Vancomycin dosing and monitoring in the intensive care unit: Guideline adherence and efficacy

Vancomycin has a narrow therapeutic window requiring careful drug dosing and monitoring to ensure efficacy while avoiding toxicity. Although protocolised prescribing and monitoring are recommended in antibiotic guidelines, adherence in clinical practice is infrequently reported.

We sought to describe compliance with a new vancomycin dosing guideline in the intensive care unit (ICU) and to describe its efficacy in reaching serum levels within the therapeutic range.

In this single-centre retrospective observational study, we assessed compliance with, and efficacy of a newly implemented vancomycin prescribing protocol. All ICU patients prescribed intravenous vancomycin between May and July 2024 were screened for inclusion. Collected data included indication, weight, age, creatinine, urine output, loading dose, maintenance dose, plasma vancomycin concentration, and timing of monitoring. Augmented renal clearance (ARC) was defined as a creatinine level below the reference range and/or an urine output >3 L in 24 h.

A total of 148 patients were included. Protocol compliance was 82% for the loading dose (101/123), 49% for maintenance dosing (49/101), and 51% for timing of monitoring (46/91). Compliance across all protocol domains occurred in 27% of instances (17/64). Therapeutic drug levels were achieved in only 20% of prescribing episodes. Central nervous system (CNS) infection vs non-CNS infection (odds ratio [OR]: 9.5, 95% confidence interval [CI]: 2.7-41.3; P < 0.01) and ARC vs no ARC (OR: 15.1, 95% CI: 4.0-80.4; P < 0.01) were independently associated with subtherapeutic levels, while impaired renal function (glomerular filtration rate: <60 mL/min) vs normal renal function (glomerular filtration rate ≥60 mL/min) was associated with supratherapeutic levels (OR: 3.6, 95% CI: 1.1-13.2; P < 0.05). Protocol compliance was not associated with therapeutic levels.

Vancomycin protocol adherence in a mixed medical-surgical ICU was low; however, adherence was not associated with therapeutic levels. Patients with CNS infection, ARC, or renal impairment are at risk of nontherapeutic levels.