Impact of carbon dioxide and helium insufflation on cardiorespiratory function during prolonged pneumoperitoneum in an experimental rat model

Background: Experimental studies on laparoscopic surgery are often performed in rats, However, the hemodynamic and respiratory responses related to the pneumoperitoneum. have not been studied extensively in rats. Therefore, the aim of this study was to investigate in spontaneously breathing rats the effects of CO(2) and helium, insufflation pressure, and duration of pneumoperitoneum on blood pressure, arterial pH, PCO(2), pO(2), HCO((3) over bar), base excess, and respiratory rate. Methods: Five groups of 9 Brown Norway rats were anesthetized and underwent CO(2) insufflation (6 or 12 mmHg), helium insufflation (6 or 12 mmHg), or abdominal wall lifting (gasless control) for 120 min, Blood pressure was monitored by an indwelling carotid artery catheter. Baseline measurements of mean arterial pressure (MAP), respiratory rate, arterial blood pH, pCO(2), pO(2), HCO((3) over bar), and base excess were recorded. Blood gases were analyzed at 5, 30, 60, 90, and 120 min during pneumoperitoneum, and MAP and respiratory rate were recorded at 5 and 15 min and at 15-min intervals thereafter for 2 h. Results: CO(2) insufflation (at both 6 and 12 mmHg) caused a significant decrease in blood pH and increase in arterial pCO(2). Respiratory compensation was evident since pCO(2) returned to preinsufflation levels during CO(2) insufflation at 12 mmHg. There was no significant change in blood pH and pCO(2) in rats undergoing either helium insufflation or gasless procedures. Neither insufflation pressure nor the type of insufflation gas had a significant effect on MAP over time. Conclusion: The cardiorespiratory changes during prolonged pneumoperitoneum in spontaneously breathing rats are similar to those seen in clinical practice. Therefore, studies conducted in this animal model can provide valuable physiological data relevant to the study of laparoscopic surgery.