950

Abstract

Introduction: Vancomycin dosing of 15 to 20 mg/kg to achieve target serum trough concentrations of 15 to 20 mg/L is recommended in several national guidelines. However, there is limited data describing the performance of this dosing strategy, especially in patients with obesity, acute kidney injury, altered fluid status, sepsis requiring vasopressor therapy, and/or concomitant nephrotoxic agents. A high dose vancomycin nomogram (HDVN) was developed to recommend a dose and frequency to target troughs of 15 to 20 mg/L. Methods: Adult patients 18 years or older who were started on vancomycin using the HDVN and had at least one vancomycin trough drawn at steady state between July 2011 and June 2012 were included. Patients with creatinine clearance < 25 ml/min or were on any form of renal replacement therapy were excluded. Multivariate regression analysis was performed to evaluate risk factors for supratherapeutic and subtherapeutic vancomycin troughs, and nephrotoxicity. Potential risk factors evaluated include age > 65 years, body mass index > 35, ICU admission, nephrotoxic medications, Charlson Index > 5, daily vancomycin dose > 4 grams, baseline renal dysfunction, IV contrast, and vasopressor therapy. Results: Mean vancomycin trough was 17.28 mg/L (range of 4.8 to 59 mg/L), with 60 (35.5%) patients admitted to the ICU during vancomycin therapy. A large proportion of vancomycin troughs were not therapeutic; 76 (46%) patients had subtherapeutic troughs and 54 (32%) patients had supratherapeutic troughs. Age > 65 years (OR 1.98, CI 0.264 – 0.926, p = 0.033) was the only statistically significant risk factor for subtherapeutic troughs, and BMI > 35 (OR 2.454, CI 1.035-5.819, p = 0.042) was the only statistically significant risk factor for supratherapeutic vancomycin troughs. Vasopressors (OR 0.040, CI 1.042 – 6.010, p=0.04) and concomitant nephrotoxic agents (OR 1.043 – 6.845, p=0.41) were associated with nephrotoxicity. Conclusions: This was the first study that assessed the use of a high dose vancomycin nomogram in a wide variety of hospitalized patients. Utilization of a high dose vancomycin nomogram resulted in a large proportion of patients with subtherapeutic or supratherapeutic vancomycin serum concentrations. Deviation from the HDVN and frequent monitoring should be strongly considered in patients who are older than 65 years of age, morbidly obese, receiving nephrotoxic medications, or on vasopressor therapy.