Changes in plasma concentrations of atrial natriuretic peptide during exchange transfusion in premature infants.

Plasma concentrations of atrial natriuretic peptide (ANP) and hemodynamic parameters were investigated in five premature infants undergoing exchange transfusion. Baseline values of ANP were 51.7 +/- 21.2 fmol/ml. Volume depletion by withdrawal of 10 ml blood did not cause changes in systolic blood pressure (79.4 +/- 4.3 vs. 71.4 +/- 5.6 mmHg) and heart rate (115 +/- 5.2 vs. 115 +/- 2.4 b/min). ANP levels in plasma remained unaltered (53.4 +/- 24.9 fmol/ml). Replacement of 10 ml blood increased central venous pressure by 33% and ANP concentration in the plasma by nearly 30%, while heart rate and blood pressure remained unchanged. Our data indicate that the heart of the premature infant responded to acute blood replacement with increased ANP-release, while blood removal appeared not to influence hormone regulation.