Isoflurane anesthesia for equine colic surgery. Comparison with halothane anesthesia

The Threshold Effect of Swine Epidemics on the Pig Supply in China

The pig industry is the pillar industry of animal husbandry in China, and epidemics can lead to drastic changes in pig supply, affecting the healthy development of the pig industry and residents’ quality of life. This study analyzed the mechanism of the effect of swine epidemics on nonlinear shocks to pig supply, and monthly data on pig supply from January 2012 to June 2020 were applied to study the threshold effect of swine epidemics on pig stock and slaughter in China empirically, using the index of swine epidemics’ width (ISEW) as the threshold variable. The results of this study were as follows: (1) The influence of the ISEW over 7 months on pig stock in China was divided into two ranges, and the pig stock did not change significantly when the ISEW was less than 0.25. Swine epidemics had a significantly negative impact on the pig stock when the ISEW was larger than 0.25. (2) The influence of the ISEW over 8 months on pig slaughter was also divided into two ranges. When the ISEW was less than 0.33, epidemics had a positive and significant effect on pig slaughter, while epidemics had a marked negative impact on pig slaughter when the ISEW was greater than 0.33. Based on these conclusions, this study proposed relevant measures for the prevention and control of swine epidemics.

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.

Is isoflurane safer than halothane in equine anaesthesia? Results from a prospective multicentre randomised controlled trial

REASONS FOR PERFORMING STUDY

Approximately 1 in 100 horses suffer unexpectedly from anaesthetic-related death. Identification and use of the safest anaesthetic drugs should support this aim. Experimental evidence has suggested that isoflurane should be a safer maintenance agent in equine anaesthesia than halothane.

HYPOTHESIS

The death rate would be reduced in horses being maintained with isoflurane compared to halothane.

METHODS

A multicentre randomised controlled trial was undertaken to compare the effects of isoflurane and halothane for maintenance of equine anaesthesia for all types of operation. Data were analysed from 8242 horses in which anaesthesia was maintained with either halothane or isoflurane using mixed effects logistic regression models.

RESULTS

No overall benefit of either drug was detected. However, although not part of the primary hypothesis, data showed that the overall death rate was significantly reduced in horses age 2-5 years with isoflurane and that death from cardiac arrest was also reduced with isoflurane, particularly in high risk cases.

CONCLUSIONS AND POTENTIAL RELEVANCE

Halothane remains an acceptable anaesthetic for maintenance of anaesthesia in horses, but isoflurane may be safer in the young horse and in high risk cases.

Comparison of hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of anesthesia with isoflurane and halothane in horses undergoing arthroscopic surgery

OBJECTIVE

To compare hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of halothane and isoflurane in horses undergoing arthroscopic surgery.

ANIMALS

8 healthy adult horses.

PROCEDURE

Anesthesia was maintained with isoflurane or halothane (crossover study). At 6 intervals during anesthesia and surgery, cardiopulmonary variables and related derived values were recorded. Recovery from anesthesia was assessed; gastrointestinal tract motility was subjectively monitored for 72 hours after anesthesia. Horses were administered chromium, and fecal chromium concentration was used to assess intestinal transit time. Venous blood samples were collected for clinicopathologic analyses before and 2, 24, and 48 hours after anesthesia.

RESULTS

Compared with halothane-anesthetized horses, cardiac index, oxygen delivery, and heart rate were higher and systemic vascular resistance was lower in isoflurane-anesthetized horses. Mean arterial blood pressure and the dobutamine dose required to maintain blood pressure were similar for both treatments. Duration and quality of recovery from anesthesia did not differ between treatments, although the recovery periods were somewhat shorter with isoflurane. After isoflurane anesthesia, gastrointestinal motility normalized earlier and intestinal transit time of chromium was shorter than that detected after halothane anesthesia. Compared with isoflurane, halothane was associated with increases in serum aspartate transaminase and glutamate dehydrogenase activities, but there were no other important differences in clinicopathologic variables between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Compared with halothane, isoflurane appears to be associated with better hemodynamic stability during anesthesia, less hepatic and muscle damage, and more rapid return of normal intestinal motility after anesthesia in horses undergoing arthroscopic procedures.

Complications associated with anaesthesia for ocular surgery: a retrospective study 1989-1996

This retrospective study was initiated to identify complications of anaesthesia occurring during ocular surgery. Records of 74 horses anaesthetised for eye enucleation, 65 horses anaesthetised for surgery of the eye and adnexa, and 51 horses anaesthetised for splint bone excision were reviewed. Fifty-three percent of the horses anaesthetised for eye enucleation moved during surgery which was significantly more frequent than in the other groups (P = 0.001). The incidence of moving was significantly reduced by use of an anaesthetic gas analyser for monitoring (P = 0.001). Transient hypertension was measured in 6 horses during removal of the eye. One horse experienced a momentary decrease in heart rate from 36 to 26 beats/min at the start of surgery involving a mass on the third eyelid. The incidence of unsatisfactory recovery from anaesthesia involving multiple attempts to stand was significantly greater after ocular surgery than after splint bone excision (P = 0.036). Our conclusions were 1) the oculocardiac reflex was not active in these horses undergoing ocular surgery, 2) increased attention must be paid to provision of analgesia and adequate depth of anaesthesia, which may be facilitated by use of an anaesthetic gas analyser and 3) horses were at greater risk for unsatisfactory recoveries from anaesthesia after ocular surgery.

The recovery of horses from inhalant anesthesia: a comparison of halothane and isoflurane

OBJECTIVE

Recovery is one of the more precarious phases of equine general anesthesia. The quality and rate of recovery of horses from halothane and isoflurane anesthesia were compared to determine differences in the characteristics of emergence from these commonly used inhalant anesthetics.

EXPERIMENTAL DESIGN

Prospective, randomized blinded clinical trial.

SAMPLE POPULATION

A total of 96 Thoroughbred and 3 Standardbred racehorses admitted for elective distal forelimb arthroscopy.

METHODS

All horses were premedicated with intravenous xylazine, induced with guaifenesin and ketamine, and maintained on a large animal circle system fitted with an out of the circle, agent specific vaporizer. Recoveries were managed by a blinded scorer with a standardized protocol. A 10 category scoring system was used to assess each horse's overall attitude, purposeful activity, muscle coordination, strength and balance from the time of arrival in recovery to standing. Times to extubation, sternal recumbency and standing were recorded. Median recovery scores and mean times to extubation, sternal and standing were compared using the Mann-Whitney U test and student's t test, respectively.

RESULTS

The median score for horses recovering from halothane was lower (20.0; range, 10 to 57) than that for horses recovering from isoflurane (27.5; range, 10 to 55). Horses in the two groups were extubated at similar mean times (halothane, 11.3 +/- 5.5 and isoflurane, 9.5 +/- 5.2 minutes) but horses recovering from isoflurane achieved sternal recumbency (halothane, 37.7 +/- 12.1 and isoflurane, 24.7 +/- 8.8 minutes) and stood (halothane, 40.6 +/- 12.9 and isoflurane, 27.6 +/- 9.6 minutes) sooner than those recovering from halothane.

CONCLUSIONS

The recovery of horses from isoflurane anesthesia was more rapid but less composed than that from halothane.

CLINICAL RELEVANCE

The quality of recovery following isoflurane was worse than after halothane anesthesia using the criteria chosen for this study. However, the range of recovery scores was similar for both groups and all horses recovered without significant injury.