Calibrated pneumoperitoneal venting to prevent N₂O accumulation in the CO₂ pneumoperitoneum during laparoscopy with inhaled anesthesia: An experimental study in pigs

Nitrous oxide (N₂O) accumulates in the CO₂ pneumoperitoneum during laparoscopy when N₂O is used as an adjuvant for inhaled anesthesia. This may worsen the consequences of gas embolism and introduce a fire risk. In this study, we quantified the pneumoperitoneal gas venting necessary to prevent significant contamination by inhaled N₂O. Four domestic pigs (26-30 kg) were anesthetized and ventilated with 66% N₂O in oxygen. A CO₂ pneumoperitoneum was insufflated and maintained at a pressure of 12 mm Hg. Each animal underwent three experimental conditions, in random sequence, for 70 min each: 1) no pneumoperitoneal leak, 2) leak of 2 L every 10 min (12 L/h), and 3) leak of 4 L every 10 min (24 L/h). Every 10 min, pneumoperitoneal gas samples were analyzed for fractions (FPn) of N₂O and CO₂. Without leaks, FPnN₂O increased continually and reached 29.58% ± 3.15% at 70 min. With leaks of 2 and 4 L every 10 min (12 and 24 L/h), FPnN₂O reached a plateau of <10% after 30 min. We conclude that calibrated pneumoperitoneal venting of 12 or 24 L/h is enough to prevent the constitution of potentially dangerous pneumoperitoneal gas mixtures if venting is constant.