Plasma levels and dialysance of atrial natriuretic peptide in terminal renal failure

Abstract

Plasma immunoreactive atrial natriuretic peptide (irANP) levels, their chromatographic profile, relationship with hemodynamic variables, and responses to hemodialysis (HD) or postural changes were investigated in HD patients. Peripheral venous supine plasma irANP averaged 167 ± 31 (± SEM) pg/ml in 12 normal subjects (age 63 ± 2 yr). In 42 HD patients (mean age 65 ± 1 yr), plasma irANP in peripheral arterio-venous fistulae was high (447 ± 50 pg/ml, P < 0.01) before HD and decreased (P < 0.001) to 164 ± 24 pg/ml after HD. The latter reduced body weight by -2.3 ± 0.2 kg (P < 0.001) and blood pressure from 139/77 ± 4/2 to 126/73 ± 4/2 mm Hg (P < 0.01). Pre-dialysis plasma irANP in right atrium, pulmonary artery or av-fistula correlated with pulmonary capillary wedge pressure (N = 10, r = 0.66 to 0.73; P < 0.05); HD-induced changes in these variables were also correlated (r = 0.80 to 0.90; P < 0.05 to < 0.01). Compared with supine values, upright posture decreased plasma irANP in 12 normal subjects and 8 HD patients (-40 and -42%, respectively, P < 0.01). IrANP clearance from plasma averaged 24 ± 5 ml/min across the hemodialyzer (N = 6) and 46 ± 3 ml/min across the hemofilter (N = 4). We conclude that in terminal renal failure, circulating irANP consists largely of αANP, is often elevated before HD, decreases with the change from recumbency to standing, falls after removal of excess fluid, and may depend strongly on left atrial and pulmonary arterial pressures. Elimination of irANP across dialyzers or ultrafilters contributes only little to reduction in plasma irANP during HD. In addition to the cardiac state, age and posture should be considered when interpreting plasma irANP levels as a possible index of fluid overload.