EVALUATION OF 5 COMMON INDUCTION PROTOCOLS BY COMPARISON OF HEMODYNAMIC-RESPONSES TO SURGICAL MANIPULATION IN HALOTHANE-ANESTHETIZED HORSES

Objective-To determine whether hemodynamic responses of halothane-anes thetized horses undergoing surgical procedures depended on anesthetic induction protocols used, and to determine whether hemodynamic respons es to surgical manipulation could be detected. Design-Prospective expe rimental study without controls. Animals-36 clinically normal horses. Procedure-Horses were allotted to 5 groups according to anesthetic ind uction protocol: acepromazine/guaifenesin/thiamylal, acepromazine/guai fenesin/ketamine, xylazine/guaifenesin/thiamylal, xylazine/guaifenesin /ketamine, and xylazine/diazepam/ketamine. Anesthesia was maintained w ith halothane. Hemodynamic measurements and blood gas values were obta ined prior to the start of surgery, during surgery, and after surgery. Results-Few differences in hemodynamic measurements existed between h orses in which anesthesia was induced by 5 anesthetic induction protoc ols, whether prior to the start of surgery or for pooled values for al l 3 measurement periods. Hemodynamic responses to surgical manipulatio n were marked and included increased mean arterial pressure and system ic vascular resistance, and decreased cardiac index and oxygen deliver y. Clinical Implications-Choice of anesthetic induction protocol has l ittle impact on hemodynamic function during surgery in halothane-anest hetized horses. Surgical stimulation may increase blood pressure, but does not improve cardiac index or oxygen delivery.