Validation of the bispectral index as an indicator of anesthetic depth in Thoroughbred horses anesthetized with sevoflurane

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.

Correlation between bispectral index value and modified Glasgow Coma Scale score in dogs with altered level of consciousness

OBJECTIVE

This study aims to identify the correlation between bispectral index (BIS) value and modified Glasgow Coma Scale (MGCS) score in dogs with altered level of consciousness (ALOC).

DESIGN

This prospective, observational, clinical study was conducted from February 2016 to March 2017, and follow-up was conducted until the death of dogs or their discharge from the hospital.

SETTING

This study was performed at the Small Animal Teaching Hospital.

ANIMALS

A total of 31 client-owned dogs (males, 20; females, 11) with ALOC and MGCS score <18 with no restrictions for age, breed, sex, and body weight were included. Dogs that received neuromuscular blocking agents before MGCS score evaluation were excluded.

INTERVENTIONS

BIS values were measured using the Covidien BIS Loc 2 Channel OEM module and a pediatric 4 sensor with a bifrontal application pattern.

MEASUREMENTS AND MAIN RESULTS

Minimal databases of initial neurological assessment, blood profiles, and chest and skull radiographs were developed. In addition, MGCS scores and BIS values were recorded. The mean BIS values for mild, moderate, and severe brain injuries were 89.14 ± 6.52, 77.21 ± 9.82, and 50.58 ± 27.04, respectively. Correlation analysis revealed a significantly positive relationship between BIS values and MGCS scores (r = 0.75; P < 0.001).

CONCLUSIONS

The significant correlation observed between MGCS scores and BIS values in dogs with ALOC demonstrated the usefulness of BIS as an alternative to MGCS for monitoring consciousness in patients with ALOC caused by traumatic brain injury, encephalitis, etc.

The Modification and Performance of a Large Animal Anesthesia Machine (Tafonius®) in Order to Deliver Xenon to a Horse

Introduction

Xenon, due to its interesting anesthetic properties, could improve the quality of anesthesia protocols in horses despite its high price. This study aimed to modify and test an anesthesia machine capable of delivering xenon to a horse.

Materials and methods

An equine anesthesia machine (Tafonius, Vetronic Services Ltd., UK) was modified by including a T-connector in the valve block to introduce xenon, so that the xenon was pushed into the machine cylinder by the expired gases. A xenon analyzer was connected to the expiratory limb of the patient circuit. The operation of the machine was modeled and experimentally tested for denitrogenation, wash-in, and maintenance phases. The system was considered to consist of two compartments, one being the horse’s lungs, the other being the machine cylinder and circuit. A 15-year-old, 514-kg, healthy gelding horse was anesthetized for 70 min using acepromazine, romifidine, morphine, diazepam, and ketamine. Anesthesia was maintained with xenon and oxygen, co-administered with lidocaine. Ventilation was controlled. Cardiorespiratory variables, expired fraction of xenon (FeXe), blood gases were measured and xenon was detected in plasma. Recovery was unassisted and recorded.

Results

FeXe remained around 65%, using a xenon total volume of 250 L. Five additional boli of ketamine were required to maintain anesthesia. PaO₂ was 45 ± 1 mmHg. The recovery was calm. Xenon was detected in blood during the entire administration time.

Conclusion

This pilot study describes how to deliver xenon to a horse. Although many technical problems were encountered, their correction could guide future endeavors to study the use of xenon in horses.