The Clinical Utility of Kinetic Glomerular Filtration Rate in the Assessment of Renal Function and Prediction of Outcomes Among Critically Ill Patients With Acute Kidney Injury: A Single-Center Retrospective Cohort Study

Abstract

Objective:\xa0To determine the discriminatory ability of kinetic glomerular filtration rate (kGFR) to detect acute kidney injury\xa0(AKI) when compared with established GFR equations and criteria and relating it to mortality, renal replacement therapy initiation and renal recovery. Methods:\xa0This was a retrospective analysis using data from chart review of 109 intensive care unit (ICU) patients at the University of Santo Tomas Hospital (USTH). The renal function estimates using Chronic Kidney Disease Epidemiology Collaboration (CKD-Epi), modification of diet in renal disease (MDRD), Kidney Disease Improving Global Outcomes Acute Kidney Injury (KDIGO AKI), as well as kinetic GFR equations were compared and correlated with renal and cardiovascular outcomes. Results:\xa0The renal function assessed by kGFR, CKD-Epi, MDRD and KDIGO staging based on serum creatinine (SCr) showed no significant association with mortality outcomes. However, AKI diagnosed based on urine output (UO), and combined SCr and urine output (KDIGO) showed association with all-cause mortality. The UO detected severe stages of AKI while SCr (based on KDIGO) better identified the earlier stages of AKI. The criteria for KDIGO AKI when combined also shows mortality prediction since it joins together the effects of SCr and UO. There was a remarkable 3.5 times increase \xa0in hemodialysis initiation (p=0.0001) and 12.89 times increase in peritoneal dialysis initiation (p=0.01) for every stage increase in the KDIGO classification. kGFR, CKD-Epi and MDRD have 5%, 6%, and 6% decrease, respectively in the odds of initiating hemodialysis. There was however, no association for peritoneal dialysis. Conclusion:\xa0kGFR was the least able in detecting AKI and KDIGO AKI criteria remains to be the standard in identifying AKI in the critical care setting. Increase in SCr was a sensitive tool in diagnosing AKI due to its ability to detect AKI based on a small increase in SCr regardless of\xa0the baseline renal function. Decreasing UO, however, is the prognosticating variable in KDIGO AKI criteria, in that it portends higher probability of initiation of renal replacement therapy (RRT) and ultimately higher mortality when present.