Laboratory correlation between vancomycin levels and serum creatinine in the nephrotoxicity of vancomycin

Reports about relationship on renal function and vancomycin exposure are conflicted and limited. Goals: To identify if high serum vancomycin levels precede changes in serum creatinine or if it is secondary to reduced glomerular filtration and to analyze associated clinical conditions. Methods: retrospective cohort study, initially of 56.555 measurements of vancomycin levels from 511 patients admitted from December 2011 to June 2012 was analyzed. Patients with uncompleted dates were excluded and the correlation analysis was performed in 127 patients that were divided into four groups based on vancomycin levels (20 mg/mL) and creatinine (1.4 mg/dL) levels. After that, 80 medical charts of these patients was reviewed for the presence of comorbidities, sepsis, acute kidney injury and use of other nephrotoxic drugs. Results: there was a significant increase in vancomycin levels, when creatinine > 1.4 mg/dL and vancomycin ≤ 20 mg/mL (Group 3) on the first measurement. It was identified there was a significant association between creatinine > 1.4 mg/mL and vancomycin > 20 mg/mL, n = 7 (Group 4) in patients aged 50–59 years. Acute kidney injury was present in patients with previous higher vancomycin levels. Conclusions: Impaired renal function occurred before vancomycin levels measurements were taken, influencing the serum levels of vancomycin in the following days. In these patients the elevation of vancomycin did not lead to a worsening in renal function. There was a positive correlation between elevated creatinine and vancomycin levels in elderly, male and septic. Patients who need more attention were those with acute kidney injury who have previous higher vancomycin levels.