Elizabeth A Leece

Alfaxalone induction dose following administration of medetomidine and butorphanol in the dog.

OBJECTIVE To determine in dogs the effects of medetomidine and butorphanol, alone and in combination, on the induction dose of alfaxalone and to describe the induction and intubation conditions. STUDY DESIGN Prospective, randomized, blinded clinical trial. ANIMALS Eighty-five client-owned dogs (ASA 1 or 2). METHODS Subjects were block randomized to treatment group according to temperament. The treatment groups were: medetomidine 4 microg kg(-1) (M), butorphanol 0.1 mg kg(-1) (B), or a combination of both (MB), all administered intramuscularly. After 30 minutes, a sedation score was assigned, and alfaxalone 0.5 mg kg(-1) was administered intravenously over 60 seconds by an observer who was unaware of treatment group. Tracheal intubation conditions were assessed and, if tracheal intubation was not possible after 20 seconds, further boluses of 0.2 mg kg(-1) were given every 20 seconds until intubation was achieved. Induction dose and adverse events (sneezing, twitching, paddling, excitement, apnoea and cyanosis) were recorded; induction quality and intubation conditions were scored and recorded. RESULTS The mean dose of alfaxalone required for induction was similar for groups M and B: 1.2 +/- 0.4 mg kg(-1). The mean dose requirement for group MB (0.8 +/- 0.3 mg kg(-1)) was lower than groups M and B (p < 0.0001). Induction dose was not influenced by temperament or level of sedation. Induction and intubation scores did not differ between treatment groups. Adverse events were noted in 16 dogs; there was no association with treatment group, temperament or level of sedation. CONCLUSIONS AND CLINICAL RELEVANCE Medetomidine and butorphanol administered in combination reduce the anaesthetic induction dose of alfaxalone compared to either agent alone. This difference should be taken into account when using this combination of drugs in a clinical setting.

Comparison of ketamine and alfaxalone for induction and maintenance of anaesthesia in ponies undergoing castration

OBJECTIVE To compare alfaxalone with ketamine for total intravenous anaesthesia in ponies undergoing castration. STUDY DESIGN Prospective, randomised, blinded clinical study. ANIMALS Forty-two, 12-month-old Welsh Mountain ponies. METHODS Ponies were assigned randomly to receive ketamine or alfaxalone. After administration of romifidine 100 μg kg(-1) and butorphanol 50 μg kg(-1) intravenously (IV), sedation and response to tactile stimulation were scored. If sedation was insufficient, romifidine 30 μg kg(-1) was administered IV. Anaesthesia was induced with ketamine 2.2 mg kg(-1) or alfaxalone 1 mg kg(-1) , both in combination with diazepam 20 μg kg(-1) IV. Time from end of injection to lateral recumbency was recorded. Simple descriptive scores were used to score quality of induction, surgical conditions and recovery. Ketamine 0.5 mg kg(-1) or alfaxalone 0.2 mg kg(-1) were administered if movement was observed. Times to first head lift, sternal recumbency and standing, and number of attempts needed were recorded. All scores were performed by the same observer, unaware of treatment. Normally distributed data were compared using t-test and non-normally distributed data with Mann-Whitney test. Level of significance was set at p<0.05. RESULTS Three ponies needed additional sedation. Mean induction times were 30 ± 6 and 18 ± 4 seconds following ketamine and alfaxalone respectively (p<0.0001). Additional doses were required by four ponies given ketamine and seven given alfaxalone. Sedation, induction and surgical scores were similar for both groups. Recovery scores (scale of 1-4 with 1 best) differed statistically between groups [ketamine group, median 1 (1-2); alfaxalone group 1.5 (1-4) (p=0.04)]. No differences in anaesthesia time or times taken from end of surgery to head lift, sternal recumbency and standing were detected. CONCLUSION AND CLINICAL RELEVANCE Induction times following alfaxalone were shorter than following ketamine. Both anaesthetic agents provided acceptable quality of anaesthesia for castration.

The sedative effects of low-dose medetomidine and butorphanol alone and in combination intravenously in dogs

OBJECTIVE To evaluate the sedative effects of intravenous (IV) medetomidine (1 μg kg-1) and butorphanol (0.1 mg kg-1) alone and in combination in dogs. STUDY DESIGN Prospective, blinded, randomized clinical trial. ANIMALS Sixty healthy (American Society of Anesthesiologists I) dogs, aged 6.2 ± 3.2 years and body mass 26 ± 12.5 kg. METHODS Dogs were assigned to four groups: Group S (sodium chloride 0.9% IV), Group B (butorphanol IV), Group M (medetomidine IV) and Group MB (medetomidine and butorphanol IV). The same clinician assessed sedation before and 12 minutes after administration using a numerical scoring system in which 19 represented maximum sedation. Heart rate (HR), respiratory rate, pulse quality, capillary refill time and rectal temperature were recorded after each sedation score assessment. Sedation scores, sedation score difference (score after minus score before administration) and patient variables were compared using one-way anova for normally distributed variables and Kruskal-Wallis test for variables with skewed distributions and/or unequal variances. Where significance was found, further evaluation used Bonferroni multiple comparisons for pair-wise testing. RESULTS Breed, sex, neuter status, age and body mass did not differ between groups. Sedation scores before substance administration were similar between groups (p = 0.2). Sedation scores after sedation were significantly higher in Group MB (mean 9.5 ± SD 5.5) than in group S (2.5 ± 1.8) (p < 0.001), group M (3.1 ± 2.5) (p < 0.001) and group B (3.7 ± 2.0) (p = 0.003). Sedation score difference was significantly higher in Group MB [7 (0-13)] than in Group S [0 (-1 to 4)] (p < 0.001) and Group M [0 (0-6)] (p < 0.001). HR decreased significantly in Groups M and MB compared with Group S (p < 0.05). CONCLUSION AND CLINICAL RELEVANCE Low-dose medetomidine 1 μg kg-1 IV combined with butorphanol 0.1 mg kg-1 IV produced more sedation than medetomidine or butorphanol alone. HR was significantly decreased in both medetomidine groups.

Alfaxalone in cyclodextrin for induction and maintenance of anaesthesia in ponies undergoing field castration

OBJECTIVE To evaluate the induction and maintenance of anaesthesia using alfaxalone following pre-anaesthetic medication with romifidine and butorphanol in ponies undergoing castration in the field. STUDY DESIGN Prospective clinical study. ANIMALS Seventeen male ponies weighing 169 +/- 29 kg. METHODS The ponies were sedated with romifidine and butorphanol intravenously (i.v.). Induction time was recorded following administration of alfaxalone 1 mg kg(-1) and diazepam 0.02 mg kg(-1) i.v.. If movement during surgery occurred, alfaxalone 0.2 mg kg(-1) was administered i.v.. The quality of anaesthetic induction, and recovery were scored on a subjective scale of 1 (good) to 5 (poor). The number of attempts to attain sternal recumbency and standing, quality of recovery and times from induction to end of surgery, first head lift, sternal recumbency and standing were recorded. RESULTS Induction quality was good [median score (range) 1 (1-3)] with a mean +/- SD time of 29 +/- 6 seconds taken to achieve lateral recumbency. Ten ponies required incremental doses of alfaxalone during surgery. Mean times to the end of surgery, first head lift, sternal recumbency and standing were 26 +/- 9 minutes, 31 +/- 9 minutes, 33 +/- 9 minutes and 34 +/- 9 minutes respectively. The number of attempts to attain sternal recumbency was 1(1-1) and to attain standing was 1(1-2). Quality of recovery was good, with a recovery score of 1(1-2). CONCLUSIONS AND CLINICAL RELEVANCE Alfaxalone provided smooth induction and recovery characteristics and was considered suitable for maintenance of anaesthesia for castration in ponies.

Castration of horses under total intravenous anaesthesia: analgesic effects of lidocaine

OBJECTIVE To evaluate the effects of local anaesthesia with lidocaine for castration of horses under intravenous anaesthesia. STUDY DESIGN Prospective, randomized, blinded clinical trial. ANIMALS Fifteen equidae, scheduled to undergo castration under total intravenous anaesthesia, were randomly distributed in two groups. One group received lidocaine injections (group L: two ponies, four horses, two donkeys) and the other received saline (group S: two ponies, three horses, two donkeys). METHODS Behaviour, heart rate (HR) and respiratory rate (f(R)) were evaluated prior to anaesthesia. Body mass was measured using an electronic scale and testicular volumes were estimated. The animals were anaesthetized with acepromazine intramuscularly and romifidine intravenously followed 10 minutes later by ketamine. Following romifidine administration lidocaine or saline was administered subcutaneously along the incision line and by intratesticular and intrafunicular injection. Based on clinical observations (movement, f(R), and cranial nerve reflexes) incremental intravenous doses of ketamine and romifidine were administered. HR, f(R), oscillometric mean arterial blood pressure (MAP), duration of surgery, movement and additional doses were recorded. Surgical conditions were assessed using a visual analogue scale (VAS) and a simple descriptive scale (SDS). Recovery was assessed by two assistants, unaware of treatment, acting separately using a VAS and a SDS. Group means were compared using Mann-Whitney and Wilcoxon tests and the Kruskal-Wallis signed rank test for matched pairs used to compare groups at different points (p < 0.05). RESULTS The number (median, range) of incremental doses (4 [1-5] compared to 1.5 [1-4]) and movements (1 [1-5] compared to 0 [0-1]) were higher (p = 0.01 for both) in the control group than in the lidocaine group. Groups were similar for other recorded variables. CONCLUSIONS AND CLINICAL RELEVANCE These results show the effectiveness of lidocaine used as a local anaesthetic adjunct to intravenous anaesthesia in horses undergoing castration.

A comparison of recovery times and characteristics with sevoflurane and isoflurane anaesthesia in horses undergoing magnetic resonance imaging

OBJECTIVE To compare recovery times and quality following maintenance of anaesthesia with sevoflurane or isoflurane after a standard intravenous induction technique in horses undergoing magnetic resonance imaging (MRI). STUDY DESIGN Prospective, randomised, blinded clinical study. Animals One hundred ASA I/II horses undergoing MRI. MATERIALS AND METHODS Pre-anaesthetic medication with intravenous acepromazine and romifidine was followed by induction of anaesthesia with diazepam and ketamine. The animals were randomised into two groups to receive either sevoflurane or isoflurane in oxygen. Horses were subjectively scored (0-5) for temperament before sedation, for quality of sedation, induction and maintenance and anaesthetic depth on entering the recovery area. Recoveries were videotaped and scored by an observer, unaware of the treatment, using two scoring systems. Times to the first movement, head lift, sternal recumbency and standing were recorded along with the number of attempts to achieve sternal and standing positions. Variables were compared using a Student t-test or Mann-Whitney U-test (p < 0.05), while the correlation between subjective recovery score and other relevant variables was tested calculating the Spearman Rank correlation coefficient and linear regression modelling performed when significant. RESULTS Seventy-seven horses entered the final analysis, 38 received isoflurane and 39 sevoflurane. Body mass, age and duration of anaesthesia were similar for both groups. There were no differences in recovery times, scoring or number of attempts to achieve sternal recumbency and standing between groups. Weak, but significant, correlations were found between the subjective recovery score for the pooled data from both groups and both temperament and time in sternal recumbency. CONCLUSIONS No differences in recovery times or quality were detected following isoflurane or sevoflurane anaesthesia after intravenous induction. Clinical relevance Sevoflurane affords no obvious advantage in recovery over isoflurane following a standard intravenous induction technique in horses not undergoing surgery.

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

INTRODUCTION Immersion anaesthetic techniques are commonly used in amphibian species. Alfaxalone has been reported as an immersion anaesthetic in fish but not amphibians. CASE HISTORY AND EXAMINATION A 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) . MANAGEMENT The 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-UP No obvious adverse effects of anaesthesia were observed immediately post-anaesthesia or, according to the owner, in the following week. Conclusions  Axolotls can be anaesthetized using alfaxalone administered via immersion and branchial/transcutaneous irrigation offering an alternative technique for anaesthetising axolotls for clinical and research purposes.

Comparison of pain on injection during induction of anaesthesia with alfaxalone and two formulations of propofol in dogs

OBJECTIVE To compare the incidence of pain during injection of three intravenous induction agents in dogs. STUDY DESIGN Prospective, crossover, randomized, blinded, clinical study. ANIMALS Thirty dogs requiring anaesthesia for radiotherapy. METHODS Dogs were anaesthetized on three occasions at weekly intervals. An IV cephalic catheter was placed, flushed with saline and alfentanil 0.01 mg kg(-1) and atropine 0.02 mg kg(-1) administered. After 30 seconds either: propofol lipid macroemulsion (Drug(P) ), propofol lipid-free microemulsion (Drug(PC) ) or alfaxalone (Drug(A)) was administered over 60 seconds. Each induction agent was administered once to each dog. Induction was recorded by video and reviewed by an assessor, unaware of treatment. Catheter placement (number of attempts, site, size and recent vein use) were recorded. Behavioural changes associated with pain or excitation, were recorded. Severity of pain on injection was recorded (mild, moderate or severe pain). Incidence of pain was analysed using logistic regression, excitation using McNemars test (p < 0.05) and association of pain with induction agent and catheter placement using the Akaike Information Criterion (AIC). RESULTS No dogs reacted to saline or Drug(A,) thus Drug(A) was excluded from analysis. Pain on injection occurred in six dogs (20%) with Drug(PC) and one dog (3.3%) with Drug(P). Pain was severe in four dogs with Drug(PC). Drug(P) resulted in a trend for reduced risk of pain compared to Drug(PC) (p = 0.076, odds ratio [confidence intervals] 0.14 [0.027-0.86]). Both propofol formulations resulted in greater risk of excitation than Drug(A) (p = 0.0003, odds ratio 4.5 [1.86-10.90]). Induction agent was associated with pain, whilst catheter placement was not. One dog developed facial oedema and one other dog skin necrosis adjacent to the catheter site following Drug(PC.) The study was terminated early due to ethical concerns about the severity of reactions with Drug(PC). conclusions and clinical relevance: Drug(PC) was associated with clinically relevant moderate to severe pain behaviour whilst Drug(A) and Drug(P) were not.

Analgesic effects of maxillary and inferior alveolar nerve blocks in cats undergoing dental extractions

The aim of this study was to evaluate the analgesic effects of maxillary and/or inferior alveolar nerve blocks with lidocaine and bupivacaine in cats undergoing dental extractions. Twenty-nine cats were enrolled. Using an adapted composite pain scale, cats were pain scored before the dental procedure and 30 mins, and 1, 2 and 4 h after isoflurane disconnection. Cats were sedated with buprenorphine (20 µg/kg), medetomidine (10 µg/kg) and acepromazine (20 µg/kg) intramuscularly. Anaesthesia was induced using alfaxalone (1–2 mg/kg) intravenously and maintained with isoflurane in oxygen. Each cat was randomly assigned to receive maxillary and/or inferior alveolar nerve blocks or no nerve blocks prior to dental extractions. Each nerve block was performed using lidocaine (0.25 mg/kg) and bupivacaine (0.25 mg/kg). Heart rate, systolic arterial blood pressure, respiratory rate, end tidal carbon dioxide and isoflurane vaporiser settings were recorded 5 mins before and after the dental extractions, and the difference calculated. Group mean differences (mean ± SD) for heart rate (−9.7 ± 10.6 vs 7.6 ± 9.5 beats/min [nerve block vs control group, respectively], P <0.0001), systolic arterial blood pressure (−10.33 ± 18.44 vs 5.21 ± 15.23 mmHg, P = 0.02) and vaporiser settings (−0.2 ± 0.2 vs 0.1 ± 0.4, P = 0.023) were significantly different between groups. The control group had higher postoperative pain scores (median [interquartile range]) at 2 h (3 [1.75–4.00] vs 1 [0–2], P = 0.008) and 4 h (4 [2–6] vs 2 [1–2], P = 0.006) after the dental extractions. Maxillary and inferior alveolar nerve blocks with lidocaine and bupivacaine administered prior to dental extractions resulted in a reduction in heart rate and blood pressure while allowing for a reduction in isoflurane. Cats receiving nerve blocks had lower postoperative pain scores than the group without nerve blocks.

Diabetes mellitus affects the duration of action of vecuronium in dogs

OBJECTIVE To compare the duration of action of vecuronium in diabetic dogs with a control group. STUDY DESIGN Prospective clinical study. ANIMALS Forty client-owned diabetic (n = 20) and non-diabetic dogs. METHODS Dogs were considered free from other concurrent disease based on clinical examination and laboratory data. After pre-anaesthetic medication with acepromazine and methadone, anaesthesia was induced with intravenous (IV) propofol and maintained with isoflurane-nitrous oxide in oxygen. Neuromuscular blockade (NMB) was achieved with vecuronium, 0.1 mg kg(-1) IV and its effects recorded by palpation (pelvic limb digital extension) and electromyography (m. tibialis cranialis) of responses (twitches; T) to repeated train-of-four (TOF) nerve stimulation. Time to onset of NMB was the period between vecuronium injection and loss of fourth twitch (T4) in the TOF pattern recorded by EMG and palpation. Duration of NMB was defined as the time from drug administration to return of T1 by palpation (T1(tactile) ) and EMG (T1(EMG) ). Times to return of T2-4 were also recorded. Time from induction of anaesthesia to vecuronium injection was recorded. Heart rate, non-invasive mean arterial pressure, body temperature, end-tidal isoflurane and end-tidal CO(2) concentrations were recorded at onset of NMB and when T1(EMG) returned. Loss and return of palpable and EMG responses for diabetic and non-diabetic dogs were compared using t-tests and Mann Whitney U-tests. RESULTS There were significant (p < 0.05) differences between diabetic and non-diabetic dogs for the return of all four palpable and EMG responses. Times (mean ± SD) for return of T1(tactile) were 13.2 ± 3.5 and 16.9 ± 4.2 minutes in diabetic and non-diabetic dogs respectively. There were no differences between diabetic and non-diabetic dogs in the time to onset of vecuronium with EMG or tactile monitoring. CONCLUSIONS AND CLINICAL RELEVANCE The duration of action of vecuronium was shorter in diabetic dogs as indicated by both tactile and EMG monitoring.