Obesity and Goal-directed Intraoperative Fluid Therapy

Overview

The purpose of the study is to compare non-obese patients (BMI≤ 30 kg/m2)versus obese patients (BMI\> 30 kg/m2) in regard of their respective needs for intraoperative fluid therapy during laparoscopic surgery. Specifically the investigators will test the hypothesis that subcutaneous tissue oxygenation (PsqO2)is increased in obese patients when fluid management is optimized by means of esophageal Doppler monitoring compared to obese patients undergoing standard fluid management. Furthermore the investigators will test the hypothesis that PsqO2 is decreased in obese patients undergoing conventional fluid therapy compared to non-obese patients when fluid management is optimized. Thus the investigators assume that PsqO2 is similar in obese and non-obese patients when fluid management is optimized in both groups.

Hemodynamic stability and normovolemia are critical determinants of tissue perfusion and oxygenation. Adequate tissue oxygenation is essential to maintain normal physiologic functions and to reduce complications, such as wound infections. Fat tissue is relatively hypoperfused and, therefore, poorly oxygenated. Subcutaneous tissue oxygenation in the obese is thus critically low and even supplemental oxygen only slightly increases subcutaneous oxygenation.It is likely that poor subcutaneous oxygenation in the obese surgical patients results in part from inadequate intraoperative fluid replacement. It remains unknown how to hydrate obese surgical patients best. The most physiologic approach for perioperative fluid replacement is now thought to be goal-directed management, using stroke volume as the treatment parameter.