Adrenergic Response to Morphine-Diazepam Anesthesia for Myocardial Revascularization

Abstract

To evaluate sympathetic nervous system activity during narcotic-hypnotic “balanced anesthesia,” plasma catecholamine concentrations and hemodynamic variables were assessed simultaneously in 10 men with coronary artery disease who received, sequentially, morphine sulfate, 3 mg/kg IV, and diazepam, 0.25 to 0.35 mg/kg IV, for myocardial revascularization surgery. Infusion of morphine sulfate at rates of 5 to 10 mg/min significantly decreased both mean systemic arterial pressure (from 98 ± 6 to 84 ± 5 torr, p < 0.01) and systemic vascular resistance index (from 38 ± 3 to 30 ± 5 units, p < 0.05). These changes were associated with 2-fold increases in plasma norepinephrine levels (from 246 ± 31 to 488 ± 85 pg/ml, p < 0.01) and 4-fold increases in plasma epinephrine levels (from 129 ± 20 to 570 ± 182 pg/ml, p < 0.01). Addition of diazepam further decreased systemic arterial pressure (from 84 ± 5 to 73 ± 3 torr, p < 0.01) and was associated with significant decreases in cardiac and stroke volume indices when compared with values obtained after morphine sulfate alone. Plasma concentrations of both norepinephrine and epinephrine also declined in association with these hemodynamic changes. Following skin incision, systemic arterial pressure and systemic vascular resistance index increased, the latter to the highest measured value (50 units). Norepinephrine concentrations increased significantly more than it had after morphine-diazepam anesthesia (321 ± 63 pg/ml). It was concluded that the administration of high dose morphine anesthesia acutely activates the sympathoadrenal system while producing peripheral vasodilation. Diazepam, when used following morphine to assure loss of consciousness, exacerbates the hypotensive effects produced by morphine and is associated with decreased levels of plasma catecholamines. Surgical incision produces significant peripheral sympathetic activation and increases vascular resistance during morphine-diazepam anesthesia.