Role of sympathoadrenal and renin-angiotensin system in hemodynamic state after coronary artery bypass grafting.

To evaluate the role of the sympathoadrenal and renin-angiotensin systems in postoperative hemodynamic state, plasma concentrations of catecholamines, renin activity, angiotensin, and aldosterone as well as hemodynamics were studied following coronary artery bypass grafting in 55 patients. The patients were divided into four groups: 1) uneventful, 2) hypertension (HT), 3) hypotension for which cateeholamines were administered (CAT), and 4) perioperative myocardial infarction (POMI). The mean cardiac index in the HT group was higher than that in the Uneventful group and some patients in the HT group showed high adrenaline level. A group of patients who had a hypertensive episode and then sustained low cardiac output state (HT-to-LOS group) showed marked elevation of systemic vascular resistance index and noradrenaline level. These findings suggest that the hypertensive episodes in the HT-to-LOS group may be primarily caused by the activation of the sympathetic nerve system and that those of some patients in the HT group may be caused by marked adrenal medullary secretion. Five patients (56%) in the HT group showed plasma renin activity of more than 5.0 ng/ml/hr. and three patients (33%) showed angiotensin II of more than 100 pglml. Thus, postoperative hypertension seems to be multifactorial in nature. The POMI group represented significant elevation of plasma adrenaline concentration and significantly low sensitivity to catecholamines of the ventricle accompanied with impaired left ventricular performance. Although the mean aldosterone level in the CAT group was significantly higher than that in the Uneventful group, only a few patients of the CAT group demonstrated marked elevation of aldosterone concentration which might cause a vicious circle to develop. Clinical significance of modest increase of aldosterone concentration in other patients in the CAT group is questionable.