2017年にAJICに報告された、Veteran Affairs Western New York Healthcare System
BACKGROUND:The impact of an antimicrobial stewardship program (ASP) on 30-day mortality rates was evaluated in patients prescribed vancomycin in a Veterans Affairs hospital.
We aimed to evaluate the impact of an ASP on 30-day mortality rates of patient treated with intravenous (IV) vancomycin therapy at a Veterans Affairs hospital.
A secondary outcome was to determine significant risk factors for mortality associated with vancomycin.
Setting and study design
This was a single-center, institutional review board–approved, retrospective chart review of patients that received IV vancomycin at the Veteran Affairs Western New York Healthcare System, Buffalo, New York.
Patients were obtained via medication administration reports of IV vancomycin during the 2 designated time periods of October 1, 2006-July 31, 2008 (pre-ASP) and August 1, 2011-July 31, 2014 (ASP). The time gap between pre-ASP and ASP included a development period of the ASP program during which staffing was inconsistent.
The ASP is a patient-centered design that includes an infectious diseases pharmacist with the support of infectious diseases physicians.
The ASP does not use any automated protocols or guidelines; there is individualized chart review, microbiology review, and consultation with an infectious disease physician as needed. Interventions of the ASP consist of prospective audit and feedback, including appropriate antibiotic selection and dosing, microbiology, and duration of treatment.
The ASP provides monthly education to medical house staff to educate on antimicrobial stewardship and local antimicrobial resistance patterns.
To further limit inappropriate antimicrobial use within the facility, a restricted antibiotic policy is enforced that requires infectious diseases service approval of preselected antimicrobial agents.
The primary outcome was to evaluate the 30-day mortality rate in patients that received IV vancomycin therapy. Mortality was assessed via chart review. Secondary outcomes included any significant risk factors for mortality and the impact of the ASP on vancomycin mortality rates. Baseline demographics included age, sex, race, height, weight, body mass index, serum creatinine, RIFLE (Risk, Injury, Failure, Loss of function, End-Stage Renal Disease) criteria,15 methicillin-resistant S aureus colonization nasally, and Charlson Comorbidity Index score.16 Additional data collection included service admitted to, indication for vancomycin treatment, microbiology cultures, total duration of vancomycin treatment, initial vancomycin trough, and maximum vancomycin trough. Total duration of therapy, total length of stay, and readmission to hospital within 30 days were also collected for each patient included. An initial vancomycin trough concentration was defined as a trough concentration obtained within the first 96 hours of starting vancomycin therapy. Vancomycin trough concentration is a laboratory value of serum concentration of vancomycin obtained 30 minutes prior to a dose of vancomycin. All troughs were taken within 30 minutes of the next scheduled dose of vancomycin. Nephrotoxicity was defined as an increase in serum creatinine of at least 0.5 mg/dL from baseline or a 50% increase from baseline for 2 consecutive days.
Patients in the ASP group had higher creatinine clearance (79.9 ± 33.1 vs 66.8 ± 29.3 mL/min; P < .0001).
There were more patients admitted to medicine service during the stewardship time frame and more patients admitted to the surgical service during the pre-ASP time frame.
Regarding vancomycin, the stewardship program made on average 4.12 ± 2.4 recommendations per patient. Patients in the stewardship program had an average of 1.93 ± 1.31 pharmacokinetic levels. Doses were adjusted 1.74 ± 1.06 per patient. Additional recommen- dations included imaging or echocardiogram; cultures; and initiation, discontinuation, or change in therapy.
The retrospective quasiexperimental study design relies on the accuracy of the electronic medical record, and selection bias must be a consideration.
General improvements in clinical practice over time and other confounders not included in the design of the study could impact mortality rates outside of ASP interventions.
Because this study was conducted at a single institution and in a veteran population with a relatively small sample size, its external validity may be limited.
The generalizability to high-risk sicker patients is limited because of the exclusion of patients on vasopressors. Additionally, it must be acknowledged that the data compared was not concurrent time periods.
Decreased mortality rates in patients treated with vancomycin were observed after implementation of the ASP. A bundled stewardship approach with multidisciplinary interventions has proven to be effective in the reduction of mortality. Safer use of antibiot- ics, especially a prevalently used antibiotic such as vancomycin, may be one mechanism for reduction of mortality.