Background: Interhospital transfer patients experience substantially higher morbidity and mortality than those admitted from the emergency department, yet predictors of early deterioration after transfer remain poorly defined. Rapid ICU escalation within 24 hours is distressing to receiving teams and may reflect challenges in triage, pre-arrival risk assessment, or communication between referring and receiving centers. Clarifying the outcomes of early ICU escalation after transfer is essential for identifying high-risk patients and guiding systems-level interventions to improve transfer safety and reliability. We hypothesized that clinical outcomes would be poor among transfer patients experiencing early escalation to the ICU.
Methods: This retrospective cohort study included all adult medical interhospital transfers to a tertiary academic center from January 2024 to August 2025. Transfers admitted to acute, intermediate, or ICU care were included, and non-medical services were excluded. Early escalation was defined as ICU transfer within 24 hours of arrival at a lower level of care. Variables collected included demographics, transfer characteristics, timing, requested level of care, and clinical outcomes. The primary outcome was in-hospital mortality; secondary outcomes were hospice discharge, hospital length of stay, ICU length of stay, and multiple ICU admissions. Outcomes for early escalators were compared with those transferred directly to the ICU and with patients who required ICU care later in hospitalization.
Results: A total of 2806 interhospital transfers were included of which 63.9% (1794/2806) were to acute or intermediate care. Among these, 4% (72/1794) required ICU escalation within 24 hours. Early escalators had higher in-hospital mortality than patients transferred directly ICU-to-ICU (38% [27/72] vs 23% [228/1012], p=.006), but there was no significant difference in mortality based on ICU escalation in the first 24 hours compared to later in hospitalization (38% [27/72] vs 38% [83/219], p=>0.9). There were no significant differences between early escalating patients and ICU-ICU transfers regarding age, sex, race or ethnicity, insurer, or time of day of transfer arrival. Patients with early escalation experienced a mean ICU stay of 10 days, versus a mean ICU stay of 6 days in those transferred directly to the ICU.
Conclusions: Escalation to the ICU after interhospital transfer was associated with a higher mortality than direct ICU-to-ICU transfer regardless of timing of escalation, with early escalators appearing to have a more protracted ICU course. This finding challenges an assumption that the high mortality among patients who escalate rapidly represents inappropriately triaged transfers, and suggests that illness severity or other factors may drive the high mortality. The overall very high mortality risk for all interhospital transfers highlights the importance of pre-arrival risk assessments, transfer triage, and candid appraisal of risks and benefits of transfer, recognizing that a transfer potentially separates a patient from their loved ones and community. Further evaluation is needed to improve interhospital transfer safety.
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