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

Objective and rationaleTo investigate if the 2-hour creatinine clearance (Ccr2) provides a more precise and timely assessment of renal function in critically ill patients compared to the Cockcroft-Gault formula (CrC-G).Materials and MethodsThis cohort study incorporated 74 patients who were hospitalized for more than 48 hours in the Intensive Care Unit over 6 months. A 24-hour urine collection protocol was observed, and concurrently, 316 two-hour urine specimens were obtained. Then calculated and analyzed the correlation and consistency between Ccr2, CrC-G, and 24-hour creatinine clearance (Ccr24) values. The rates of change in Ccr2(ΔCcr2) and CrC-G(ΔCrC-G) were compared over two consecutive samples.ResultsThe R-values of Ccr2 and Ccr24 in the early, middle and late 24 hours were 0.640, 0.886 and 0.854 (P<0.001), with biases of -2.1, 1.7, and 6.3 ml/min/1.73m2, respectively. Meanwhile, the R-values for CrC-G and Ccr24 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/1.73m2, respectively. For patients with Ccr24≥60 ml/min/1.73m2, the R-value of Ccr2 and Ccr24 during the middle two hours was 0.852(P<0.001), while the R-values for CrC-G and Ccr24 were 0.763(P<0.001), with biases of -2.3 ml/min/1.73m2 and -14.2 ml/min/1.73m2 respectively. For the group with Ccr24 ≥ 120 ml/min/1.73m2 (n=72), both Ccr2 and Ccr24 displayed a statistically significant elevation compared to CrC-G (P < 0.001), yet no significant difference was observed between Ccr2 and Ccr24 (P = 0.289). Out of 50 patients, 46(92%) experienced a ΔCcr2≥20% at least once, compared to 20(40%) with a ΔCrC-G≥20%(P<0.001). 25(50%) with a ΔCcr2≥50%, compared to 3(6%) with a ΔCrC-G≥50%(P<0.001).ConclusionCcr2 demonstrates a more accurate and more timely indicator of renal function in critically ill patients than CrC-G.