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  • Title: Long-term vascular volume expansion maintains elevated thoracic duct lymph flow.
    Author: Valenzuela GJ.
    Journal: Am J Obstet Gynecol; 1992 Nov; 167(5):1453-8. PubMed ID: 1332479.
    Abstract:
    OBJECTIVE: To investigate the mechanisms responsible for edema seen during pregnancy, we tested whether lymph vessels are able to pump high volumes over long periods of time. STUDY DESIGN: In six chronically catheterized nonpregnant ewes, we examined left thoracic duct lymph flow rate and fluid balance responses to the administration of a balanced isotonic solution at a rate of 1 L/hr for 20 hours. Because estrogen administration decreases lymphatic contractility against outflow pressure, we also administered conjugated estrogens (Premarin) during the last 3 hours of the fluid infusion (experimental time 17 to 20 hours). RESULTS: After volume loading for 16 hours, the mean +/- SEM lymph flow rate, blood volume, and arterial pressure rose 100% +/- 26%, 20% +/- 2.3%, and 16% +/- 8.1%, respectively. Vascular compliance decreased significantly and, as evidenced by a lack of body weight changes, interstitial fluid volume failed to change (p < 0.05, analysis of variance). The transcapillary oncotic pressure difference increased by 2 mm Hg; venous pressure increased by 5.2 mm Hg. These data suggest that transcapillary forces favored fluid movement into the interstitium. Lymph flow rate remains elevated after blood volume expansion to a level similar to that described during pregnancy in sheep. A transient decrease in urinary output (approximately 20%) occurred with no changes in lymph flow rate, arterial pressure, or blood volume. CONCLUSION: Lymph flow rate is able to compensate for the increased capillary filtration observed during prolonged blood volume expansion.
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