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Objective: To compare the cardiopulmonary effects of propofol total intravenous anaesthesia (TIVA) with isoflurane in cheetahs (Acinonyx jubatus) to evaluate feasibility for field use., Study Design: Prospective clinical study., Animals: A group of 24 adult cheetahs, 12 per group., Methods: Cheetahs were immobilized with zolazepam/tiletamine (1.2 mg kg -1 ) and medetomidine [40 μg kg -1 , both intramuscular (IM)] by darting. A maintenance protocol of propofol TIVA (group P) or isoflurane inhalation (group I) was assigned randomly to each cheetah. Anaesthesia was maintained for at least 60 minutes. Cheetahs breathed spontaneously throughout; oxygen was supplemented at 3 L minute -1 . Cardiopulmonary parameters were recorded at 5 minute intervals and three arterial blood gas samples were analysed. Following maintenance, atipamezole was administered IM (200 μg kg -1 ) and recovery was observed. Data are reported as mean±standard deviation; variables over time were compared using a linear mixed model (fixed: time, treatment; random: cheetah)., Results: Lack of response to manipulations was maintained in all cases (end-tidal isoflurane percentage 1.1±0.1%, propofol rate maintained at 0.1 mg kg -1  minute -1 ). The heart and respiratory rates were acceptable throughout maintenance. The end-tidal carbon dioxide tension increased slowly [44.0±5.0 mmHg (5.87±0.67 kPa)] with no differences between groups. All cheetahs were initially markedly hypertensive [mean arterial blood pressure (MAP): (163±17 mmHg)]. The MAP normalized for group I (125±30 mmHg) but remained high for group P (161±17 mmHg) (p < 0.001). Arterial carbon dioxide tension [48.9±14.6 mmHg (6.52±1.95 kPa)] never differed between groups. Initial arterial oxygen tension indicated borderline hypoxaemia, but improved with oxygen supplementation. Recovery time was 10.8±5.0 and 51.9±23.5 minutes for group I and group P, respectively., Conclusions and Clinical Relevance: Both protocols provided acceptable cardiopulmonary values. Propofol may be an alternative to isoflurane for field use, but the prolonged recovery may make it less suitable for long-term anaesthesia., (Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Background: In mammals, homeostasis and survival are dependent on effective trans-membrane movement of ions and enzyme function, which are labile to extreme acid-base changes, but operate efficiently within a narrow regulated pH range. Research in patients demonstrating a pH shifts outside the narrow regulated range decreased the cardiac output and systemic vascular resistance and altered the oxygen binding to haemoglobin. These cardiopulmonary observations may be applicable to the risks associated with anaesthesia and performance of wildlife ungulates on game farms. The aim of this study was to compare blood pH changes over time in impala immobilised and anaesthetised with two different drug protocols (P-TMP - immobilisation: thiafentanil-medetomidine; maintenance: propofol-ketamine-medetomidine; P-EME - immobilisation: etorphine-medetomidine; maintenance: etorphine-ketamine-medetomidine). Additionally, we discuss the resultant blood pH using both the Henderson-Hasselbalch and the Stewart approaches. Two data collection time points were defined, Time1 before maintenance of general anaesthesia and Time 2 at end of maintenance of general anaesthesia. We hypothesise that blood pH would not be different between drug protocols and would not change over time., Results: Significant differences were detected over time but not between the two drug protocols. Overall, the blood pH decreased over time from 7.37 ± 0.04 to 7.31 ± 0.05 (p = 0.001). Overall, over time arterial partial pressure of carbon dioxide changed from 51.3 ± 7.5 mmHg to 72.6 ± 12.4 mmHg (p < 0.001); strong ion difference from 44.6 ± 2.4 mEq/L to 46.9 ± 3.1 mEq/L (p < 0.001); anion gap from 15.0 ± 3.1 mEq/L to 10.9 ± 2.2 mEq/L (p < 0.001); and total weak acids from 16.1 ± 1.2 mmol/L to 14.0 ± 1.1 mmol/L (p < 0.001). The bicarbonate changed from 29.6 ± 2.7 mEq/L to 36.0 ± 4.1 mEq/L (p < 0.001); and lactate changed from 2.9 ± 1.5 mEq/L to 0.3 ± 0.03 mEq/L (p < 0.001) over time., Conclusions: The profound increase in the partial pressure of carbon dioxide that worsened during the total intravenous anaesthesia in both protocols initiated a substantial metabolic compensatory response to prevent severe acidaemia. This compensation resulted in a clinically acceptable mild acidaemic state, which worsened over time but not between the protocols, in healthy impala. However, these important compensatory mechanisms require normal physiological function and therefore when immobilising ill or anorexic wild ungulates their acid-base status should be carefully assessed.

Objective: To characterize a propofol-medetomidine-ketamine total intravenous anaesthetic in impala (Aepyceros melampus)., Study Design: Prospective clinical study., Animals: Ten adult female impala., Materials and Methods: Impala were immobilized at 1253 m above sea level with 2.0 mg thiafentanil and 2.2 mg medetomidine via projectile darts. Propofol was given to effect (0.5 mg kg -1 boluses) to allow endotracheal intubation, following which oxygen was supplemented at 2 L minute -1 . Anaesthesia was maintained with a constant-rate infusion of medetomidine and ketamine at 5 μg kg -1 hour -1 and 1.5 mg kg -1 hour -1 , respectively, and propofol to effect (initially 0.2 mg kg -1 minute -1 ) for 120 minutes. The propofol infusion was titrated according to reaction to nociceptive stimuli every 15 minutes. Cardiopulmonary parameters were monitored continuously and arterial blood gas samples were analysed intermittently. After 120 minutes' maintenance, the thiafentanil and medetomidine were antagonized using naltrexone (10:1 thiafentanil) and atipamezole (5:1 medetomidine), respectively., Results: All impala were successfully immobilized. The median dose [interquartile range (IQR)] of propofol required for intubation was 2.7 (1.9-3.3) mg kg -1 . The propofol-medetomidine-ketamine combination abolished voluntary movement and ensured anaesthesia for the 120 minute period. Propofol titration showed a generally downward trend. Median (IQR) heart rate [57 (53-61) beats minute -1 ], respiratory rate [10 (9-12) breaths minute -1 ] and mean arterial blood pressure [101 (98-106) mmHg] were well maintained. Arterial blood gas analysis indicated hypoxaemia, hyper- capnia and acidaemia. Butorphanol (0.12 mg kg -1 ) was an essential rescue drug to counteract thiafentanil-induced respiratory depression. All impala regurgitated frequently during the maintenance period. Recovery was calm and rapid in all animals. Median (IQR) time to standing from antagonist administration was 4.4 (3.2-5.6) minutes., Conclusions and Clinical Relevance: A propofol-medetomidine-ketamine combination could provide adequate anaesthesia for invasive procedures in impala. The propofol infusion should begin at 0.2 mg kg -1 minute -1 and be titrated to clinical effect. Oxygen supplementation and airway protection with a cuffed endotracheal tube are essential., (Copyright © 2016 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

There is a growing necessity to perform long-term anesthesia in wildlife, especially antelope. The costs and logistics of transporting wildlife to veterinary practices make surgical intervention a high-stakes operation. Thus there is a need for a field-ready total intravenous anesthesia (TIVA) infusion to maintain anesthesia in antelope. This study explored the feasibility of an etorphine-ketamine-medetomidine TIVA for field anesthesia. Ten wild-caught, adult impala ( Aepyceros melampus ) were enrolled in the study. Impala were immobilized with a standardized combination of etorphine (2 mg) and medetomidine (2.2 mg), which equated to a median (interquartile range [IQR]) etorphine and medetomidine dose of 50.1 (46.2-50.3) and 55.1 (50.8-55.4) μg/kg, respectively. Recumbency was attained in a median (IQR) time of 13.9 (12.0-16.5) min. Respiratory gas tensions, spirometry, and arterial blood gas were analyzed over a 120-min infusion. Once instrumented, the TIVA was infused as follows: etorphine at a variable rate initiated at 40 μg/kg per hour (adjusted according to intermittent deep-pain testing); ketamine and medetomidine at a fixed rate of 1.5 mg/kg per hour and 5 μg/kg per hour, respectively. The etorphine had an erratic titration to clinical effect in four impala. Arterial blood pressure and respiratory and heart rates were all within normal physiological ranges. However, arterial blood gas analysis revealed severe hypoxemia, hypercapnia, and acidosis. Oxygenation and ventilation indices were calculated and highlighted possible co-etiologies to the suspected etorphine-induced respiratory depression as the cause of the blood gas derangements. Impala recovered in the boma post atipamezole (13 mg) and naltrexone (42 mg) antagonism of medetomidine and etorphine, respectively. The etorphine-ketamine-medetomidine TIVA protocol for impala may be sufficient for field procedures of up to 120-min duration. However, hypoxemia and hypercapnia are of paramount concern and thus oxygen supplementation should be considered mandatory. Other TIVA combinations may be superior and warrant further investigation.