A MODEL OF FLUID RESUSCITATION FOLLOWING BURN INJURY - FORMULATION AND PARAMETER-ESTIMATION

A dynamic compartmental model is developed to describe the redistribut ion of fluid and albumin between the circulation and the intact and in jured interstitia following burn injury in humans. Transcapillary flui d and albumin exchange is described by a coupled Starling mechanism, w hile the effect of the burn is represented by time-dependent perturbat ions to all three compartments. The unknown model parameters are deter mined for two groups of patients, having less than and greater than 25 % total body surface area burns, by statistical fitting of model predi ctions to patient data from two sources. The parameters include the pe rturbations to the fluid filtration coefficients in uninjured and inju red tissue, G(kF,Tl) and G(kF,BT), respectively, the relaxation coeffi cient, r, which describes the exponential decay of the perturbations, and the exudation factor, EXFAC, which relates the protein concentrati on in the exudate to that in the injured tissue. Perturbations to othe r parameters, including the membrane permeability-surface area product and the albumin reflection coefficient in the injured and uninjured t issues, are determined based on interrelationships with G(kF,Tl) and G (kF,BT). The values of G(kF,BT) when corrected for tissue destruction and decreased post-injury perfusion, are in reasonable agreement with the limited experimental data available from the literature. The model and its parameters are further validated by comparing the simulated p atient responses to the clinical data used in the parameter estimation as well as to data available from two additional sources.