Hazards of Nitrous Oxide Anesthesia in Bowel Obstruction and Pneumothorax

Abstract

An enclosed gas-filled space in the body will expand if gas within it is less soluble than the gas respired. Blood arriving at such a space can discharge a greater quantity of the soluble gas into the space than that blood can take up, assuming the tension gradient of each gas is equal. This results from the greater capacity of blood for the more soluble agent. When air was placed in the intestinal lumens of 3 dogs and nitrous oxide respired, intestinal gas volume increased 75 to 100% in 2 hours and 100-200% in 4 hours. Similarly, 300 ml of air placed in the pleural space doubled in volume in 10 minutes, tripled in 45 minutes, and in one dog quadrupled in 2 hours. Nitrous oxide concentrations rose concomitantly in both the intestinal and pleural spaces. With either gas in the intestine or in the pleural space, no volume changes were seen when the animal respired oxygen and halothane alone. These results suggest that nitrous oxide is relatively contraindicated in cases of intestinal obstruction or pneumothorax.