Background: Current guidelines from the Infectious Diseases Society of America and the American Society of Health-System Pharmacists recommend vancomycin troughs of 15 mg/L to 20 mg/L for serious methicillin-resistant Staphylococcus aureus infections. The pharmacokinetics of vancomycin are altered in critically ill patients, leading to inadequate serum levels. Rates of initial therapeutic vancomycin troughs have ranged from 17.6% to 33% using intermittent infusions (i.e., 15-20 mg/L) and approximately 60% using continuous infusions (i.e., 15-25 mg/L) in critically ill trauma patients (1-4). We hypothesized that our dosing protocol would achieve higher rates of initial therapeutic troughs compared with previously published reports due to more aggressive loading doses than those seen in previously published reports.
Methods: This was a retrospective study of all critically ill trauma patients admitted to a Level I trauma intensive care unit over a 39-month period who had a suspected serious infection, who were treated with empiric vancomycin per the "pharmacy to dose" protocol, and who had an appropriately drawn steady state trough level. The primary outcome was the rate of initial therapeutic troughs, which was defined as 14.5 mg/L to 20.5 mg/L.
Results: One hundred ninety-seven patients were screened. Seventy patients met inclusion criteria. The study cohort had a median age of 47.5 years and a median Injury Severity Score of 28. Augmented renal clearances were observed, with a median creatinine clearance of 159.1 mL/min and a median Augmented Renal Clearance in Trauma Intensive Care (ARCTIC) score of 7. The median vancomycin loading dose was 24.6 mg/kg with an initial maintenance dose of 17.71 mg/kg. An every eight hour dosing interval was initiated on 47.14% of the patients, and 45.71% of the patients were initially started on an every 12 hour dosing interval. Only 15.71% of the study patients achieved an initial therapeutic trough; 42.86% were less than 10 mg/L, and 8.57% were greater than 20.5 mg/L. Acute kidney injury occurred in 10% based on the Infectious Diseases Society of America/American Society of Health-System Pharmacists vancomycin guidelines and in 11.4% based on the Acute Kidney Injury Network criteria.
Conclusion: Our incidence of initial therapeutic troughs was slightly below previously reported studies. Based on our results, which are consistent with previous literature, it would appear that our guideline-adherent protocol of intermittent vancomycin is insufficient to achieve troughs of 15 mg/L to 20 mg/L.
Level of evidence: Therapeutic, level III.