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.     

Induction of anesthesia and recovery in donkeys sedated with xylazine: a comparison of midazolam–alfaxalone and midazolam–ketamine

Objective

To compare the induction and recovery characteristics and selected cardiopulmonary variables of midazolam–alfaxalone or midazolam–ketamine in donkeys sedated with xylazine.

Induction dose and recovery quality of propofol and alfaxalone with or without midazolam coinduction followed by total intravenous anesthesia in dogs

Objectives

To compare propofol and alfaxalone, with or without midazolam, for induction of anesthesia in fentanyl-sedated dogs, and to assess recovery from total intravenous anesthesia (TIVA).

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 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.     

Effects of ketamine or midazolam continuous rate infusions on alfaxalone total intravenous anaesthesia requirements and recovery quality in healthy dogs: a randomized clinical trial

ObjectiveTo determine the alfaxalone dose reduction during total intravenous anaesthesia (TIVA) when combined with ketamine or midazolam constant rate infusions and to assess recovery quality in healthy dogs.Study designProspective, blinded clinical study.AnimalsA group of 33 healthy, client-owned dogs subjected to dental procedures.MethodsAfter premedication with intramuscular acepromazine 0.05 mg kg^-1 and methadone 0.3 mg kg^-1, anaesthetic induction started with intravenous alfaxalone 0.5 mg kg^-1 followed by either lactated Ringer’s solution (0.04 mL kg^-1, group A), ketamine (2 mg kg^-1, group AK) or midazolam (0.2 mg kg^-1, group AM) and completed with alfaxalone until endotracheal intubation was achieved. Anaesthesia was maintained with alfaxalone (6 mg kg^-1 hour^-1), adjusted (±20%) every 5 minutes to maintain a suitable level of anaesthesia. Ketamine (0.6 mg kg^-1 hour^-1) or midazolam (0.4 mg kg^-1 hour^-1) were employed for anaesthetic maintenance in groups AK and AM, respectively. Physiological variables were monitored during anaesthesia. Times from alfaxalone discontinuation to extubation, sternal recumbency and standing position were calculated. Recovery quality and incidence of adverse events were recorded. Groups were compared using parametric analysis of variance and nonparametric (Kruskal-Wallis, Chi-square, Fisher’s exact) tests as appropriate, p < 0.05.ResultsMidazolam significantly reduced alfaxalone induction and maintenance doses (46%; p = 0.034 and 32%, p = 0.012, respectively), whereas ketamine only reduced the alfaxalone induction dose (30%; p = 0.010). Recovery quality was unacceptable in nine dogs in group A, three dogs in group AK and three dogs in group AM.Conclusions and clinical relevanceMidazolam, but not ketamine, reduced the alfaxalone infusion rate, and both co-adjuvant drugs reduced the alfaxalone induction dose. Alfaxalone TIVA allowed anaesthetic maintenance for dental procedures in dogs, but the quality of anaesthetic recovery remained unacceptable irrespective of its combination with ketamine or midazolam.     

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.

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.     

A comparison of the pharmacodynamic effects of intravenous ketamine–xylazine with alfaxalone in mute swans (Cygnus olor) presenting at a wildlife veterinary hospital

ObjectiveTo compare effects of intravenous (IV) alfaxalone with ketamine–xylazine combination on anaesthetic induction, recovery and cardiopulmonary variables in mute swans.Study designRandomized, controlled, clinical study.AnimalsA group of 58 mute swans.MethodsSwans were given either alfaxalone (10 mg kg^–1; group A) or a combination of ketamine (12.5 mg kg^–1) and xylazine (0.28 mg kg^–1) (group KX) IV. Heart and respiratory rates, end-tidal carbon dioxide and peripheral haemoglobin oxygen saturation were recorded at 5 minute intervals during anaesthesia. Time from anaesthetic induction to intubation, from cessation of isoflurane to extubation, to lifting head, sternal recumbency and absence of head/neck ataxia were recorded. Anaesthetic and recovery quality were scored (1 = very poor; 5 = excellent). Data are presented as median (interquartile range). Significance was set at p < 0.05.ResultsIn group A, 44% (12/27) of swans required mechanical ventilation for 2–14 minutes versus 3.2% (1/31) of swans in group KX (p = 0.0002). Heart rate was higher in group A than in group KX [146 (127–168) versus 65.5 (56–78) beats minute^–1, respectively; p < 0.0001]. The isoflurane concentration required to maintain anaesthesia was higher in group A than in group KX [2.5% (2.0–3.0%) versus 1.5% (1.0–2.0%), respectively; p = 0.0001]. Time from cessation of isoflurane administration to lifting head was significantly longer in group A than in group KX [12 (9–17) versus 6 (4–7.75) minutes, respectively; p < 0.0001]. Anaesthesia quality scores were significantly better in group KX than in group A [4 (4–5) versus 4 (3–4), respectively; p = 0.0011], as were recovery scores [4 (3–5) versus 2 (2–3), respectively; p = 0.0005].Conclusions and clinical relevanceAlfaxalone is a suitable anaesthetic induction agent for use in mute swans. There is a greater incidence of postinduction apnoea and a higher incidence of agitation on recovery with alfaxalone than with ketamine–xylazine.     

Comparison between three dosages of intramuscular alfaxalone and a ketamine–dexmedetomidine–midazolam–tramadol combination in golden-headed lion tamarins (Leontopithecus chrysomelas)

ObjectivesTo characterize the cardiopulmonary and anesthetic effects of alfaxalone at three dose rates in comparison with a ketamine–dexmedetomidine–midazolam–tramadol combination (KDMT) for immobilization of golden-headed lion tamarins (GHLTs) (Leontopithecus chrysomelas) undergoing vasectomy.Study designProspective clinical trial.AnimalsA total of 19 healthy, male, wild-caught GHLTs.MethodsTamarins were administered alfaxalone intramuscularly (IM) at 6, 12 or 15 mg kg^–1, or KDMT, ketamine (15 mg kg^–1), dexmedetomidine (0.015 mg kg^–1), midazolam (0.5 mg kg^–1) and tramadol (4 mg kg^–1) IM. Immediately after immobilization, lidocaine (8 mg kg^–1) was infiltrated subcutaneously (SC) at the incision site in all animals. Physiologic variables, anesthetic depth and quality of immobilization were assessed. At the end of the procedure, atipamezole (0.15 mg kg^–1) was administered IM to group KDMT and tramadol (4 mg kg^–1) SC to the other groups; all animals were injected with ketoprofen (2 mg kg^–1) SC.ResultsA dose-dependent increase in sedation, muscle relaxation and immobilization time was noted in the alfaxalone groups. Despite the administration of atipamezole, the recovery time was longer for KDMT than all other groups. Muscle tremors were noted in some animals during induction and recovery with alfaxalone. No significant differences were observed for cardiovascular variables among the alfaxalone groups, whereas an initial decrease in heart rate and systolic arterial blood pressure was recorded in KDMT, which increased after atipamezole administration.Conclusions and clinical relevanceAlfaxalone dose rates of 12 or 15 mg kg^–1 IM with local anesthesia provided good sedation and subjectively adequate pain control for vasectomies in GHLTs. KDMT induced a deeper plane of anesthesia and should be considered for more invasive or painful procedures. All study groups experienced mild to moderate hypothermia and hypoxemia; therefore, the use of more efficient heating devices and oxygen supplementation is strongly recommended when using these protocols.     

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.     

Comparison of alfaxalone and propofol on haematological and serum biochemical variables in cats undergoing radiotherapy with sevoflurane maintenance

ObjectiveTo evaluate effects of repeated alfaxalone or propofol administration on haematological and serum biochemical variables in cats undergoing radiotherapy.Study designProspective, block-randomized, clinical trial.AnimalsA group of 39 client-owned cats.MethodsAfter butorphanol (0.2 mg kg^–1) and midazolam (0.1 mg kg^–1) sedation, cats were randomly assigned to receive either alfaxalone or propofol for induction of anaesthesia and sevoflurane maintenance. Cats were anaesthetized daily with the same induction agent for 10–12 days. Complete blood counts, reticulocytes, Heinz body score and serum biochemistry were performed before the first treatment (T1), at T6, T10 and 3 weeks after the final treatment (T21). Cumulative induction agent dose for each cat at each time point was evaluated for an effect on Heinz body score. Data are shown as mean ± standard deviation; p < 0.05.ResultsAt baseline there were no significant differences in signalment or blood variables between groups. A significant decrease in haematocrit of 2.3% ± 0.77 (p = 0.02) between T1-T6 and T1-T10 [mean 4.1% (± 0.78, p < 0.0001)] was detected, with a significant increase in haematocrit of 2.1% ± 0.80 (p = 0.046) between T6-T21 and 4.0% ± 0.8 (p < 0.001) between T10-T21. Heinz body score significantly increased by 1.86 ± 0.616 (p = 0.013) between T1-T10. In the propofol group, reticulocytes increased significantly between T1-T6 [mean 23,090 μL^–1 ± 7670 (p = 0.02)] and T1-T10 [mean 27,440 μL^–1 ± 7990 (p = 0.007)]. Mean cumulative dose at T10 was 19.65 mg kg^–1 ± 5.3 and 43.4 mg kg^–1 ± 14.4 for alfaxalone and propofol, respectively, with no significant effect on Heinz body formation at any time point.Conclusions and Clinical relevanceHaematocrit decreased in both groups with recovery after 3 weeks. Repeated alfaxalone and propofol administration was not associated with marked haematological or serum biochemistry changes.     

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.     

Dose and cardiopulmonary effects of propofol alone or with midazolam for induction of anesthesia in critically ill dogs

ObjectiveTo determine the dose and cardiopulmonary effects of propofol alone or with midazolam for induction of anesthesia in American Society of Anesthesiologists status ≥III dogs requiring emergency abdominal surgery.Study designProspective, randomized, blinded, clinical trial.AnimalsA total of 19 client-owned dogs.MethodsDogs were sedated with fentanyl (2 μg kg^–1) intravenously (IV) for instrumentation for measurement of heart rate, arterial blood pressure, cardiac index, systemic vascular resistance index, arterial blood gases, respiratory rate and rectal temperature. After additional IV fentanyl (3 μg kg^–1), the quality of sedation was scored and cardiopulmonary variables recorded. Induction of anesthesia was with IV propofol (1 mg kg^–1) and saline (0.06 mL kg^–1; group PS; nine dogs) or midazolam (0.3 mg kg^–1; group PM; 10 dogs), with additional propofol (0.25 mg kg^–1) IV every 6 seconds until endotracheal intubation. Induction/intubation quality was scored, and anesthesia was maintained with isoflurane. Variables were recorded for 5 minutes with the dog in lateral recumbency, breathing spontaneously, and then in dorsal recumbency with mechanical ventilation for the next 15 minutes. A general linear mixed model was used with post hoc analysis for multiple comparisons between groups (p < 0.05).ResultsThere were no differences in group demographics, temperature and cardiopulmonary variables between groups or within groups before or after induction. The propofol doses for induction of anesthesia were significantly different between groups, 1.9 ± 0.5 and 1.1 ± 0.5 mg kg^–1 for groups PS and PM, respectively, and the induction/intubation score was significantly better for group PM.Conclusions and clinical relevanceMidazolam co-induction reduced the propofol induction dose and improved the quality of induction in critically ill dogs without an improvement in cardiopulmonary variables, when compared with a higher dose of propofol alone.     

Alfaxalone for total intravenous anaesthesia in dogs undergoing ovariohysterectomy: a comparison of premedication with acepromazine or dexmedetomidine

ObjectiveTo describe alfaxalone total intravenous anaesthesia (TIVA) following premedication with buprenorphine and either acepromazine (ACP) or dexmedetomidine (DEX) in bitches undergoing ovariohysterectomy.Study designProspective, randomised, clinical study.AnimalsThirty-eight healthy female dogs.MethodsFollowing intramuscular buprenorphine (20 μg kg^?1) and acepromazine (0.05 mg kg^?1) or dexmedetomidine (approximately 10 μg kg^?1, adjusted for body surface area), anaesthesia was induced and maintained with intravenous alfaxalone. Oxygen was administered via a suitable anaesthetic circuit. Alfaxalone infusion rate (initially 0.07 mg kg^?1 minute^?1) was adjusted to maintain adequate anaesthetic depth based on clinical assessment. Alfaxalone boluses were given if required. Ventilation was assisted if necessary. Alfaxalone dose and physiologic parameters were recorded every 5 minutes. Depth of sedation after premedication, induction quality and recovery duration and quality were scored. A Student's t-test, Mann–Whitney U and Chi-squared tests determined the significance of differences between groups. Data are presented as mean ± SD or median (range). Significance was defined as p < 0.05.ResultsThere were no differences between groups in demographics; induction quality; induction (1.5 ± 0.57 mg kg^?1) and total bolus doses [1.2 (0 – 6.3) mg kg^?1] of alfaxalone; anaesthesia duration (131 ± 18 minutes); or time to extubation [16.6 (3–50) minutes]. DEX dogs were more sedated than ACP dogs. Alfaxalone infusion rate was significantly lower in DEX [0.08 (0.06–0.19) mg kg^?1 minute^?1] than ACP dogs [0.11 (0.07–0.33) mg kg^?1 minute^?1]. Cardiovascular variables increased significantly during ovarian and cervical ligation and wound closure compared to baseline values in both groups. Apnoea and hypoventilation were common and not significantly different between groups. Arterial haemoglobin oxygen saturation remained above 95% in all animals. Recovery quality scores were significantly poorer for DEX than for ACP dogs.Conclusions and clinical relevanceAlfaxalone TIVA is an effective anaesthetic for surgical procedures but, in the protocol of this study, causes respiratory depression at infusion rates required for surgery.     

Pharmacokinetics and pharmacodynamics of intramuscular alfaxalone in central bearded dragons (Pogona vitticeps): effect of injection site

ObjectiveTo evaluate the pharmacodynamic effects and pharmacokinetics of a single intramuscular (IM) injection of alfaxalone in central bearded dragons (Pogona vitticeps) when injected at a cranial versus a caudal site.Study designProspective, masked, randomized crossover study.AnimalsA total of 13 healthy bearded dragons weighing 0.48 ± 0.1 kg.MethodsAlfaxalone (10 mg kg^–1) was administered IM to 13 bearded dragons in the triceps muscle (cranial treatment) or the quadriceps muscle (caudal treatment) separated by 4 weeks. Pharmacodynamic variables included movement score, muscle tone score and righting reflex. Blood was obtained from the caudal tail vein using a sparse sampling methodology. Plasma alfaxalone concentrations were determined using liquid chromatography–mass spectrometry, and pharmacokinetic analysis was performed using nonlinear mixed-effects modeling. Differences in variables between injection sites were analyzed using a nonparametric Wilcoxon signed-rank test for paired data with significance set at p ≤ 0.05.ResultsTime to loss of righting reflex score was not different, median (interquartile range), between cranial and caudal treatments [8 (5–11) and 8 (4–12) minutes, respectively, p = 0.72]. Time to recovery of righting reflex was also not different between cranial and caudal treatments [80 (44–112) and 64 (56–104) minutes, respectively, p = 0.75]. Plasma alfaxalone concentrations were not significantly different between treatments. The population estimate (95% confidence intervals) for volume of distribution per fraction absorbed was 1.0 (0.79–1.20) L kg^–1, clearance per fraction absorbed was 9.6 (7.6–11.6) mL minute^–1 kg^–1, absorption rate constant was 2.3 (1.9–2.8) minute^–1 and elimination half-life was 71.9 (52.7–91.1) minutes.Conclusions and clinical relevanceRegardless of the injection site, IM alfaxalone (10 mg kg^–1) produced reliable chemical restraint in central bearded dragons, appropriate for nonpainful diagnostic procedures or anesthetic premedication.