Subeschar tissue fluid: a source of cell-mediated immune suppression in victims of severe thermal injury

Thermal injury results in pronounced physiologic alterations in microcirculation at the site of tissue damage. The consequence of these changes is an increase in microvascular permeability, leading to the accumulation of tissue edema, or subeschar tissue fluid (STF). One of the adverse properties of edema is its capacity in vitro to inhibit cell-mediated immune function. Since previous studies evaluated STF collected 5 to 7 days after thermal injury, the present study was designed to determine the time frame during which STF demonstrates its immune suppressive nature. Seven patients with severe thermal injury (30% to 100% total body surface area) were entered into the study. STF was collected in serial fashion, beginning as early as 9 hours after injury and continuing until fascial excision or patient death (maximum of 139 hours after injury). The addition of STF to cultures of lymphocytes obtained from healthy donors resulted in complete inhibition of mitogen-induced lymphocyte proliferation (MILP). Serum collected concomitantly from this group of patients was also capable of inhibiting MILP. From its inception, STF possesses the ability to inhibit MILP; this suppressive nature is stable, persisting for prolonged periods of time. The gradual absorption of STF likely contributes to the serologic evidence of cell-mediated immune suppression documented in victims of severe thermal injury.