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GENERAL ARTICLES

Calibrated Pneumoperitoneal Venting to Prevent N₂O Accumulation in the CO₂ Pneumoperitoneum During Laparoscopy with Inhaled Anesthesia: An Experimental Study in Pigs

Pierre A. Diemunsch, MD^*, Thomas Van Dorsselaer^*, Klaus D. Torp, MD^*, Roland Schaeffer, MD^*, and Bernard Geny, MD, PhD

*Département d’Anesthésiologie, I.R.C.A.D., Hôpitaux Universitaires, Strasbourg, France; and Institut de Physiologie, Faculté de Médecine, Strasbourg, France

Address correspondence and reprint requests to Pierre A. Diemunsch, MD, I.R.C.A.D., Hôpitaux Universitaires, 1, Place de l’Hôpital, 67000 Strasbourg, France.

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.

IMPLICATIONS: External venting calibrated at four or eight initial pneumoperitoneal volumes per hour with compensation by fresh CO₂ is sufficient to prevent nitrous oxide buildup of more than 10% in the pneumoperitoneum during laparoscopy with inhaled general anesthesia if venting is constant.