Acute volume expansion in normal pregnancy and preeclampsia: Effects on plasma atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (cGMP) concentrations and feto-maternal circulation

Objective. To compare normal pregnancy with pregnancy-induced hypertension (PIH)/preec-lampsia with respect to the effects of acute volume expansion on plasma atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP) and fetal-maternal circulation. Design. Observational study.Setting. University hospital.Subjects. Fifteen women with PIH/ preeclampsia and 15 healthy pregnant controls. Interventions. Before and after 30 minutes' infusion of a crystalloid solution (15 ml/kg), maternal venous blood was sampled for ANP and cGMP analysis and echocardiography and Doppler investigations were performed.Results. Basal median (range) ANP and cGMP levels were significantly higher in the PIH/ preeclampsia group compared to the controls: 6.5 (3.8-30.4) compared to 3.9 (2.0-6.7) pmol/1, p≤0.01 and 5.8 (2.4-11.6) compared to 4.0 (2.3-10.8) nmol/1, p≤0.05. The response to volume load was enhanced: 4.6 (-4.5-21.8) compared to 0.7 (-4.1-8.8), p≤0.05 and 2.9 (0.1-10.9) compared to 1.2 (- 5.0-6.0), p≤0.05, respectively. Systemic vascular resistance was initially higher in the patient group, 22.3 (14.1-36.7) compared to 15.6 (10.0-25.5) peripheral resistance units, p≤ 0.01 but the response to volume load was similar in both groups (12-13% decrease). The pulsatility index of the uterine artery, 0.85 (0.46-1.38) compared to 0.72 (0.49-1.26) and umbilical artery 0.89 (0.66-1.57) compared to 0.97 (0.74-1.31) did not differ between the groups. Volume expansion did not affect any of these variables.Conclusions. The pulsatility index of the uterine artery remained unaffected in both preeclamptic patients and healthy controls despite an increase of ANP and cGMP concentration and a systemic vasodilatation during acute volume expansion. This finding may indicate the absence of a vasodilatation of the uteroplacental vascular bed.