The effect of daily repeated sedation using ketamine or ketamine combined with medetomidine on physiology and anesthetic characteristics in Rhesus Macaques

Background Non-human primates are frequently sedated to permit handling that can alter physiological values. The purpose of this study was to identify the effects of daily serial sedation using ketamine (K) or ketamine combined with medetomidine (KM). We hypothesized KM would reduce observed effects of repeated sedation. Methods Eight rhesus macaques were anesthetized for three consecutive days. Physiological data were recorded daily at 5-minute intervals. Time intervals from injection to ataxia, recumbency, first movement and recovery were recorded. Depth of anesthesia was evaluated. Results Data showed an 11.7% increased heart rate at 5 minutes between the first and third day of injection with K and 17.9% with KM. Time from injection to ataxia increased 13.7% with K and 14.3% with KM. Time to recumbency increased 34.7% with K and 37.1% with KM. Conclusion These findings demonstrate repeated anesthesia with ketamine can initiate changes suggesting a tolerance effect.