Hemodynamic Changes during Fentanyl—Oxygen Anesthesia for Aortocoronary Bypass Operation

Abstract

Fentanyl in doses of 50-60 .mu.g/kg produced anesthesia with remarkable hemodynamic stability in patients with coronary artery disease (CAD). As hypertension and tachycardia was observed in response to noxious stimulation during aortocoronary bypass (ACB) operations in fentanyl anesthetized patients hemodynamic changes and anesthetic conditions produced by fentanyl/O2 per relaxant anesthesia was studied in patients undergoing elective ACB. Twelve patients with left ventricular (LV) ejection fractions > 0.4 were maintained on propranolol until 10 h before operation and were premediated with fentanyl, diazepam and scopolamine. Cannulae were inserted before the study commenced for measurement of intravascular pressures, arterial blood gases and thermodilution cardiac output. The patients breathed 100% O2 throughout the study. Controlled ventilation aided by succinylcholine to reduce truncal rigidity maintained Pa[aterial partial pressure]CO2 at 30-45 torr. Measurements were made after each of the following: breathing O2 (control), 10 .mu.g/kg fentamyl, 50 .mu.g/kg fentanyl, and 0.1 mg/kg pancuronium, tracheal intubation, skin incision, and sternotomy. Fentanyl produced no significant hemodynamic changes. Fentanyl and pancuronium in combination produced increased heart rate and reduced stroke volume. Significant and progressively greater increases in mean arterial pressure and systemic vascular resistance followed intubation, skin incision, and sternotomy. Chest rigidity occurred in every patient at a lower fentanyl dose than did unresponsiveness. While fentanyl, 62.4 .+-. 2.9 .mu.g/kg (SE), produced minor hemodynamic changes, it failed to block hemodynamic responses to noxious stimulation. Such changes increased cardiac work and could have affected myocardial O2 balance unfavorably. In 8 of the 12 patients, after the last set of measurements, supplementary anesthetic agents were required to maintain hemodynamic stability during the surgical procedure. The fentanyl/O2 per relaxant technique should be modified for patients with severe CAD and reasonably good LV function.