Hemodynamic and respiratory changes in surgery of the morbidly obese.

The risk of surgery for the morbidly obese is well known. Suprisingly little information is available regarding the hemodynamic changes during surgery. This study provides data on this important subject and compares them with those of normal nonobese patients. Obese patients demonstrated signifying elevated preoperative, intraoperative, and postoperative right atrial, mean pulmonary artery, and pulmonary artery wedge pressures. Preoperatively, hemodynamic variables were in the high range of normal in obese patients. Significantly greater decreases in cardiac index, right ventricular stroke work (RVSW), and left ventricular stroke work (LVSW) were noticed intraoperatively. Although the RVSW returned to baseline values in the postoperative period, the cardiac index and LVSW remained depressed. Left ventricular function as assessed by Sarnoff curves demonstrated persistent shifts to the right during and after operation. No such shifts were noticed in nonobese patients. Although they were hemodynamically stable and without any other clinical evidence of cardiac abnormality, asymptomatic obese patients had reduced left ventricular contractility (LVSW/pulmonary artery wedge [PAW] pressure ratio) even in the resting state. Obese patients reacted to the stress of surgery and anesthesia by a more specific left ventricular dysfunction that was greater after intubation and in the immediate postoperative period.