81 Augmented Creatinine Clearance in Severely Injured Burn Patients

This is the authors' abstract. We don't add key points for this paper.

Most trauma surgeons assume that serum creatinine (SCr) reflects glomerular filtration rate (GFR). However, new evidence suggests augmented renal clearance (ARC= creatinine clearance (CLCr) >130 ml/min) occurs in up to 60% of critically ill patients. ARC is associated with subtherapeutic drug concentrations, may lead to adverse clinical outcomes, and has yet to be reported in the burn population. Unfortunately, actual CLCr is usually not measured in the burn ICU and estimates of glomerular filtration rate (eGFR) have not been validated in critically ill burn ICU patients. To fill this gap, we test the hypothesis that ARC is common in burn ICU patients and is dissociated from eGFR. In 15 consecutive burn ICU patients with total body surface area burns (TBSA) > 10%, 24 hr CLCr was correlated with demographics, iatrogenic factors, and clinical estimates of GFR: Cockroft-Gault (CG), modification of diet in renal disease (MDRD), and chronic kidney disease epidemiology (CKD-EPI). Univariate and multivariate logistic regression were used to identify risk factors of ARC. Values are M±SD if parametric and median [interquartile range] otherwise. Differences are assessed at p<0.05. The study population was 43 ± 16y, 60% males, 47% Caucasian, BMI 28.8 ± 8 kg/m2, with TBSA of 23[13–42]%. Length of stay was 26 ± 14d and overall mortality was 20% (n=3). Serum creatinine was 0.74[0.69–1.11] mg/dL and CLCr was 139 ± 66 ml/min. Urine output was 0.93 ± 0.43 cc/kg/h. In this sample of 15 patients, 67% (n=10) had ARC, 7% (n=1) had normal GFR, and 27% (n=4) were in acute renal failure. Hypertension, diabetes, age, amount of crystalloid in the first 24 hours and fluid balance were all associated with ARC on univariate analysis (all p<0.05), but TBSA, gender, race, smoking history, pressor use, weight, mechanical ventilation, admission vitals and creatinine were not. After controlling for confounders, none of these factors were independent risk factors for ARC. CKD-EPI, MDRD, and CG, underestimated CLCr by an average of 12% (p<0.031), 7% (p<0.071), and 9%, (p<0.0001), respectively. These preliminary data are the first demonstration that ARC is common in critically-ill burn ICU patients, is independent of patient-specific and iatrogenic factors, and is not accurately detected by current clinical estimates. Increased renal clearance can have adverse effects on drug concentrations, such as antibiotics and thromboprophylaxis, and ultimately clinical outcomes. More accurate estimates of CLCr are needed to minimize treatment failure in this population, and further studies are warranted to assess clinical outcomes of this phenomenon.