Outpatient Parenteral Antimicrobial Therapy at Large Veterans Administration Medical Center | Page 2
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
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.
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.
Complications related to OPAT were noted in 96 of 393 (24.4%) episodes (Table 3). The major categories of complincations were hospital readmission, adverse drug events, an PICC-related complications.
Readmissions. The most common complication was readmission, which occurred in 49 of 393 (12.5%) episodes. Of these 49 admissions, 13 (26.5%) were deemed to be unrelated to either OPAT or the underlying infectious process. Excluding these unrelated hospitalizations, our overall hospital readmission rate was 36 out of 393 (9.2%). Of the 36 potentially relevant readmissions, 9 were due to PICC-related complications and 8 were due to adverse drug events. Readmission due to “failure to improve” while receiving OPAT occurred in 15 cases. Four patients were rehospitalized at outside facilities; in these cases, records were not sufficiently detailed to reliably determine the cause for hospitalization. One of these 4 patients subsequently expired during this hospitalization; the cause of death was unclear due to paucity of records.
Adverse Drug Events. Overall, 40 of 393 (10.2%) courses were notable for an adverse drug event, resulting in shortening of OPAT (including switches to oral antimicrobial therapy) in 29 of those 40 (72.5%) courses. The most commonly encountered events were acute kidney injury (11/40, 27.5%), pruritus/rash (10/40, 25%), and leukopenia (7/40, 17.5%).Vancomycin accounted for 40% of all adverse drug events recorded during the study period, followed by ertapenem (20%) and ceftriaxone (17.5%). However, when expressed as a percentage of total courses administered, an adverse drug event was recorded in 16 of 146 (11%) courses of vancomycin, 7 of 79 (8.9%) courses of ertapenem, and 8 of 109 (7.3%) courses of ceftriaxone. The most common adverse drug event due to vancomycin was acute kidney injury (8/16), followed by leukopenia (4/16). In 5 of the cases of acute kidney injury, a clinical decision was made to discontinue vancomycin. The overall rate of acute kidney injury in patients receiving vancomycin was 5.5% (8/146). In all cases, acute kidney injury in patients receiving vancomycin was reversible and did not result in any permanent sequelae.
Line-Related Complications. Our overall line-related complication rate was 6.4% (25/393) over the 4-year study period. The majority were related to PICC (22 of 25 cases), with the 3 remaining complications due to peripheral intravenous line placement. The most commonly reported line-related complications were mechanical in nature (occlusion/accidental displacement) and accounted for 9 of 25 events. Of these 25 events, 6 were self-limited local reactions (erythema, tenderness), nd therapy was not interrupted in any of these cases. Six bloodstream infections attributed to line-related complications were diagnosed.
Of the 25 line-related complications, 13 were deemed grade 1, 6 were grade 2, and 6 were grade 3. Therefore, our rates of minor, moderate, and major line-related complications were, respectively, 3.3%, 1.5%, and 1.5%. In all 6 cases of moderate line-related complications, venous access was discontinued prior to the scheduled end date after evaluation by the infectious diseases or OPAT service, and transition to oral therapy was deemed to be appropriate.
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