THORACIC DUCT FUNCTION IN FETAL, NEWBORN, AND ADULT SHEEP

Abstract

We measured thoracic duct lymph flow rate versus outflow pressure in 7 chronicallycatheterized adult sheep and in 6 newborn lambs and compared our results to data previouslyobtained from 10 fetal sheep. In fetal sheep the thoracic duct lymph flow rate was 34.5±17.2ml/hr or 11.7±6.0 ml/kg/hr. Fetal thoracic duct lymph flow deviated from baseline between 8 and12 torr outflow pressure and lymph stopped at 18±2.5 torr. In newborn lambs the thoracic ductlymph flow rate was 49.5±22.0 ml/hr or 7.4±2.5 ml/kg/hr. The range of outflow pressures overwhich newborn lymph flow deviated from baseline was between 15 and 18 torr and lymph flowstopped at 26.2±6.4 torr. Adult sheep thoracic duct lymph flow rate was 130±74 ml/hr or 2.3±1.3ml/kg/hr. Adult lymph flow deviated from baseline between 25 and 35 torr and stopped at anoutflow pressure of 41.7±6.7 torr. The ability of the thoracic duct to return lymph against anoutflow pressure improves with maturation. However, lymph flow rate corrected for body weightis greatest in immature animals. The higher corrected lymph flow rate in conjunction with thedecreased ability to pump against an outflow pressure may help account for immature animalspredisposition for edema.