The effects on cardio-respiratory and acid-base variables of the anaesthetic alfaxalone in a 2-hydroxypropyl-β-cyclodextrin (HPCD) formulation in sheep

Impact of procedural handling on the physiological effects of alfaxalone anaesthesia in the ball python (Python regius)

To describe the cardiovascular changes following intramuscular (handled) and intravascular (undisturbed, via intraarterial catheter) alfaxalone administration, we studied 20 healthy ball pythons (Python regius) in a randomised, prospective study. The pythons were instrumented with occlusive arterial catheters to facilitate undisturbed, continuous monitoring of heart rate and blood pressure. Six pythons were administered intramuscular (IM) saline, followed by 20 mg/kg IM alfaxalone, and were manually restrained for both injections. Six pythons received intraarterial (IA) saline, followed by 10 mg/kg IA alfaxalone, and remained undisturbed for both injections. Arterial blood samples were taken at 0, 12 and 60 min post-injection, and heart rate and blood pressure were recorded for 60 min. The remaining eight snakes received 20 mg/kg IM or 10 mg/kg IA alfaxalone (n = 4 per treatment) and were not handled for intubation 10 min post-injection, to examine the effects of handling during anaesthesia. IM administration of 20 mg/kg alfaxalone or an equivalent volume of saline elicited a profound tachycardia and hypertension, which recovered to resting values after 20 min. However, when 10 mg/kg alfaxalone or saline were injected IA, mild hypotension and a lower magnitude tachycardia occurred. Arterial PCO2 and PO2, pH and lactate concentrations did not change following IA alfaxalone, but an acidosis was observed during IM alfaxalone anaesthesia. There were no significant changes in plasma catecholamines and corticosterone among treatments. Handling for injection and during anaesthesia associated with intubation significantly affects cardiovascular parameters, whereas alfaxalone per se only elicits minor changes in cardiovascular physiology.

The use of alfaxalone for short-term anesthesia can confound serum progesterone measurements in the common marmoset: a case report

Alfaxan^® (alfaxalone) is a steroid general anesthetic widely used in veterinary medicine for induction and maintenance of anesthesia in several species. While the use of alfaxalone in veterinary practice has several benefits compared to the use of other anesthetic agents, the fact that it is derived from progesterone may confound the measurement of the latter in the blood of animals under alfaxalone treatment. In the present case study, we report the measurement of serum progesterone in an individual common marmoset (Callithrix jacchus) during five ovarian cycles in which luteolysis was induced by PGF2α. Blood samples were usually taken from the awake animal with the exception of the fifth cycle in which the sample was collected under alfaxalone anesthesia in connection with a tooth extraction. In contrast to the previous four cycles in which luteolysis resulted in the expected marked decrease in progesterone concentrations, the – apparent – progesterone level in the cycle under alfaxalone treatment remained unexpectedly high. Cross-reactivity of the non-specific antibody used in the progesterone assay with alfaxalone most likely explains this finding.

Determination of the Minimum Infusion Rate of Alfaxalone Combined with Electroacupuncture in Goats

Simple Summary

Goats have been used as animal models in research and are increasingly kept as pets like dogs and cats. Total intravenous anesthesia (TIVA) is increasingly used in companion animals. Electroacupuncture (EA) has been proven to produce analgesia, therefore, the objective of this study was to investigate the effect of EA on alfaxalone-based TIVA in goats. In this current study, the minimum infusion rate (MIR) of alfaxalone was determined in a combination with EA. The findings found that EA reduces the alfaxalone MIR required to prevent purposeful movement of the extremities in response to standardized noxious. In conclusion, EA provided analgesia, reduced the MIR of alfaxalone-based IV anesthesia, and thereby alleviated the adverse cardiorespiratory effects associated with alfaxalone anesthesia in goats.

Abstract

Total intravenous anesthesia (TIVA) is increasingly used in companion animals. The effect of electroacupuncture (EA) on alfaxalone-based TIVA has not been previously reported in goats. Therefore, the objective of this study was 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 combination with EA in goats. Twelve clinically healthy goats weighing 18.5 ± 2 kg were randomly assigned to two groups (six goats/group). Alfaxalone alone (ALF group) and alfaxalone combined with EA (EA-ALF group). In the EA-ALF, alfaxalone was administered 30 min after EA stimulation. For induction of anesthesia, a bolus of alfaxalone was given at 3 mg/kg IV, and an infusion dose of 9.6 mg/kg/h was initially set for maintenance. The MIR of alfaxalone in both groups was determined by testing for responses to stimulation (clamping on a digit with Vulsellum forceps) at 10-min intervals after induction of anesthesia till the entire period of the experiment. Cardiopulmonary parameters and nociceptive threshold were measured throughout anesthesia. The median alfaxalone MIR was significantly lower in the EA-ALF group than the ALF group [9 (4.8–9.6) and 12 (11.4–18)], respectively; p = 0.0035). In the ALF group, goats anesthetized with MIR showed a significant increase in heart rate and cardiac output (p < 0.0001 and 0.0312, respectively), and decrease in respiratory rate (p < 0.0001), hemoglobin oxygen saturation (p = 0.0081), and rectal temperature (p = 0.0046) compared with those in the EA-ALF. Additionally, goats in the EA-ALF showed a higher nociceptive threshold than those in the ALF group (p < 0.0001). EA provided analgesia, reduced the MIR of alfaxalone-based IV anesthesia and thereby alleviated the adverse cardiorespiratory effects associated with alfaxalone anesthesia in goats.

The utility of a novel formulation of alfaxalone in a remote delivery system

OBJECTIVE

To quantify induction time, reliability, physiological effects, recovery quality and dart volume of a novel formulation of alfaxalone (40 mg mL^-1) used in combination with medetomidine and azaperone for the capture and handling of wild bighorn sheep.

STUDY DESIGN

Prospective clinical study.

ANIMALS

A total of 23 wild bighorn sheep (Ovis canadensis) in Sheep River Provincial Park, AB, Canada.

METHODS

Free-ranging bighorn sheep were immobilized using medetomidine, azaperone and alfaxalone delivered with a remote delivery system. Arterial blood was collected for measurement of blood gases, physiologic variables (temperature, heart and respiratory rates) were recorded and induction and recovery length and quality were scored.

RESULTS

Data from 20 animals were included. Administered dose rates were alfaxalone (0.99 ± 0.20 mg kg^-1; 40 mg mL^-1), azaperone (0.2 ± 0.04 mg kg^-1; 10 mg mL^-1) and medetomidine (0.16 ± 0.03 mg kg^-1; 30 mg mL^-1). The mean drug volume injected was 1.51 mL. The median (range) induction time was 7.7 (5.8-9.7) minutes, and recovery was qualitatively smooth.

CONCLUSIONS AND CLINICAL RELEVANCE

An increased concentration formulation of alfaxalone was administered in combination with medetomidine and azaperone, and resulted in appropriate anesthesia for the capture and handling of bighorn sheep. The dart volume was small, with potential for reducing capture-related morbidity.

The Effect of Xylazine Premedication on the Dose and Quality of Anesthesia Induction with Alfaxalone in Goats

Goats have been used as animal models in research and are increasingly kept as companion animals. However, information about effective anesthetic drugs is scarce in this species. The objective of this study was to evaluate the effect of xylazine premedication on alfaxalone induction. Twelve clinically healthy goats weighing 18.5 ± 2 kg were randomly assigned to two groups. Induction was performed with alfaxalone alone intravenously (ALF group) or with xylazine premedication before alfaxalone administration (XYL-ALF group). The quality of induction was scored, induction doses of alfaxalone were determined, and cardiorespiratory parameters and nociceptive thresholds were measured before any treatment(s) (baseline) and at 5, 15, 25 and 35 min after alfaxalone administration. The mean dose of alfaxalone required for induction in the ALF group was greater than that in the XYL-ALF group (p < 0.001). There were no significant changes in diastolic arterial pressure (DAP), mean arterial pressure (MAP) or systolic arterial pressure (SAP) compared to baseline in either group, while hemoglobin oxygen saturation (SpO2) was lower from 5 to 25 min (p < 0.5) in the XYL-ALF group. The nociceptive threshold was significantly higher at 5 min in the XYL-ALF group than in the ALF group (p = 0.0417). Xylazine premedication reduced the required dose of alfaxalone for anesthetic induction and produced better antinociception than alfaxalone alone. In addition, the combination of xylazine and alfaxalone allowed for successful induction; however, oxygen supplementation is necessary to counteract xylazine-associated hypoxemia.

Evaluation of the anesthetic and cardiorespiratory effects of intramuscular alfaxalone administration and isoflurane in budgerigars (Melopsittacus undulatus) and comparison with manual restraint

OBJECTIVE To evaluate the anesthetic and cardiorespiratory effects of IM alfaxalone and isoflurane administration in budgerigars (Melopsittacus undulatus) and compare use of these agents with use of manual restraint. ANIMALS 42 healthy budgerigars. PROCEDURES For dose comparison, birds received alfaxalone (5 or 10 mg/kg [2.27 or 4.54 mg/lb], IM; groups A5 and A10, respectively; n = 6/group). For treatment comparison, birds received alfaxalone (10 mg/kg, IM) or isoflurane (via face mask) or were manually restrained (groups A, I, and M, respectively; n = 10/group). Data were obtained on onset, degree, and duration of sedation or anesthesia; heart and respiratory rates; and recovery times. Birds in the treatment comparison underwent physical examination and blood gas analysis. RESULTS All group A5 birds became sedate, but not recumbent. In group A10, 5 of 6 birds lost the righting reflex; however, none lost the noxious stimulus response. Median time to initial effects was significantly shorter and mean time to complete recovery was significantly longer in group A10 than in group A5. Heart and respiratory rates in group A10 remained clinically acceptable; however, some birds had signs of excitement during induction and recovery. Times to initial effects, recumbency, and complete recovery were significantly longer, yet clinically practical, in group A than in group I. Plasma lactate concentrations were significantly higher in group M than in groups A and I. CONCLUSIONS AND CLINICAL RELEVANCE Alfaxalone administered IM at 10 mg/kg produced effective sedation in healthy budgerigars and may be a viable alternative to isoflurane and manual restraint for brief, minimally invasive procedures. Brief manual restraint resulted in a significant increase in plasma lactate concentration.

Continuous Rate Infusion of Alfaxalone during Ketamine-Xylazine Anesthesia in Rats

Alfaxalone is an injectable anesthetic agent that is used in veterinary medicine for general anesthesia. We evaluated the safety and efficacy of alfaxalone delivered through continuous rate infusion by comparing ketamine-xylazine-alfaxalone (KXA) anesthesia with ketamine-xylazine (KX) anesthesia in Sprague-Dawley rats. Anesthesia was induced in male and female rats by using subcutaneous KX. After induction, rats in the KXA group received alfaxalone (10 mg/kg/h IV) for 35 min, whereas rats in the KX group did not receive alfaxalone. At the end of the trial, alfaxalone was discontinued, and xylazine was reversed in all rats by using atipamezole. Throughout anesthesia, we assessed forepaw withdrawal reflex (FPWR), hindpaw withdrawal reflex (HPWR), response to surgical stimulation, heart rate, respiratory rate, SpO₂, body temperature, and time to standing. KXA produced a reliable surgical plane of anesthesia, as evidenced by the loss of both FPWR and HPWR and lack of response to surgical stimulation in all 16 rats, whereas only 6 of the 16 rats in the KX group lost HPWR. No rat in the KXA group regained a paw withdrawal reflex during alfaxalone administration, whereas 3 of the 12 rats (25%) in the KX group that reached a surgical plane of anesthesia exited that plane within the 35-min timeframe. Neither heart rate, respiratory rate, SpO₂, body temperature, nor time to standing differed between KXA and KX groups; and there were no sex-associated differences in anesthesia response. These results indicate that alfaxalone (10 mg/kg/h IV) delivered through continuous rate infusion, in combination with ketamine and xylazine, provides a safe, prolonged, and reliable surgical plane of anesthesia in rats.

Comparison of intravenous anesthetic induction doses and physiologic effects of ketamine or alfaxalone in goats undergoing surgery with isoflurane anesthesia

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.

Anesthetic and cardiorespiratory effects of single-bolus intravenous alfaxalone with or without intramuscular xylazine-premedication in calves

The anesthetic and cardiorespiratory effects of xylazine-alfaxalone combination were evaluated in calves. Six calves (age: 6–9 months old; weight: 114–310 kg) were anesthetized with intravenous alfaxalone 15 min after administration of intramuscular saline (0.5 ml/100 kg) or xylazine (0.1 mg/kg; 0.5 ml/100 kg of a 2% xylazine solution). Anesthesia induction was smooth and orotracheal intubation was achieved in all calves. The calves anesthetized with xylazine-alfaxalone required a smaller induction dose of alfaxalone (1.23 ± 0.17 mg/kg, P=0.010) and accepted endotracheal intubation for a significantly longer period (16.8 ± 7.2 min, P=0.022) than the calves anesthetized with alfaxalone alone (2.28 ± 0.65 mg/kg 7.3 ± 1.6 min). At 5 min after induction, tachycardia (heart rate: 166 ± 47 beats/min of heart rate), hypertension (mean arterial blood pressure: 147 ± 81 mmHg) and hypoxemia (partial pressure of arterial blood oxygen [PaO₂]: 43 ± 10 mmHg) were observed in the calves anesthetized with alfaxalone alone, whereas hypoxemia (PaO₂: 47 ± 7 mmHg) and mild hypercapnia (partial pressure of arterial blood carbon dioxide: 54 ± 5 mmHg) were observed in the calves anesthetized with xylazine-alfaxalone. Premedication with xylazine provided a sparing effect on the induction dose of alfaxalone and a prolongation of anesthetic effect. Oxygen supplementation should be considered to prevent hypoxemia during anesthesia.

Determination of the minimum infusion rate of alfaxalone during its co-administration with midazolam in goats

INTRODUCTION

The minimum infusion rate (MIR) of alfaxalone when co-administered with midazolam in goats was evaluated.

MATERIALS AND METHODS

Eight goats (four does and four wethers) were anaesthetised, on separate occasions, with alfaxalone at an initial dose of 9.6 mg/kg/hour combined with one of three midazolam treatments: a bolus of 0.1 mg/kg followed by constant rate infusion (CRI) of 0.1 mg/kg/hour (treatment LMID), 0.3 mg/kg followed by CRI of 0.3 mg/kg/hour (MMID), 0.9 mg/kg followed by CRI of 0.9 mg/kg/hour (HMID), intravenously. Responses to stimulation (clamping on the proximal part of one digit of the hoof with Vulsellum forceps for 60 seconds) were tested every 30 minutes. In the absence or presence of a response to stimulation, the infusion rate was reduced or increased by 1.9 mg/kg/hour. Alfaxalone MIR was calculated as the mean of the infusion rates that allowed and abolished movement. Cardiopulmonary parameters were measured.

RESULTS

Alfaxalone MIR was 6.7 (6.7-8.6) mg/kg/hour, 6.7 (4.8-6.7) mg/kg/hour and 2.9 (1.0-4.8) mg/kg/hour for LMID, MMID and HMID respectively. Cardiopulmonary function was minimally affected, with hypoxaemia observed two minutes into anaesthesia during all treatments. Recovery from anaesthesia was excitement-free.

CONCLUSIONS

Midazolam causes a dose-dependent reduction of alfaxalone MIR in goats. Oxygen supplementation is recommended during anaesthesia with alfaxalone and midazolam in goats.

Evaluation of intravenous administration of alfaxalone, propofol, and ketamine-diazepam for anesthesia in alpacas

OBJECTIVE

To evaluate the effects of induction of anesthesia with alfaxalone in alpacas.

STUDY DESIGN

Prospective, randomized, crossover design.

ANIMALS

Five healthy alpacas (96.7 ± 19.9 kg, 9.6 ± 3.1 years old).

METHODS

The alpacas were anesthetized on three occasions with alfaxalone, propofol, or ketamine-diazepam by intravenous injection. Quality of induction and intubation was assessed using a simple descriptive scale, and quality of recovery was scored: 1 (very poor)-5 (excellent). The auricular artery was catheterized for measurement of systolic (SAP), mean (MAP), and diastolic (DAP) arterial pressures and collection of blood. Variables measured were hemoglobin oxygen saturation (SpO2 ), respiratory rate, and end-tidal carbon dioxide partial pressure (Pe'CO2 ), and ECG. Repeated measures anova was used to assess effects of drug and time. Significance was set at p < 0.05.

RESULTS

Mean dose of alfaxalone sufficient to allow intubation was 2.1 mg kg(-1) . Induction was excellent with all protocols. Heart rate (HR), SAP and MAP were significantly higher following alfaxalone compared to ketamine-diazepam. Blood lactate concentration when standing following alfaxalone was higher compared to minutes 1 and 6, and to propofol (p < 0.05). All alpacas required oxygen supplementation and mechanical ventilation to treat SpO2  < 90% or Pe'CO2  > 60 mmHg. Time from induction to standing was longer with alfaxalone (34.1 ± 3.2 minutes) than propofol (19.0 ±4.3 minutes) or ketamine-diazepam (24.9 ±1.7 minutes). Recovery quality median scores were clinically and statistically different: 2 (alfaxalone), 4 (ketamine-diazepam), and 5 (propofol). Tremors, paddling, rolling, seizure-like activity and thrashing characterized recovery from alfaxalone.

CONCLUSION

Recovery quality was worst with alfaxalone. HR, SAP, MAP were increased at minute 1 in all protocols. Transient hypercapnia and hypoxia was observed with all protocols.

CLINICAL RELEVANCE

All protocols were adequate for induction of anesthesia. Alfaxalone alone in unpremedicated alpacas is not recommended.

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.

Optimal management of the critically ill: anaesthesia, monitoring, data capture, and point-of-care technological practices in ovine models of critical care

Animal models of critical illness are vital in biomedical research. They provide possibilities for the investigation of pathophysiological processes that may not otherwise be possible in humans. In order to be clinically applicable, the model should simulate the critical care situation realistically, including anaesthesia, monitoring, sampling, utilising appropriate personnel skill mix, and therapeutic interventions. There are limited data documenting the constitution of ideal technologically advanced large animal critical care practices and all the processes of the animal model. In this paper, we describe the procedure of animal preparation, anaesthesia induction and maintenance, physiologic monitoring, data capture, point-of-care technology, and animal aftercare that has been successfully used to study several novel ovine models of critical illness. The relevant investigations are on respiratory failure due to smoke inhalation, transfusion related acute lung injury, endotoxin-induced proteogenomic alterations, haemorrhagic shock, septic shock, brain death, cerebral microcirculation, and artificial heart studies. We have demonstrated the functionality of monitoring practices during anaesthesia required to provide a platform for undertaking systematic investigations in complex ovine models of critical illness.

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 alfaxalonesparing 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 ofmidazolam 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 gasparameters 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.

Maternal and foetal cardiovascular effects of the anaesthetic alfaxalone in 2-hydroxypropyl-β-cyclodextrin in the pregnant ewe

The objective of this study was to determine the pharmacodynamics effects of the anaesthetic alfaxalone in 2-hydroxypropyl-β-cyclodextrin in pregnant sheep after the intravenous injection of a 2 mg/kg weight dose. Six pregnant Ripollesa sheep, weighing 47.1 ± 4.4 kg, were used. Twenty-four hours after instrumentation, sheep were anaesthetized with intravenous alfaxalone in cyclodextrin. Time to standing from anaesthesia was 30.0 ± 10.81 min. Foetal heart rate increased significantly during the first 5 min after alfaxalone administration. Significant differences were observed in maternal diastolic arterial blood pressure between minute 10 and minutes 90, 120, 150, 180, 210, and 240. Significant differences were observed for foetal systolic arterial blood pressure between 5 and 30 min after alfaxalone administration. Significant differences in foetal pH were detected during the entire study period, whereas maternal pH returned to baseline values by 60 min after alfaxalone administration. The present study indicated that alfaxalone in 2-hydroxypropyl-β-cyclodextrin administered as an intravenous bolus at 2 mg/kg body weight produced minimal adverse effects and an uneventful recovery from anaesthesia in pregnant sheep and their foetus.

Intravenous anaesthesia in goats: A review

Intravenous anaesthesia is gradually becoming popular in veterinary practice. Traditionally, general anaesthesia is induced with intravenous drugs and then maintained with inhalation agents. Inhalation anaesthetic agents cause more significant dose-dependent cardiorespiratory depression than intravenous anaesthetic drugs, creating a need to use less of the inhalation anaesthetic agents for maintenance of general anaesthesia by supplementing with intravenous anaesthesia drugs. Better still, if anaesthesia is maintained completely with intravenous anaesthetic drugs, autonomic functions remain more stable intra-operatively. Patient recovery from anaesthesia is smoother and there is less pollution of the working environment than happens with inhalation anaesthetic agents. Recently, a number of drugs with profiles (pharmacokinetic and pharmacodynamic) suitable for prolonged intravenous anaesthesia have been studied, mostly in humans and, to a certain extent, in dogs and horses. There is currently very little scientific information on total intravenous anaesthesia in goats, although, in the past few years, some scholarly scientific articles on drugs suitable for partial intravenous anaesthesia in goats have been published. This review article explored the information available on drugs that have been assessed for partial intravenous anaesthesia in goats, with the aim of promoting incorporation of these drugs into total intravenous anaesthesia protocols in clinical practice. That way, balanced anaesthesia, a technique in which drugs are included in anaesthetic protocols for specific desired effects (hypnosis, analgesia, muscle relaxation, autonomic stabilisation) may be utilised in improving the welfare of goats undergoing general anaesthesia.

Anaesthetic and cardiorespiratory effects of a constant-rate infusion of alfaxalone in desflurane-anaesthetised sheep

A prospective, randomised, blinded controlled study was performed to determine the anaesthetic and cardiorespiratory effects of a constant-rate infusion (CRI) of alfaxalone in 12 sheep anaesthetised with desflurane, and undergoing experimental orthopaedic surgery. Sheep were sedated with dexmedetomidine (4 μg/kg, intravenously) and butorphanol (0.3 mg/kg, intravenously). Anaesthesia was induced with alfaxalone (1 mg/kg/minute to effect, intravenously) and maintained with desflurane in oxygen and alfaxalone 0.07 mg/kg/minute or saline for 150 minutes (range 150-166 minutes). The anaesthetic induction dose of alfaxalone, the desflurane expiratory fraction required for anaesthetic maintenance, cardiorespiratory measurements and blood-gases were recorded at predetermined intervals. Quality of sedation, anaesthetic induction and recovery were assessed. The alfaxalone induction dose was 1.7 mg/kg (1.2 to 2.6 mg/kg). The desflurane expiratory fraction was lower (22 per cent) in sheep receiving alfaxalone CRI (P=0). Also, heart rate (P=0), cardiac index (P=0.002), stroke index (P=0) and contractility (P=0) were higher, and systemic vascular resistance (P=0.002) was lower. Although respiratory rate tended to be higher with alfaxalone, there was no difference in PCO2 between the groups. Recovery times were significantly longer in sheep given alfaxalone (25.4 v 9.5 minutes) but recovery quality was similar. Alfaxalone reduced requirements of desflurane and maintained similar cardiorespiratory function, but recovery time was more prolonged.