Pathophysiology of pressure changes during intrauterine transfusion

Abstract

Intraperitoneal and umbilical vein pressure readings were obtained during intrauterine transfusion in patients with Rh alloimmunization. In 15 nonacidotic fetuses, mean umbilical vein pressure before transfusion (4.5 mm Hg, SD = 2.3) increased by 4.6 mm Hg (Δ umbilical vein pressure confidence intervals +2.8 to +6.4; p < 0.0001) with transfusion. Δ Umbilical vein pressure correlated positively with the increase in hematocrit level (r = 0.55; p < 0.05) and negatively with gestational age (r = -0.58; p < 0.05). Basal umbilical vein pressure was raised in the only acidotic fetus, whereas A umbilical vein pressure was 0. Intraperitoneal pressure was recorded in 11 fetuses before and after transfusion, five of which were associated with fetal heart rate changes or preexisting ascites. Basal intraperitoneal pressure (2.5 mm Hg, confidence intervals 1.4 to 3.6) was significantly lower than basal umbilical vein pressure (confidence intervals, 3.2 to 5.8; p < 0.02). In uncomplicated intraperitoneal transfusions, intraperitoneal pressure rose significantly (A intraperitoneal pressure = +5.8; confidence intervals 2.9 to 8.8; p < 0.005). In four transfusions associated with fetal bradycardia or tachycardia, A intraperitoneal pressure (range, 16 to 26) was greater than in uncomplicated transfusions (range, 1 to 9). t1 Intraperitoneal pressure was 0 in the fetus with ascites. These results implicate increases in umbilical vein pressure and intraperitoneal pressure in immediate complications of intrauterine transfusion, and support a role for intraperitoneal pressure monitoring during intraperitoneal transfusion. (Am J Obstet Gynecol 1989;160:1139-45.)