Evaluation of hemodynamic measurements, including lithium dilution cardiac output, in anesthetized dogs undergoing ovariohysterectomy.

OBJECTIVE To measure cardiac output in healthy female anesthetized dogs by use of lithium dilution cardiac output and determine whether changes in mean arterial pressure were caused by changes in cardiac output or systemic vascular resistance. DESIGN Prospective clinical study. ANIMALS 20 healthy female dogs. PROCEDURE Dogs were anesthetized for ovariohysterectomy. Ten dogs breathed spontaneously throughout anesthesia, and 10 dogs received intermittent positive-pressure ventilation. Cardiovascular and respiratory measurements, including lithium dilution cardiac output, were performed during anesthesia and surgery. RESULTS Mean arterial pressure and systemic vascular resistance index were low after induction of anesthesia and just prior to surgery and increased significantly after surgery began. Cardiac index (cardiac output indexed to body surface area) did not change significantly throughout anesthesia and surgery. CONCLUSIONS AND CLINICAL RELEVANCE Results provide baseline data for cardiac output and cardiac index measurements during clinical anesthesia and surgery in dogs. Changes in mean arterial pressure do not necessarily reflect corresponding changes in cardiac index.