Sedation with dexmedetomidine-butorphanol or xylazine-butorphanol continuous intravenous infusions during unilateral ovariectomy in standing donkeys.

BACKGROUND: Intravenous infusions of alpha-2 adrenoceptor sedatives and opioids can potentially facilitate surgery in donkeys while standing. Literature on this subject matter is scant. OBJECTIVES: Evaluation of efficacy of sedation from α2 -adrenoceptors (dexmedetomidine or xylazine) and butorphanol during ovariectomy in standing donkeys. STUDY DESIGN: Randomised, masked in vivo experiment. METHODS: Thirteen female donkeys were sedated with butorphanol (0.05 mg/kg bwt followed by 0.05 mg/kg bwt/h) IV. Concomitantly, 6 of the 13 jennies were sedated with dexmedetomidine 2.5 mcg/kg bwt followed by 2.5 mcg/kg bwt/h (Dex-B group), while seven jennies were sedated with xylazine 0.5 mg/kg bwt followed by 0.5 mg/kg bwt/h (Xyl-B group). A line block of the left flank and an infiltration block around uterine ligament were performed with lidocaine. While the jennies underwent ovariectomies standing, sedation scores and head height above ground were assessed at 2 and 10 min after sedative boluses and every 10 min thereafter. If sedation was too light or too deep, the dose of dexmedetomidine or xylazine was increased or decreased by 25% of the original infusion rate, while butorphanol infusion rate was constant. Physiological parameters were measured. Normally distributed data were compared using the two-sample t test while repeatedly measured data were tested for differences between and within groups using repeated measures analysis of variance (ANOVA) by ranks followed by a Wilcoxon test with Tukey Honest Significant Difference for multiple testing. Statistical significance was set at p < 0.05. RESULTS: Both Dex-B and Xyl-B caused moderate to marked sedation adequate for ovariectomy in donkeys. Evident sedation was absent by 60 min of termination of infusions. No adverse physiological effects were observed. MAIN LIMITATIONS: Study on ovariectomy cases only, no pharmacokinetic profiling. CONCLUSIONS: Dexmedetomidine or xylazine and butorphanol sedation is feasible for ovariectomy in standing donkeys.

The minimum infusion rate of alfaxalone during its co-administration with lidocaine at three different doses by constant rate infusion in goats.

OBJECTIVE: To determine the minimum infusion rate (MIR) of alfaxalone required to prevent purposeful movement in response to standardized stimulation while co-administered with lidocaine at three different doses by constant infusion rate infusion (CRI) in goats. STUDY DESIGN: Prospective, blinded, randomized crossover, experimental. ANIMALS: A total of eight healthy goats: four does and four wethers. METHODS: Anaesthetic induction was with lidocaine at 1 mg kg-1 [low dose of lidocaine (L-Lid)], 2 mg kg-1 [moderate dose (M-Lid)] or 4 mg kg-1 [high dose (H-Lid)] and alfaxalone at 2 mg kg-1. Anaesthetic maintenance was with alfaxalone initially at 9.6 mg kg-1 hour-1 combined with one of three lidocaine treatments: 3 mg kg-1 hour-1 (L-Lid), 6 mg kg-1 hour-1 (M-Lid) or 12 mg kg-1 hour-1 (H-Lid). The MIR of alfaxalone was determined by testing for responses to a stimulation in the form of clamping on a digit with a Vulsellum forceps every 30 minutes during lidocaine CRI. Basic cardiopulmonary parameters were measured. RESULTS: The alfaxalone MIRs were 8.64 (6.72-10.56), 6.72 (6.72-8.64) and 6.72 (6.72-6.72) mg kg-1 hour-1 during L-Lid, M-Lid and H-Lid, respectively, without any significant differences among treatments. Compared to the initial rate of 9.6 mg kg-1 hour-1, these reductions in MIR are equivalent to 10, 30 and 30%, respectively. Significant increases in heart rate (HR) and arterial carbon dioxide partial pressure (PaCO2) and decreases in arterial haemoglobin saturation (SaO2), arterial oxygen partial pressure (PaO2) and respiratory frequency (fR) immediately after induction were observed during all lidocaine treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Lidocaine reduces the alfaxalone MIR by up to 30% with a tendency towards a plateauing in this effect at high CRIs. Immediate oxygen supplementation might be required to prevent hypoxaemia.

Determination of the minimum infusion rate of alfaxalone during its co-administration with fentanyl at three different doses by constant rate infusion intravenously in goats.

OBJECTIVE: To determine the minimum infusion rate (MIR) of alfaxalone required to prevent purposeful movement of the extremities in response to standardized noxious stimulation during its co-administration with fentanyl at three different doses by constant rate infusion (CRI) intravenously (IV) in goats. STUDY DESIGN: Prospective, blinded, randomized crossover, experimental. ANIMALS: Eight healthy goats; four does and four wethers. METHODS: For induction of anaesthesia, a bolus of fentanyl was administered at 0.005 mg kg(-1) (LFent), 0.015 mg kg(-1) (MFent) or 0.03 mg kg(-1) (HFent) followed by alfaxalone at 2.0 mg kg(-1) . For maintenance, the goats received alfaxalone at an initial infusion rate of 9.6 mg kg(-1)  hour(-1) and one of three fentanyl treatments: 0.005 mg kg(-1)  hour(-1) (LFent), 0.015 mg kg(-1)  hour(-1) (MFent) or 0.03 mg kg(-1) hour(-1) (HFent). The MIR of alfaxalone was determined during fentanyl CRI by testing for responses to stimulation (clamping on a digit with Vulsellum forceps) every 30 minutes. Some cardiopulmonary parameters were measured. RESULTS: The alfaxalone MIR median (range) was 6.7 (6.7-8.6), 2.9 (1.0-6.7) and 1.0 (1.0-4.8) mg kg(-1)  hour(-1) during LFent, MFent and HFent, respectively. Alfaxalone MIR was significantly lower during MFENT and HFENT compared to LFENT. Significantly low oxygen haemoglobin saturation (SaO2 ) and arterial oxygen partial pressure (PaO2 ), observed 2 minutes into anaesthesia after all fentanyl treatments, were the most remarkable adverse cardiopulmonary effects observed. Recovery from anaesthesia was severely affected by high doses of fentanyl with excitatory behavioural signs predominant for up to 2 hours post-administration after MFent and HFent. CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl reduces alfaxalone MIR in goats in a dose-dependent manner. Immediate oxygen supplementation after induction of general anaesthesia is recommended to prevent hypoxaemia. Doses of fentanyl equal to or greater than 0.015 mg kg(-1)  hour(-1) tend to be associated with severe excitatory behaviour and should be avoided when fentanyl is administered to goats.

Determination of the minimum infusion rate of propofol required to prevent purposeful movement of the extremities in response to a standardized noxious stimulus in goats.

OBJECTIVE: To determine the minimum infusion rate (MIR) of propofol required to prevent purposeful movement in response to a standardized stimulus in goats. STUDY DESIGN: Prospective, experimental study. ANIMALS: Eight healthy goats (four does, four wethers). METHODS: Anaesthesia was induced with 4 mg kg(-1) propofol intravenously (IV). A continuous IV infusion of propofol at 0.6 mg kg(-1)  minute(-1) was initiated immediately to maintain anaesthesia. Following endotracheal intubation, goats breathed spontaneously via a circle breathing system delivering supplementary oxygen. The initial propofol infusion rate was maintained for 30 minutes before responses to noxious stimulation provided by clamping the proximal part of the claw with a Vulsellum forceps for 60 seconds were tested. In the presence or absence of purposeful movements of the extremities, the infusion rate was increased or reduced by 0.1 mg kg(-1)  minute(-1) and held constant for 30 minutes before claw clamping was repeated. The propofol MIR for each goat was calculated as the mean of the infusion rates that allowed and abolished movement. Basic cardiopulmonary parameters were monitored, recorded and tested for statistical significance using Wilcoxon's signed rank test with Bonferroni adjustment for multiple testing. The quality of recovery from anaesthesia was assessed and scored. RESULTS: The median MIR of propofol was 0.45 mg kg(-1)  minute(-1) (range: 0.45-0.55 mg kg(-1)  minute(-1) ). Induction and recovery were free of adverse behaviour. No statistically significant cardiopulmonary changes in comparison with baseline were observed, but clinically relevant hypoxaemia at 2 minutes after induction of anaesthesia was consistently observed. Chewing during anaesthesia was observed in three goats. Median times to extubation and standing were 3 minutes (range: 2-6 minutes) and 10 minutes (range: 7-21 minutes), respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Propofol induction and maintenance of general anaesthesia minimally compromise cardiopulmonary function when oxygen is supplemented in goats.

Determination of the minimum infusion rate (MIR) of alfaxalone required to prevent purposeful movement of the extremities in response to a standardised noxious stimulus in goats.

OBJECTIVE: To determine the minimum infusion rate (MIR) of alfaxalone required to prevent purposeful movement of the extremities in response to noxious stimulation. STUDY DESIGN: Prospective, experimental. ANIMALS: Eight healthy goats; four does and four wethers. METHODS: Anaesthesia was induced with alfaxalone 3 mg kg(-1) intravenously (IV). A continuous IV infusion of alfaxalone, initially at 0.2 mg kg(-1)  minute(-1) , was initiated. Following endotracheal intubation the goats breathed spontaneously via a circle breathing circuit delivering supplementary oxygen. The initial infusion rate was maintained for 30 minutes before testing for responses. The stimulus was clamping on the proximal (soft) part of one digit of the hoof with Vulsellum forceps for 60 seconds. In the absence or presence of purposeful movement of the extremities, the infusion rate was reduced or increased by 0.02 mg kg(-1)  minute(-1) and held constant for 30 minutes before claw-clamping again. Alfaxalone MIR was calculated as the mean of the infusion rates that allowed and abolished movement. Cardio-respiratory parameters were measured. Recovery from general anaesthesia was timed and quality scored. Results are presented as median (range). RESULTS: The MIR of alfaxalone was 0.16 (0.14-0.18) mg kg(-1)  minute(-1) or 9.6 (8.4-10.8) mg kg(-1)  hour(-1) . Induction of and recovery from anaesthesia were excitement-free. Cardio-respiratory changes were minimal, although compared to baseline HR increased, and at 2 minutes post-induction, (prior to oxygen supplementation), PaO2 decreased significantly from 84 (80-88) to 70 (51-72) mmHg [11.2 (10.7-11.7) to 9.3 (6.8-9.6) kPa]. Sporadic muscle twitches, unrelated to depth of anaesthesia, were observed during the period of general anaesthesia. Time (minutes) to sternal recumbency and standing were 4.0 (3.0-10.0) and 41.5 (25.0-57.0) respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Alfaxalone can be used for total intravenous anaesthesia (TIVA) in goats and is associated with minimal adverse effects. Oxygen supplementation is advised, especially when working at higher altitudes.

The effects of midazolam and butorphanol, administered alone or combined, on the dose and quality of anaesthetic induction with alfaxalone in goats.

Goats are rarely anaesthetised; consequently, scant information is available on the efficacy of anaesthetic drugs in this species. Alfaxalone is a relatively new anaesthetic agent, of which the efficacy in goats has not yet been studied. In this study, the sedative and alfaxalone sparing effects of midazolam and butorphanol, administered alone or concomitantly, in goats were assessed. Eight clinically healthy goats, four does and four wethers, were enlisted in a randomised crossover manner to receive intramuscular sedative treatments consisting of saline 0.05 mL/kg, or midazolam 0.30 mg/kg, or butorphanol 0.10 mg/kg, or a combination of midazolam 0.30 mg/kg with butorphanol 0.10 mg/kg before intravenous induction of general anaesthesia with alfaxalone. Following induction, the goats were immediately intubated and the quality of anaesthesia and basic physiological cardiorespiratory and blood-gas parameters were assessed until the goats had recovered from anaesthesia. The degree of sedation, quality of induction and recovery were scored. When compared with saline (3.00 mg/kg), midazolam,administered alone or with butorphanol, caused a statistically significant increased level of sedation and a reduction in the amount of alfaxalone required for induction (2.00 mg/kg and 1.70 mg/kg, respectively). Butorphanol alone (2.30 mg/kg) did not cause significant changes in level of sedation or alfaxalone-induction dose. During induction and recovery, the goats were calm following all treatments, including the control group. Cardiorespiratory and blood-gas parameters were maintained within clinically acceptable limits. The present study showed that midazolam, administered alone or combined with butorphanol, produces a degree of sedation that significantly reduces the dose of alfaxalone required for induction of general anaesthesia in goats, without causing any major adverse cardiorespiratory effects.

Effects of propofol on isoflurane minimum alveolar concentration and cardiovascular function in mechanically ventilated goats.

OBJECTIVE: To evaluate the effects of propofol, on isoflurane minimum alveolar concentration (MAC) and cardiovascular function in mechanically ventilated goats. STUDY DESIGN: Prospective, randomized, crossover experimental study. ANIMALS: Six goats, three does and three wethers. METHODS: General anaesthesia was induced with isoflurane in oxygen. Following endotracheal intubation, anaesthesia was maintained with isoflurane in oxygen. Intermittent positive pressure ventilation was applied. Baseline isoflurane MAC was determined, the noxious stimulus used being clamping a claw. The goats then received, on separate occasions, three propofol treatments intravenously: bolus of 0.5 mg kg(-1) followed by a constant rate infusion (CRI) of 0.05 mg kg(-1) minute(-1) (treatment LPROP); bolus of 1.0 mg kg(-1) followed by a CRI of 0.1 mg kg(-1) minute(-1) (treatment MPROP), bolus of 2.0 mg kg(-1) followed by a CRI of 0.2 mg kg(-1) minute(-1) (treatment HPROP). Isoflurane MAC was re-determined following propofol treatments. Plasma propofol concentrations at the time of MAC confirmation were measured. Cardiopulmonary parameters were monitored throughout the anaesthetic period. Quality of recovery was scored. The Friedman test was used to test for differences between isoflurane MACs. Medians of repeatedly measured cardiovascular parameters were tested for differences between and within treatments using repeated anova by ranks (p<0.05 for statistical significance). RESULTS: Isoflurane MAC [median (interquartile range)] was 1.37 (1.36-1.37) vol%. Propofol CRI significantly reduced the isoflurane MAC, to 1.15 (1.08-1.15), 0.90 (0.87-0.93) and 0.55 (0.49-0.58) vol% following LPROP, MPROP and HPROP treatment, respectively. Increasing plasma propofol concentrations strongly correlated (Spearman rank correlation) with decrease in MAC (Rho=0.91). Cardiovascular function was not affected significantly by propofol treatment. Quality of recovery was satisfactory. CONCLUSIONS AND CLINICAL RELEVANCE: In goats, propofol reduces isoflurane MAC in a dose-dependent manner with minimal cardiovascular effects.

Total intravenous anaesthesia (TIVA) with propofol-fentanyl and propofol-midazolam combinations in spontaneously-breathing goats.

OBJECTIVE: To compare the efficacy and cardiopulmonary effects of propofol and fentanyl, with propofol and midazolam for total intravenous anaesthesia. STUDY DESIGN: Prospective, randomized, crossover experimental study. ANIMALS: Six goats; three does and three wethers. METHODS: Goats received either fentanyl 0.02 mg kg(-1) (treatment FP) or midazolam 0.3 mg kg(-1) (treatment MP) intravenously. One minute later anaesthesia was induced with propofol, then maintained by constant rate infusion of propofol 12.0 mg kg(-1) hour(-1) and fentanyl 0.02 mg kg(-1) hour(-1) (treatment FP) or propofol 12.0 mg kg(-1) hour(-1) and midazolam 0.3 mg kg(-1) hour(-1) (treatment MP) for 90 minutes. Response to noxious stimulus was tested every 10 minutes and propofol dose adjusted to prevent purposeful movement. Cardiopulmonary parameters were measured continuously, and arterial blood-gas analysis performed intermittently. Recovery was timed and quality scored. Results are presented as median (IQR). RESULTS: Differences in the propofol induction dose [4.00 (3.96-4.01) and 3.97 (3.91-4.00) mg kg(-1) for treatments FP and MP, respectively] were not significant. Quality of induction in both groups was smooth. The median propofol dose for maintenance was less (p = 0.004) with treatment FP (12.0 mg kg(-1) hour(-1) than MP (18.0 mg kg(-1) hour(-1). Cardiopulmonary function was well maintained with both treatments. Recovery times in minutes from the end of anaesthetic infusion for treatments FP and MP respectively were; to extubation 3.0 (3.0-3.0) and 4.5 (3.3-5.0); to sternal position, 4.5 (3.3-5.0) and 5.0 (5.0-6.5) and to standing 13.0 (10.3-15.0) and 15.0 (11.3-17.3). Quality of recovery was acceptable in both groups, but abnormal behavioural signs were observed after treatment FP. CONCLUSIONS AND CLINICAL RELEVANCE: Total intravenous anaesthesia with propofol and fentanyl or propofol and midazolam, at the doses studied, in spontaneously-breathing, oxygen-supplemented goats is practicable. Recovery from the fentanyl-propofol combination is not always smooth.