CHANGE IN ATRIAL-NATRIURETIC-PEPTIDE CONCENTRATION AFTER ACUTE PLASMA-VOLUME EXPANSION IN NORMAL-PREGNANCY AND PREECLAMPSIA

Atrial natriuretic peptide (ANP) is found to be elevated in preeclampt ic patients despite the presence of hemodynamic characteristics such a s vasoconstriction and hypovolemia. In this study, the effect on ANP s ecretion of plasma volume expansion with crystalloid solutions was inv estigated. Seven preeclamptic and seven normotensive pregnant women in their last trimester were compared. After basal ANP measurements, 0.9 % Ringer's solution, 15 cm(3)/kg body weight was infused within 30 min to expand the plasma volume. Blood sampling was repeated after the in fusion. Maternal blood volume expansion was calculated from the decrea se in hematocrit. Plasma ANP levels were corrected according to the de gree of volume expansion. Basal. mean levels in both groups were not d ifferent. Although the postinfusion levels of ANP in normotensive preg nant women were similar to the basal levels (means +/- SE: 20.6 +/- 0. 41 and 27.2 +/- 0.52 pg/ml, respectively, p = 0.10), the postinfusion ANP levels in preeclamptic women increased significantly (21.4 +/- 0.3 1 and 34.1 +/- 0.28 pg/ml, respectively, p = 0.01). Preeclampsia is as sociated with a greater increase in plasma ANP levels in response to v olume expansion compared with normotensive pregnancy. The greater chan ge in the right atrial pressure with volume expansion, due to decrease d compliance of the capacitance vessels in preclamptic subjects might explain the greater change in the plasma level of ANP.