Atrial natriuretic peptide concentrations and hemodynamic effects of acute plasma volume expansion in normal pregnancy and preeclampsia.

Abstract

Plasma atrial natriuretic peptide (ANP) and circulatory responses were studied during rapid plasma volume expansion with crystalloid solutions. Sixteen women with preeclampsia and 16 healthy controls in the third trimester were compared. Basal mean (+/- standard error of the mean) ANP levels were not significantly higher in the preeclamptics than in controls (13.6 +/- 3.5 versus 6.4 +/- 1.1 pmol/L; not significant), but the increment following volume expansion was more pronounced (12.9 +/- 2.6 versus 6.1 +/- 2.3 pmol/L; P less than .05). The mean plasma volume expansion was less in the preeclamptic group (6.1 +/- 0.8 versus 9.3 +/- 1.1%; P less than .05), reflecting a higher capillary permeability in this disease. Left ventricular posterior-wall thickness in diastole was increased in the preeclamptics under basal conditions as compared with the controls (9.8 +/- 0.3 versus 8.9 +/- 0.3 mm; P less than .05), as was the thickness of the interventricular septum in systole (14.3 +/- 0.5 versus 12.3 +/- 0.6 mm; P less than .05). Systemic vascular resistance was higher in the preeclamptic group (19.7 +/- 0.8 versus 15.1 +/- 1.1 peripheral resistance units; P less than .01). In the controls, cardiac output increased by 23 +/- 4% and systemic vascular resistance decreased by 17 +/- 3%. The preeclamptic women reacted in a similar way. Our results indicate that preeclampsia is associated with an enhanced ANP response despite a less pronounced increase in plasma volume during acute fluid challenge.