Multivariate analysis of factors associated with post-anesthetic times to standing in isoflurane-anesthetized horses: 381 cases

Objective  To identify anesthesia-related variables which may independently predict time to standing in horses anesthetized with ketamine/diazepam/isoflurane.
Study design  Retrospective case series.
Animals  Three hundred and eighty-one horses.
Methods  Case records were searched for the years 2000–2003 and 381 horses older than 12 months which weighed at least 200 kg were identified. Data were extracted from the records, and only horses that were anesthetized with xylazine, ketamine, diazepam and isoflurane were included in the analysis. Multiple linear regression was used to relate time to standing with demographic, intraoperative and anesthetic variables.
Results  Most (326; 86%) horses recovered unassisted and 55 (14%) were assisted in recovery. The model for unassisted recovery had an R ² of 0.228 with colic ( p  < 0.0001), anesthesia duration ( p  < 0.02), temperature nadir ( p  < 0.02) and duration of hypotension ( p  < 0.0001) being significant predictors of time to standing. The final model for predicting assisted recovery time had an R ² of 0.314 with emergency status ( p  < 0.0001), warm-blood breed ( p  < 0.04) and intraoperative administration of ketamine ( p  < 0.004) being the significant predictor.
Conclusions and clinical relevance  Variables which could be impacted by the anesthetist which would result in a faster time to standing include duration of anesthesia, hypothermia and intraoperative hypotension. However, the contribution of anesthesia factors explained <23% of the variability in recovery time, suggesting that other, more important factors contribute to anesthesia recovery time in horses.