The Effects of Nitrous Oxide on Myocardial Metabolism and Hemodynamics during Fentanyl or Enflurane Anesthesia in Patients with Coronary Disease

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Abstract
Twenty patients about to have coronary artery bypass grafts were studied before and after 15 min of 50% N2O added to either fentanyl (75 .mu.g/kg) or enflurane (0.5%) anesthesia. Arterial and central pressures and cardiac output were measured, plus coronary sinus blood flow and arterio-coronary sinus differences in O2, Hb and lactate contents. Fentanyl-N2O and enflurane-N2O both decreased systemic resistance, heart rate, cardiac output, and hence arterial pressure. Stroke work decreased significantly with little or no change in wedge pressure; ventricular function was impaired. coronary flow and myocardial O2 consumption decreased with fentanyl-N2O. O2 extraction increased with enflurane-N2O, as did lactate contents of coronary sinus blood. Hemodynamic depression occurred from the combined effects of N2O and fentanyl or enflurane. The .beta.-blocked myocardia of nonstimulated coronary patients were becoming ischemic globally on 50% O2, after significant hypotension. From this and other evidence, it is concluded that N2O may not be benign in patients with coronary arterial disease.

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