Effects of acetylpromazine or morphine on urine production in halothane-anesthetized dogs

Objective-To assess the influence of preanesthetic administration of acetyl promazine or morphine and fluids on urine production, arginine vasopressin (AVP; previously known as antidiuretic hormone) concentrations, mean arteri al blood pressure (MAP), plasma osmolality (Osm), PCV, and concentration of total solids (TS) during anesthesia and surgery in dogs. Animals-19 adult dogs. Procedure-Concentration of AVP indirect MAP Osm, PCV, and concentration of TS were measured at 5 time points (before administration of acetylpromazine or morphine, after administration of those drugs, after induction of anest hesia, I hour after the start of surgery, and 2 hours after the start of su rgery). Urine output and end-tidal halothane concentrations were measured 1 and 2 hours after the start of surgery. All dogs were administered lactate d Ringer's solution (20 ml/kg of body weight/h, IV) during surgery. Results-Compared with values for acetylpromazine, preoperative administrati on of morphine resulted in significantly lower urine output during the surg ical period. Groups did not differ significantly for AVP concentration, Osm , MAP and end-tidal halothane concentration; however, PCV and concentration of TS decreased over time in both groups and were lower in dogs given acet ylpromazine. Conclusions and Clinical Relevance-Preanesthetic administration of morphine resulted in significantly lower urine output, compared with values after a dministration of acetylpromazine, which cannot be explained by differences in AVP concentration or MAP When urine output is used as a guide for determ ining rate for IV administration of fluids in the perioperative period, the type of preanesthetic agent used must be considered.