Measurement of net whole-body transcapillary fluid transport and effective vascular compliance in humans
Watenpaugh, D.E.; Gaffney, F.A.; Schneider, S.M.
Journal of Trauma 45(6): 1062-1068
1998
ISSN/ISBN: 0022-5282 PMID: 9867049 Document Number: 1734
Background. Net whole-body transcapillary fluid transport (TFT) between the circulation and the interstitial (extravascular) space may be calculated as: IV - DELTAPV - UV - IL, where IV = infused or ingested volume (when applicable), DELTAPV = change in plasma volume, UV = urine volume, and IL = insensible loss. Results: Infusion of 30 mL/kg isotonic saline over 25 minutes increased supine TFT from a basal capillary reabsorption of - 106 +- 24 mL/h (mean +- SE) to a net filtration of 1,229 +- 124 mL/h. One hour after infusion, reabsorption of -236 +- 102 mL/h was seen, and control reabsorption levels returned by 3 hours. Four hours of 30 mm Hg lower body negative pressure (LBNP) elicited no net TFT, probably because of upper body reabsorptive compensation for lower body capillary filtration. When ingestion of 1 L of isotonic saline accompanied LBNP, filtration of 145 +- 10 mL/h occurred. Reabsorption of extravascular fluid into the circulation always followed LBNP. Conclusion: Application of this technique could aid understanding of physiologic conditions, experimental interventions, disease states, and therapies that cause or are influenced by fluid shifts between intravascular and interstitial compartments.
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