Intraoperative changes in blood pressure, heart rate, plasma vasopressin, and urinary noradrenalin during elective ovariohysterectomy in dogs: repeatability at removal of the 1st and 2nd ovary.

Objective: To investigate the physiologic reactions after removal of 1st ovary and whether this is repeated during removal of the 2nd ovary in elective ovariohysterectomy.

Study Design: Prospective study.

Animals: Dogs (n = 10).

Methods: Dogs were premedicated with acepromazine, carprofen, and methadone and anesthetized with propofol and isoflurane. Blood pressure, heart rate, and end-tidal isoflurane concentration were measured every minute. The effects of various events during surgery on physiologic variables were analyzed using mixed linear models. Blood and urine samples were collected before anesthesia, before incision, before and after removal of ovaries with a 15 minute pause between ovary removal, and after abdominal closure. Plasma vasopressin and urinary noradrenalin and creatinine concentrations were analyzed.

Results: The magnitude of blood pressure increase at removal of the 1st ovary was greater than for the 2nd ovary because of an elevation in baseline. Similarly, the heart rate increased at the removal of the 1st ovary but not at removal of the 2nd ovary. Plasma vasopressin concentration increased at removal of both ovaries. Urinary noradrenalin/creatinine ratio increased at anesthesia, removal of both ovaries, and was elevated at closure of the abdomen. End-tidal isoflurane concentration did not change. Blood pressure and vasopressin concentrations changed in parallel using z-scores for comparison.

Conclusions: Peak values for blood pressure, heart rate, plasma vasopressin concentration, and urinary noradrenalin/creatinine ratio did not differ between removals of the ovaries. Relative changes differed between repeated noxious stimuli, which should be considered in evaluation of methods at ovary removal.