Changes in cortisol concentration in response to stress and postoperative pain in client-owned cats and correlation with objective clinical variables.

OBJECTIVE: To identify clinical variables that indicate postoperative pain in cats after ovariohysterectomy in a veterinary hospital setting. ANIMALS: 40 cats. PROCEDURE: Cats were anesthetized and ovariohysterectomized by senior veterinary students. Butorphanol (0.1 mg/kg [n = 20] or 0.3 mg/kg [20] of body weight) was administered IM after surgery. Blood samples were obtained before, during, and after the anesthetic period for measurements of PCV and blood glucose and cortisol concentrations. Clinical variables measured included heart rate, systolic blood pressure, respiratory rate, and rectal temperature. Data for these variables were compared with changes in cortisol concentrations and with similar data-which was used as historical control data-obtained from 20 cats in another study (10 that had been ovariohysterectomized but had not received butorphanol and 10 that had only been anesthetized).
RESULTS: Surgical durations were longer in this study, and cats had higher cortisol concentrations, compared with historical control cats. Objective clinical variables did not consistently correlate with changes in cortisol concentration.
CONCLUSIONS: Cortisol concentration increased in response to surgical stress and pain. This response was greater in cats in which duration of surgery was longer. CLINICAL RELEVANCE: The objective clinical variables evaluated in this study were not consistent indicators of pain in an uncontrolled, clinical situation.