PREDICTION EQUATION ESTIMATES OF CREATININE CLEARANCE IN THE INTENSIVE-CARE UNIT

Objective: To assess the accuracy of 4 mathematical equations used to estimate creatinine clearance versus the 24-h creatinine clearance in ICU patients. Design: Prospective study of renal function prediction. Setting: The general adult ICUs of 3 metropolitan hospitals. Patients: 199 critically ill patients with indwelling foley catheters. Intervention and measurements: Routine 24 h creatinine clearances were evaluated only in patients whose urine volume recorded by the nurses was within 10% of the laboratory's measured volume. Four mathematical equations utilizing age, sex, body weight, height, and plasma creatinine were used as a comparison. There was no difference in estimated creatinine clearance by 3 published methods when the 24 h creatinine clearance exceeded 100 ml/min. When the 24 h creatinine clearance was less than 100 ml/min, however, one prediction equation adjusted for lean body weight (LBW), was the most accurate. This equation accurately predicted creatinine clearance in the range of 30-100 ml/min and slightly overestimated creatinine clearance at 0-30 ml/min (p < 0.01, ANOVA all groups, p < 0.05 Fisher and Scheffe post-hoc tests) with a mean difference+/-95% confidence interval of -5+/-3.1 ml/min. Conclusion: An initial rapid estimate of creatinine clearance in critically ill ICU patients with reduced renal function can be determined by an equation adjusted for LBW.