Factors predicting vancomycin therapy outcomes in hemodialysis outpatients and the role of the nephrology stewardship pharmacist.

BACKGROUND

Vancomycin is the default antibiotic to treat methicillin-resistant Staphylococcus aureus (MRSA) in hemodialysis (HD) units. Current guidelines recommend a vancomycin trough range of 15 to 20 mg/L for serious infections. Data regarding the clinical success of these recommendations are scarce in HD patients.

PURPOSE: The purpose of this studies is to evaluate the treatment outcomes of vancomycin in HD patients.

METHODS

A retrospective chart review of HD outpatients who received parenteral vancomycin for suspected or documented MRSA infections in a community hospital in southwestern Ontario, Canada. Stepwise binary logistic regression analysis was conducted to identify the independent predictors of the treatment outcomes.

RESULTS

Of 77 HD patients, 113 vancomycin treatment courses were identified. The unadjusted bivariate comparisons suggested that there was no difference between treatment success and failure groups in terms of: mean loading dose (1663.6 ± 451.9 mg vs. 1614.3 ± 471 mg, P = 0.621), mean pre-HD concentration after loading dose (12.78 ± 4.4 mg/L vs. 13.34 ± 4.5 mg/L, P = 0.601), and mean maintenance dose (1012.1 ± 108 mg vs. 1069.7 ± 227 mg, P = 0.093). The groups were, however, different on their mean pre-HD drug concentration after maintenance dose (15.99 ± 4.6 mg/L vs. 19.9 ± 5.8 mg/L, P = 0.002). The adjusted logistic regression results, however, suggested that the type of infection was the only independent predictor of vancomycin success (OR = 11.07; 95% confidence interval [CI] = 3.2-38.48). Specifically, patients treated for bacteremia were 11 times more likely to experience cure as compared with diabetic foot infection and/or osteomyelitis. Similarly, those with skin and soft tissue infections were 10.7 times more likely to experience cure than those with diabetic foot infection and/or osteomyelitis (OR = 10.7; 95% CI = 3.63-31.58).

CONCLUSION

The suggested vancomycin pre-HD concentration in the guidelines did not predict the treatment outcomes. Patients with bacteremia and/or skin or soft tissue infections were more likely to achieve clinical cure than patients with diabetic foot/osteomyelitis infections.