Patient outcomes after interhospital transfer: the impact of early intensive care unit upgrade

There is little known about the prevalence and outcomes of medical patients requiring early intensive care unit upgrade (EIU) following interhospital transfer, and previous studies of EIU focus on patients admitted through the emergency room. We aimed to examine the characteristics and risk factors for poor outcome among medical patients undergoing EIU after interhospital transfer. The publicly available Medical Information Mart for Intensive Care (MIMIC) IV database (2008–2019) was queried to identify non-surgical patients undergoing interhospital transfer. Patients who subsequently underwent EIU, defined as ICU admission within 24 hours of arrival after interhospital transfer, were compared to those who did not experience EIU for differences in mortality and length-of-stay (LOS.) We used multivariate logistic regression to identify risk factors for hospital death in this population and negative binomial regression to estimate the impact of EIU on hospital LOS. We identified 5,619 patients who underwent interhospital transfer, of which 339 (6.0%) experienced EIU and 5280 (94.0%) did not. Patients undergoing EIU after interhospital transfer were significantly older (median age 69 vs. 64 years; <i>p</i> = 0.001,) but there was no difference in sex. After risk-adjustment, we found an association between EIU and a higher risk of mortality (aOR 6.9, 95%CI 5.24–9.08). Increased comorbidity burden as measured by Charlson Comorbidity Index (CCI) was linked to higher odds of death (aOR 1.26, 95% CI 1.22–1.31,) as was nonwhite race (aOR 1.69, 95% CI 1.34–2.14). EIU was associated with a longer hospital LOS (IRR 1.40, 95%CI 1.28–1.54). EIU after interhospital transfer is associated with higher mortality and longer LOS. Further study will help identify process features of transfer and patient characteristics contributing to poor outcome after arrival from an outlying facility and guide efforts to mitigate risk and provide equitable care across the transfer continuum.