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
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.