Adrenergic Response to Morphine-Diazepam Anesthesia for Myocardial Revascularization

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 or morphine sulfate rates of 5 to 10 mg/min significantly decreased both mean systemic arterial pressure (from 98 plus or minus 6 to 84 plus or minus 5 torr, p less than 0.01) and systemic vascular resistance index (from 38 plus or minus 3 to 30 plus or minus 5 units, p less than 0.05). These changes were associated with 2-fold increases in plasma norepinephrine levels (from 246 plus or minus 31 to 488 plus or minus 85 pg/ml, p less than 0.01) and 4-fold increases in plasma epinephrine levels (from 129 plus or minus 20 to 570 plus or minus 182 pg/ml, p less than 0.01). Addition of diazepam further decreased systemic arterial pressure (from 84 plus or minus 5 to 73 plus or minus 3 torr, p less than 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 plus or minus 63 pg/ml). It was concluded that the administration oif 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.