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Summary: Background: Electrical impedance tomography (EIT) is a method to measure regional impedance changes within the thorax. The total tidal impedance variation has been used to measure changes in tidal volumes in pigs, dogs and men. Objectives: To assess the ability of EIT to quantify changes in tidal volume in anaesthetised mechanically ventilated horses. Study design: In vivo experimental study. Methods: Six horses (mean ± s.d.: age 11.5 ± 7.5 years and body weight 491 ± 40 kg) were anaesthetised using isoflurane in oxygen. The lungs were mechanically ventilated using a volume‐controlled mode. With an end‐tidal carbon dioxide tension in the physiological range, and a set tidal volume (VTvent) of 11–16 mL/kg (baseline volume), EIT data and VT measured by conventional spirometry were collected over 1 min. Thereafter, VTvent was changed in 1 L steps until reaching 10 L. After, VTvent was reduced to 1 L below the baseline volume and then further reduced in 1 L steps until 4 L. On each VT step data were recorded for 1 min after allowing 1 min of stabilisation. Impedance changes within the predefined two lung regions of interest (EITROI) and the whole image (EITthorax) were calculated. Linear regression analysis was used to assess the relationship between spirometry data and EITROI and EITthorax for individual horses and pooled data. Results: Both EITROI and EITthorax significantly predicted spirometry data for individual horses with R2 ranging from 0.937 to 0.999 and from 0.954 to 0.997 respectively. This was similar for pooled data from all six horses with EITROI (R2 = 0.799; P<0.001) and EITthorax (R2 = 0.841; P<0.001). Main limitations: The method was only tested in healthy mechanically ventilated horses. Conclusions: The EIT can be used to quantify changes in tidal volume. [ABSTRACT FROM AUTHOR]

This case report details an incident of hyperkalaemia that developed under general anaesthesia in a domestic cat with no prior health concerns. A 5-year-old male neutered domestic short-haired cat presented for dental extractions and subsequently developed severe bradycardia and electrocardiographic abnormalities during the procedure. Initial treatment with atropine provided limited improvement, and further investigation revealed a serum potassium concentration of 7.7 mmol/L. Despite interventions, the anaesthetic procedure was aborted due to persistent hyperkalaemia. The cat recovered smoothly postoperatively with complete resolution of hyperkalaemia. This case highlights the importance of monitoring serum potassium levels and electrocardiographic changes in anaesthetised feline patients. Anaesthesia-associated hyperkalaemia in domestic cats is a condition that is under-recognised in Australia. Future studies should focus on the mechanisms behind this electrolyte disturbance, as well as establishing preventive measures and management protocols during general anaesthesia., (© 2025 Australian Veterinary Association.)

Objective: To explore the influence of acepromazine on the cardiovascular effects of dobutamine in isoflurane-anaesthetised horses premedicated with romifidine., Study Design: Prospective randomised clinical trial., Animals: A total of 18 horses undergoing elective arthroscopy were enrolled, of which 12 horses requiring dobutamine were included., Methods: Horses were randomised to receive acepromazine 0.02 mg kg -1 (Group A+) intravenously (IV) or none (Group A-), 35 minutes before anaesthesia. Horses received xylazine 0.2 mg kg -1 concurrently to facilitate IV access. Horses were premedicated with romifidine 0.08 mg kg -1 , induced with ketamine 2.2 mg kg -1 and diazepam 0.08 mg kg -1 IV, and maintained with isoflurane in oxygen. Dobutamine infusion was commenced when mean arterial pressure (MAP) was < 60 mmHg. Cardiovascular data were collected prior to dobutamine, and at a target MAP of ≥ 70 mmHg. Dobutamine start time from induction, duration and dose to reach target MAP were compared using Mann-Whitney U test. Cardiovascular variables were compared using repeated measures ANOVA and post-hoc Fisher's least significant difference test., Results: Cardiac index (CI) and its percentage change from baseline were significantly higher at target MAP in group A+ [62.0 (49.9-74.2) mL minute -1 kg -1 ; 42.8 (17.0-68.7) %] than in A- [49.5 (39.6-59.5) mL minute -1 kg -1 ; -4.05 (-21.2-13.0) %] (p = 0.049; p = 0.003). Group A+ required significantly earlier dobutamine [20 (18-25) minutes] than group A- [36 (27-60) minutes] (p = 0.02). Group A+ required significantly higher dobutamine dose [1.5 (1-2.5) μg kg -1 minute -1 ] to reach target MAP than group A- [0.5 (0.5-1) μg kg -1 minute -1 ] (p = 0.009)., Conclusion and Clinical Relevance: Dobutamine significantly increased MAP and CI following pre-anaesthetic acepromazine sedation, in isoflurane-anaesthetised horses premedicated with romifidine. Without acepromazine, dobutamine increased MAP but not CI. Interactions between acepromazine, romifidine and dobutamine on the cardiovascular system should be considered., Competing Interests: Conflict of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Juvenile male pigs were sedated for castration. Eight five-month old boars were sedated twice (two weeks apart) with a combination of detomidine (0.1 mg/kg), midazolam (0.2 mg/kg) and either butorphanol (0.2 mg/kg) (Group MDB, n = 8) or morphine (0.2 mg/kg) (Group MDM, n = 8) intramuscularly. The boars were positioned in lateral recumbency and lidocaine (200 mg total) was injected into the testicle and scrotal skin. Castration of a single testicle was performed on two occasions. Sedation and reaction (to positioning and surgery) scores, pulse rate, respiratory rate, haemoglobin oxygen saturation, body temperature, arterial blood gas parameters and the times to immobility and then recovery were recorded. Atipamezole was administered if spontaneous recovery was not evident within 60 min of sedative administration. Data were compared with either a paired-sample t -test or a Wilcoxon-Signed Rank Test. There was no difference in sedation score, body temperature, respiratory rate and haemoglobin oxygen saturation between MDB and MDM. Mild hypoxaemia was noted in both groups. There was less reaction to castration after MDB. The pulse rate was higher after MDM sedation. The times to immobility and then recovery were similar. The combination of MDB provided more reliable sedation than MDM. MDB may be useful for sedation for short procedures in pigs, though oxygen supplementation is recommended to avoid hypoxaemia., Competing Interests: The authors declare no conflict of interest.

Objective: To compare adequacy of oxygen delivery and severity of shock during maintenance of anaesthesia with isoflurane or alfaxalone infusion in greyhounds experiencing blood loss., Study Design: Prospective, randomised study., Animals: Twenty-four greyhounds (ASA I)., Methods: All greyhounds were premedicated with methadone (0.2 mg kg(-1) ) intramuscularly. Anaesthesia was induced with alfaxalone 2.5 mg kg(-1) intravenously. Following endotracheal intubation, the dogs were connected to an anaesthetic circle circuit delivering oxygen. Dogs were allocated to receive inhaled isoflurane or an intravenous infusion of alfaxalone for maintenance of anaesthesia. Isoflurane was initially administered to achieve an end-tidal concentration of 1.4% and alfaxalone was initially administered at 0.13 mg kg(-1)  minute(-1) . The dose of isoflurane or alfaxalone was adjusted during instrumentation to produce a clinically equivalent depth of anaesthesia. All dogs were mechanically ventilated to normocapnia (Pa CO2 35-40 mmHg; 4.67-5.33 kPa). Passive warming maintained core body temperature between 37 and 38 °C. Measured and calculated indices of cardiovascular function, including mean arterial blood pressure (MAP), cardiac index (CI), systemic vascular resistance index (SVRI), oxygen delivery index (D˙O2I), oxygen consumption index (V˙O2I) and oxygen extraction ratio (OER), were determined at baseline (60 minutes after start of anaesthesia) and after removal of 32 mL kg(-1) and 48 mL kg(-1) of blood., Results: In all dogs, blood loss resulted in a significant decrease in MAP, CI, D˙O2 , and a significant increase in SVRI, V˙O2I , and OER. The changes in each of the indices did not differ significantly between dogs receiving isoflurane and dogs receiving alfaxalone., Conclusion and Clinical Relevance: No difference in oxygen delivery or severity of shock was observed when either inhaled isoflurane or intravenous alfaxalone infusion was used for maintenance of anaesthesia in greyhounds experiencing blood loss. There appears to be no clinical advantage to choosing one anaesthetic agent for maintenance of anaesthesia over the other in a dog experiencing blood loss., (© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.)

Objective: To describe sudden onset of generalized pulmonary atelectasis following thoracic lavage in 3 dogs., Series Summary: Thoracic lavage was performed following ligation of a patent ductus arteriosus in case 1, prior to closure of a large traumatic full thickness wound in the chest wall in case 2, and during investigation of an idiopathic spontaneous pneumothorax in case 3. In each case anesthesia and surgery were uneventful until thoracic lavage was performed, after which sudden generalized pulmonary atelectasis was observed. The atelectasis was visualized and was associated with oxyhemoglobin desaturation, decreased end-tidal carbon dioxide partial pressure (ETCO(2)), and a marked increase in the peak inspiratory pressure (PIP) required to achieve visible lung inflation. Occlusion of the endotracheal tube and cervical trachea was directly eliminated as the cause of atelectasis in cases 1 and 2, and indirectly eliminated in case 3. Improvement in pulmonary function occurred in all cases in response to increased PIP ± positive end expiratory pressure (PEEP)., New or Unique Information Provided: Generalized atelectasis should be considered a possible complication of thoracic lavage performed during thoracotomy. In the cases presented here, it is suspected that pre-existing reduction in lung volume (due to inadequate ventilation, surgical compression, absorption atelectasis) was exacerbated by the addition of the lavage fluid to the thoracic cavity. This pre-existing lung collapse is believed to have resulted in reduction of lung volume and that further reduction below the critical closing volume occurred following instillation of saline into the thorax resulting in the subsequent development of generalized atelectasis. The performance of regular arterial blood gas analyses and different ventilation protocols may have prevented the marked atelectasis that was observed in these cases., (© Veterinary Emergency and Critical Care Society 2012.)