Rationale: Cardiac output (CO) response to pneumoperitoneum is difficult to predict because of multiple, often contradictory physiologic effects. It remains uncertain whether arterial waveform variables can predict changes in CO during pneumoperitoneum. We hypothesized that changes of arterial waveform variables following pneumoperitoneum will correlate with CO changes.

Objectives: Patients scheduled for major elective laparoscopic surgery were recruited to the study. CO and stroke volume variation (SVV) were continuously monitored by non-invasive cardiac output monitor (NICOM). Arterial waveforms were recorded before and during pneumoperitoneum of 15 mmHg. Systolic and pulse pressure variations (SPV and PPV) were determined offline.

Findings: Pneumoperitoneum resulted in minimal changes in heart rate and mild increase of mean arterial blood pressure and pulse pressure. Cardiac output decreased significantly following pneumoperitoneum, while SPV and its delta down (dDown) component increased by 34 and 23%, respectively. Changes in SVV and PPV were not significant. Baseline SPV, PPV and dDown correlated weakly with changes in CO caused by pneumoperitoneum. Changes in dDown and PPV following PnP correlated with changes in CO (r=-0.385, P=0.002; r=-0.274, P=0.034, respectively), while those in SPV and SVV did not.

Conclusion: Our study has shown that CO changes following pneumoperitoneum are preload dependent. Arterial waveform variables, especially dDown, correlated significantly with changes in CO during pneumoperitoneum.