Significance of adrenomedullin under cardiopulmonary bypass in children during surgery for congenital heart disease

To elucidate the effect of adrenomedullin (AM) on fluid homeostasis under c ardiopulmonary bypass (CPB), we investigated the serial changes in plasma A M and other parameters related to fluid homeostasis in 13 children (average age, 28.2 months) with congenital heart disease during cardiac surgery und er CPB. Arterial blood and urine samples were collected just after initiati on of anesthesia, just before commencement of CPB, 10 min before the end of CPB, 60 min after CPB, and 24 h after operation. Plasma AM levels increase d significantly 10 min before the end of CPB and decreased 24 h after opera tion. Urine volume increased transiently during CPB, which paralleled chang es in AM. Simple regression analysis showed that plasma AM level correlated significantly with urinary vasopressin, urine volume, urinary sodium excre tion, and plasma osmolarity. Stepwise regression analysis indicated that ur ine volume was the most significant determinant of plasma AM levels. Percen t rise in AM during CPB relative to control period correlated with that of plasma brain natriuretic peptide (r = 0.57, P < 0.01). Our results suggest that AM plays an important role in fluid homeostasis under CPB in cooperati on with other hormones involved in fluid homeostasis.