Prediction equation estimates of creatinine clearance in the intensive care unit

Abstract

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 Scheffé 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.