Objective: To estimate the usefulness of 2-h creatinine clearance (CrCl) in the ICU and define variables that may reduce agreement.
Design: Prospective study.
Setting: Polyvalent ICU of a university hospital.
Patients: 359 patients.
Interventions: We compared 24-h CrCl (CrCl-24h), as the standard measure, with 2-h CrCl (CrCl-2h) (at the start of the period) and the Cockroft-Gault equation (Ck-G).
Measurements and results: The 2-h sample was lost in two patients (0.6%) and the 24-h sample was lost in 50 patients (13.9%). The mean Ck-G was 87.4+/-3.05, with CrCl-2h 109.2+/-4.46 and CrCl-24h 100.9+/-4.21 ml/min/1.73 m2 (r2 of 0.88 for CrCl-2h and 0.84 for Ck-G). The differences from ClCr-24h were 21.8+/-3.3 (p<0.001) for the Ck-G and 8.3+/-2.6 (p<0.05) for CrCl-2h (p<0.05). In the subgroup of patients with CrCl-24h<100 ml/min/1.73 m2, the CrCl-24h value was 52.9+/-2.71 vs. 51.6+/-2.14 for CrCl-2h (p=ns) and 57.6+/-2.56 (p<0.001) for the Ck-G. Patients with CrCl<100 ml/min only showed variability in hyperglycemia during the 24-h period.
Conclusions: In intensive care patients, 24-h CrCl results in a large proportion of non-valid determinations, even under conditions of close monitoring. Two-hour CrCl is an adequate substitute, even in patients who are unstable or who have irregular diuresis where a 24-h collection is impossible. The Cockroft-Gault equation seems less useful in this setting.