Sympathetic nervous system tonicity and post-coronary artery bypass hypertension.

To elucidate the pathogenesis of hypertension following coronary bypass surgery, blood pressure and plasma catecholamine concentration were measured in 28 patients with coronary artery disease who were undergoing myocardial revascularization procedures. Measurements were obtained on arrival in the operating room and 1 and 4 h after surgery. One hour after surgery, plasma norepinephrine (NE) increased significantly by 495 +/- 108 pg/ml (P less than 0.001) in the coronary artery disease group which developed hypertension, but the increase was not significant in the coronary artery patients who remained normotensive after surgery. However, 4 h after surgery, plasma NE increased significantly and to the same extent in both coronary artery disease groups, regardless of the change in blood pressure. Plasma epinephrine (E) also increased significantly 1 and 4 h after surgery in both groups. The observed change in plasma catecholamine concentration is direct evidence that the stress of surgery is a potent adrenergic stimulus, but the hemodynamic significance of the plasma catecholamine change remains unclear.