Hyperaldosteronism after heart surgery in children. Part II: Regulation of aldosterone secretion

The relative importance of the various mechanisms responsible for development of postoperative hyperaldosteronism (HA) is not known. Therefore, serum sodium (NA), plasma-renin activity (PRA) and plasma cortisol (PC) were evaluated in pediatric patients with transient HA following heart surgery. PRA and PC were elevated and NA was depressed postoperatively. Plasma aldosterone (PA) was negatively correlated with NA (r = -0.77; p less than 0.001) and positively correlated with PRA (r = 0.68; p less than 0.01) but was not significantly correlated with PC. PRA and NA were significantly negatively correlated (r = 0.53; p less than 0.005). Multiple regression analysis revealed that NA had the strongest influence on PA, with PRA having a somewhat lesser but still significant influence; PC had no influence. Despite the significant negative correlation between PRA and NA, the interaction of the two variables in influencing PA was not significant (partial F-test; F = 0.12; p greater tha 0.5). It is concluded that in the postoperative state sodium depletion stimulates secretion of aldosterone not only via the angiotensin-renin system but also in a significant manner by a mechanism unrelated to the angiotensin-renin system. ACTH does not seem to play an important role in postoperative HA.