Clinical assessment of anesthesia with isoflurane and medetomidine in 300 equidae

Klinische Anwendung von Isofluran/Medetomidin-Anästhesie bei 300 Equiden

Kalchofner K S, Ringer S K, Boller J, Kästner S B R, Lischer C J, Bettschart-Wolfensberger R

DOI: 10.21836/PEM20060309
Year: 2006
Volume: 22
Issue: 3
Pages: 301-308

A new anesthetic protocol for horses was evaluated in 300 clinical patients. Particular attention was paid to cardiopulmonary function and recovery, as poor recoveries and bad cardiovascular function represent the main causes for the high mortality rate associated with equine anesthesia. 300 equidae of mixed breed, mean age of 8 years and mean weight of 486 kg were anaesthetised. Horses were premedicated with acepromazine IM. Following sedation with medetomidine IV, anaesthesia was induced with ketamine and diazepam IV. Anesthesia was maintained with isoflurane in oxygen and constant rate infusion of medetomidine. Horses were allowed to breathe spontaneously, unless apnea necessitated artificial ventilation. Heart rates, respiratory rates, arterial blood pressure, and composition of inhaled and exhaled gases were monitored continuously. Arterial blood gases were measured regularly. Incremental boli of ketamine or thiopentone were noted. Morphine and medetomidine were administered for recovery. Recovery time was recorded and recovery quality was scored on a 1-5 scale (1=best, 5= worst). Mean duration of anaesthesia was 149 minutes. Hypotension or hypoxemia occurred in a small number of horses. Both resolved when either additional fluids and sympathomimetics or a higher concentration of inspiratory oxygen was administered. 146 horses received supplemental ketamine and 29 thiopentone respectively. Recovery was scored excellent or good in 299 horses, poor in one horse. Mean duration of recovery was 50 minutes. Results suggest that the described anesthetic protocol is suitable to maintain anesthesia in horses for various procedures of considerable duration. Cardiopulmonary function was well maintained and recoveries were of exceptionally good quality.