Atrial natriuretic peptide may not play a role in diuresis and natriuresis after cardiac operations

Human atria through release of atrial natriuretic peptide play an important role in extracellular fluid homeostasis. This study investigates the perioperative role of atrial natriuretic peptide, renin, angiotensin, aldosterone, and vasopressin in patient response to cardiopulmonary bypass after coronary artery bypass operations. Serum levels of these hormones were measured, along with hemodynamic profiles, urine output, and urine electrolytes, before induction of anesthesia, after discontinuation of cardiopulmonary bypass, 1 hour postoperatively, and 3 hours postoperatively. Serum levels of atrial natriuretic peptide were found to be significantly elevated immediately after discontinuation of cardiopulmonary bypass. These elevations did not correspond temporally to elevated central venous pressure or tachycardia. Significant natriuresis and diuresis were observed during the first postoperative hour. This diuresis failed to correspond temporally with alterations noted in serum levels of atrial natriuretic peptide, renin, angiotensin, aldosterone, and vasopressin. The mechanism responsible for the increases in serum atrial natriuretic peptide and the postoperative natriuresis and diuresis after cardiopulmonary bypass remain unknown.