Vancomycin clearance compared to creatinine clearance by timed urine collection in the intensive care unit

Prior literature elucidating the ratio of vancomycin clearance by the kidneys to creatinine clearance is conflicting. Further studies are warranted evaluating vancomycin clearance, especially in the critically ill population.

This retrospective exploratory analysis includes data from a decade of pulmonary/medical or cardiac ICU admissions where a serum creatinine, vancomycin concentration, and 24-hour timed urine collection were obtained within a 72-hour period. Patients with dialysis prior to, or 48 hours after, urine collection were excluded. The primary outcome was the ratio of vancomycin clearance (CLv) to creatinine clearance measured by timed urine collection (mCLcr). Exploratory outcomes also included (1) P30 accuracy and bias of CLv, BSA adjusted 2021 CKD-Epidemiology Collaboration (EPI) creatinine eGFR, Jelliffe creatinine clearance, and Cockcroft-Gault creatinine clearance equations when compared to mCLcr; (2) the correlations of clearances to mCLcr; and (3) the number of patients with augmented renal clearance for each kidney function estimating equation.

A total of 56 eligible subjects were analysed. The ratio of CLv to mCLcr was 0.64. Although CLv showed the lowest P30 accuracy, it was the most correlated with mCLcr along with the 2021 CKD-EPI creatinine eGFR to mCLcr.

In critically ill patients who warrant medical, pulmonary, or cardiac ICU admission, the ratio of total vancomycin clearance to mCLcr measured by timed urine collection may differ from other populations. CLv and the 2021 CKD-EPI creatinine equation may be more correlated to mCLcr by timed urine collection. Larger studies are needed to confirm these results.