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Objective: To determine if in vivo cryoneurolysis inhibits ex vivo compound action potential (CAP) conduction in the porcine saphenous nerve and if this occurs rapidly enough to justify performing the technique before stifle surgery., Study Design: Blinded, controlled, randomized, preclinical study., Animals: A group of eight healthy, 8 weeks old, intact, female pigs anesthetized for an unrelated terminal study., Methods: Both saphenous nerves of each pig were exposed surgically, and 15 mm of a 20 gauge, closed-tip, commercial cryoneurolysis cannula were inserted cranial to each nerve within the neurovascular fascial sheath along its long axis. The cannula was only actuated on one limb, according to random allocation. Nerves were excised within 15 minutes of actuation and underwent testing in a nerve conduction chamber, where stimulus voltage was increased sequentially (from 0.1 to ≤ 1.9 V). An anesthesiologist blinded to treatment viewed recordings of time versus voltage for each nerve and answered 'yes' or 'no' when asked if an evoked CAP was observed. Fisher's exact test evaluated the incidence of CAP conduction between groups (p < 0.05 considered significant). Nerves were submitted for hematoxylin and eosin staining for blinded histopathological examination., Results: A CAP was conducted in 8/8 and 1/8 of the control and treated nerves, respectively (p = 0.001). Maximal responses in control nerves were 1.92 ± 0.19 mV (mean ± standard error). In the single treated nerve that conducted a CAP, the maximal CAP amplitude was 0.4 mV, lower than the lowest maximal CAP (1.19 mV) in the control nerves. All control nerves were histologically normal, and all treated nerves displayed mild perivascular and perineural inflammation (cuffs of lymphocytes, plasma cells and eosinophils, and edema)., Conclusions and Clinical Relevance: The rapid inhibition of CAP conduction warrants clinical investigation of saphenous cryoneurolysis for both intraoperative antinociception and postoperative analgesia in pigs undergoing experimental stifle surgery., (Copyright © 2024 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: Novel locoregional techniques use dye studies to confirm successful nerve targeting. The goal was to objectively quantify and compare nerve staining characteristics of dye mixtures commonly reported in the literature using image analysis software., Study Design: Prospective, randomized cadaveric study., Methods: Thirty-six brachial plexus nerves from unpreserved pig cadavers were randomized into three groups of 12: FD (1:10 mixture of blue food dye and bupivacaine 0.5%), MB (methylene blue 1%) and TM (0.1:10 mixture of blue tissue marker and lidocaine 2%). Nerves were immersed in dye for 1, 15, 30 or 60 minutes (n = 3 each). Images of nerves before immersion (baseline) and at each time point with epineurium intact (superficial staining) and after longitudinal bisection (deep staining) were processed using image analysis software. Color saturation values were divided into quartiles (dark, medium-dark, medium-light or light). Percentage of stained nerve area in each quartile was calculated and compared using two-way anova., Results: Superficially, at minute 1, dark saturation covered 40% of nerve area in FD versus 19% in MB (p = 0.04) and 0% in TM (p < 0.0001). In bisected nerves, dark and medium-dark saturations occurred only in FD; medium-light saturation comprised anywhere from 4% to 22.5% over time in FD versus <1% at any time in MB (p = 1.000; p = 0.343; p = 0.383; p = 0.262). Deep staining was not found in TM at any point., Conclusion and Clinical Relevance: Food dye rapidly stains superficial and deep nerve layers. Based on these characteristics, investigators can choose the appropriate dye for their study., (Copyright © 2023 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To compare the effects of intramuscular premedication with a novel nonanalgesic [alfaxalone-midazolam-acepromazine (AMA)] and an analgesic [ketamine-midazolam-detomidine (KMD)] protocol on sedation end points and propofol requirements for induction of anesthesia in swine., Study Design: Prospective experimental study., Animals: A total of 27 Yorkshire cross gilts weighing approximately 30 kg., Methods: Two sedation protocols, AMA and KMD, were compared. Time from intramuscular injection to ataxia, recumbency and nonresponsiveness to tactile stimulation was recorded. The propofol dose requirement for induction of general anesthesia and tracheal intubation, and any adverse events (paddling, twitching), were recorded. Data were tested for normality using a Shapiro-Wilk test. Propofol requirements were compared using a Student's t test. Times from injection to sedation end points were compared using a Mood's test, and significance was confirmed using a Kaplan-Meier curve with Wilcoxon test survival analysis., Results: Sedation end points were reached significantly faster with KMD than with AMA. Nonresponsiveness occurred in 5 (0-16) and 9.5 (5-36) minutes for KMD and AMA, respectively (p = 0.011). No significant difference (p = 0.437) was found between propofol doses used in either group (KMD; 64.38 ± 5.98 mg, AMA; 72.00 ± 7.57 mg). More adverse events were noted with AMA (11/16 pigs) than with KMD (1/11 pigs)., Conclusions and Clinical Relevance: In pigs, AMA can be used as a reliable sedation protocol. Frequency of adverse events and time to reach sedation end points between AMA and KMD differed, but the dose of propofol needed to induce general anesthesia was not significantly different., (Copyright © 2023 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To test whether the use of a flexible endotracheal tube introducer (ETI) facilitates intubation of cats by veterinary students with little or no experience., Animals: 125 healthy cats., Procedures: Cats were sedated with dexmedetomidine and morphine IM, and anesthesia was induced with propofol. They were randomly assigned to be intubated by supervised veterinary students using an ETI within a tracheal tube or an endotracheal tube alone (3.0, 3.5, or 4.0 internal diameter sizes). Success rate at first attempt, number of attempts to intubate (up to 3), and time to intubate were recorded. Multivariate logistic regression was used to test associations between several factors such as use of an ETI, cat's weight, endotracheal tube size, administration of ketamine for sedation, and first-attempt success. Significance was considered when P < 0.05., Results: Success rate for the first attempt was higher with an ETI (79% [51/64) than without it (46% [28/61]), and attempts to intubate were fewer when an ETI was used (both P < 0.001). Time to intubate did not differ between groups (ETI, 30 seconds [4 to 143 seconds]; endotracheal tube, 28 seconds [5 to 180 seconds]). Use of an ETI was positively associated with improved first-attempt success, and the 3.0-mm internal diameter of the tube was negatively associated (both P ≤ 0.001)., Clinical Relevance: The use of a flexible ETI improved the success of first-attempt intubation of cats by veterinary students. This technique may help minimize the number of attempts during intubation and incidence of complications that could arise from multiple attempts.

Objective: Several factors affect the quality of recovery from general anesthesia in horses. These can increase the likelihood of injury. Body and limb position during recovery may correlate with successful standing. The objective of this study was to identify the prevalence of and the factors associated with successful standing at the first attempt in horses undergoing general anesthesia., Study Design: Retrospective study., Methods: Video of recovery and anesthetic records from 221 equine patients were reviewed by six veterinary students. Cases with poor video quality or incomplete anesthetic records were excluded. Demographic variables, type of procedure, perioperative drugs administered, assistance during recovery and body and limb positions during the first attempt to stand were recorded. Association between putative variables (including specific descriptors for body and limb position) and success for standing were analyzed using backward logistic regression; significance was set at 0.05. A decision tree for a successful attempt was created to predict the outcome of a recovery attempt based on these variables., Results: Extension of the carpal joints, head and neck alignment with the thoracic limbs, greater time in lateral recumbency, coordination during sternal recumbency, longer time to first attempt to stand and pelvic limb position were associated with successful standing at the first attempt. The association between extension of the carpal joints with wide base positioning of the pelvic limbs provided the best success rate for standing, whereas the association of flexed carpal joints and head and neck orientation different from the thoracic limbs resulted in a worse success rate., Conclusions and Clinical Relevance: Results suggest that certain limb and body positions displayed by horses during recovery may be associated with the likelihood of successful standing at the first attempt. These variables may be useful for assessing recovery quality in future research., (Copyright © 2021 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

African pygmy hedgehogs and sugar gliders are common zoologic companion animals frequently presented to veterinarians for routine preventive care and illness. Given their small size, intravascular access, intubation, and monitoring can be challenging, and hypothermia is a common problem during chemical immobilization. Studied injectable sedation options are limited, but can provide an alternative to general anesthesia for minor procedures. Anesthetic induction and maintenance are most commonly performed with inhalant anesthetics, such as isoflurane or sevoflurane. Preparation of all necessary equipment and emergency drugs before chemical immobilization increases the chance of a successful procedure., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: To collect data about the current practice of recovering horses from general anesthesia and recovery personnel safety., Study Design: Online survey., Methods: An online questionnaire, including questions on general demographic data, recovery drugs, modality and characteristics of equine recovery and morbidity and mortality, was designed and distributed via e-mail to equine practitioners worldwide., Results: Practitioners from 22 countries completed 373 questionnaires; 53% of the participants were board-certified equine surgeons, and the remainder were board-certified anesthesiologists (18%), large animal residents (8%), general practitioners (7%), large animal interns (6%), anesthesia residents (4.5%) and veterinary technicians (1.6%). Respondents were employed by academia (58%) or private practice (42%). Of the respondents employed at a university, 93% had a board-certified anesthesiologist on staff compared with 7% of respondents employed at a private practice. Most of the respondents assist horses during recovery, with 23% assisting every recovery and 44% assisting recovery in the majority of cases. Reasons for choosing to assist horses during recovery were: orthopedic procedures (57%), neurological deficits (49%), bad health (47%), history of poor recovery (44%), foals (42%), draft breeds (30%), magnetic resonance imaging (17%) and computed tomography (16%). Unacceptable recoveries were reported by 77% of participants. Commonly reported complications during recovery with any method were: orthopedic injury (66%), myopathy (54%), skin abrasion (53%) and airway obstruction (37%). The incidences of unacceptable quality of recovery (p = 0.09) or personnel injury (p = 0.56) were not different between assisted and nonassisted recoveries; however, more equine fatalities were reported for assisted recoveries (p < 0.006). Practitioners in academia reported more unacceptable recoveries (p < 0.0007) and personnel injuries (p < 0.002) compared with those in private practice., Conclusions: The method of recovery differs among hospitals. Recovery personnel injuries associated with assisting horses during recovery are an important and previously unreported finding., (Copyright © 2021 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To evaluate the efficacy, duration and safety of greater auricular and auriculotemporal nerve blocks in rabbits., Study Design: Prospective, randomized, crossover, experimental study., Animals: A total of 11 healthy adult Dutch-belted rabbits., Methods: The rabbits underwent general anesthesia and injections of the greater auricular and auriculotemporal nerves using either bupivacaine (0.3 mL kg -1 , 0.5%) or the same volume of saline. After anesthesia, the efficacy and duration of nerve blocks were assessed using analgesiometry forceps on the pinna and cotton-tipped applicators within the vertical ear canal. Rabbits were monitored for abnormal carriage of the ear and auriculopalpebral nerve block of the ipsilateral eye. Body weight, food intake, fecal output and fecal pellet diameter were measured daily for 6 days after the nerve blocks were performed and compared with baseline to assess short-term effects., Results: The greater auricular nerve was successfully blocked in 12/16 (75%) ears for mean ± standard deviation duration of 88 ± 52 minutes. In successfully blocked ears, altered ear position was noted in five/16 (31%) cases. The auriculotemporal nerve was blocked in one/16 ears for 120 minutes. The auriculopalpebral nerve was inadvertently blocked in three/16 ears. Food intake and fecal output decreased significantly during the treatment day but returned to pretreatment values after 24 hours. There was no change in body weight or fecal pellet diameter for either treatment., Conclusions and Clinical Relevance: The results suggest that duration of the greater auricular nerve block with 0.5% bupivacaine was short-lived in the live rabbit. Auriculotemporal nerve block was only achieved in one ear; therefore, further studies are warranted to evaluate the contribution of these blocks in the pain management of rabbits undergoing auricular surgery., (Copyright © 2020 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To determine whether the addition of bupivacaine or contrast medium to methylene blue dye would affect dye distribution following ultrasound (US)-guided transversus abdominis plane (TAP) injections., Study Design: Prospective, randomized, blinded cadaveric study., Animals: A total of 29 fresh Beagle dog cadavers., Methods: Each hemiabdomen (n = 58) was randomized into one of three groups: group M, 1% methylene blue; group MB, 50:50 mixture of 1% methylene blue and 0.5% bupivacaine; group MC, 25:75 mixture of 1% methylene blue and contrast agent (iohexol). TAP injections (0.5 mL kg -1 ) were performed bilaterally by a trained individual followed by dissection of the abdominal walls. Craniocaudal and dorsoventral spread along tissue planes was measured. Staining of branches of the thoracic and lumbar spinal nerves was considered successful when dye on the nerve was >10 mm. One-way anova with post hoc Tukey test was used to compare craniocaudal and dorsoventral spread and Kruskal-Wallis test to compare incidence of nerve staining among groups., Results: TAP injections were successful in 52 out of 58 hemiabdomens. Dorsoventral spread was greater for group M (60 ± 10 mm) compared with MC (49 ± 9 mm; p = 0.01) but not MB (52 ± 9 mm; p = 0.09). No difference was found in craniocaudal spread or number of nerves stained among groups., Conclusion and Clinical Relevance: The significant difference found in spread of tissue staining between methylene blue alone and methylene blue mixed with contrast in the TAP blocks should be kept in mind when interpreting dye-based cadaveric regional anesthesia studies., (Copyright © 2020 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. All rights reserved.)

Objective: To describe the landmarks for localization and to determine the methodology and volume of methylene blue dye to adequately stain the auricular nerves in rabbit cadavers., Study Design: Prospective, randomized, cadaveric study., Animals: A total of 26 rabbit cadavers (Dutch-Belted and New Zealand White breeds)., Methods: Part I: anatomical dissections were performed to identify the sensory auricular nerves and to establish the ideal injection approach and volume of dye required for nerve staining. Part II: a single injection technique using 0.1 mL kg -1 dye was evaluated for staining the greater auricular nerve and two techniques (perpendicular and angled needle approaches) using 0.075 mL kg -1 dye were evaluated for the auriculotemporal nerve. Dye spread was evaluated through cadaveric dissections and nerve staining graded using a 0-2 point scale. Injections were considered successful if the nerve was stained circumferentially. Cadavers were assessed for staining of the mandibular nerve owing to the close proximity to the auriculotemporal nerve. Fisher's exact test and mixed effects logistic regression model were used for statistical analysis., Results: The greater auricular nerve was stained in 24/27 (88.9%) injections. The auriculotemporal nerve was stained in 7/12 injections (58.3%) with the perpendicular needle approach; staining success increased to 80% (12/15 injections) with the angled needle approach; however, this difference was not statistically significant (p = 0.228). Mandibular nerve staining occurred on seven auriculotemporal injections with no statistically significant difference in the incidence of nerve staining between techniques., Conclusions and Clinical Relevance: Results suggest that the auricular nerves in rabbit cadavers can be successfully located and stained using anatomic landmarks and the described injection techniques., (Copyright © 2019 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Background: Video otoscopy is a valuable tool for the diagnosis and treatment of otitis externa (OE) and otitis media (OM) in dogs. Procedures performed by video otoscopy often are painful and it can be challenging to maintain steady anaesthetic depth and provide smooth anaesthetic recovery. A multimodal approach to analgesia and anaesthesia is ideal to minimize complications associated with high doses of anaesthetic drugs while providing the patient with adequate analgesia., Hypothesis/objective: To describe a technique for regional anaesthesia of the canine ear., Animals: One canine cadaver, obtained as part of a teaching laboratory class for other clinical techniques, with institutional approval, was used for illustration purposes., Results: Clinical technique for regional anaesthesia of the canine ear., Conclusions and Clinical Importance: Nerve blocks for regional anaesthesia are an important aspect of a multimodal anaesthetic approach. A technique for blocking the two major sensory nerves to the canine ear is described., (© 2019 ESVD and ACVD.)

Objectives: To describe an ultrasound-guided thoracic paravertebral block and determine the distribution after injection of two volumes of methylene blue in dog cadavers., Study Design: Prospective experimental cadaveric study., Animals: Twelve dog cadavers weighing 11 ± 3 kg., Methods: Ultrasound-guided injections aimed at the fifth thoracic (T5) paravertebral space were performed in randomized order using 0.1 or 0.3 mL kg -1 dye solution (six dogs for each volume). Anatomic dissections determined dye spread characteristics, including the presence and degree of staining of spinal nerves, and the presence of intercostal and sympathetic trunk spread. Staining of mediastinum, epidural, intrapleural and contralateral thoracic paravertebral space was recorded., Results: There was no significant difference in dye distribution between groups. The use of anatomic landmarks resulted in the inaccurate identification of the T5 paravertebral space. The T4, T5 and T6 paravertebral spaces were injected in four, five and three of 12 dogs, respectively. Complete staining of the spinal nerve of the thoracic paravertebral space injected was observed in 11 of 12 dogs, and partial staining in one dog in the low-volume group. Multisegmental distribution was demonstrated with staining of contiguous spinal nerves in one dog in the high-volume group, and multiple segments of intercostal (three dogs) and sympathetic trunk (four dogs) spread in both groups. No mediastinal, epidural, intrapleural or contralateral thoracic paravertebral space staining was observed., Conclusions and Clinical Relevance: Ultrasound-guided injection at the thoracic paravertebral space resulted in staining of the spinal nerve in all dogs. However, T5 paravertebral space was not accurately identified using anatomic landmarks. Dye distribution was not significantly different between the two groups; therefore, the use of the lower-volume and multiple-site injections would be potentially necessary in clinical cases to achieve ipsilateral blockade of the thoracic wall., (Copyright © 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)