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Kidney Week

Abstract: FR-OR023

Impact of Kinetic Glomerular Filtration Rate Estimation on Medication Dosing in AKI

Session Information

Category: Acute Kidney Injury

  • 101 AKI: Epidemiology, Risk Factors, and Prevention

Authors

  • Kwong, Yuenting Diana, University of California at San Francisco School of Medicine, San Francisco, California, United States
  • Chen, Sheldon, MD Anderson, Houston, Texas, United States
  • Liu, Kathleen D., University of California at San Francisco School of Medicine, San Francisco, California, United States
Background

Medication dosing during acute kidney injury (AKI) is often based on Cockcroft-Gault (CG) creatinine clearance (CrCl) or estimated glomerular filtration rate (eGFR) equations (Dowling et al, Pharmacotherapy 2010). However, these equations are not valid in AKI as serum creatinine (SCr) is not in steady state. A kinetic estimate of CrCl or eGFR (keGFR) may be a more accurate method of estimating renal function. The aim of this study was to determine the impact of using kinetic estimates of renal function on drug dosing in critically ill patients with fluctuating SCrs.

Methods

We used data from subjects in the NIH ARDS Network Fluid and Catheters Treatment Trial (Wiedemann et al, NEJM 2006) with more than 2 serial SCrs. SCrs post-dialysis initiation were censored. Daily renal function was calculated using the 1)CG CrCl 2)MDRD and 3)CKD-EPI equations. Kinetic estimates of each formula were calculated using: [Steady State or baseline SCr X CrCl or eGFR/mean SCr at 2 time points]X(1-[(24X△Scr)/(△Time (h) X Max△SCr/day)]. We evaluated the frequency with which the kinetic estimate of each formula changed medication dosing categories (≥60, 30-59, 15-29, and <15mL/min) compared with the use of CG CrCl, eGFRMDRD, or eGFRCKD-EPI.

Results

Among 947 subjects, 46.0%, 28.5% and 30.0% of the population required recategorization of the dosing category if the kinetic estimate was used instead of CG CrCl, eGFRMDRD, and eGFRCKD-EPI , respectively. Recategorization occurred more in those with AKI by AKIN criteria. If CG CrCl was adjusted using the kinetic counterpart, 62.8% of those with AKI would change dosing categories, compared to 25.6% of patients without AKI.

Conclusion

In a critically ill population, use of kinetic estimates of renal function would change medication dosing in the majority of subjects with AKI on at least one calendar day. Further studies will be needed to test whether use of keGFR in clinical practice would lower the incidence of medication toxicity and avoid subtherapeutic dosing during renal recovery.

Subjects requiring recategorization using kinetic estimates within 7 days of Acute Respiratory Distress Syndrome
 AKI (n= 521)No AKI (n= 426)
 No change±1 category±2 categoriesNo change±1 category±2 categories
Cockcroft-Gault CrCl194 (37.2%)314 (60.3%)13 (2.5%)317 (74.4%)107 (25.1%)2 (0.5%)
MDRD291 (55.9%)220 (42.2%)10 (1.9%)386 (90.6%)39 (9.2%)1 (0.2%)
CKD-EPI276 (53.0%)236 (45.3%)9 (1.7%)387 (90.8%)38 (8.9%)1 (0.2%)

Funding

  • Other NIH Support