RENAL AND VASCULAR EFFECTS OF ATRIAL-NATRIURETIC-FACTOR DURING CARDIOPULMONARY BYPASS

Study Objective: To evaluate renal and vasodilator effects of synthetic atrial natriuretic factor (ANF) in patients undergoing cardiopulmonary bypass (CPB) with special reference to the applicability of ANF as a diuretic and natriuretic. Design: The study consisted of two parts. The first 15 consecutive patients in a university hospital received a pharmacologically effective bolus dose of 100-mu-g ANF, as demonstrated previously in other studies, or placebo. After analysis of the bolus data (see "Results" section below), the 12 subsequent patients were administered ANF 50-mu-g as a constant 30-min infusion at a rate of 1.67-mu-g/min or placebo. Patients: The patients were scheduled for elective coronary artery bypass grafting operation. There was no evidence of congestive heart failure in any patient, and no one bad an endocrine or renal disorder. Interventions: After achievement of hypothermia (29 to 30-degrees-C of rectal temperature) during CPB, a bolus dose of ANF 100-mu-g was given or an infusion of ANF 1.67-mu-g/min for 30 min, ie, a total dose of 50-mu-g was started. The control patients received placebo correspondingly. Intravenous fluids were administered according to a predetermined scheme. Measurements and Main Results: For the pharmacologic effects of ANF urine volume, urinary sodium excretion and mean arterial pressure (MAP) were measured. Only three of the eight patients receiving the bolus dose of ANF had a diuretic and natriuretic response to the drug, and the responses were significantly related (r = 0.91, p < 0.05 and r = 0.98, p < 0.001, respectively) to the prevailing MAP at the time of the bolus administration. The bolus dose of ANF decreased MAP significantly (p < 0.001 vs placebo) from 65 +/- 6 (mean +/- SEM) to 55 +/- 6 mm Hg within 5 min. The infusion of ANF did not affect MAP, but it increased urine output (16.1 +/- 5.0 ml/min, when the data obtained during the 30-thin infusion and a 30-min period after the infusion were combined) and urinary sodium excretion (1,651 +/- 514-mu-g-Eq/min) significantly (p < 0.05 and p < 0.01, respectively) as compared with the corresponding values of 3.3 +/- 1.1 ml/min and 386 +/- 141-mu-Eq/min after placebo. Conclusions: Prevailing arterial pressure is an important determinant of the diuretic and natriuretic activity of synthetic ANF in patients undergoing CPB. A low-dose infusion of ANF (50-mu-g within 30 min) provides diuresis and natriuresis without significant changes in MAP in these patients.