THE EFFECT OF 4 DIFFERENT SURGICAL PRONE POSITIONS ON CARDIOVASCULAR PARAMETERS IN HEALTHY-VOLUNTEERS

Twenty healthy volunteers were placed in four different surgical prone positions: on pillows, on an evacuatable mattress, on pelvic props an d in the knee-chest position. The normal supine position was used as a control for the measurement of cardiovascular parameters. Mean arteri al pressure was measured by automated oscillotonometry. Transthoracic electrical bioimpedance was used to measure cardiac output and heart r ate. Cardiac index and total vascular resistance index were derived fr om these data. No significant changes in heart rate or mean arterial p ressure occurred when the volunteers were moved from the supine positi on to any of the four prone positions or when returned to the supine p osition again. Cardiac index decreased significantly on going front th e supine to the knee-chest position (20%) and onto the props (17%) but not onto the evacuatable mattress (11%) or the pillows (3%).