Characterization of acute renal failure in the burned patient.

In a retrospective review of 35 patients seen over a two-year period with second- and third-degree burns of 30% or more of their body surface area, six died within 48 hours. Of the remaining 29 patients, polyuric renal failure developed in ten. The functional pattern of this polyuric renal failure appears to be different from other forms of polyuric acute renal failure in that fractional excretion of urinary sodium remains low and the urine to plasma osmolality ratio is commonly above unity. This functional pattern is consistent with a reduction in glomerular filtration rate with a proximal tubular defect such that a "downstream" osmotic diuresis occurs. The distal nephron appears to be intact and functioning.