Minimum infusion rate of alfaxalone for total intravenous anaesthesia after sedation with acepromazine or medetomidine in cats undergoing ovariohysterectomy

ObjectiveTo determine the induction doses, then minimum infusion rates of alfaxalone for total intravenous anaesthesia (TIVA), and subsequent, cardiopulmonary effects, recovery characteristics and alfaxalone plasma concentrations in cats undergoing ovariohysterectomy after premedication with butorphanol-acepromazine or butorphanol-medetomidine.Study designProspective randomized blinded clinical study.AnimalsTwenty-eight healthy cats.MethodsCats undergoing ovariohysterectomy were assigned into two groups: together with butorphanol [0.2 mg kg^?1 intramuscularly (IM)], group AA (n = 14) received acepromazine (0.1 mg kg^?1 IM) and group MA (n = 14) medetomidine (20 μg kg^?1 IM). Anaesthesia was induced with alfaxalone to effect [0.2 mg kg^?1 intravenously (IV) every 20 seconds], initially maintained with 8 mg kg^?1 hour^?1 alfaxalone IV and infusion adjusted (±0.5 mg kg^?1 hour^?1) every five minutes according to alterations in heart rate (HR), respiratory rate (f_R), Doppler blood pressure (DBP) and presence of palpebral reflex. Additional alfaxalone boli were administered IV if cats moved/swallowed (0.5 mg kg^?1) or if f_R >40 breaths minute^?1 (0.25 mg kg^?1). Venous blood samples were obtained to determine plasma alfaxalone concentrations. Meloxicam (0.2 mg kg^?1 IV) was administered postoperatively. Data were analysed using linear mixed models, Chi-squared, Fishers exact and t-tests.ResultsAlfaxalone anaesthesia induction dose (mean ± SD), was lower in group MA (1.87 ± 0.5; group AA: 2.57 ± 0.41 mg kg^?1). No cats became apnoeic. Intraoperative bolus requirements and TIVA rates (group AA: 11.62 ± 1.37, group MA: 10.76 ± 0.96 mg kg^?1 hour^?1) did not differ significantly between groups. Plasma concentrations ranged between 0.69 and 10.76 μg mL^?1. In group MA, f_R, end-tidal carbon dioxide, temperature and DBP were significantly higher and HR lower.Conclusion and clinical relevanceAlfaxalone TIVA in cats after medetomidine or acepromazine sedation provided suitable anaesthesia with no need for ventilatory support. After these premedications, the authors recommend initial alfaxalone TIVA rates of 10 mg kg^?1 hour^?1.     

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.     

Assessment of the effects of intramuscular administration of alfaxalone with and without medetomidine in Horsfield's tortoises (Agrionemys horsfieldii)

ObjectiveTo characterise four different intramuscular (IM) anaesthetic protocols, two with alfaxalone and two with alfaxalone in combination with medetomidine in terrestrial tortoises.Study designBlinded, randomized, cross‐over experimental study.AnimalsNine healthy adult male Horsfield's tortoises (Agrionemys horsfieldii).MethodsEach tortoise was randomly assigned to one of four different protocols: 1) 10 mg kg^?1 alfaxalone; 2) 10 mg kg^?1 alfaxalone + 0.10 mg kg^?1 medetomidine; 3) 20 mg kg^?1 alfaxalone; and 4) 20 mg kg^?1 alfaxalone + 0.05 mg kg^?1 medetomidine. During the experiment, the following variables were recorded: heart rate; respiratory rate; peripheral nociceptive responses; muscle strength; ability to intubate; palpebral, corneal and tap reflexes; and cloacal temperature.ResultsProtocols 1 and 2 resulted in moderate sedation with no analgesia, and moderate to deep sedation with minimal analgesia, respectively. Protocols 3 and 4 resulted in deep sedation or anaesthesia with variable analgesic effect; these two protocols had the longest total anaesthetic time and allowed intubation in 6/9 and 8/9 tortoises respectively. The total anaesthesia/sedation time produced by alfaxalone was significantly increased (p <0.05) by the addition of medetomidine. There were no significant differences regarding time to plateau phase and duration of plateau phase. Baseline heart rate of 53 ± 6 beats minute^?1 decreased significantly (p <0.05) with all protocols, and was lower (p <0.05) in protocols 3 and 4. Heart rate increased after atipamezole administration, but the increase was transient. In two tortoises, extreme bradycardia with no cardiac activity for 10 minutes was observed with protocols 3 and 4.Conclusion and clinical relevanceAlfaxalone 10 and 20 mg kg^?1 IM can be used for sedation for non‐painful procedures. Alfaxalone in combination with medetomidine can be used for deeper sedation or anaesthesia, but the observed respiratory and cardiovascular depression may limit its use.     

An evaluation of anaesthetic induction in healthy dogs using rapid intravenous injection of propofol or alfaxalone

ObjectiveTo evaluate quality of anaesthetic induction and cardiorespiratory effects following rapid intravenous (IV) injection of propofol or alfaxalone.Study designProspective, randomised, blinded clinical study.AnimalsSixty healthy dogs (ASA I/II) anaesthetized for elective surgery or diagnostic procedures.MethodsPremedication was intramuscular acepromazine (0.03 mg kg^?1) and meperidine (pethidine) (3 mg kg^?1). For anaesthetic induction dogs received either 3 mg kg^?1 propofol (Group P) or 1.5 mg kg^?1 alfaxalone (Group A) by rapid IV injection. Heart rate (HR), respiratory rate (f_R) and oscillometric arterial pressures were recorded prior to induction, at endotracheal intubation and at 3 and 5 minutes post-intubation. The occurrence of post-induction apnoea or hypotension was recorded. Pre-induction sedation and aspects of induction quality were scored using 4 point scales. Data were analysed using Chi-squared tests, two sample t-tests and general linear model mixed effect anova (p < 0.05).ResultsThere were no significant differences between groups with respect to sex, age, body weight, f_R, post-induction apnoea, arterial pressures, hypotension, SpO₂, sedation score or quality of induction scores. Groups behaved differently over time with respect to HR. On induction HR decreased in Group P (?2 ± 28 beats minute^?1) but increased in Group A (14 ± 33 beats minute^?1) the difference being significant (p = 0.047). However HR change following premedication also differed between groups (p = 0.006). Arterial pressures decreased significantly over time in both groups and transient hypotension occurred in eight dogs (five in Group P, three in Group A). Post-induction apnoea occurred in 31 dogs (17 in Group P, 14 in Group A). Additional drug was required to achieve endotracheal intubation in two dogs.Conclusions and Clinical relevanceRapid IV injection of propofol or alfaxalone provided suitable conditions for endotracheal intubation in healthy dogs but post-induction apnoea was observed commonly.     

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.     

A comparison of cardiopulmonary effects and anaesthetic requirements of two dexmedetomidine continuous rate infusions in alfaxalone-anaesthetized Greyhounds

Objective

To determine the effects of two dexmedetomidine continuous rate infusions on the minimum infusion rate of alfaxalone for total intravenous anaesthesia (TIVA), and subsequent haemodynamic and recovery effects in Greyhounds undergoing laparoscopic ovariohysterectomy.

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

ObjectiveTo determine the minimum infusion rate (MIR) of alfaxalone required to prevent purposeful movement of the extremities in response to noxious stimulation.Study DesignProspective, experimental.AnimalsEight healthy goats; four does and four wethers.MethodsAnaesthesia 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).ResultsThe 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 RelevanceAlfaxalone 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.     

Comparison of alfaxalone and propofol administered as total intravenous anaesthesia for ovariohysterectomy in dogs

ObjectiveTo compare the anaesthetic and cardiopulmonary effects of alfaxalone with propofol when used for total intravenous anaesthesia (TIVA) during ovariohysterectomy in dogs.Study designA prospective non-blinded randomized clinical study.AnimalsFourteen healthy female crossbred bitches, aged 0.5–5 years and weight 16–42 kg.MethodsDogs were premedicated with acepromazine 0.01 mg kg^?1 and morphine 0.4 mg kg^?1. Anaesthesia was induced and maintained with either propofol or alfaxalone to effect for tracheal intubation followed by an infusion of the same agent. Dogs breathed spontaneously via a ‘circle’ circuit, with oxygen supplementation. Cardiopulmonary parameters (respiratory and heart rates, end-tidal carbon dioxide, tidal volume, and invasive blood pressures) were measured continuously and recorded at intervals related to the surgical procedure. Arterial blood samples were analysed for blood gas values. Quality of induction and recovery, and recovery times were determined. Non-parametric data were tested for significant differences between groups using the Mann–Whitney U-test and repeatedly measured data (normally distributed) for significant differences between and within groups by anova.ResultsBoth propofol and alphaxalone injection and subsequent infusions resulted in smooth, rapid induction and satisfactory maintenance of anaesthesia. Doses for induction (mean ± SD) were 5.8 ± 0.30 and 1.9 ± 0.07 mg kg^?1 and for the CRIs, 0.37 ± 0.09 and 0.11 ± 0.01 mg kg^?1 per minute for propofol and alfaxalone respectively. Median (IQR) recovery times were to sternal 45 (33–69) and 60 (46–61) and to standing 74 (69–76) and 90 (85–107) for propofol and alphaxalone respectively. Recovery quality was good. Cardiopulmonary effects did not differ between groups. Hypoventilation occurred in both groups.Conclusions and clinical relevanceFollowing premedication with acepromazine and morphine, both propofol and alphaxalone produce good quality anaesthesia adequate for ovariohysterectomy. Hypoventilation occurs suggesting a need for ventilatory support during prolonged infusion periods with either anaesthetic agent.     

Immersion and branchial/transcutaneous irrigation anaesthesia with alfaxalone in a Mexican axolotl

IntroductionImmersion anaesthetic techniques are commonly used in amphibian species. Alfaxalone has been reported as an immersion anaesthetic in fish but not amphibians.Case history and examinationA Mexican 56 g axolotl was presented with a 3 day history of anorexia. Anaesthesia was required for the surgical retrieval of two gastric foreign bodies. Prior to anaesthesia, on visual inspection the axolotl was bright and active. Branchial and gular respiratory movements occurred at approximately 24 respirations minute^?1 and heart rate was approximately 52 beats minute^?1.ManagementThe axolotl was exposed to increasing concentrations (up to 5 mg L^?1) of alfaxalone (Alfaxan; Vetóquinol, UK) in a water bath. After becoming sedated the axolotl was removed from the water bath. Anaesthesia was induced and maintained with alfaxalone (5 mg L^?1) via continuous irrigation of the gills (branchial) and skin (cutaneous) with additional 30 μL drops of alfaxalone (10 mg mL^?1) administered branchially as required. Endoscopy and surgery were performed to remove two gastric foreign bodies. Branchial and gular respiratory movements persisted at what was considered an appropriate anaesthetic depth. Anaesthetic depth could be rapidly deepened by branchial irrigation of alfaxalone solutions and lightened by irrigation using fresh water. Anaesthesia lasted approximately 1 hour and recovery was rapid (within 15 minutes). Recovery was assisted through branchial and cutaneous irrigation with fresh water.Follow-upNo obvious adverse effects of anaesthesia were observed immediately post-anaesthesia or, according to the owner, in the following week.ConclusionsAxolotls can be anaesthetized using alfaxalone administered via immersion and branchial/transcutaneous irrigation offering an alternative technique for anaesthetising axolotls for clinical and research purposes.     

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.     

Effects of different doses of dexmedetomidine on anaesthetic induction with alfaxalone – a clinical trial

ObjectiveTo document the effects of two doses of dexmedetomidine on the induction characteristics and dose requirements of alfaxalone.Study designRandomized controlled clinical trial.AnimalsSixty one client owned dogs, status ASA I-II.MethodsDogs were allocated randomly into three groups, receiving as pre-anaesthetic medication, no dexmedetomidine (D₀), 1 μg kg^?1 dexmedetomidine (D₁) intramuscularly (IM) or 3 μg kg^?1 dexmedetomidine IM (D₃). All dogs also received 0.2 mg kg^?1 methadone IM. Level of sedation was assessed prior to induction of anaesthesia. Induction of general anaesthesia was performed with alfaxalone administered intravenously to effect at a rate of 1 mg kg^?1 minute^?1; the required dose to achieve tracheal intubation was recorded. Anaesthesia was maintained with isoflurane in oxygen. Cardiopulmonary parameters were recorded throughout the anaesthetic period. Quality of intubation, induction and recovery of anaesthesia were recorded. Quantitative data were compared with one-way anova or Kruskal-Wallis test. Repeated measures were log-transformed and analysed with repeated measures anova (p < 0.05).ResultsTreatment groups were similar for categorical data, with exception of sedation level (p < 0.001). The doses (mean ± SD) of alfaxalone required for intubation were D₀ 1.68 ± 0.24, D₁ 1.60 ± 0.36 and D₃ 1.41 ± 0.43, the difference between D₀ and D₃ being statistically significant (p = 0.036). Heart and respiratory rates during the anaesthetic period were significantly different over time and between groups (p < 0.001); systolic arterial blood pressure was significantly different over time (p < 0.001) but not between groups (p = 0.833). Induction quality and recovery scores were similar between groups (p = 1.000 and p = 0.414, respectively).Conclusions and clinical relevanceThe administration of alfaxalone resulted in a good quality anaesthetic induction which was not affected by the dose of dexmedetomidine. Dexmedetomidine at 3 μg kg^?1 IM combined with methadone provides good sedation and enables a reduction of alfaxalone requirements.     

Sedative and analgesic effects of buprenorphine,combined with either acepromazine or dexmedetomidine,for premedication prior to elective surgery in cats and dogs

ObjectiveTo evaluate the sedative and analgesic effects of intramuscular buprenorphine with either dexmedetomidine or acepromazine, administered as premedication to cats and dogs undergoing elective surgery.Study designProspective, randomized, blinded clinical study.AnimalsForty dogs and 48 cats.MethodsAnimals were assigned to one of four groups, according to anaesthetic premedication and induction agent: buprenorphine 20 μg kg^?1 with either dexmedetomidine (dex) 250 μg m^?2 or acepromazine (acp) 0.03 mg kg^?1, followed by alfaxalone (ALF) or propofol (PRO). Meloxicam was administered preoperatively to all animals and anaesthesia was always maintained using isoflurane. Physiological measures and assessments of pain, sedation and mechanical nociceptive threshold (MNT) were made before and after premedication, intraoperatively, and for up to 24 hours after premedication. Data were analyzed with one-way, two-way and mixed between-within subjects anova, Kruskall–Wallis analyses and Chi squared tests. Results were deemed significant if p ≤ 0.05, except where multiple comparisons were performed (p ≤ 0.005).ResultsCats premedicated with dex were more sedated than cats premedicated with acp (p < 0.001) and ALF doses were lower in dex cats (1.2 ± 1.0 mg kg^?1) than acp cats (2.5 ± 1.9 mg kg^?1) (p = 0.041). There were no differences in sedation in dogs however PRO doses were lower in dex dogs (1.5 ± 0.8 mg kg^?1) compared to acp dogs (3.3 ± 1.1 mg kg^?1) (p < 0.001). There were no differences between groups with respect to pain scores or MNT for cats or dogs.ConclusionChoice of dex or acp, when given with buprenorphine, caused minor, clinically detectable, differences in various characteristics of anaesthesia, but not in the level of analgesia.Clinical relevanceA combination of buprenorphine with either acp or dex, followed by either PRO or ALF, and then isoflurane, accompanied by an NSAID, was suitable for anaesthesia in dogs and cats undergoing elective surgery. Choice of sedative agent may influence dose of anaesthetic induction agent.     

Comparison of the effects of propofol or alfaxalone for anaesthesia induction and maintenance on respiration in cats

ObjectiveTo compare the effects of propofol and alfaxalone on respiration in cats.Study designRandomized, ‘blinded’, prospective clinical trial.AnimalsTwenty cats undergoing ovariohysterectomy.MethodsAfter premedication with medetomidine 0.01 mg kg⁻¹ intramuscularly and meloxicam 0.3 mg kg⁻¹ subcutaneously, the cats were assigned randomly into two groups: group A (n = 10) were administered alfaxalone 5 mg kg⁻¹ minute⁻¹ followed by 10 mg kg⁻¹ hour⁻¹ intravenously (IV) and group P (n = 10) were administered propofol 6 mg kg⁻¹ minute⁻¹ followed by 12 mg kg⁻¹hour⁻¹ IV for induction and maintenance of anaesthesia, respectively. After endotracheal intubation, the tube was connected to a non-rebreathing system delivering 100% oxygen. The anaesthetic maintenance drug rate was adjusted (± 0.5 mg kg⁻¹ hour⁻¹) every 5 minutes according to a scoring sheet based on physiologic variables and clinical signs. If apnoea > 30 seconds, end-tidal carbon dioxide (Pe′CO₂) > 7.3 kPa (55 mmHg) or arterial haemoglobin oxygen saturation (SpO₂) < 90% occurred, manual ventilation was provided. Methadone was administered postoperatively. Data were analyzed using independent-samples t-tests, Fisher's exact test, linear mixed-effects models and binomial test.ResultsManual ventilation was required in two and eight of the cats in group A and P, respectively (p = 0.02). Two cats in both groups showed apnoea. Pe′CO₂ > 7.3 kPa was recorded in zero versus four and SpO₂ < 90% in zero versus six cats in groups A and P respectively. Induction and maintenance dose rates (mean ± SD) were 11.6 ± 0.3 mg kg⁻¹ and 10.7 ± 0.8 mg kg⁻¹ hour⁻¹ for alfaxalone and 11.7 ± 2.7 mg kg⁻¹ and 12.4 ± 0.5 mg kg⁻¹ hour⁻¹ for propofol.Conclusion and clinical relevanceAlfaxalone had less adverse influence on respiration than propofol in cats premedicated with medetomidine. Alfaxalone might be better than propofol for induction and maintenance of anaesthesia when artificial ventilation cannot be provided.     

Clinical efficacy and cardiorespiratory effects of alfaxalone, or diazepam/fentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk

ObjectiveTo evaluate the clinical efficacy and cardiorespiratory effects of alfaxalone as an anaesthetic induction agent in dogs with moderate to severe systemic disease.Study designRandomized prospective clinical study.AnimalsForty dogs of physical status ASA III-V referred for various surgical procedures.MethodsDogs were pre-medicated with intramuscular methadone (0.2 mg kg^?1) and allocated randomly to one of two treatment groups for induction of anaesthesia: alfaxalone (ALF) 1–2 mg kg^?1 administered intravenously (IV) over 60 seconds or fentanyl 5 μg kg^?1 with diazepam 0.2 mg kg^?1± propofol 1–2 mg kg^?1 (FDP) IV to allow endotracheal intubation. Anaesthesia was maintained with isoflurane in oxygen and fentanyl infusion following both treatments. All dogs were mechanically ventilated to maintain normocapnia. Systolic blood pressure (SAP) was measured by Doppler ultrasound before and immediately after anaesthetic induction, but before isoflurane administration. Parameters recorded every 5 minutes throughout subsequent anaesthesia were heart and respiratory rates, end-tidal partial pressure of carbon dioxide and isoflurane, oxygen saturation of haemoglobin and invasive systolic, diastolic and mean arterial blood pressure. Quality of anaesthetic induction and recovery were recorded. Continuous variables were assessed for normality and analyzed with the Mann Whitney U test. Repeated measures were log transformed and analyzed with repeated measures anova (p < 0.05).ResultsTreatment groups were similar for continuous and categorical data. Anaesthetic induction quality was good following both treatments. Pre-induction and post-induction systolic blood pressure did not differ between treatments and there was no significant change after induction. The parameters measured throughout the subsequent anaesthetic procedures did not differ between treatments. Quality of recovery was very, quite or moderately smooth.Conclusions and clinical relevanceInduction of anaesthesia with alfaxalone resulted in similar cardiorespiratory effects when compared to the fentanyl-diazepam-propofol combination and is a clinically acceptable induction agent in sick dogs.     

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).

Alfaxalone anaesthesia in the green iguana (Iguana iguana)

ObjectiveTo characterise the anaesthetic effects of alfaxalone administered intramuscularly (IM) at 10, 20, and 30 mg kg^?1.Study designProspective, randomized cross-over study.AnimalsTen juvenile green iguanas (Iguana iguana) of mean body weight (±SD) 480 ± 134 g.MethodsAlfaxalone was administered IM in the triceps of both thoracic limbs. Times for anaesthetic induction, plateau and recovery periods were recorded. Skeletal muscle tone of the jaw, neck, thoracic limbs, pelvic limbs, and tail was scored. The palpebral, corneal and righting reflexes, and the response to painful stimuli were also assessed. Pulse rate and respiratory rate were recorded. Comparisons between different dosages and over time were made using anova.ResultsTimes are given for 10, 20 and 30 mg kg^?1 dosages respectively: mean time to maximal effect was 7.7 ± 2.2, 5.4 ± 1.7 and 3.9 ± 1.2 minutes; duration of the plateau phase was 11.3 ± 3.8, 22.1 ± 6.5 and 39.1 ± 11.5 minutes; recovery time was 10 ± 2.4, 17.5 ± 8.6 and 25 ± 7.1 minutes; and total anaesthetic duration was 29 ± 35.7, 45 ± 8.2 and 68 ± 9.8 minutes. Endotracheal intubation was possible in 40% of the subjects given 10 mg kg^?1 and in 100% subjects given both 20 and 30 mg kg^?1. Loss of response to a painful stimulus was seen in 0/10, 8/10 and 9/10 animals at 10, 20, and 30 mg kg^?1 respectively. There was an initial dose-dependent depression of respiration followed by a significant increase in frequency over time. In contrast, pulse rates decreased by 20% over the duration of the anaesthetic events.Conclusions and clinical relevanceIntramuscular administration of alfaxalone is a simple, rapid and reliable means of achieving relatively brief sedation or anaesthesia in healthy green iguanas. A dosage of 10 mg kg^?1 provides light sedation, appropriate for examination and venipuncture; 20 mg kg^?1 provides a level suitable for minor procedures or for endotracheal intubation and supplementation with inhalational anaesthesia; 30 mg kg^?1 produces an anaesthetic plane suitable for surgical procedures of limited duration (up to 40 minutes).     

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.     

Severe cardiovascular depression in a cat following a mandibular nerve block with bupivacaine

ObservationsA 12 year old cat was presented for anaesthesia to remove a mandibular squamous cell carcinoma. After intramuscular premedication with dexmedetomidine and methadone, anaesthesia was induced with alfaxalone, administered intravenously (IV) to effect, and maintained with isoflurane vaporized in oxygen, following oro-tracheal intubation. Approximately 5 minutes after performing a mandibular nerve block with 1.16 mg kg^?1 of bupivacaine, the cat developed severe cardiovascular depression. Anaesthetic delivery was discontinued and cardiopulmonary resuscitation instituted. Drug administration consisted of atropine (0.02 mg kg^?1 IV, repeated three times), followed by atipamezole (0.08 mg kg^?1 IV). Dobutamine was subsequently administered (1 μg kg^?1 minute^?1 IV) until cardiovascular performance was considered satisfactory. During recovery from anaesthesia the cat exhibited seizure-like activity, which was controlled by a variable rate infusion of propofol. The cat made an uneventful recovery following discontinuation of propofol infusion, without residual neurological signs, and the surgical procedure was postponed.ConclusionsThis clinical report describes successful management of cardiovascular and neurological complications following a mandibular nerve block with bupivacaine in a cat. Although treatment was successful, the role played by the drugs administered during resuscitation remains uncertain.