(108) Infective Endocarditis in the Overdose Crisis: Addiction Care and Healthcare Utilization

Background & Introduction: While patients with injection drug use (IDU)-associated infective endocarditis (IE) are often younger and have fewer comorbidities than patients with non-IDU IE, many of these patients require cardiac surgery, have post-discharge ED visits, and experience in-hospital mortality at similar rates to patients with non-IDU IE.1 These findings reflect the increased medical and psychosocial vulnerability of people who use drugs and the need for improved addiction medicine care in the inpatient setting for people with IDU-IE. This need is especially acute in medically underserved communities, including rural areas.

In 2016, Maine Medical Center (MMC) implemented an inpatient consult service to support inpatients with substance use disorders – the Integrated Medication for Addiction Treatment (IMAT) program. Similar programs have yielded varying results on health service utilization outcomes among patients with severe IDU-related infections.2–4 Further clarification of the impact of multidisciplinary addiction consult services on health service utilization outcomes in IDU-IE is needed, particularly in rural states like Maine where access to post-discharge substance use disorder and harm reduction services can be challenging.5 In this study, we compare patient demographics and clinical characteristics pre- and post- IMAT program. We also examine the association between the IMAT program and health outcomes and care utilization.

Methods: This study included all hospitalized patients receiving transesophageal echocardiograms (TEE) from 01/01/2013 through 01/01/2019 with definite or possible IE (by Duke’s criteria). We conducted a retrospective chart review to collect patient demographics, clinical characteristics and health service utilization data from index hospitalizations before (01/01/2013 – 12/31/2015) and after (01/01/2016-01/01/2019) the implementation of the IMAT program. The primary outcome was post-discharge ED visits and hospital readmissions within 90 and 30 days, respectively. Secondary outcomes included post-discharge prescriptions for medication for opioid use disorder (MOUD), naloxone and key vaccinations. We summarized data using descriptive statistics and performed a bivariate analysis to compare variables between study participants with or without a primary outcome. We included non-collinear variables in a multivariable regression model based on statistical significance (p < 0.10 in unadjusted bivariate analyses) and clinical relevance. The same approach was used to assess secondary outcomes. The multivariable models for primary and secondary outcomes included: housing status, primary care provider, hepatitis C, cardiac device, definite or possible IE, native or prosthetic valve IE, affected valve, alcohol use disorder, insurance type and any vascular or infectious complications. Patients who died during their IE admission and within 90 days following discharge were excluded from the regression analyses.

Results: The overall study population included 289 unique patients undergoing TEE within the study period; 99 (34%) with IDU-IE were identified. Demographic and health characteristics differed between patients with IDU and non-IDU IE, consistent with previously reported results.1 Notably, descriptive characterization of patients with IDU-IE in the three years preceding and the three years following the implementation of the IMAT program differed only with respect to alcohol use (33% pre-IMAT, 16% post-IMAT, p=0.041) and increased incidence of native valve over prosthetic valve endocarditis (79% pre-IMAT, 93% post-IMAT, p=0.036). Among patients with IDU-IE, there were no statistically significant differences in 90-day post discharge ED visits (37% pre-IMAT, 37% post-IMAT, p >0.9) or 30-day readmissions (22% incidence pre-IMAT, 18% post-IMAT, p = 0.7). There was, however, a statistically significant increase in the proportion of patients with IDU-associated IE receiving MOUD (24% pre-IMAT, 80% post-IMAT, p< 0.001) and naloxone (2% pre-IMAT, 14% post-IMAT, p = 0.067) after discharge pre-and post IMAT implementation, respectively. Among patients with indication for immunization, rates of receiving immunization at discharge increased significantly for Hepatitis A (9.8% to 24%, p=0.069), Hepatitis B (29% to 51%, p=0.037) and Tdap (7.3% to 41%, p< 0.001) before and after the implementation of the IMAT program.

In the multivariable logistic regression model assessing the association between the IMAT program and health care utilization, no statistically significant difference was observed in either 90-day ED visits (OR 0.81 CI(0.27-2.4)) or 30-day hospital readmissions (OR 0.95 CI(0.25-3.7)) among patients with IDU-IE following the implementation of the IMAT program.

Among secondary outcomes, the adjusted odds of receiving naloxone and MOUD upon discharge were 11 (CI: 0.76-670) and 51 (CI: 10-420), respectively. This indicates a statistically significant improvement in MOUD prescribing, but no statistically significant change in naloxone prescribing at discharge. The adjusted odds ratios for receiving vaccinations among IDU-IE patients with indication for immunization were 4.1 (CI: 0.83-31), 29 (CI: 0.25-15,000) and 3.3 (CI: 0.63-21) for Hepatitis A, Hepatitis B, and Tdap, respectively, indicating no statistically significant independent association between the implementation of the IMAT program and immunization.

Conclusion & Discussion: In this study, the implementation of an inpatient addiction consult service was not associated with changes in acute health service utilization, however we found a significant independent association between the IMAT program and increased prescriptions for medication for opioid use disorder. One notable limitation of this study, which sought to capture the impact of a multidisciplinary addiction consult service at a single tertiary care center in a rural state, is that it is limited by sample size. While we did not find significant differences in health service utilization in this study, differences in outcomes related to addiction care may be most discernable several months or years following patients’ index hospitalizations for IE. MOUD prescriptions, as well as naloxone prescriptions and immunizations (which both tended to improve following IMAT implementation), may provide more immediate insight into the effectiveness of addiction medicine care in the acute care setting. Our study provides important information on the unique context of addiction care in the acute care setting in a rural state. This study demonstrates the need for further research to understand the long-term impact of addiction medicine care in the inpatient setting, particularly among people with IDU-IE.

References: 1. Thakarar, K., Rokas, K. E., Lucas, F. L., Powers, S., Andrews, E., DeMatteo, C., Mooney, D., Sorg, M. H., Valenti, A., & Cohen, M. (2019). Mortality, morbidity, and cardiac surgery in Injection Drug Use (IDU)-associated versus non-IDU infective endocarditis: The need to expand substance use disorder treatment and harm reduction services. PloS One, 14(11), e0225460. https://doi.org/10.1371/journal.pone.0225460

2. Nolan, N. S., Marks, L. R., Liang, S. Y., & Durkin, M. J. (2021). Medications for Opioid use Disorder Associated With Less Against Medical Advice Discharge Among Persons Who Inject Drugs Hospitalized With an Invasive Infection. Journal of Addiction Medicine, 15(2), 155–158. https://doi.org/10.1097/ADM.0000000000000725

3. Ray, V., Waite, M. R., Spexarth, F. C., Korman, S., Berget, S., Kodali, S., Kress, D., Guenther, N., & Murthy, V. S. (2020). Addiction Management in Hospitalized Patients With Intravenous Drug Use-Associated Infective Endocarditis. Psychosomatics, 61(6), 678–687. https://doi.org/10.1016/j.psym.2020.06.019

4. Wang, S. J., Wade, E., Towle, J., Hachey, T., Rioux, J., Samuels, O., Bonner, C., Kirkpatrick, C., O’Loughlin, S., & Foster, K. (2020). Effect of Inpatient Medication-Assisted Therapy on Against-Medical-Advice Discharge and Readmission Rates. The American Journal of Medicine, 133(11), 1343–1349. https://doi.org/10.1016/j.amjmed.2020.04.025

5. Thakarar, K., Sankar, N., Murray, K., Lucas, F. L., Burris, D., & Smith, R. P. (2021). Injections and infections: Understanding syringe service program utilization in a rural state. Harm Reduction Journal, 18(1), 74. https://doi.org/10.1186/s12954-021-00524-1