Parenteral Tx not associated with increased rates of new bloodstream infections, mortality,

New bloodstream infections (BSIs) can affect nearly one-fourth (19.5%) of people who inject drugs (PWIDs) hospitalized for infective endocarditis, but discharging them for outpatient parenteral treatment is not associated with increases in either the incidence of new BSIs or with mortality, according to results from a study published in JAMA Network Open.

“Infective endocarditis in PWIDs is rising in incidence, coinciding with the opioid epidemic. Prolonged parenteral antimicrobial treatment is the standard of care for infective endocarditis in PWID,” wrote authors led by Charlie Tan, MD, of the Schulich School of Medicine and Dentistry, London, Ontario, Canada. “Outpatient parenteral antimicrobial therapy (OPAT) is safe, efficacious, and cost-effective for treating many infections, but PWID are generally not considered candidates. This decision is in part due to the risk of BSIs from ongoing intravenous drug use (IVDU), commonly through central venous catheters inserted for antimicrobial treatment,” they added.

Thus, Tan and colleagues sought to determine the clinical factors and characteristics of new BSIs in PWID receiving treatment for infective endocarditis, and to compare new BSI rates in inpatient and outpatient settings and assess any associations between new BSIs and treatment settings with mortality.

In this retrospective cohort study, they included 420 consecutive episodes of infective carditis that occurred in 309 PWIDs (mean age: 35.7 yeas; 50.7% male) admitted to three tertiary care hospitals in London, Ontario, Canada. Most had Staphylococcus aureus endocarditis (77.6%) of the tricuspid valve (70.5%). The most frequently injected substances were opiates (86.9%), and 76.4% of patients used more than one substance.

In 46.2% of patients, ongoing IVDU was confirmed by physicians and in 65.5%, via urine toxicology results. The most common infecting microorganisms were aerobic gram-negative bacilli (53.8%) and Candida species (28.2%).

In 19.5% of patients, infective endocarditis was complicated by new BSIs. Tan and colleagues found that a significantly higher rate of new BSIs was associated with:

  • Physician-documented inpatient intravenous drug use (HR: 5.07; 95% CI: 2.68-9.60).
  • Inpatient treatment (HR: 4.49; 95% CI: 2.30-8.76).
  • Previous infective endocarditis (HR: 1.89; 95% CI: 1.20-2.98).

A significantly lower rate of new BSIs was associated with inpatient addiction treatment (HR: 0.53; 95% CI: 0.32-0.88).

Surprisingly, rates of new BSIs were higher in inpatients, at 9.60 BSIs per 1,000 days of IV access (95% CI: 7.95-11.5), compared with the outpatient new BSI rate of 5.23 BSIs per 1,0000 days (95% CI: 3.50-7.46; incidence rate ratio: 1.84; 95% CI: 1.20-2.90; P=0.003).

Although new BSIs demonstrated no significant association with 90-day mortality (HR: 1.76; 95% CI: 0.78-4.02), the following factors were significantly associated with higher 90-day mortality:

  • Admission to an intensive care unit (HR: 9.51; 955 CI: 491-18.42).
  • Inpatient treatment for infective endocarditis (HR: 3.39; 95% CI: 1.53-7.53).
  • Infective endocarditis caused by methicillin-resistant Staphylococcus aureus (HR: 1.77; 95% CI: 1.03-3.03).

Significantly lower mortality rates were associated with right-sided infective endocarditis (HR: 0.41; 95% CI: 0.25-0.67).

Limitations of the study include its retrospective, nonrandomized nature, underestimations in patients receiving OPAT due to less stringent monitoring as compared with inpatients, and variations in OPAT treatment programs across facilities.

In an editorial accompanying the study, Andrew J. Stewardson, MBBS, MS(Epi), PhD, of Monash University, Melbourne, Australia, and Steven Y.C. Tong, MBBS, PhD, of Royal Melbourne Hospital and the University of Melbourne, Melbourne, Australia, re-iterated current perceptions of managing these patients in an outpatient setting.

“There has traditionally been hesitation to manage PWID with OPAT because of perceived risk to both staff and patients themselves, and among the most prominent of these is the possibility of a new BSI resulting from ongoing drug use. To some extent, this belief has origins in the mutual mistrust that has characterized hospital care of PWID,” they wrote.

However, results from Tan and colleagues bolster previous findings that found OPAT to be safe and effective in these patients, noted Stewardson and Tong:

“A review of OPAT among PWID has previously suggested that OPAT may be both effective and safe, but the study from Tan and colleagues provides new evidence regarding the safety for carefully selected patients and the health benefits of OPAT for them. These findings align with previous evidence suggesting that from the patient perspective, rather than being the safe alternative, the ’social and structural conditions [in hospitals] produce discharges against medical advice and, in turn, more complicated and protracted medical treatment.’”

They added: “Importantly, Tan and colleagues found that outpatient treatment was not associated with an increase in frequency of new BSIs compared with inpatient treatment, challenging dogmatic concerns around the safety of OPAT for PWID. Rather, patients who had been predominantly treated in an inpatient setting (compared with an OPAT setting) experienced both a higher rate of new BSIs (HR: 4.49; 95% CI: 2.30-8.76) and higher 90-day mortality (HR: 3.39; 95% CI: 1.53-7.53).”

Thus, in carefully selected, low-risk PWIDs, OPAT may be a viable option, Stewardson and Tong concluded.

“It is clearly time to move beyond descriptions and to either implement the delivery of such services for as many PWID with infectious endocarditis as possible or, if resources are limited, to consider randomizing patients to such services,” they wrote.

  1. Among people who inject drugs (PWIDs) with infective endocarditis, new bloodstream infections (BSIs) are common, occurring in 19.5% of patients in this study.

  2. Outpatient treatment of infective carditis PWID) was not associated with an increase in frequency of new BSIs compared with inpatient treatment.

E.C. Meszaros, Contributing Writer, BreakingMED™

This study was supported by the Ontario HIV Treatment Network and the St. Joseph’s Health Care Foundation.

Tan reported no conflicts of interest.

Stewardson received a National Health and Medical Research Early Career Fellowship, and Tong has received a National Health and Medical Research Development Fellowship.

Cat ID: 144

Topic ID: 87,144,730,914,190,192,144