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September 13, 1976

Nitrous Oxide in Myocardial Infarction-Reply

Author Affiliations

Perth Medical Centre Perth, Western Australia

JAMA. 1976;236(11):1238. doi:10.1001/jama.1976.03270120015012

Evaluation of possible adverse effects of inhaling nitrous oxide in the presence of myocardial infarction was a major concern of our study. Our findings demonstrating the safety of 35% nitrous oxide in 89 patients with acute myocardial infarction concur with the more detailed hemodynamic studies of Kerr et al1 using 50% nitrous oxide. Nevertheless, no effective therapeutic agent is entirely free of adverse effects. Dr Dolan's comments emphasize the need for careful supervision, especially when the patient begins inhaling nitrous oxide.

Dr Dolan's major point of disagreement is based on the reports of adverse hemodynamic effects in patients receiving nitrous oxide and high dose morphine (0.5 to 3.0 mg/kg) during cardiac surgery. These dose levels are 35 to 210 mg for a 70-kg man, many times the "usual" dose of morphine, 5 to 10 mg. It seems unlikely (and it was not observed in our study) that