Comparative analysis of two-hour creatinine clearance and the C-G formula for renal function assessment in critically ill patients.

Objective And Rationale: To investigate if the 2-h creatinine clearance (Ccr) provides a more precise and timely assessment of renal function in critically ill patients compared to the Cockcroft-Gault formula (Cr).

Materials And Methods: This cohort study incorporated 74 patients who were hospitalized for more than 48 h in the Intensive Care Unit over 6 months. A 24-h urine collection protocol was observed, and concurrently, 316 2-h urine specimens were obtained. Then calculated and analyzed the correlation and consistency between Ccr, Cr, and 24-h creatinine clearance (Ccr) values. The rates of change in Ccr(ΔCcr) and Cr(ΔCr) were compared over two consecutive samples.

Results: The R-values of Ccr and Ccr in the early, middle and late 24 h were 0.640, 0.886 and 0.854 (P < 0.001), with biases of -2.1, 1.7, and 6.3 ml/min/1.73 m, respectively. Meanwhile, the R-values for Cr and Ccr at these time points were 0.618, 0.822, and 0.828(P < 0.001), with biases of -14.0, -5.2, and -1.8 ml/min/1.73 m, respectively. For patients with Ccr≥60 ml/min/1.73 m, the R-value of Ccr and Ccr during the middle 2 h was 0.852(P < 0.001), while the R-values for Cr and Ccr were 0.763(P < 0.001), with biases of -2.3 ml/min/1.73 m and -14.2 ml/min/1.73 m respectively. For the group with Ccr ≥ 120 ml/min/1.73 m (n = 72), both Ccr and Ccr displayed a statistically significant elevation compared to Cr (P < 0.001), yet no significant difference was observed between Ccr and Ccr (P = 0.289). Out of 50 patients, 46(92 %) experienced a ΔCcr≥20 % at least once, compared to 20(40 %) with a ΔCr≥20 %(P < 0.001). 25(50 %) with a ΔCcr≥50 %, compared to 3(6 %) with a ΔCr≥50 %(P < 0.001).

Conclusion: Ccr demonstrates a more accurate and more timely indicator of renal function in critically ill patients than Cr.