Alfaxalone is a synthetic neurosteroid anesthetic used in many countries as an IV induction agent. Similar to propofol in regard to good quality of anesthetic induction and cardiopulmonary variables, it may be given IV to effect or as a continuous rate infusion. It is unclear, however, if alfaxalone provides any analgesia. Ketamine and medetomidine are often used in cats in combination for premedication and induction. This combination is known to provide good anesthesia and some postoperative analgesia.
The objective of this prospective, blinded study was to compare physiologic parameters and postoperative pain in cats undergoing ovariohysterectomy (OHE) using alfaxalone vs ketamine-medetomidine anesthesia. Twenty-one cats were randomly divided into 2 groups. One group received alfaxalone at 5 mg/kg IV, followed by 2 mg/kg IV boluses given if response to surgical stimuli or a 20% increase in blood pressure over anesthetic baseline were noted. The second group received medetomidine at 30 µg/kg IM followed by ketamine at 5 mg/kg IV; 2 mg/kg IV ketamine was given as described for alfaxalone. All cats received meloxicam at 0.2 mg/kg IV postoperatively. Postoperative physiologic parameters, sedation, and pain were assessed at multiple times. Results showed that ketamine-medetomidine produced better analgesia after OHE than alfaxalone. Both groups, however, developed a primary hyperalgesia. The authors suggest that alfaxalone is appropriate for the induction and maintenance of anesthesia for OHE in cats but that additional sedatives and analgesics should be given.