Haemodynamic effects of pneumoperitoneum for laparoscopic surgery: a comparison of CO2 with N2O insufflation

We studied the haemodynamic effects of intra-abdominal insufflation with either CO2 (n = 15) or N2O (n = 15) in patients undergoing laparoscopic surgery. Haemodynamic variables were measured at increasing levels of intra-abdominal pressure up to 20 mmHg. In the CO2 group cardiac index decreased from 2.6 +/- 0.6 to 2.0 +/- 0.4 litre min-1 m-2 (mean +/- SD, P < 0.001) and in the N2O group from 2.6 +/- 0.5 to 1.8 +/- 0.4 litre min-1 m-2 (P < 0.001)). In the CO2 group, this was accompanied by increases in mean arterial pressure, systemic vascular resistance index and central venous pressure without change in heart rate. In contrast, during N2O insufflation mean arterial pressure decreased (from 77 +/- 8 to 63 +/- 15 mmHg (P < 0.001)) without change in vascular resistance. No further changes in haemodynamic variables were observed during head-up tilt in both groups. After desufflation mean arterial pressure increased in the N2O group to pre-insufflation levels and cardiac index increased in both groups (P < 0.001), but reached pre-insufflation levels only in the CO2 group. In both groups central venous O2 tension and saturation decreased at maximum intra-abdominal pressure and increased after release of the pneumoperitoneum. The results indicate that laparoscopic insufflation with either CO2 or N2O results in cardiovascular depression. Insufflation with N2O may decrease blood pressure, whereas mean arterial pressure is better preserved with CO2 insufflation.