Outpatient Parenteral Antimicrobial Therapy at Large Veterans Administration Medical Center

Outpatient parenteral antimicrobial therapy was successfully delivered in our facility despite significant comorbidity and geographic limitations.
Published Online: September 13, 2013
Andrew Lai, MD; Thuong Tran, PharmD; Hien M. Nguyen, MD; Jacob Fleischmann, MD; David O. Beenhouwer, MD; and Christopher J. Graber, MD, MPH
Objectives: To evaluate our outpatient parenteral antimicrobial therapy (OPAT) program to determine its impact on infection management in a facility notable for high patient comorbidity and a large catchment area that includes most of Southern California.

Study Design: Retrospective chart review.

Methods: We reviewed all episodes of patients receiving OPAT from our institution from 2006 through 2009 for patient utilization characteristics and assessment of complications.

Results: A total of 333 patients received 393 courses of OPAT for a mean of 21.1 days. Diabetes mellitus (53.5%), psychiatric disease (39%), and chronic kidney disease (31%) were common; more than half the patients lived more than 20 miles from our medical center. Osteomyelitis (39.7%) and bacteremia (19.3%) accounted for the majority of OPAT indications. Staphylococcus aureus (36.4%) was the most frequent infecting organism, and vancomycin (37.4%) was the most frequently prescribed medication. Complications including hospital readmission, adverse drug reactions, or line-related complications were noted in 96 of 393 (24.4%) episodes, but most were minor, reversible, or not directly related to the OPAT given. Serious line-related complications that required hospital readmission were noted in only 6 (1.5%) episodes. OPAT was completed as planned in 313 (79.6%) episodes; end-stage renal disease was associated with OPAT noncompletion in multivariable analysis (odds ratio = 2.20, P = .047). We estimated that OPAT saved our medical center $4 million per year.

Conclusions: Despite our patients’ high level of comorbidity and our facility’s large catchment area, we were able to deliver OPAT successfully and safely with significant cost savings.

Am J Manag Care. 2013;19(9):e317-e324
Outpatient parenteral antimicrobial therapy (OPAT) improves patient convenience and ecreases hospital stay for patients requiring long-term parenteral antimicrobials.
  • OPAT can be delivered safely in populations with significant comorbidity and in facilities that serve large catchment areas.

  • Involvement of a pharmacist trained in infectious diseases was important for our program’s success.
First described in 1974,1 outpatient parenteral antimicrobial therapy (OPAT) has become integral in decreasing duration of hospitalization and reducing healthcare costs. Outpatient parenteral antimicrobial therapy facilitates hospital discharge for  patients  who would otherwise require ongoing hospitalization for the sole purpose of receiving intravenous antibiotics. Prolonged hospital stays have been associated with an increased risk of nosocomial infections,2 including hospital-acquired pneumonia, catheter-related bloodstream infections (CR-BSIs), and Clostridium difficile–associated diarrhea. One study estimated that an average hospital stay is associated with a 17.6% chance of infection and that each additional day of stay increases this risk by 1.6%.3 Another study estimates that, when it occurs, nosocomial infection further multiplies length of stay  by a  factor of 2.87.4 Furthermore, increased lengths of hospitalization have been associated with deconditioning5 and have been shown to predict poor functional outcomes in the elderly.6 While few prospective studies evaluating outcomes of OPAT versus continued inpatient therapy have been performed, retrospective data have demonstrated comparable rates of treatment success.7,8 The purpose of this study is to review our program’s utilization data to determine rates of OPAT completion and related complications in a population with a substantial rate of background comorbidities.

METHODS

Study Design and Patient Selection


The Department of Veterans Affairs Greater Los Angeles Healthcare System (VAGLA) OPAT program was established in 2003. Our OPAT team consists of an infectious diseases faculty attending physician, an infectious diseases fellow, an infectious diseases pharmacist, and a home health coordinator. The majority of patients in our cohort were initially hospitalized at VAGLA for their illness and subsequently identified by their healthcare providers as potential candidates for OPAT. A small percentage of OPAT patients were referred from clinics or initially hospitalized at outside facilities. The final decision to administer OPAT, as well as antibiotic selection and duration, was made only after consultation with the OPAT team, who reviewed all OPAT requests for appropriate selection and duration of antimicrobial therapy, typically in consultation with the infectious diseases consulting service for OPAT candidate inpatients at VAGLA. The Department of Veterans Affairs Greater Los Angeles Healthcare System arranges fee-basis services with home infusion pharmacies and nursing agencies for the delivery of antimicrobials and nursing services over a broad catchment area extending as far north as Bakersfield, as far west as San Luis Obispo, as far south as Orange County, and as far east as the San Gabriel Valley. The decision about whether the antimicrobial is to be self-administered by the patient or administered by a healthcare professional is made after a collective evaluation by home healthcare professionals and the OPAT team; both types of patients were included in the analysis.

All patients who received OPAT through our program between January 1, 2006, and December 31, 2009, were identified. Patient data from this period were collected from the VA Computerized Patient Record System. Extracted data included patient  diagnosis and demographics (including medication copay status, with “exempt” status serving as a surrogate marker for limited financial means, based on a yearly income of approximately $12,000-$25,000 according to the patient’s number of dependents), medical comorbidities, zip code where patient received OPAT, antibiotics received, duration of treatment,  microbiology, and information pertaining to complications and readmissions. We excluded patients who were discharged to community nursing homes, primarily because detailed records from these facilities were not available through the VA Computerized Patient Record System.

Complications during OPAT were recorded, including all-cause readmission, any line-related complaint, any adverse drug event consisting of a laboratory result or subjective complaint attributable to an administered antibiotic, or death. Acute kidney injury was defined as an increase in glomerular filtration rate of more than 50% above the recorded value at time of hospital discharge (if hospitalized) or at initiation of OPAT (if outpatient). Leukopenia was defined as an absolute white blood cell count of less than 4000/μL. The decision to continue, switch, or terminate therapy following an adverse drug event was made on an individualized basis by the infectious diseases and OPAT team. We defined a line-related complication as any adverse event pertaining to intravenous access, ranging from self-limited insertion site irritation to readmission for line-related sepsis. We further stratified these complications by assigning a severity grade ranging from 1 (least severe) to 3 (most severe).  Complications that were self-limited and ultimately had no impact on duration and route of therapy were assigned a severity grade of 1. Complications that resulted in a truncated duration of intravenous therapy or change in route of administration were assigned a severity grade of 2. Complications that required hospitalization due to CR-BSI or exit site infections were assigned a severity grade of 3. We specifically chose to differentiate patients with a severity grade of 3 from patients readmitted due to a line-related complication, as several patients were briefly admitted solely for peripherally inserted central catheter (PICC) placement after a mechanical complication (eg, PICC line displaced). Using our grading system, these patients would receive a severity grade of 1 despite being readmitted due to a line-related complication.

We defined treatment completion as a patient who received a course of outpatient intravenous antibiotics for the duration prescribed at the onset of therapy. Patients who required a switch to an alternative intravenous agent (eg, due to an adverse drug event) but who still completed the prescribed course length were also counted as completions. Patients who required a switch to oral medications or had intravenous therapy stopped early due to OPAT complication, or who were admitted for any reason during their OPAT course, were counted as incomplete treatments. Logistic regression analysis of OPAT noncompletion was performed with Stata release 10 (StataCorp LP, College Station, Texas).

An informal cost analysis was conducted by subtracting outpatient costs related to OPAT from the projected costs of continued hospitalization. The cost of OPAT was determined by adding per diem nursing visit charges, cost of antibiotics (provided by contracted pharmacy), and per diem pharmacy charges. The projected inpatient cost was calculated by adding the total inpatient antimicrobial cost (VA price) and cost of continued hospitalization (average daily bed cost multiplied by total hospital days). The projected length of hospitalization was obtained by assuming that patients would have remained hospitalized for the duration of IV therapy.

RESULTS

Patient Enrollment and Demographics

From 2006 to 2009, 393 OPAT courses were received by 333 individual patients (Table 1). Average age was 62 years, and mean duration of outpatient treatment was 21.1 days (range, 0-88 days; interquartile ratio, 9-30 days). A total of 37 (9.4%) OPAT courses were referred from an outside facility and 41 (10.4%) OPAT courses were referred from an outpatient clinic within our system, 22 of which were from the infectious diseases clinic. Initial and/or ongoing infectious diseases consultation was obtained in 274 (69.7%) OPAT courses. Medical comorbidities were frequent in our population, particularly diabetes mellitus (53.5%), psychiatric disease (39.0%), congestive heart failure (38.7%), coronary artery disease (31.5%), and chronic kidney disease with estimated glomerular filtration rate of less than 60 mL/min (30.9%). A total of 27 (8.1%) patients had end-stage renal disease (ESRD), defined as an estimated glomerular filtration rate of less than 15 mL/min and/or receipt of hemodialysis at the time of OPAT initiation. Most (253/333, 76%) patients had limited financial means (as determined from exemption from VA copay), and 205 (62%) lived more than 20 miles away from our facility.

Diagnosis and Microbiology

Principal diagnoses were made by the physicians initiating the OPAT consult, with additional assistance from infectious diseases and the OPAT team. The most common indication for OPAT was osteomyelitis of the foot (113/393, 28.8%), which most commonly occurred in diabetic patients (Table 2). The second-leading diagnosis was bacteremia, which included both primary and secondary bacteremia (76/393, 19.3%) Other common indications included nonfoot osteomyelitis (43/393, 10.9%) and soft tissue infections (40/393,  10.2%).

The most commonly isolated pathogen was Staphylococcus aureus (143/393, 36.4%), of which 80 of 143 (56%) were methicillin-resistant S aureus. Other frequently isolated microorganisms included Streptococcus species (50/393, 12.7%) and Pseudomonas aeruginosa (38/393, 9.7%). In 92 of 393 courses (23.4%), treatment was given empirically in the absence of an isolated pathogen or relevant culture.

The most commonly prescribed antibiotics were vancomycin (147/393, 37.4%), ceftriaxone (109/393, 27.7%), and ertapenem (79/393, 20.1%). In 50 of 393 (12.7%) OPAT courses, patients were treated with 2 intravenous agents simultaneously.

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