Cardiopulmonary and anesthetic effects of the combination of butorphanol,midazolam and alfaxalone in Beagle dogs

ObjectiveTo evaluate the physiological variables, arterial blood gas values, induction of anesthesia quality, and recovery quality using the combination of butorphanol, midazolam and alfaxalone in dogs.AnimalsTen healthy adult Beagle dogs weighing 8.3 ± 3.1 kg.MethodsRectal temperature (T), pulse rate (PR), respiratory rate (f_R), mean arterial pressure (MAP), and arterial blood gases were measured and recorded prior to intravenous (IV) administration of butorphanol, prior to administration of both midazolam and alfaxalone IV 10 minutes later, then every 5 minutes for 20 minutes. M-mode echocardiographic left ventricular (LV) indices were measured before and 5 minutes after administration of alfaxalone. Qualitative scores for induction of anesthesia and recovery were allocated, duration of anesthesia and recovery were calculated, and adverse events were recorded.ResultsScores for induction and recovery quality were excellent. No significant adverse events were observed. Mean ± SD time from induction to extubation and to standing (full recovery) was 29 ± 6 and 36 ± 8 minutes, respectively. There were statistically significant changes in PR, f_R and MAP after drug administration. Transient hypercarbia developed after alfaxalone injection. The echocardiographic LV indices were reduced after alfaxalone injection, although those changes were not statistically significant.Conclusions and clinical relevanceThe combination of butorphanol, midazolam and alfaxalone provided excellent quality of induction of anesthesia and exerted minimal cardiopulmonary effects in healthy dogs.     

The pharmacokinetics and pharmacodynamics of the injectable anaesthetic alfaxalone in the horse

ObjectiveTo determine the pharmacokinetics and pharmacodynamics of the neurosteroidal anaesthetic, alfaxalone, in horses after a single intravenous (IV) injection of alfaxalone, following premedication with acepromazine, xylazine and guaiphenesin.Study designProspective experimental study.AnimalsTen (five male and five female), adult, healthy, Standardbred horses.MethodsHorses were premedicated with acepromazine (0.03 mg kg^?1 IV). Twenty minutes later they received xylazine (1 mg kg^?1 IV), then after 5 minutes, guaiphenesin (35 mg kg^?1 IV) followed immediately by IV induction of anaesthesia with alfaxalone (1 mg kg^?1). Cardiorespiratory variables (pulse rate, respiratory rate, pulse oximetry) and clinical signs of anaesthetic depth were evaluated throughout anaesthesia. Venous blood samples were collected at strategic time points and plasma concentrations of alfaxalone were assayed using liquid chromatography-mass spectrometry (LC/MS) and analysed by noncompartmental pharmacokinetic analysis. The quality of anaesthetic induction and recovery was scored on a scale of 1–5 (1 very poor, 5 excellent).ResultsThe median (range) induction and recovery scores were 4 (3–5) (good: horse slowly and moderately gently attained recumbency with minimal or no rigidity or paddling) and 4 (1–5) (good: horse stood on first attempt with some knuckling and ataxia) respectively. The monitored cardiopulmonary variables were within the range expected for clinical equine anaesthesia. The mean ± SD durations of anaesthesia from induction to sternal recumbency and from induction to standing were 42.7 ± 8.4 and 47 ± 9.6 minutes, respectively. The mean ± SD plasma elimination half life (t_1/2), plasma clearance (Clp) and volume of distribution (V_d) for alfaxalone were 33.4 minutes, 37.1 ± 11.1 mL minute^?1 kg^?1 and 1.6 ± 0.4 L kg^?1, respectively.Conclusions and clinical relevanceAlfaxalone, in a 2-hydroxypropyl-beta-cyclodextrin formulation, provides anaesthesia with a short duration of recumbency that is characterised by a smooth induction and satisfactory recovery in the horse. As in other species, alfaxalone is rapidly cleared from the plasma in the horse.     

Evaluation of alfaxalone and midazolam with or without flumazenil reversal in Egyptian fruit bats (Rousettus aegyptiacus)

ObjectivesTo evaluate alfaxalone–midazolam anesthesia in Egyptian fruit bats (Rousettus aegyptiacus) and the effect of flumazenil administration on recovery time and quality.Study designRandomized, blinded, crossover and controlled, experimental trial.AnimalsA total of 10 male Egyptian fruit bats.MethodsBats were anesthetized with alfaxalone (15 mg kg^?1) and midazolam (2 mg kg^?1) administered subcutaneously. During anesthesia, vital signs, muscle tone and reflexes were monitored every 10 minutes. Flumazenil (0.3 mg kg^?1) or saline at an equal volume was administered subcutaneously 60 minutes after anesthetic administration. Time to induction, time to first movement and recovery time (flying) were measured. Quality of induction, anesthesia and recovery were assessed on a 1–3 scale (1, poor; 2, good; 3, excellent).ResultsTime to induction was 4.2 ± 1.9 minutes (mean ± standard deviation), with median quality score of 2 (range, 1–3). Anesthesia quality score was 3 (1–3). During anesthesia, heart rate and respiratory frequency decreased significantly and penis relaxation, indicating muscle tone, increased significantly. Administration of flumazenil significantly reduced mean recovery time compared with saline (10 ± 5 versus 45 ± 17 minutes, respectively), and significantly improved the quality of recovery [2.5 (2–3) versus 1 (1–2), respectively].Conclusions and clinical relevanceAlfaxalone–midazolam anesthesia resulted in good induction, muscle relaxation and sufficient anesthesia to perform routine diagnostic and therapeutic procedures for approximately 40 minutes. Reversal of midazolam with flumazenil is recommended, resulting in quicker and better recovery.     

Plasma pharmacokinetics and pharmacodynamics of alfaxalone in neonatal foals after an intravenous bolus of alfaxalone following premedication with butorphanol tartrate

ObjectiveTo determine the pharmacokinetics and pharmacodynamics of the neurosteroid anaesthetic, alfaxalone, in neonatal foals after a single intravenous (IV) injection of alfaxalone following premedication with butorphanol tartrate.Study designProspective experimental study.AnimalsFive clinically healthy Australian Stock Horse foals of mean ± SD age of 12 ± 3 days and weighing 67.3 ± 12.4 kg.MethodsFoals were premedicated with butorphanol (0.05 mg kg^?1 IV) and anaesthesia was induced 10 minutes later by IV injection with alfaxalone 3 mg kg^?1. Cardiorespiratory variables (pulse rate, respiratory rate, direct arterial blood pressure, arterial blood gases) and clinical signs of anaesthetic depth were evaluated throughout anaesthesia. Venous blood samples were collected at strategic time points and alfaxalone plasma concentrations were assayed using liquid chromatography-mass spectrometry (LC/MS) and analysed by noncompartmental pharmacokinetic analysis.ResultsThe harmonic, mean ± SD plasma elimination half life (t½) for alfaxalone was 22.8 ± 5.2 minutes. The observed mean plasma clearance (Cl_p) and volume of distribution (Vd) were 19.9 ± 5.9 mL minute kg^?1 and 0.6 ± 0.2 L kg^?1, respectively. Overall, the quality of the anaesthetic inductions and recoveries was good and most monitored physiological variables were clinically acceptable in all foals, although some foals became hypoxaemic for a short period following recumbency. The mean durations of anaesthesia from induction to first movement and from induction to standing were 18.7 ± 7 and 37.2 ± 4.7 minutes, respectively.ConclusionsThe anaesthetic protocol used provided a predictable and consistent plane of anaesthesia in the five foals studied, with minimal cardiovascular depression. In foals, as in the adult horse, alfaxalone has a short elimination half life.Clinical relevanceAlfaxalone appears to be an adequate anaesthetic induction agent in foals and the pharmacokinetics suggest that, with continuous infusion, it might be suitable to provide more prolonged anaesthesia. Oxygen supplementation is recommended.     

INTRAVENOUS ALFAXALONE ANAESTHESIA IN LEOPARD GECKOS (EUBLEPHARIS MACULARIUS)

Intravenous alfaxalone, administered at a dose of 5 mg/kg in the jugular vein, was evaluated in 20 leopard geckos (Eublepharis macularius) to ascertain its ability to provide anesthesia. The induction time, time to loss of mandibular tone, interval of deep anesthesia, and full recovery time were 27.5 ± 30.7 seconds (10 to 56 seconds), 1.3 ± 1.4 minutes (11 seconds to 4 minutes), 12.5 ± 2.2 minutes (11.11 to 15.39 minutes), and 18.8 ± 12.1 minutes (10.4 to 52.31 minutes), respectively. A significant reduction in heart rate (74 ± 12.9 beats/minute) was recorded between 2 and 24 minutes after alfaxalone administration. A significant decrease in respiratory rate (26.8 ± 10.1 breaths/minute) was recorded 2 minutes after alfaxalone administration, and respiratory rate remained lower than the basal rate (31.4 ± 3.1 breaths/minute) for 24 minutes but without statistical significance. The intravenous administration of alfaxalone in leopard geckos achieved a rapid onset of anesthesia and a suitable recovery time. Based on this investigation, an afaxalone dose of 5 mg/kg intravenously proved to be suitable for sedation before tracheal intubation. Moreover, the administration route via the jugular vein, was acceptable in leopard geckos; a species in which other venipuncture sites can be challenging or inaccessible.     

Preemptive Analgesia,Including Morphine,Does Not Affect Recovery Quality and Times in Either Pain-Free Horses or Horses Undergoing Orchiectomy

Recovery quality and times from general anesthesia in horses may be influenced by surgery, analgesia with morphine or combinations of both. Twenty-three adult healthy horses were enrolled in this prospective experimental trial in a clinical setting and were randomly allocated to one of the following groups: anesthesia only (GA; n = 6), preemptive analgesia and anesthesia (GAA; n = 5), anesthesia and castration (GC; n = 6), or preemptive analgesia, anesthesia, castration, and intraoperative local analgesia (GCA; n = 6). All horses were sedated with intramuscular (IM) xylazine (0.5 mg/kg). Anesthesia was induced with intravenous (IV) guaifenesin (100 mg/kg) and thiopental (5 mg/kg) and maintained with isoflurane in oxygen. Animals in groups with preemptive analgesia received IM morphine (0.2 mg/kg) and dipyrone (10 mg/kg) and IV flunixin meglumine (1.0 mg/kg) immediately before sedation. Recoveries from general anesthesia were rope-assisted. Recovery scores (from 8 [excellent recovery] to 70 [worst recovery]) and times were compared between groups, using a one-way analysis of variance followed by a Tukey's test (P < .05). Mean ± standard deviation (SD) and range recovery scores were 22 ± 14 (8–45), 9 ± 2 (8–12), 14 ± 5 (8–22), and 12 ± 1 (10–13) in groups GA, GAA, GC, and GCA, respectively. Mean ± SD times to stand in minutes were 21 ± 10, 18 ± 7, 33 ± 12, and 35 ± 21 in groups GA, GAA, GC and GCA, respectively. No statistically significant differences were found for any of the variables. Neither preoperative administration of analgesics, including morphine, nor castration interfered with the recovery qualities and times in horses undergoing general anesthesia. Preemptive morphine did not worsen anesthetic recovery quality in horses.     

A comparison of cardiopulmonary and anesthetic effects of an induction dose of alfaxalone or propofol in dogs

ObjectiveTo compare the physiological parameters, arterial blood gas values, induction quality, and recovery quality after IV injection of alfaxalone or propofol in dogs.Study designProspective, randomized, blinded crossover.AnimalsEight random-source adult female mixed-breed dogs weighing 18.7 ± 4.5 kg.MethodsDogs were assigned to receive up to 8 mg kg^?1 propofol or 4 mg kg^?1 alfaxalone, administered to effect, at 10% of the calculated dose every 10 seconds. They then received the alternate drug after a 6-day washout. Temperature, pulse rate, respiratory rate, direct blood pressure, and arterial blood gases were measured before induction, immediately post-induction, and at 5-minute intervals until extubation. Quality of induction, recovery, and ataxia were scored by a single blinded investigator. Duration of anesthesia and recovery, and adverse events were recorded.ResultsThe mean doses required for induction were 2.6 ± 0.4 mg kg^?1 alfaxalone and 5.2 ± 0.8 mg kg^?1 propofol. After alfaxalone, temperature, respiration, and pH were significantly lower, and PaCO₂ significantly higher post-induction compared to baseline (p < 0.03). After propofol, pH, PaO₂, and SaO₂ were significantly lower, and PaCO₂, HCO₃, and PA-aO₂ gradient significantly higher post-induction compared to baseline (p < 0.03). Post-induction and 5-minute physiologic and blood gas values were not significantly different between alfaxalone and propofol. Alfaxalone resulted in significantly longer times to achieve sternal recumbency (p = 0.0003) and standing (p = 0.0004) compared to propofol. Subjective scores for induction, recovery, and ataxia were not significantly different between treatments; however, dogs undergoing alfaxalone anesthesia were more likely to have ≥1 adverse event (p = 0.041). There were no serious adverse events in either treatment.Conclusions and clinical relevanceThere were no clinically significant differences in cardiopulmonary effects between propofol and alfaxalone. A single bolus of propofol resulted in shorter recovery times and fewer adverse events than a single bolus of alfaxalone.     

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

ObjectiveTo 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 designProspective clinical study.AnimalsA total of 23 wild bighorn sheep (Ovis canadensis) in Sheep River Provincial Park, AB, Canada.MethodsFree-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.ResultsData 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 relevanceAn 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.     

Effect of alfaxalone infusion on the electroencephalogram of dogs anaesthetized with halothane

ObjectiveTo describe the effects of alfaxalone on the canine electroencephalogram (EEG).Study designExperimental study.AnimalsEight healthy adult Huntaway dogs.MethodsAnaesthesia was induced with propofol and maintained with halothane (0.85-0.95 end-tidal volume %) in oxygen. Animals were ventilated to maintain stable end-tidal CO₂ and halothane concentrations. Following a 30 minute stabilisation period, alfaxalone (0.5 mg kg^?1) was infused intravenously over a 5 minute period. The electroencephalogram was recorded from the beginning of the stabilisation period until 60 minutes following the start of alfaxalone treatment. Data were subjected to fast Fourier transformation, and median frequency, 95% spectral edge frequency and total EEG power were calculated. Two-factorial repeated measures anova (time and EEG channels were factors) was used for statistical analysis (p<0.05).ResultsA shift in the dominant frequency band from beta to delta after alfaxalone treatment and occasional burst suppression were observed. Median frequency decreased significantly below baseline (9.2 ± 1.4 Hz) (mean ± SD) during alfaxalone infusion. The lowest value (4.8 ± 1.2 Hz) was recorded 5 minutes after the start of infusion. Spectral edge frequency also decreased below baseline (26.2 ± 1.5 Hz) and the lowest value (22.6 ± 1.5 Hz) also was detected at 5 minutes after the start of infusion. Total EEG power did not change significantly. In some frequencies EEG power increased soon after the start of alfaxalone infusion, then decreased below baseline later (biphasic pattern).Conclusions and clinical relevanceAlfaxalone induced biphasic changes on EEG and decreased F₅₀ and F₉₅ in halothane anaesthetized dogs.     

Effect of anesthetic induction with propofol,alfaxalone or ketamine on intraocular pressure in cats: a randomized masked clinical investigation

ObjectiveTo compare the effect of propofol, alfaxalone and ketamine on intraocular pressure (IOP) in cats.Study designProspective, masked, randomized clinical trial.AnimalsA total of 43 ophthalmologically normal cats scheduled to undergo general anesthesia for various procedures.MethodsFollowing baseline IOP measurements using applanation tonometry, anesthesia was induced with propofol (n = 15), alfaxalone (n = 14) or ketamine (n = 14) administered intravenously to effect. Then, midazolam (0.3 mg kg^?1) was administered intravenously and endotracheal intubation was performed without application of topical anesthesia. The IOP was measured following each intervention. Data was analyzed using one-way anova and repeated-measures mixed design with post hoc analysis. A p-value <0.05 was considered significant.ResultsMean ± standard error IOP at baseline was not different among groups (propofol, 18 ± 0.6; alfaxalone, 18 ± 0.7; ketamine, 17 ± 0.5 mmHg). Following induction of anesthesia, IOP increased significantly compared with baseline in the propofol (20 ± 0.7 mmHg), but not in the alfaxalone (19 ± 0.8 mmHg) or ketamine (16 ± 0.7 mmHg) groups. Midazolam administration resulted in significant decrease from the previous measurement in the alfaxalone group (16 ± 0.7 mmHg), but not in the propofol group (19 ± 0.7 mmHg) or the ketamine (16 ± 0.8 mmHg) group. A further decrease was measured after intubation in the alfaxalone group (15 ± 0.9 mmHg).Conclusions and clinical relevancePropofol should be used with caution in cats predisposed to perforation or glaucoma, as any increase in IOP should be avoided.     

Evaluating the efficacy of alfaxalone in corn snakes (Pantherophis guttatus)

ObjectiveAlfaxalone is a popular veterinary anesthetic; however, research on this anesthetic in snakes has been limited to ball pythons, garter snakes and several Australian species. The objective was to evaluate the anesthetic effects of alfaxalone in corn snakes (Pantherophis guttatus), a popular pet snake.Study designProspective, randomized crossover study.AnimalsA total of eight corn snakes.MethodsIn phase I, snakes were subcutaneously administered three doses of alfaxalone (5, 10 and 15 mg kg^–1) in the cranial third of the body to determine the most effective dose. In phase II, a dose of 15 mg kg^–1 was administered in the cranial and caudal thirds of the snakes to determine if injection site affected anesthesia duration. Heart rate (HR), respiratory rate (f_R), righting reflex, escape response, tail pinch, needle prick and tongue flick were monitored at baseline and 5 minute intervals until the snakes fully recovered.ResultsDuration of anesthesia differed significantly, with higher doses lasting longer than lower doses: 5 mg kg^–1 [23.8 ± 4.4 (15–30) minutes]; 10 mg kg^–1 [40.6 ± 9.4 (25–55) minutes]; and 15 mg kg^–1 [56.9 ± 8.4 (50–70) minutes], mean ± standard deviation (range). The tail pinch reflex was not completely lost in phase 1. There was a significant change in f_R over time, but this was not related to dose. HR was not different by time or dose. Duration of anesthesia was not different after administration of alfaxalone (15 mg kg^–1) in the cranial third versus the caudal third of the body; however, there was a significant decrease in HR and f_R at this dose, regardless of injection site.Conclusions and clinical relevanceBased on these results, alfaxalone (15 mg kg^–1) provides adequate anesthesia for brief procedures or intubation; however, additional analgesia is required for painful procedures.     

Alfaxalone anaesthesia in Lemur catta following dexmedetomidine–butorphanol–midazolam sedation

Objective

To evaluate the clinical effects and quality of sedation, induction, maintenance and recovery in Lemur catta after dexmedetomidine–butorphanol–midazolam sedation and alfaxalone anaesthesia.

Immersion anaesthesia in goldfish (Carassius auratus) with three concentrations of alfaxalone

Objective

To evaluate the anaesthetic effects of three different alfaxalone doses to induce anaesthesia in goldfish.

Physiologic and biochemical measurements and response to noxious stimulation at various concentrations of MS‐222 in Koi (Cyprinus carpio)

ObjectiveTo evaluate the physiological effect and response to noxious stimulation at five concentrations of MS-222 in koi (Cyprinus carpio).Study designProspective experimental study.AnimalsTwenty-one healthy adult unknown sex koi fish weighing mean 450 ± SD 120 g.MethodsEach fish was exposed to five different concentrations of MS-222 (50, 70, 110, 150 and 190 mg L^?1) in a random sequence during the same anaesthetic event. For each concentration of MS-222, vital functions such as heart rate (HR) (via Doppler) and opercular rate (OpR) were recorded after a standardized induction period. Response to two noxious stimuli in the form of haemostat clamp pressure applied on the tail and the lip was evaluated, and blood was drawn to measure biochemical and blood gas values.ResultsDecrease in response to noxious stimulation with an increase of MS-222 concentration both for the lip (p = 0.0027) and the tail (p < 0.0001) stimulus was observed. Biochemical values were unaffected by the concentration of MS-222 with the exception of lactate concentration which was weakly correlated with the duration of anaesthesia (r = 0.31, p < 0.001) and the number of times the fish was clamped or bled prior to sampling (r = 0.23, p < 0.001). Opercular rate decreased with the increase in anaesthetic concentration, and HR was not affected.Conclusions and clinical relevanceOur results indicated a decrease in response to stimulus and a decrease in OpR that were associated with increased concentrations of MS-222. This may assist in establishing anaesthetic protocols using MS-222 in fish and supports the use of supramaximal pressure stimuli to teleost fish under variable MS-222 concentrations as a model for future studies.     

Evaluation of xylazine–alfaxalone anesthesia for field castration in donkey foals

ObjectiveTo evaluate the anesthetic and cardiopulmonary effects of xylazine–alfaxalone anesthesia in donkey foals undergoing field castration.Study designProspective clinical study.AnimalsA group of seven standard donkeys aged [median (range)] 12 (10–26) weeks, weighing 47.3 (37.3–68.2) kg.MethodsDonkeys were anesthetized with xylazine (1 mg kg⁻¹) intravenously (IV) followed 3 minutes later by alfaxalone (1 mg kg⁻¹) IV. Additional doses of xylazine (0.5 mg kg⁻¹) and alfaxalone (0.5 mg kg⁻¹) IV were administered as needed to maintain surgical anesthesia. Intranasal oxygen was supplemented at 3 L minute⁻¹. Heart rate (HR), respiratory rate (f_R) and mean arterial pressure (MAP) by oscillometry were recorded before drug administration and every 5 minutes after induction of anesthesia. Peripheral oxygen saturation (SpO₂) was recorded every 5 minutes after induction. Time to recumbency after alfaxalone administration, time to anesthetic re-dose, time to first movement, sternal and standing after last anesthetic dose and surgery time were recorded. Induction and recovery quality were scored (1, very poor; 5, excellent).ResultsMedian (range) induction score was 5 (1–5), and recovery score 4 (1–5). Overall, two donkeys were assigned a score of 1 (excitement) during induction or recovery. HR and MAP during the procedure did not differ from baseline. f_R was decreased at 5 and 10 minutes but was not considered clinically significant. SpO₂ was <90% at one time point in two animals.Conclusions and clinical relevanceXylazine–alfaxalone anesthesia resulted in adequate conditions for castration in 12 week old donkeys. While the majority of inductions and recoveries were good to excellent, significant excitement occurred in two animals and may limit the utility of this protocol for larger donkeys. Hypoxemia occurred despite intranasal oxygen supplementation.     

The effect of three anaesthetic protocols on the stress response in cane toads (Rhinella marina)

ObjectiveThree anaesthetics (MS222, clove oil and a mixture of ketamine/diazepam) were administered to cane toads to determine their effect on the hypothalamic-pituitary-adrenal (HPA) axis. Time to induction and recovery and any adverse events were also evaluated.Study designProspective randomized experimental trial.AnimalsThirty adult male cane toads (Rhinella marina) with body mass ranging between 130 and 250 g were captured from the field.MethodsThree groups of 10 toads were anaesthetized with ketamine (200 mg kg^?1) and diazepam (0.2 mg kg^?1) by intramuscular injection, MS222 (3 g L^?1) or clove-oil (0.3 mL L^?1) both by immersion. Blood samples were collected to determine plasma corticosterone concentrations. Induction and recovery time were recorded in each treatment. After full recovery animals were euthanized and a complete post-mortem examination was performed.ResultsSignificant differences were found in the activation of the HPA axis and in the times of induction and recovery between treatments (p < 0.001). Animals anaesthetized with clove-oil had the highest levels of corticosterone in plasma (42.5 ± 21.6 ng mL^?1). No differences were found between ketamine/diazepam (15.0 ± 13.3 ng mL^?1) and MS222 (22.0 ± 13.6 ng mL^?1) groups. The mean ± SD induction (minutes) and recovery (hours) times respectively were; ketamine/diazepam 66.5 ± 11 and 8 ± 3, clove oil 39 ± 12 and 7.6 ± 3, and MS222 42.5 ± 11 and 1.5 ± 0.5. Clove oil exposure had 30% mortality. Death followed a period of respiratory distress with changes consistent with non-cardiogenic oedema observed at post-mortem examination.Conclusions and Clinical relevanceBased on shorter induction and recovery times and minimal activation of HPA, MS222 is the anaesthetic of choice in cane toads. If it is not possible to use immersion methods of anaesthesia, ketamine/diazepam can be used but induction and recovery times are prolonged. Clove oil had unacceptable mortality in this study and should be used with extreme caution.     

Evaluation of alfaxalone total intravenous anesthesia in rabbits (Oryctolagus cuniculus) premedicated with dexmedetomidine or dexmedetomidine and buprenorphine

ObjectiveTo evaluate alfaxalone for total intravenous anesthesia (TIVA) in rabbits premedicated with dexmedetomidine or dexmedetomidine and buprenorphine.Study designCrossover study (part 1) with observational study (part 2).AnimalsA total of eight New Zealand White rabbits (Oryctolagus cuniculus), four female and four male, aged 12–16 weeks and weighing 2.8–3.5 kg in part 1. Separately, four additional rabbits in part 2.MethodsCrossover study design with eight rabbits per treatment. Rabbits were administered treatment D, dexmedetomidine (0.2 mg kg^–1), or treatment DB, dexmedetomidine (0.1 mg kg^–1) and buprenorphine (0.05 mg kg^–1) intramuscularly. Anesthesia was induced with alfaxalone intravenously until a supraglottic airway device was placed to deliver 100% oxygen. Anesthesia was maintained with alfaxalone (TIVA). Infusion rates were adjusted to achieve an absent pedal withdrawal reflex. Heart rate, respiratory rate, noninvasive blood pressure, end-tidal carbon dioxide partial pressure and peripheral hemoglobin oxygen saturation (SpO₂) were recorded every 5 minutes. Subsequently, four rabbits underwent ovariohysterectomy using treatment DB and alfaxalone TIVA.ResultsThe mean ± standard deviation alfaxalone infusion rate was 9.6 ± 2.6 and 4.5 ± 1.3 mg kg^–1 hour^–1 for treatments D and DB, respectively. In both treatments, blood pressure remained within acceptable range and SpO₂ was > 95%. Postinduction apnea and respiratory depression were observed in both treatments and managed with manual positive pressure ventilation. Four separate rabbits underwent successful ovariohysterectomy with treatment DB and alfaxalone TIVA. One rabbit required supplementation with inhalant anesthesia; three rabbits were successfully maintained using alfaxalone TIVA alone.Conclusions and clinical relevancePremedication with dexmedetomidine–buprenorphine combined with alfaxalone TIVA may be a viable alternative for performing abdominal surgery in the rabbit. The use of supplemental oxygen and ability to provide respiratory support are advised.     

Intramuscular administration of alfaxalone in red‐eared sliders (Trachemys scripta elegans) – effects of dose and body temperature

ObjectiveTo characterise the effects of alfaxalone by intramuscular (IM) injection in red-eared slider turtles and the influence of body temperature on anaesthetic duration and depth.Study designProspective, randomised part-blinded experimental trial.AnimalsTen healthy adult female red-eared sliders.MethodsEach turtle was anaesthetized four times with 10 and 20 mg kg^?1 alfaxalone at 20 and 35 °C respectively. Time to maximal effect and plateau and recovery periods were recorded. Skeletal muscle tone, presence of various reflexes, response to noxious stimuli, and heart rate were assessed.ResultsResults are given for protocols 10 mg kg^?1 20 °C; 20 mg kg^?1 20 °C; 10 mg kg^?1 35 °C and 20 mg kg^?1 35 °C, respectively: mean time (±SD) to maximal effect was 16 ± 8, 19 ± 6, 5 ± 2 and 7 ± 5 minutes; duration of the plateau phase was 13 ± 12, 28 ± 13, 8 ± 5 and 8 ± 5 minutes and recovery time was 76 ± 20, 126 ± 17, 28 ± 9 and 41 ± 20 minutes. Endotracheal intubation was successful in 80%, 100%, 0% and 30% of turtles, respectively. At 35 °C, all animals retained nociceptive sensation in the front limbs, hind limbs and vent, whereas at 20 °C a few turtles lost peripheral nociceptive sensation. Corneal and tap reflexes were retained in all trials. Mean heart rates were 30 ± 2 and 66 ± 4 beats minute^?1 at 20 and 35 °C, respectively.Conclusions and clinical relevanceAlfaxalone administered IM in red-eared sliders provided smooth, rapid induction and uneventful recovery. At 35 °C either dosage provided only short (5–10 minutes) and light sedation. At 20 °C, 10 mg kg^?1 provided sedation suitable for short non-invasive procedures. About 20 mg kg^?1 provided anaesthesia of approximately 20 minutes duration, appropriate for induction of inhalational anaesthesia or for brief surgical procedures with supplemental analgesia.     

Field immobilization using alfaxalone and alfaxalone–medetomidine in free-ranging koalas (Phascolarctos cinereus): a randomized comparative study

ObjectiveTo characterize and compare two intramuscular drug protocols using alfaxalone and alfaxalone–medetomidine combination for the field immobilization of free-ranging koalas.Study designBlinded, randomized, comparative field study.AnimalsA total of 66 free-ranging koalas from the Mount Lofty Ranges, South Australia.MethodsKoalas were randomly allocated into two groups. Group A animals were given alfaxalone alone at 3.5 mg kg^–1. Group AM animals were given alfaxalone 2 mg kg^–1 and medetomidine 40 μg kg^–1, reversed with atipamezole at 0.16 mg kg^–1. Blinded operators recorded heart rate (HR), respiratory rate (f_R), cloacal temperature, depth of sedation and times to: first effect, sedation suitable for clinical interventions, first arousal and full recovery. Data were analysed using independent t test, Mann–Whitney U test, chi-square analysis and log-rank test at 5% level of significance.ResultsSuitable immobilization for clinical examination and sample collection was achieved in all animals. In groups A and AM, median time to working depth was 6.5 minutes (range: 3.4–15) and 8.1 minutes (range: 4.3–24) and time to complete recovery was 66 minutes (range: 12–138) and 34 minutes (range: 4–84), respectively, following reversal. Time to first effect was significantly shorter in group A (p = 0.013), whereas time to full arousal was significantly shorter in group AM (p = 0.007) probably due to the administration of atipamezole. Maximum HR was 117 ± 28 beats minute^–1 in group A, which was a significant increase from baseline values (p < 0.0001), whereas group AM showed a significant tachypnoea of 67 ± 25 (normal f_R 10–15; p < 0.0001).Conclusions and clinical relevanceBoth the protocols produced immobilization, enabling clinical examination and sample collection; however, protocol AM was more suitable for field work due to shorter recovery times.