Thoracic duct lymph flow responses to hemorrhage in the ovine fetus. Brace, Robert A. Division of Perinatal Medicine, Department of Reproductive Medicine, University of California, San Diego, La Jolla, California 92093-0802
APStracts 2:0158H, 1995.
In the fetus, blood volume returns toward normal after hemorrhage much more rapidly than in the adult due to a rapid entry of fluid and plasma proteins into the fetal circulation. One potential source of fetal fluids and plasma proteins is the lymphatic system since basal lymph flow rate and interstitial protein concentration are high in the fetus. Further, studies in adults suggest that lymph flow rate may increase following hemorrhage. To test the hypothesis that hemorrhage induces an increase in lymph flow in the fetus, 15 late gestation ovine fetuses underwent left thoracic duct catheterization with low resistance catheters and were studied 5 or more days after surgery at 134 +/- 1 (SE) days gestation. The protocol included 3 successive 30 min periods: control, hemorrhage, and recovery. During the first 5 min of the hemorrhagic period, 61 +/- 4 ml of fetal blood were removed. The blood was reinfused over the first 5 min of the recovery period. Following the hemorrhage, fetal arterial pressure, venous pressure and heart rate decreased (ANOVA, P<0.001). These variables significantly increased above basal levels following blood reinfusion. Fetal hematocrit (P<0.001) and plasma protein concentration (P<0.05) also decreased after the hemorrhage and returned to control values after the reinfusion. Fetal lymph flow rate was 0.55 +/- 0.06 (SE) ml/min prior to the hemorrhage and decreased by a maximum of 30.3% +/- 6.3% (P<0.001) at 8 min after the end of the hemorrhage. Lymph flow rate was reduced by an average of 19.1% +/- 6.6% during the hemorrhagic period and returned to prehemorrhage levels following blood reinfusion. In summary, this study shows that fetal lymph flow rate decreases rather than increases following acute hemorrhage. Thus, augmented fetal lymph flow does not appear to play a role in the rapid restoration of fetal blood volume following hemorrhage. 

Received 30 January 1995; accepted in final form 11 April 1995.
APS Manuscript Number H82-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.