Impact of overweight and pneumoperitoneum on hemodynamics and oxygenation during prolonged laparoscopic surgery

Anesthesia adversely affects respiratory function and hemodynamics in obese patients. Although many studies have been performed in morbidly obese patients, data are limited concerning overweight patients [BMI 25-29.9 kg m(-2)]. The aim of this study was to evaluate the effects of prolonged pneumoperitoneum in Trendelenburg position on hemodynamics and gas exchange in normal and overweight patients.

We studied 15 overweight and 15 non-obese [BMI 18.5-24.9 kg m(-2)] patients who underwent totally endoscopic robot-assisted radical prostatectomy under general anesthesia with an inspired oxygen fraction of 0.5. A standardized anesthetic regimen was used, and patients were examined at standard times: after induction of anesthesia and Trendelenburg posture, every 30 minutes after establishing pneumoperitoneum, and after the release of the pneumoperitoneum with the patient still in Trendelenburg position.

After induction of anesthesia and Trendelenburg positioning arterial oxygen pressure [P(a)O2] and alveolar-arterial difference in oxygen tension [A(a)DO2] differed significantly between both groups with lower P(a)O2 [235 +/- 27 versus 164 +/- 51 mmHg] and higher A(a)DO2 [149 +/- 48 versus 76 +/- 28 mmHg] values in overweight patients. During pneumoperitoneum, P(a)O2 transient increased above baseline values in overweight patients, whereas A(a)DO2 decreased. Hemodynamic parameters [HR, MAP, and CVP] did not differ significantly between groups.

Arterial oxygenation and A(a)DO2 are significantly impaired in overweight patients under general anesthesia in Trendelenburg posture. In overweight patients pneumoperitoneum transient reduced the impairment of arterial oxygenation and lead to a decrease in A(a)DO2. Hemodynamic parameters were not affected by body weight.