Evaluation of the use of midazolam as a co-induction agent with ketamine for anaesthesia in sedated ponies undergoing field castration

Effects of brotizolam as a co-agent with ketamine for induction of anaesthesia in calves

Anaesthesia in food producing animals in the EU and UK is legally limited to a narrow choice of drugs; the only licensed benzodiazepine being brotizolam. The aim of this study was to investigate the effects of brotizolam as a co-agent with ketamine on the quality of induction, intubation, muscle relaxation and recovery from isoflurane anaesthesia. Seventeen calves were enrolled in this prospective, blinded, randomized experimental study. Calves were sedated with 0.05 mg/kg xylazine and 0.1 mg/kg butorphanol IV. After assessing the quality of sedation, anaesthesia was induced with 2 mg/kg ketamine (group KETA) or 2 mg/kg ketamine with 2 μg/kg brotizolam IV (group BROTI). An additional 1 mg/kg ketamine was administered IV every 2 min until intubation was possible. Anaesthesia was maintained with isoflurane in a mixture of oxygen and air. The amount of ketamine required, quality of induction, intubation, muscle relaxation, and recovery were scored and compared between groups using ordinal regression models (P < 0.05 was considered statistically significant). Sedation scores did not differ significantly between groups but were positively associated with the quality of recovery (P = 0.0098). Group BROTI was associated with a lower quality of induction (P < 0.0001), intubation (P = 0.0203) and muscle relaxation (P = 0.0043). The sedation score and treatment had no effect on the number of attempts of intubation, additional ketamine doses, time to extubation and recovery time. Brotizolam had a negative effect on the quality of induction, intubation, and muscle relaxation compared to ketamine alone. We do not recommend using brotizolam under these circumstances.

Recovery of horses from general anaesthesia: A systematic review (2000-2020) of the influence of anaesthetic protocol on recovery quality

BACKGROUND

The recovery phase after equine general anaesthesia (GA) is a time of considerable risk and therefore has been the subject of extensive research over the last 20 years. Various pharmacological interventions have been developed and studied with the objective of improving recovery quality and reducing anaesthetic-related mortality and morbidity. Nevertheless, some controversy remains regarding the influence of anaesthetic protocol choice on recovery quality from GA and its implications for recovery-related mortality and morbidity. A systematic review of the literature investigating the influence of anaesthetic protocol choice on recovery quality is currently lacking.

OBJECTIVES

To perform a detailed evaluation of the equine veterinary literature investigating the effect of anaesthetic protocol choice on equine recovery quality utilising the GRADE framework.

STUDY DESIGN

A systematic evaluation of the equine veterinary literature was performed using the GRADE framework.

METHODS

A literature search was performed and studies were assessed for eligibility by both authors utilising PRISMA guidelines. Studies meeting inclusion criteria were evaluated by both authors, categorically summarised and the quality of evidence for each sub-topic was assessed using the GRADE framework.

RESULTS

A total of 124 studies were identified which directly assessed the impact of anaesthetic protocol choice on recovery quality after GA in horses. Evaluation of the available evidence indicated that certain partial intravenous anaesthesia (PIVA) agents, cessation of intravenous lidocaine 30 minutes prior to recovery and provision of adequate analgesia improves recovery quality.

MAIN LIMITATIONS

The validity of the results of some studies may have been compromised by missing data and small sample sizes.

CONCLUSIONS

There is evidence to indicate that certain PIVA agents, cessation of intravenous lidocaine 30 minutes prior to recovery and provision of adequate analgesia improves recovery quality.

Recovery after General Anaesthesia in Adult Horses: A Structured Summary of the Literature

Simple Summary

Recovery is the most dangerous phase of general anaesthesia in horses. Numerous publications have reported about this phase, but structured reviews that try to reduce the risk of bias of narrative reviews/expert opinions, focussing on the topic are missing. Therefore, the aim of the present article was to publish the first structured review as a summary of the literature focussing on the recovery phase after general anaesthesia in horses. The objective was to summarise the available literature, taking into account the scientific evidence of the individual studies. A structured approach was followed with two experts in the field independently deciding on article inclusion and its level of scientific evidence. A total number of 444 articles, sorted by topics and classified based on their levels of evidence, were finally included into the present summary. The most important findings were summarised and discussed. The present structured review can be used as a compilation of the publications that, to date, focus on the recovery phase after general anaesthesia in adult horses. This type of review tries to minimise the risk of bias inherent to narrative reviews/expert opinions.

Abstract

Recovery remains the most dangerous phase of general anaesthesia in horses. The objective of this publication was to perform a structured literature review including levels of evidence (LoE) of each study with the keywords “recovery anaesthesia horse”, entered at once, in the search browsers PubMed and Web of Science. The two authors independently evaluated each candidate article. A final list with 444 articles was obtained on 5 April 2021, classified as: 41 “narrative reviews/expert opinions”, 16 “retrospective outcome studies”, 5 “surveys”, 59 “premedication/sedation and induction drugs”, 27 “maintenance with inhalant agents”, 55 “maintenance with total intravenous anaesthesia (TIVA)”, 3 “TIVA versus inhalants”, 56 “maintenance with partial intravenous anaesthesia (PIVA)”, 27 “other drugs used during maintenance”, 18 “drugs before/during recovery”, 18 “recovery systems”, 21 “respiratory system in recovery”, 41 “other factors”, 51 “case series/reports” and 6 “systems to score recoveries”. Of them, 167 were LoE 1, 36 LoE 2, 33 LoE 3, 110 LoE 4, 90 LoE 5 and 8 could not be classified based on the available abstract. This review can be used as an up-to-date compilation of the literature about recovery after general anaesthesia in adult horses that tried to minimise the bias inherent to narrative reviews.

Comparison of xylazine and detomidine in combination with midazolam/ketamine for field castration in Quarter Horses

BACKGROUND

The ideal field anaesthetic protocol for castration will offer an adequate duration and depth of anaesthesia using a single injection without compromising safety or recovery quality.

OBJECTIVES

The objective of this study was to compare intravenous (IV) xylazine and detomidine as sedatives in combination with midazolam and ketamine for induction of anaesthesia in horses undergoing field castration.

STUDY DESIGN

Randomised, blinded, clinical study.

METHODS

Fifty-seven male Quarter Horses were randomly assigned to receive xylazine (group X) (1.1 mg/kg bwt) or detomidine (group D) (0.03 mg/kg bwt) as premedication with midazolam (0.05 mg/kg bwt) and ketamine (2.2 mg/kg bwt) anaesthesia. Using simple descriptive scales, quality of sedation, induction, surgical conditions and recovery were scored by blinded observers. Induction, surgery, recovery time and time from induction to standing were recorded.

RESULTS

There were a greater number of horses with lower sedation score in group D when compared with horses in group X at 5 minutes after the first dose of sedation (11.1%, 66.7% and 2.2% of horses from group D with sedation scores of 1, 2 and 3, vs 0%, 52% and 48% from group X, respectively, P = .05). A significant (P < .01) difference was found between surgical condition scores for group D (63%, 14.8%, 11.1% and 11.1% with surgery scores of 1, 2, 3 and 4, respectively) and group X (28%, 4%, 28% and 40%). Horses in Group D were less likely to require maintenance doses of ketamine (P = .05) with only 26% (7 of 27 horses) in this group requiring additional doses compared to 68% (17 of 25 horses) in group X. Recovery time in minutes (Group D: 24.74 ± 14.80, Group X: 13.08 ± 8.00; P < .01) and induction to standing time in minutes (Group D: 42.2 ± 13.8, Group X: 29.8 ± 8.2; P < .01) were significantly longer for horses in group D compared with group X.

MAIN LIMITATIONS

Multiple surgeons and multiple blinded observers.

CONCLUSIONS

Detomidine as compared with xylazine as premedication results in good quality sedation and surgical conditions and prolonged surgical plane of anaesthesia, without significant differences in induction or recovery quality.

A comparison of two ketamine doses for field anaesthesia in horses undergoing castration

BACKGROUND

Ketamine at 2.2 mg/kg given i.v. is often used to induce anaesthesia for surgical procedures in horses under field conditions. Commonly, additional doses are needed to complete the surgery. We hypothesised that surgical conditions would be improved when 5 mg/kg of ketamine was used to induce anaesthesia, while induction and recovery qualities would not differ from those when 2.2 mg/kg ketamine was used.

OBJECTIVE

To compare the anaesthetic effects of two ketamine doses (5 and 2.2 mg/kg) during field anaesthesia for castration of horses.

STUDY DESIGN

Prospective, randomised, blinded, clinical study.

METHOD

Seventy-seven client-owned Icelandic horses presented for castration under field conditions were studied. Pre-anaesthetic medication was xylazine (0.7 mg/kg) butorphanol (25 μg/kg) and acepromazine (50 μg/kg) injected i.v. Anaesthesia was induced with either 2.2 mg/kg (K2.2) or 5 mg/kg (K5) i.v. of ketamine mixed with diazepam (30 μg/kg). The quality of induction, surgical conditions and recovery were compared using subjective and objective measures, and the number of additional ketamine doses recorded.

RESULTS

Ketamine 5 mg/kg provided better surgical conditions and a more rapid induction. Recovery quality was subjectively better in K2.2. Five horses in K2.2 and two in K5 required additional ketamine doses.

MAIN LIMITATIONS

While the pre-anaesthetic sedation and benzodiazepine doses were consistent among horses, the level of sedation and muscle relaxation achieved differed.

CONCLUSION

A ketamine dose of 5 mg/kg can be used to improve the quality of field anaesthesia for castration in Icelandic horses. Although recovery quality is subjectively better when using 2.2 mg/kg, no adverse events were observed during recovery with either dose The Summary is available in Portuguese - see Supporting Information.