Nitrous Oxide May Up Risk of Myocardial Infarction

Nitrous oxide anesthesia linked to increased long-term risk of myocardial infarction, not death

THURSDAY, March 10 (HealthDay News) -- The administration of nitrous oxide in surgeries longer than two hours is linked to an increased long-term risk of myocardial infarction (MI), but not death or stroke, according to a report in the February issue of Anesthesia & Analgesia.

Kate Leslie, M.B.B.S., M.D., from the Royal Melbourne Hospital in Australia, and colleagues evaluated the risk of long-term cardiovascular events in patients exposed to nitrous oxide for an extended period of time. The researchers identified 2,050 ENIGMA trial participants who had noncardiac surgery lasting more than two hours and had been randomized to receive either nitrous oxide-based or nitrous oxide-free anesthesia.

The researchers found that, after an average 3.5 years of follow-up, nitrous oxide did not appear to significantly increase the risk of death (hazard ratio, 0.98). They found that 91 (4.5 percent) of the patients had an MI and 44 (2.2 percent) had a stroke. The adjusted odds ratio for MI in the patients who received nitrous oxide was 1.59 (P = 0.04) and for stroke was 1.01 (P = 0.97).

"The administration of nitrous oxide was associated with increased long-term risk of MI but not of death or stroke in patients enrolled in the ENIGMA trial. The exact relationship between nitrous oxide administration and serious long-term adverse outcomes requires investigation in an appropriately designed large randomized controlled trial," the authors write.

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