Hypertension and the renin-angiotensin system following open-heart surgery
Taylor, K.M.; Morton, I.J.; Brown, J.J.; Bain, W.H.; Caves, P.K.
Journal of Thoracic and Cardiovascular Surgery 74(6): 840-845
1977
ISSN/ISBN: 0022-5223 PMID: 303727 Document Number: 117668
Plasma angiotensin II (AII) levels were measured by radioimmunoassay in 10 patients subjected to open-heart surgical procedures using standard normothermic, nonpulsatile bypass (bypass group) and in 6 patients subjected to closed mitral valvotomy (control group). In both groups, plasma AII levels were normal preoperatively (< 35 pg/ml) and rose slightly after the chest was opened (< 60 pg/ml in both groups). In the bypass group, plasma AII levels rose markedly during the period of extracorporeal circulation (ECC) to a mean level of 170 pg/ml .+-. 33 SEM AII levels fell rapidly and had returned to normal 4-24 h after the operation in all but 1 patient. In this patient there was a progressive rise in AII postoperatively to a plasma AII level of 385 pg/ml at 24 h. He died 48 h after the operation from low cardiac output associated with subendocardial necrosis. There was no further rise in AII levels during or after the operation in the control group (P < 0.01). Marked elevation in the plasma AII level occurs during and for several hours after nonpulsatile cardiopulmonary bypass (CPB). The renin-angiotensin system plays an important role in the occurrence of peripheral vasoconstriction and hypertension in the early postoperative period. It may be an important factor in the production of the low-output syndrome.