Myocardial Blood Flow and Oxygen Consumption during High-dose Fentanyl Anesthesia in Patients with Coronary Artery Disease

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Abstract
The effects of high dose fentanyl-O2 anesthesia (100 .mu.g/kg) on myocardial blood flow, myocardial O2 consumption, myocardial lactate balance and cardiovascular dynamics were studied in 9 patients undergoing 3 vessel coronary artery bypass operations. All patients were on maintenance doses of a .beta.-receptor blocker (pindolol). Except for pindolol all medication was discontinued 48 h prior to the study. Measurements were performed in the awake state, after 10 .mu.g/kg fentanyl, after 100 .mu.g/kg fentanyl and during sternotomy. Moderate doses of fentanyl (10 .mu.g/kg) produced minimal changes in myocardial blood flow, myocardial O2 consumption and cardiovascular dynamics; myocardial O2 balance was well maintained. Large doses of fentanyl (100 .mu.g/kg) produced a 16% decrease in mean aortic pressure, cardiac index did not change significantly, while stroke volume index decreased by 23%. Myocardial O2 consumption decreased by 14% and myocardial blood flow by 10%. Myocardial lactate production was observed in 5 patients, indicating myocardial ischemia. During sternotomy arterial pressure and heart rate increased 8 and 29%, respectively, resulting in an increase in myocardial work, as reflected by a 38% increase in myocardial O2 consumption and by a 54% increase in myocardial blood flow. Myocardial lactate production was observed in 7 of 9 patients. Evidently in patients on maintenance doses of .beta.-receptor blockers, large doses of fentanyl as the sole anesthetic produce incomplete anesthesia and fail to protect the myocardium from ischemia due to noxious stimuli during coronary artery surgery.