 45 minutes via IV infusion of xylazine (0.016 mg kg -1 minute -1 ) and ketamine (0.03 mg kg -1 minute -1 ) combined with midazolam at 0.002 mg kg -1 minute -1 (MKX), propofol at 0.05 mg kg -1 minute -1 (PKX low ) or propofol at 0.1 mg kg -1 minute -1 (PKX high ). Additional ketamine was administered if a horse moved spontaneously. Cardiopulmonary variables, blood gases, lactate concentration, packed cell volume and total solids were recorded before sedation (baseline), at 10, 20, 30 and 45 minutes during TIVA and 10 minutes after standing. Recovery variables and quantitative recovery scores were compared. Significance was set at p < 0.05., Results: Additional ketamine was required for 50% of MKX horses. Systolic arterial pressure was elevated in MKX at 20 minutes compared with baseline (p = 0.043), at 10 and 20 minutes compared with PKX high (p = 0.007, p = 0.024) and at 20 and 30 minutes compared with PKX low (p = 0.009, p = 0.02). MKX horses (5/8) were hypertensive compared with PKX low (1/8; p = 0.017). All horses became hypoxemic (PaO 2 ≤80 mmHg; 10.7 kPa) during TIVA. Recovery variables did not differ among treatments., Conclusions and Clinical Relevance: PKX low and PKX high had similar cardiopulmonary and recovery performance compared with MKX. PKX combinations provided superior quality of anesthesia to that of MKX. A combination of propofol, ketamine and xylazine administered as TIVA can be used in horses to provide anesthesia for short procedures. Supplemental oxygen is recommended., (Published by Elsevier Ltd.)

Objective: To study the effect of alternating the order of midazolam and alfaxalone administration on the incidence of behavioural changes, alfaxalone induction dose and some cardiorespiratory variables in healthy dogs., Study Design: Prospective, randomized, controlled, clinical trial., Animals: A total of 33 client-owned dogs undergoing elective procedures., Methods: Following intramuscular acepromazine (0.02 mg kg -1 ) and morphine (0.4 mg kg -1 ) premedication, anaesthesia was induced intravenously (IV) with a co-induction of either midazolam (0.25 mg kg -1 ) prior to alfaxalone (0.5 mg kg -1 ; group MA), or alfaxalone followed by midazolam at identical doses (group AM). The control group (CA) was administered normal saline IV prior to alfaxalone administration. Additional alfaxalone (0.25 mg kg -1 increments) was administered as required in all groups until orotracheal intubation was possible. Changes in behaviour, quality of induction, ease of intubation and incidence of adverse events at induction were recorded. Heart rate (HR), respiratory rate (f R ) and systolic arterial blood pressure (SAP) were measured before treatments (baseline values), 30 minutes after premedication and at 0, 2, 5 and 10 minutes postintubation., Results: The incidence of excitement was higher in group MA compared with groups CA (p=0.005) and AM (p=0.013). The mean induction dose of alfaxalone was lower in group AM compared with group CA (p=0.003). Quality of induction and ease of intubation were similar among groups. Mean HR values decreased after premedication and increased after alfaxalone administration in all groups. Mean SAP values were similar between groups. The number of animals that required manual ventilation was higher in the MA group., Conclusions and Clinical Relevance: Despite a lower occurrence of adverse events at induction in group AM compared with group MA and a reduction of alfaxalone dose requirement in group AM compared with group CA, the use of an alfaxalone-midazolam co-induction does not seem to produce any cardiovascular or respiratory benefits in healthy dogs., (Copyright © 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objectives: To determine the context-sensitive half-time of alfaxalone following intravenous infusions of various durations. To estimate the time necessary for plasma concentration to decrease by up to 95%., Study Design: Prospective randomized and simulation studies., Animals: A group of six 1-year-old male castrated research cats., Methods: Cats were instrumented with catheters in a jugular and a medial saphenous vein. Alfaxalone was administered using a target-controlled infusion system, to target a plasma alfaxalone concentration of 7.6 mg L -1 . The infusion lasted 30 (n = 2), 60 (n = 2) or 240 (n = 2) minutes. Blood samples were collected prior to drug administration, and at several times during and up to 8 hours after the infusion, for the determination of plasma alfaxalone concentration using liquid chromatography/tandem mass spectrometry. Compartment models were fitted to each time-concentration profile, and a population model was fitted to data from all individuals. The context-sensitive half-time was determined from each individual model. In addition, times for plasma alfaxalone concentration to decrease by 50-95% following bolus administration and target-controlled infusions or continuous rate infusions of 0.5-8 hours were estimated by simulation using the population model., Results: Context-sensitive half-times were 2 and 8, 6 and 9, and 18 and 20 minutes for the 30, 60 and 240 minutes, respectively. Time for plasma alfaxalone concentration to decrease by 90% was predicted to range from 7 to 120 or 113 minutes following a bolus to an 8 hour target-controlled or continuous rate infusion, respectively., Conclusion and Clinical Relevance: Recovery time from alfaxalone anesthesia in cats is predicted to be influenced by the duration of target-controlled infusion., (Copyright © 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To compare the performance of an alfaxalone constant rate intravenous (IV) infusion versus a 3-step IV infusion, both following a loading dose, for the maintenance of a target plasma alfaxalone concentration of 7.6 mg L -1 (effective plasma alfaxalone concentration for immobility in 99% of the population) in cats., Study Design: Prospective randomized crossover study., Animals: A group of six healthy, adult male neutered cats., Methods: Catheters were placed in a jugular vein for blood sampling and in a medial saphenous vein for drug administration. An IV bolus of alfaxalone (2 mg kg -1 ) was administered, followed by either 0.2 mg kg -1  minute -1 for 240 minutes (single infusion; SI) or 0.4 mg kg -1  minute -1 for 10 minutes, then 0.3 mg kg -1  minute -1 for 30 minutes, and then 0.2 mg kg -1  minute -1 for 200 minutes (3-step infusion; 3-step). Plasma alfaxalone concentration was measured at six time points during the infusions. Measures of performance were calculated for each infusion regimen and compared using the paired Wilcoxon signed-rank test., Results: Median (range) absolute performance error, divergence, median prediction error and wobble were 15 (8-19)%, -8 (-12 to -6)% hour -1 , -12 (-19 to -7)% and 10 (8-19)%, respectively, in the SI treatment, and 6 (2-16)%, 0 (-13 to 2)% hour -1 , 1 (-16 to 4)% and 4 (3-6)% respectively, in the 3-step treatment and were significantly smaller in the 3-step treatment than in the SI treatment., Conclusion and Clinical Relevance: After IV administration of a bolus dose, a 3-step infusion regimen can better maintain stable plasma alfaxalone concentrations close to the target concentration than a single constant rate infusion., (Copyright © 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To compare the induction and recovery characteristics and selected cardiopulmonary variables of midazolam-alfaxalone or midazolam-ketamine in donkeys sedated with xylazine., Study Design: Randomized, blinded, crossover experimental trial., Animals: A group of seven adult male castrated donkeys weighing 164 ± 14 kg., Methods: Donkeys were randomly administered midazolam (0.05 mg kg -1 ) and alfaxalone (1 mg kg -1 ) or midazolam (0.05 mg kg -1 ) and ketamine (2.2 mg kg -1 ) intravenously following sedation with xylazine, with ≥ 7 days between treatments. Donkeys were not endotracheally intubated and breathed room air. Time to lateral recumbency, first movement, sternal recumbency and standing were recorded. Induction and recovery were assigned scores between 1 (very poor) and 5 (excellent). Heart rate (HR), respiratory rate (f R ), invasive arterial blood pressures and arterial blood gases were measured before induction and every 5 minutes following induction until first movement., Results: Time to lateral recumbency (mean ± standard deviation) was shorter after alfaxalone (29 ± 10 seconds) compared with ketamine (51 ± 9 seconds; p = 0.01). Time to first movement was the same between treatments (27 versus 23 minutes). Time to standing was longer with alfaxalone (58 ± 15 minutes) compared with ketamine (33 ± 8 minutes; p = 0.01). Recovery score [median (range)] was of lower quality with alfaxalone [3 (2-5)] compared with ketamine [5 (3-5); p = 0.03]. There were no differences in HR, f R or arterial pressures between treatments. No clinically important differences in blood gases were identified between treatments. Five of seven donkeys administered alfaxalone became hypoxemic (PaO 2 <60 mmHg; 8.0 kPa) and all donkeys administered ketamine became hypoxemic (p = 0.13)., Conclusions and Clinical Relevance: Both midazolam-alfaxalone and midazolam-ketamine produced acceptable anesthetic induction and recovery in donkeys after xylazine sedation. Hypoxemia occurred with both treatments., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Various anesthetic protocols are used in laboratory swine, each with specific advantages and disadvantages. Partial intravenous anesthetic techniques (PIVA) help minimize dose-dependent cardiopulmonary effects of inhalant drugs. The aim of this study was to determine the cardiopulmonary effects of a PIVA in laboratory swine. In a prospective, nonrandomized clinical study, 8 healthy juvenile Landrace-White pigs were premedicated with azaperone (0.20 ± 0.20 mg/kg IM), dexmedetomidine (0.02 ± 0.002 mg/kg IM), and alfaxalone (2.0 ± 0.20 mg/kg IM), and anesthesia was induced with intravenous alfaxalone. Anesthesia was maintained by using constant-rate infusion of dexmedetomidine (2 μg/kg/h) and alfaxalone (25 μg/kg/min) in combination with isoflurane. After the fraction of expired isoflurane was adjusted to 1.1% to 1.5%, respiratory rate, heart rate, systemic and pulmonary arterial pressure, central venous pressure, cardiac output, bispectral index, systemic vascular resistance, and arterial and mixed venous blood gases were recorded every 10 min for 60 min. Statistical analysis consisted of repeated-measures one-way ANOVA. Significant decreases occurred in heart rate, pulmonary mean arterial pressure, pulmonary diastolic pressure, partial pressure of arterial oxygen, partial pressure of venous oxygen; significant increases occurred in respiratory rate, minute volume index, diastolic arterial blood pressure, systemic vascular resistance, and arterial pH over time. We consider that the observed statistically significant cardiopulmonary changes were clinically important and that the PIVA protocol provided hemodynamic and respiratory stability for short-term anesthesia of laboratory swine.

This study evaluated use of midazolam, ketamine, and xylazine (MKX) for total intravenous (IV) anesthesia (TIVA) in horses. Medical records of 46 horses undergoing a clinical procedure using MKX for TIVA were reviewed. Age, breed, procedure, heart rate (HR), respiratory rate (RR), pre-anesthetic drugs, induction drugs, and total volume of MKX were recorded. Duration of anesthesia, time to standing, number of attempts to stand, and recovery score were also recorded. All horses were premedicated with an alpha-2 adrenoceptor agonist and anesthesia was induced with ketamine and midazolam. Duration of MKX infusion was 33 ± 14 min. Heart rate and RR decreased during the infusion of MKX. Time to endotracheal extubation was 19 ± 12 min. Horses stood at 33 ± 13 min. Median number of attempts to stand was 1. Maintenance of anesthesia of horses with MKX was useful for a variety of procedures and recovery from anesthesia was good.