Assessment of renal function in clinical practice at the bedside of burn patients

Aims The aim of this study was to evaluate whether the renal function of burn patients could be correctly assessed using a single serum creatinine measurement, within normal limits, and three prediction equations of glomerular filtration taking into account, serum creatinine, age, weight and sex. Methods This was a prospective study comprising 36 adult burn patients with a serum creatinine < 120 mu mol l(-1), within the second or third week following the burn injury. Renal function was assessed using serum creatinine, 24 h urinary CL(CR), and the Cockcroft-Gault, Robert, Kirkpatrick and simplified MDRD equations. Results Despite normal serum creatinine concentrations in all patients, a significant number had a decreased CL(CR). The urinary CL(CR) was < 80 ml(-1) min(-1) 1.73 m(-2) in nine patients (25%), and < 60 ml(-1) min(-1) 1.73 m(-2) in five patients (14%). Between the groups having a CL(CR) lower or greater than 80 ml(-1) min(-1) 1.73 m(-2) there were no differences in gender, burn indices, percentage of mechanically ventilated patients or length of hospital stay, but a difference in age. The highest CL(CR) (> 140 ml(-1) min(-1) 1.73 m(-2)) was found in 13 patients younger than 40 years. Regression analysis, residual and Bland-Altman plots revealed that neither the Cockcroft-Gault, Robert, Kirkpatrick nor sMDRD equations were specific enough for the assessment of renal function. Conclusions In burn patients with normal serum creatinine during the hypermetabolic phase, serum creatinine and creatine based predictive equations are imprecise in assessing renal function.