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Evaluation of five common induction protocols by comparison of hemodynamic responses to surgical manipulation in
A E Wagner1, C I Dunlop, E M Wertz
1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Fort Collins, CO, USA.
Objective:
To determine whether hemodynamic responses of halothane-anesthetized horses undergoing surgical procedures depended on anesthetic induction protocols used, and to determine whether hemodynamic responses to surgical manipulation could be detected.
Design:
Prospective experimental study without controls.
Animals:
36 clinically normal horses.
Procedure:
Horses were allotted to 5 groups according to anesthetic induction protocol: acepromazine/guaifenesin/thiamylal, acepromazine/guaifenesin/ketamine, xylazine/guaifenesin/thiamylal, xylazine/guaifenesin/ketamine, and xylazine/diazepam/ketamine. Anesthesia was maintained with halothane. Hemodynamic measurements and blood gas values were obtained prior to the start of surgery, during surgery, and after surgery.
Results:
Few differences in hemodynamic measurements existed between horses in which anesthesia was induced by 5 anesthetic induction protocols, whether prior to the start of surgery or for pooled values for all 3 measurement periods. Hemodynamic responses to surgical manipulation were marked and included increased mean arterial pressure and systemic vascular resistance, and decreased cardiac index and oxygen delivery.
Clinical Implications:
Choice of anesthetic induction protocol has little impact on hemodynamic function during surgery in halothane-anesthetized horses. Surgical stimulation may increase blood pressure, but does not improve cardiac index or oxygen delivery.