Thromboelastography (TEG) is a point-of-care device used to evaluate whole blood coagulation function. The TEG is unique as a test of coagulation function in that it measures the interaction of all components of clot formation, which is different than traditional laboratory-based tests which measure isolated components of coagulation. Little is known about fetal coagulation physiology. We sought to evaluate the impact of severe fetal anemia and intrauterine transfusion (IUT) on fetal coagulation physiology by use of the TEG, and to compare fetal TEG values to those of healthy neonates and adults.
One ml of fetal blood was collected immediately before (Pre-) and after (Post-) intrauterine transfusion of packed red blood cells (PRBCs). Sampling and transfusion were performed for fetal anemia due to hemolytic disease of the fetus and newborn. Samples were run in duplicate. For descriptive summary, duplicate Pre- and Post- values were averaged. Values for R (initiation of clot in minutes), K (clot firmness in minutes), Angle (kinetics of clot development in degrees), and MA (maximum strength in mm) were obtained for each sample and presented using (mean ± SE). Pre-IUT values for R, K, Angle and MA were compared to Post-IUT values using linear mixed effect model to account for clustering due to repeated observation from the same fetus. Pre-IUT values are compared to normal healthy term neonates, and healthy adults using Wald test. The study was approved by the University of Pittsburgh Institutional Review Board (PRO14050051).
Four fetuses underwent 9 IUTs rendering 17 Pre- and 17 Post- specimens. The mean gestational age at IUT was 31w 2d (25w 4d – 35w2d). The mean IUT volume transfused was 69 mL (30-170 mL). The mean estimated percent intravascular volume transfused was 33.4% (19-52%). Of the four variables analyzed, only R showed a significant difference, with the initiation of clot formation being modestly delayed after transfusion by an estimated 2.87 min (95% CI: [0.82-4.92], P = 0.0480). Pre- values were compared to 100 normal term neonates, and to 118 healthy adults. Compared to Pre-, only R was affected (shorter) compared to term neonates (mean ± SE = 5.46 ± 0.16 min., P < 0.001) and healthy adults (mean ± SE = 6.8 ± 0.13 min., P < 0.001).
Other than a modest prolongation of clot formation time, IUT of PRBCs of up to 52% of the estimated intravascular volume did not affect fetal coagulation function by TEG. Other than a shorter clot formation time (R), there is no difference in TEG values between anemic preterm fetuses and healthy term neonates and healthy adults. Beyond generalizable knowledge, this information could be exploited for future fetal intervention techniques. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
