Effect of detomidine or romifidine constant rate infusion on plasma lactate concentration and inhalant requirements during isoflurane anaesthesia in horses

Effect of constant rate infusion of detomidine with and without vatinoxan on blood glucose and insulin concentrations in horses

OBJECTIVE

To assess the effects of an α2-adrenoceptor agonist (detomidine) constant rate infusion (CRI) with and without an α2-adrenoceptor antagonist (vatinoxan) CRI on blood insulin and glucose concentrations, heart rate, intestinal borborygmi, and sedation during and after infusion in horses.

STUDY DESIGN

Randomized, blinded, crossover, experimental study.

ANIMALS

A total of nine healthy, adult Finnhorse mares.

METHODS

Horses were treated with an intravenous (IV) detomidine loading dose (0.01 mg kg-1), followed by CRI (0.015 mg kg-1 hour-1), and the same doses of detomidine combined with an IV vatinoxan loading dose (0.15 mg kg-1), followed by CRI (detomidine and vatinoxan; 0.05 mg kg-1 hour-1) with an 18 day washout period. Infusion time was 60 minutes and horses were monitored for 240 minutes after the infusion. Heart rate, borborygmi score and sedation were assessed, and blood glucose, insulin and triglyceride concentrations were measured. Data were analyzed using repeated measures ancova and Wilcoxon signed-rank tests. Values of p < 0.05 were considered statistically significant.

RESULTS

Insulin concentration decreased during (median nadir 1.7, range 0.0-2.9 μIU mL-1 at 60 minutes, p < 0.0001) and increased after detomidine CRI (median 36.6, range 11.7-78.4 μIU mL-1 at 180 minutes, p = 0.0001) significantly compared with detomidine and vatinoxan CRI. A significant elevation of blood glucose (peak 11.5 ± 1.6 mmol L-1 at 60 minutes, p < 0.0001) was detected during detomidine CRI. Vatinoxan alleviated the insulin changes and abolished the significant increase in blood glucose. Vatinoxan alleviated the decrease in heart rate (p = 0.0001) during detomidine infusion. No significant differences were detected in sedation scores between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Vatinoxan attenuated the negative adverse effects of detomidine CRI and thus is potentially beneficial when used in combination with an α2-adrenoceptor agonist CRI in horses.

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.

Use of adrenaline continuous infusion to treat hypotension during general anaesthesia in a cow and a calf

Background

Hypotension is one of the most common complications observed during inhalation anaesthesia in veterinary patients. Treatment of hypotension in cattle is more challenging than in other species, owing to the limited number of drugs licensed in food producing animals. The use of adrenaline as an infusion to support blood pressure has not been described previously in bovines.

Case presentation

A cow and a calf presented to University College Dublin Veterinary Hospital for bilateral mandibular fracture repair and bladder rupture repair respectively, developed severe anaesthetic related hypotension unresponsive to conventional treatments. In both cases an adrenaline infusion was started and slowly increased to effect, with infusion rates ranging from 0.01 to 0.25 μg/kg/min. Blood pressure increased as the adrenaline infusion rate increased, but clinically significant improvements in blood pressure were only observed with infusion rates exceeding 0.05 μg/kg/min. The side effect observed with adrenaline infusion was an increase in plasma lactate levels in both cases. Both animals were euthanised due to non-anaesthetic related complications.

Conclusions

Maintenance of normotension is important during bovine anaesthesia to prevent the development of post-anaesthetic complications. In the cases described here, adrenaline was effective as an additional treatment of anaesthetic related hypotension. Further research is required to establish the recommended infusion rates, cardiovascular effects and possible side effects of adrenaline infusion administration as a treatment for hypotension in bovines.

A retrospective report (2003-2013) of the complications associated with the use of a one-man (head and tail) rope recovery system in horses following general anaesthesia

Background

The mortality rate of horses undergoing general anaesthesia is high when compared to humans or small animal patients. One of the most critical periods during equine anaesthesia is recovery, as the horse attempts to regain a standing position. This study was performed in a private equine practice in Belgium that uses a purpose-designed one-man (head and tail) rope recovery system to assist the horse during the standing process.

The main purpose of the retrospective study was to report and analyse complications and the mortality rate in horses during recovery from anaesthesia using the described recovery system. Information retrieved from the medical records included patient signalment, anaesthetic protocol, duration of anaesthesia, ASA grade, type of surgery, recovery time and complications during recovery. Sedation was administered to all horses prior to recovery with the rope system. Complications were divided into major complications in which the horse was euthanized and minor complications where the horse survived. Major complications were further subdivided into those where the rope system did not contribute to the recovery complication (Group 1) and those where it was not possible to determine if the rope system was of any benefit (Group 2).

Results

Five thousand eight hundred fifty two horses recovered from general anaesthesia with rope assistance. Complications were identified in 30 (0.51%). Major complications occurred in 12 horses (0.20%) of which three (0.05%) were assigned to Group 1 and nine (0.15%) to Group 2. Three horses in Group 2 suffered musculoskeletal injuries (0.05%). Eighteen horses (0.31%) suffered minor complications, of which five (0.08%) were categorised as failures of the recovery system.

Conclusions

This study reports the major and minor complication and mortality rate during recovery from anaesthesia using a specific type of rope recovery system. Mortality associated with the rope recovery system was low. During recovery from anaesthesia this rope system may reduce the risk of lethal complications, particularly major orthopaedic injuries.