Role of thermal injury-induced hypoproteinemia on fluid flux and protein permeability in burned and nonburned tissue

We studied the role of hypoproteinemia, induced by a major burn injury, on the edema process in burned and nonburned tissues including the lung in the adults sheep. We used lymph flow (Q̇(L)) and the lymph-plasma (L/P) protein ratio as indicators of the rate of fluid and protein flux across the microcirculation and into the interstitium. We compared the response after a full-thickness burn to 30% of total body surface plus resuscitation by means of lactated Ringer's solution (n=8) with a comparable degree of hypoproteinemia produced by plasmapheresis with vascular hydrostatic pressure and cardiac output kept constant. We measured lung Q̇(L) and soft tissue (prefemoral) Q̇(L) from both the burned and nonburned areas. A twofold increase in Q̇(L) and a decrease in the L/P ratio was seen in both lung and nonburned tissue in both burn and plasmapheresis animals, indicating the postburn response to be due to hypoproteinemia with no increase in protein permeability. The Q̇(L) in burned tissue was increased five to ten times with an increase in the L/P ratio. Four burned sheep were resuscitated with pooled plasma. Restoration of plasma proteins eliminated the increase of Q̇(L) in lung and nonburned tissue but had no effect on the burn response. In summary, burn-induced hypoproteinemia plays a major role in the edema process in nonburned tissue and is corrected by restoration of plasma proteins. Edema in burned tissue does not appear to be related to this process.