Glomerular filtration rate is increased in burn patients

Urinary output, a key parameter guiding fluid resuscitation in burn trauma, is an inadequate measure of renal function. In this study, the clearance of iohexol (CL) was used to follow the glomerular filtration rate during the first week after burn. Nineteen adults with major burns received an intravenous bolus injection of iohexol every other day. Plasma concentration of iohexol was measured over 4 h and CL was calculated by a one-compartment kinetic model. The results were compared to the CL as obtained by a two-compartment model and also to the CL measured in 10 healthy controls. The results show that CL values for burn patients were high. The first day after burn, median CL was 155 mL/min/1.73 m2 (range 46–237), which exceeded that for the controls (mean 117 mL/min/1.73 m2; P < 0.01). However, on day 7 the CL approached the expected baseline (mean 122 mL/min/1.73 m2). CL was 10% lower when calculated from two-compartment kinetics, and a correction factor of 0.9 was applied to all results obtained by the one-compartment calculations to give results comparable to those from the two-compartment kinetics. In conclusion, CL is increased early after burn. The mechanism is unclear but it parallels the period of vascular dysfunction and increased cardiac output.