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Cardiopulmonary bypass (CPB) induces water retention in the third space, and the mechanism is partially associated with the activation of the renin-angiotensin-aldosterone system (RAAS). Atrial natriuretic peptide (ANP) has a gradual but strong diuretic effect and suppresses the RAAS activation. We examined the efficacy of synthetic human alpha-ANP (hANP) infusion in the management of the postoperative water balance control. Thirty patients (male:female = 18:12, 65.2 +/- 9.5 years) undergoing elective open heart operations in 2001 were allocated into one of two groups. Group H (n = 14) received 0.025 microg/kg/minute of synthetic hANP (HANP; Suntory Inc., Zeria Pharmaceutical, Tokyo, Japan) from the termination of CPB; the dose was gradually reduced to 0 until the 72nd postoperative hour. Group C (n = 16) served as control subjects. Twenty-four hours after operation, the central venous pressure, mean pulmonary arterial pressure, and pulmonary capillary wedge pressure were significantly lower in group H than in group C, and the cardiac index was significantly higher in group H. Total volume of plasma solution infused during the initial 24 postoperative hours was significantly smaller in group H. The total dosages of furosemide and potassium-chloride added during the first 72 postoperative hours were significantly smaller in group H. On the first postoperative day, plasma levels of renin activity and aldosterone were significantly lower in group H. These results suggest that postoperative hANP infusion, which provides a sufficient diuretic effect and suppresses CPB induced RAAS activation, may simplify management after open heart operations.

These results imply that renin-angiotensin system may play a role in the incidence of postoperative HT and RD, and suggest that hANP infusion is a simple, reliable, and effective method for management during the immediate period after AAA operations.