Microvascular fluid and protein flux in pulmonary and systemic circulations after thermal injury

Abstract

The local and generalized microvascular response to thermal injury, monitoring transvascular fluid flux and protein permeability in burned and nonburned soft tissue and in the lung, was studied. Chronic lymph fistulas were produced in lung and soft tissue in adult sheep. Lymph flux ( L ̇ ) and the lymph-to-plasma ( L P ) protein ratio for four protein fractions separated by gel electrophoresis, were used to monitor fluid flux and protein permeability before and for 72 hr after a 25% full-thickness skin burn. There was a marked increase in both ( L ̇ ) and the L P ratio for proteins ranging from 35- to 108-Å radius in burn tissue for the entire 72-hr period, indicating an increased protein permeability. There was a transient increase in ( L ̇ ) and L P for proteins 58 Å and less in nonburn tissue, with the permeability change lasting about 12 hr. Fluid flux was significantly increased in the lung for 24–36 hr, but protein sieving was normal as demonstrated by a decrease in L P ratio for all protein fractions, indicating the increase in ( L ̇ ) to be due to an increase in microvascular hydrostatic pressure.