Retrospective evaluation of possible renal toxicity associated with continuous infusion of vancomycin in critically ill patients

BACKGROUND: Continuous infusion of vancomycin is increasingly preferred as an alternative to intermittent administration in critically ill patients. Intermittent vancomycin treatment is associated with an increased occurrence of nephrotoxicity. This study was designed to determine the incidence and risk factors of acute kidney injury (AKI) during continuous infusion of vancomycin. METHODS: This was a retrospective, observational, two-center, cohort study in patients with microbiologically documented Gram-positive pneumonia and/or bacteremia and normal baseline renal function. Vancomycin dose was adjusted daily aiming at plateau concentrations of 15-25 μg/mL. AKI was defined as an increase in serum creatinine of 0.3 mg/dL or a 1.5 to 2 times increase from baseline on at least 2 consecutive days after the initiation of vancomycin. Primary data analysis compared patients with AKI with patients who did not develop AKI. A binary logistic regression analysis using the forward stepwise method was used to assess the risk factors associated with AKI. RESULTS: A total of 129 patients were studied of whom 38 (29.5%) developed AKI. Patients with AKI had higher body weight (77.3 ± 15 vs. 70.5 ± 15.2 kg; p = 0.02), more diabetes (79% vs. 54%; p = 0.01), and a higher vasopressor need (87% vs. 59%; p = 0.002). Serum vancomycin levels, body weight, and SAPS 3 score were identified as variables contributing to AKI. The incidence of AKI increased substantially when treatment duration was prolonged (14.9 ± 9.8 vs. 9.2 ± 4.9 days; p = 0.05) and plasma levels exceeded 30 μg/mL. CONCLUSIONS: AKI is frequently observed during continuous vancomycin infusion, particularly when conditions that cause acute (shock) or chronic (diabetes) renal dysfunction are present and vancomycin levels above target range are achieved. Although this study challenges the concept that continuous vancomycin infusion might alleviate the risk of nephrotoxicity in critically ill patients, a direct relationship between vancomycin and nephrotoxicity remains to be proven.