Hemodynamic changes during laparoscopic gastroplasty in morbidly obese patients

In nonobese patients, peritoneal insufflation has consistently been shown to influence parameters of preload and afterload as well as cardiac output. Obese patients have an abnormal and particular cardiovascular status. The aim of this study was to investigate the hemodynamic changes induced by an increase of intra-abdominal pressure in morbidly obese patients (MOP).

Standard general anesthesia was administered to 15 informed MOP (body mass index > 40 kg/m2) scheduled for laparoscopic gastroplasty. Hemodynamic parameters were measured by thermodilution through a pulmonary artery catheter and through invasive blood pressure monitoring.

CO2 insufflation with an intra-abdominal pressure of 17 mmHg caused a significant increase of mean arterial pressure (MAP) (33%, P = 0.005), mean pulmonary arterial pressure (MPAP) (40%, P = 0.001), pulmonary capillary wedge pressure (PCWP) (41%, P = 0.001), and central venous pressure (CVP) (55%, P = 0.001). The increase in diastolic filling pressures could be due to an increase in the filling volume or to a decrease in diastolic compliance. Ventricular volumes were not measured but we speculate that the rise in CVP, PCWP and MPAP is due to an increase in intrathoracic pressure as judged by the increase of pulmonary airway pressure. Stroke volume fell slightly (11%, P = 0.008), because of a reduction in transmural pressure and a fall in effective preload. Cardiac output rose slightly (16%, P = 0.005) because of an increase in heart rate (15%, P = 0.014) probably induced by sympathetic stimulation, which only became fully operative after 15 minutes.

When compared to nonobese patients our obese patients tolerated the pneumoperitoneum surprisingly well, without experiencing fall in cardiac output. The hemodynamic consequences of peritoneal insufflation seem to be different in obese and nonobese patients.