Circulating mature adrenomedullin is related to blood volume in full-term pregnancy

Plasma adrenomedullin concentration increases during pregnancy. We measured blood volume and mature adrenomedullin concentration in plasma and cerebrospinal fluid and examined whether mature adrenomedullin in plasma and cerebrospinal fluid was associated with increasing blood volume during pregnancy. We enrolled 47 women undergoing surgery with spinal anesthesia in this study. We first measured mature adrenomedullin concentration in plasma and cerebrospinal fluid of nonpregnant women undergoing orthopedic surgery, pregnant women between 15 and 18 wk of gestation undergoing gynecological surgery, and pregnant women at full-term undergoing cesarean delivery. The second study included 20 healthy and full-term parturients scheduled for cesarean delivery. We measured arterial blood pressure and blood volume by noninvasive pulse spectrophotometry using indocyanine green. Plasma-mature adrenomedullin concentration was 1.24 +/- 0.98, 2.79 +/- 1.23, 4.79 +/- 2.61 fmol/mL (mean +/- sd) in the nonpregnant, the early gestation, and the full-term groups, respectively. But in cerebrospinal fluid, mature adrenomedullin did not significantly increase. Furthermore, mature adrenomedullin in plasma, but not cerebrospinal fluid, had a significant correlation with blood volume per unit body weight (r2= 0.46; P = 0.0009). These findings demonstrate that plasma-mature adrenomedullin concentration increased and that increased plasma-mature adrenomedullin is associated with increased blood volume during pregnancy.