Comparison between the effects of postanesthetic xylazine and dexmedetomidine on characteristics of recovery from sevoflurane anesthesia in horses

Demographic, preoperative and anaesthesia-related risk factors for unsatisfactory recovery quality in horses undergoing emergency abdominal surgery

OBJECTIVE

To determine demographic, preoperative and anaesthesia-related variables that may be associated with unsatisfactory recovery quality in horses undergoing emergency abdominal surgery (colic) in an equine teaching hospital.

STUDY DESIGN

Retrospective case series.

ANIMALS

A total of 313 horses.

METHODS

The anaesthetic records of horses admitted for surgical treatment of colic between 2005 and 2018 were examined. Overall quality of recovery was assessed as dangerous, poor, fair, good or excellent. The following categories were constructed as a dichotomic variable: unsatisfactory recovery (poor and dangerous recoveries) and satisfactory recovery (excellent, good and fair recoveries). Univariable and multivariable analyses were performed to evaluate the association between all studied variables and recovery.

RESULTS

All recoveries were unassisted. Unsatisfactory recovery quality totalled 17.2% (3.5% and 13.7% were dangerous and poor recoveries, respectively), whereas satisfactory recoveries totalled 82.8% (26.2%, 40.9% and 15.7% were fair, good and excellent recoveries, respectively). Univariable analysis showed that unsatisfactory recoveries were associated with high preoperative packed cell volume, pain behaviour, poor premedication and induction quality, high intraoperative mean heart rate, low mean arterial blood pressure, dobutamine dose ≥1.5 μg kg^-1 minute^-1, non-administration of romifidine, long anaesthesia time and prolonged time to stand. The multivariable model showed that factors strongly associated with unsatisfactory recovery quality were dobutamine dose ≥1.5 μg kg^-1 minute^-1 [adjusted odds ratio (AOR) = 6.60; 95% confidence interval (CI), 2.91-14.96], poor premedication quality (AOR=4.60; 95% CI, 1.73-12.23) and a time to stand > 70 minutes (AOR=2.59; 95% CI, 1.13-5.91).

CONCLUSIONS AND CLINICAL RELEVANCE

Our study shows that high dobutamine requirements, poor premedication quality and a prolonged time to stand are risk factors for unsatisfactory recovery quality in horses undergoing anaesthesia for colic surgery. Addressing these factors may enable clinicians to improve the quality of recovery phase.

Recovery of horses from general anaesthesia: A systematic review (2000-2020) of risk factors and influence of interventions during the recovery period

BACKGROUND

In equine anaesthesia, the recovery period is a time of considerable risk and has been the focus of prolific research. Risk factors, including age, type and duration of procedure or temperament may influence recovery quality. Unfortunately, the anaesthetist is unable to control for these factors, therefore various pharmacological interventions and recovery methods have been developed with the objective of improving recovery quality. However, no consensus among anaesthetists has been reached for many of these interventions and their implications for recovery-related mortality and morbidity.

OBJECTIVES

To conduct a systematic review of the published evidence relating to risk factors and interventions in the recovery period which may influence recovery quality from equine general anaesthesia (GA).

STUDY DESIGN

A systematic evaluation of the equine veterinary literature 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

Thirty-nine studies were identified which directly assessed the impact of risk factors and recovery interventions on recovery quality after equine GA. There was evidence to support that peri-anaesthetic risk factors such as anaesthesia duration, American Society of Anesthesiologists (ASA) physical status and surgical procedure influenced recovery quality. We also identified sufficient evidence that administration of α-2 adrenoreceptor agonists immediately prior to recovery, 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

Recovery quality is influenced by factors including: anaesthesia duration, ASA physical status and surgical procedure. Recovery quality can be improved by the administration of an α-2 adrenoreceptor agonist immediately prior to recovery.

Data Collection for the Fourth Multicentre Confidential Enquiry into Perioperative Equine Fatalities (CEPEF4) Study: New Technology and Preliminary Results

Simple Summary

New technologies allow researchers to improve the methods for immediate, accurate data collection, cleaning and analysis, with minimal geographical limitations. Although much has improved in the field of equine anaesthesia in recent years, we are still far from reducing anaesthetic-related mortality in this species in comparison with small animal anaesthesia. The aim of this multicentre study was to probe the usefulness of an internet-based method that utilised an electronic questionnaire and statistical software to show the data and report outcomes from horses undergoing general anaesthesia and certain procedures using standing sedation. Within six months, 8656 cases from 69 centres were collected: 6701 procedures under general anaesthesia and 1955 under standing sedation. The results demonstrated (i) the utility of the method and (ii) that some horses died unexpectedly when undergoing not only general anaesthesia, but also standing sedation. Finally, (iii) we present some descriptive data that outline the current anaesthesia practice compared with the previous CEPEF2. We concluded that our internet-based method is suitable for this type of study. New techniques may reduce the mortality rate. However, the results presented here should be interpreted cautiously as these are only preliminary data with lower numbers than CEPEF2.

Abstract

It is almost 20 years since the largest observational, multicentre study evaluating the risks of mortality associated with general anaesthesia in horses. We proposed an internet-based method to collect data (cleaned and analysed with R) in a multicentre, cohort, observational, analytical, longitudinal and prospective study to evaluate peri-operative equine mortality. The objective was to report the usefulness of the method, illustrated with the preliminary data, including outcomes for horses seven days after undergoing general anaesthesia and certain procedures using standing sedation. Within six months, data from 6701 procedures under general anaesthesia and 1955 standing sedations from 69 centres were collected. The results showed (i) the utility of the method; also, that (ii) the overall mortality rate for general anaesthesia within the seven-day outcome period was 1.0%. In horses undergoing procedures other than exploratory laparotomy for colic (“noncolics”), the rate was lower, 0.6%, and in “colics” it was higher, at 3.4%. For standing sedations, the overall mortality rate was 0.2%. Finally, (iii) we present some descriptive data that demonstrate new developments since the previous CEPEF2. In conclusion, horses clearly still die unexpectedly when undergoing procedures under general anaesthesia or standing sedation. Our method is suitable for case collection for future studies.

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.

Pharmacokinetics and clinical effects of xylazine and dexmedetomidine in horses recovering from isoflurane anesthesia

This study determined the pharmacokinetics and compared the clinical effects of xylazine and dexmedetomidine in horses recovering from isoflurane anesthesia. Six healthy horses aged 8.5 ± 3 years and weighing 462 ± 50 kg were anesthetized with isoflurane for 2 hr under standard conditions on two occasions one-week apart. In recovery, horses received 200 μg/kg xylazine or 0.875 μg/kg dexmedetomidine intravenously and were allowed to recover without assistance. These doses were selected because they have been used for postanesthetic sedation in clinical and research studies. Serial venous blood samples were collected for quantification of xylazine and dexmedetomidine, and the pharmacokinetic parameters were calculated. Two individuals blinded to treatment identity evaluated recovery quality with a visual analog scale. Times to stand were recorded. Results (mean ± SD) were compared using paired t tests or Wilcoxon signed-ranked test with p < .05 considered significant. Elimination half-lives (62.7 ± 21.8 and 30.1 ± 8 min for xylazine and dexmedetomidine, respectively) and steady-state volumes of distribution (215 ± 123 and 744 ± 403 ml/kg) were significantly different between xylazine and dexmedetomidine, whereas clearances (21.1 ± 17.3 and 48.6 ± 28.1 ml/minute/kg), times to stand (47 ± 24 and 53 ± 12 min) and recovery quality (51 ± 24 and 61 ± 22 mm VAS) were not significantly different. When used for postanesthetic sedation following isoflurane anesthesia in healthy horses, dexmedetomidine displays faster plasma kinetics but is not associated with faster recoveries compared to xylazine.

Recovery quality following a single post-anaesthetic dose of dexmedetomidine or romifidine in sevoflurane anaesthetised horses

BACKGROUND

Post-anaesthetic sedation is administered to horses to improve recovery quality from inhalant anaesthesia and reduce the risk of catastrophic injury. A single dose of dexmedetomidine for this purpose has not been evaluated clinically.

OBJECTIVES

To determine whether dexmedetomidine improves recovery quality from sevoflurane anaesthesia compared to a previously studied dose of romifidine.

STUDY DESIGN

Prospective, randomised, masked clinical trial.

METHODS

Ninety-nine, adult, client-owned horses anaesthetised for elective procedures completed the trial. Anaesthetic protocol was standardised. Horses were randomly assigned to receive either dexmedetomidine 1 mcg/kg bwt (D) or romifidine 20 mcg/kg bwt (R) intravenously at their first spontaneous breath in recovery. Recoveries were reviewed and independently assigned subjective visual analogue scale (VAS) scores (0-100 mm, worst to best) for overall quality and standing ataxia scores (1-4, none to severe) by two anaesthesiologists blinded to treatment group. Objective anaesthesia and recovery data were also recorded. Comparisons were made using the Chi-square, Wilcoxon rank sum, linear models or Welch-Satterthwaite two-sample t-test (P ≤ .05). Predictors of VAS score were analysed independent of treatment group.

RESULTS

There were no significant differences between groups except end-tidal sevoflurane (FE´Sevo) concentration and post-induction extra ketamine dosing. Including FE´Sevo and additional ketamine in the analysis as covariates, VAS scores and time to standing were not significantly different between groups. Increased age, not receiving a nerve block, increased duration of hypotension, and having a nervous temperament were significant predictors of VAS score.

MAIN LIMITATIONS

No universal recovery scale exists for inter-study comparisons.

CONCLUSIONS

After sevoflurane anaesthesia, sedation with dexmedetomidine or romifidine provides clinically similar recovery time and quality.

Is there a place for dexmedetomidine in equine anaesthesia and analgesia? A systematic review (2005-2017)

The objective of this review was to perform a literature compilation of all the equine publications that used dexmedetomidine as the first article on this topic was published, in 2005. We also aimed to answer the question whether the use of dexmedetomidine can currently be justified. For that, we compiled information from databases, such as PubMed, Google Scholar and Web of Science and the proceedings of the last veterinary anaesthesiology meetings. Dexmedetomidine is an attractive drug to be used in horses, mainly due to its pharmacokinetic profile and pharmacodynamics that favour its use as intravenous constant rate infusion (CRI). Nowadays, its clinical use is popular for sedation in prolonged standing procedures and during partial intravenous anaesthesia (PIVA) and total intravenous anaesthesia (TIVA). However, legal requirements for its use should be taken into account.