Pneumoperitoneum in healthy humans does not affect central blood volume or cardiac output

Background: This study addresses the question of whether the elevation of the mean arterial pressure and central venous pressure in response to pneumoperitoneum for laparoscopic surgery is caused by increases in central blood volume and/or cardiac output. Methods: Eleven patients in good cardiopulmonary health and scheduled for laparoscopic cholecystectomy, with a mean age of 42 years, were included. After induction of anaesthesia with fentanyl and propofol, radial arterial and central venous lines were introduced. The central blood volume and cardiac output were determined by the indicator-dilution technique, using inline densitometric measurements of indocyanine green (ICG). The measurements were made before and after the establishment of pneumoperitoneum by insufflation of carbon dioxide to an intra-abdominal pressure level of 11-13 mmHg. Results: The mean arterial pressure (62+/-6 mmHg) increased after induction of pneumoperitoneum by 40+/-26% (P<0.05) and the central venous pressure increased from 6+/-4 mmHg to 8+/-6 mmHg (P<0.05). The cardiac output (4.3+/-0.9 L/min) and central blood volume (1.5+/-0.5 L) were not affected by the induction of pneumoperitoneum. Conclusions: In healthy anaesthetized subjects, the elevation of mean arterial pressure and central venous pressure in response to pneumoperitoneum was not caused by enhancement in cardiac output or central blood volume.