Original Research

Gap Analysis for the Conversion to Area Under the Curve Vancomycin Monitoring in a Small Rural Hospital

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Objective: Consensus guidelines for vancomycin monitoring now recommend area under the curve (AUC) calculations for optimal vancomycin efficacy and safety. This will be a major practice change for many facilities. Implementation guidance is available but has not been reported in smaller, primary care hospitals. The objective of this study was to measure the uptake of AUC monitoring implementation in a rural facility.

Methods: This is a gap analysis evaluating the appropriateness of vancomycin levels tests after the April 1, 2019 transition. All vancomycin levels between April 2019 and June 2019 after the go-live date were included with no exclusions in a retrospective chart review. The primary outcome was the proportion of levels in the appropriate time frame: peaks 1 to 2 hours after infusion with troughs at least 1 half-life after initial dose and prior to the next dose. Secondary outcomes included reasons identified for inappropriate levels and the proportion of AUC 24 calculations within therapeutic range (400-600 mg.h/L). Descriptive statistics were used to measure the scope and outcomes of this transition.

Results: The transition was effective with 97% of cases utilizing AUC-based methods. There were 65 vancomycin levels in the 3-month study period with 86% deemed appropriate. Of the 9 inappropriate levels, 4 had to be repeated for accurate monitoring. There were 28 two-level couplets used for AUC 24 calculations, 17 (61%) fell within therapeutic range.

Conclusion: Implementation strategies for the AUC transition described in tertiary medical centers can be successfully utilized in primary facilities.


 

References

The use of weight-based dosing with trough-based monitoring of vancomycin has been in clinical practice for more than a decade. The American Society of Health-System Pharmacists (ASHP), the Infectious Diseases Society of America (IDSA), and the Society of Infectious Diseases Pharmacists (SIDP) published the first guidelines for vancomycin monitoring in 2009.1 Although it has been well established that area under the curve (AUC) over the minimal inhibitory concentration (MIC) ratio > 400 mg.h/L is the best predictor of clinical efficacy, obtaining this value in clinical practice was not pragmatic. Therefore, the 2009 guidelines recommended a goal vancomycin trough of 15 to 20 mcg/ml as a surrogate marker for AUC/MIC > 400 mg.hr/L. This has since become a common practice despite little data that support this recommendation.

The efficacy and safety of trough-based monitoring has been evaluated extensively over the past several years and more recent data suggest that there is wide patient variability in AUC with this method and higher trough levels are associated with more nephrotoxicity.2,3 ASHP, IDSA, SIDP, and the Pediatric Infectious Diseases Society (PIDS) updated the consensus guidelines in 2020.4 Trough-based monitoring is no longer recommended. Instead AUC24 monitoring should be implemented with a goal range of 400 to 600 mg.h/L for efficacy and safety. Given concerns for vancomycin penetration into the central nervous system (CNS), many facility protocols utilize higher targets (> 600 mg.h/L) for CNS infections.

Some hospitals have been utilizing AUC-based monitoring for years. There are strategies from tertiary care centers that drive this practice change in the medical literature.5,6 However, it is important to reproduce these implementation practices in small, rural facilities that may face unique challenges with limited resources and may be slower to implement consensus guidelines.7,8 As this is a major practice change, it is imperative to evaluate the extent of transition and identify areas of needed improvement.

Accurate therapeutic drug monitoring ensures both the safety and efficacy of vancomycin therapy. Unfortunately, research shows that inappropriate laboratory tests are common in medical facilities.9 Drug levels taken inappropriately can lead to delays in therapeutic decision-making, inappropriate dosage adjustments and create a need for repeated drug levels, which increases the overall cost of admission.

Given the multiple affected services needed to make successful practice transitions, it is paramount that facilities evaluate progress during the transition phase. The Agency for Healthcare Research and Quality and the Institute for Healthcare Improvement provide guidance in the Plan-Do-Study-Act Cycle for quality assessment and improvement of new initiatives.10,11 A gap analysis can be used as a simple tool for evaluating the transition of research into practice and to identify areas of needed improvement.

The Veterans Health Care System of the Ozarks (VHSO) in Fayetteville, Arkansas made the transition from trough-based monitoring to 2-level AUC-based monitoring on April 1, 2019. The purpose of this study was to evaluate the effectiveness of transition methods used to implement AUC-monitoring for vancomycin treated patients in a small, primary facility. A further goal of the study was to identify areas of needed improvement and education and whether the problems derived from deficiencies in knowledge and ordering (medical and pharmacy services) or execution (nursing and laboratory services).

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