Inter-hospital transfer and clinical outcomes for people with COVID-19 admitted to intensive care units in Australia: an observational cohort study

Objectives: To examine the association between inter-hospital transfer and in-hospital mortality among people with coronavirus disease 2019 (COVID-19) admitted to intensive care units (ICUs) in Australia. Design: Retrospective cohort study; analysis of data collected for the Short Period Incidence Study of Severe Acute Respiratory Illness (SPRINT-SARI) Australia study. Setting, participants: People with COVID-19 admitted to 63 ICUs, 1 January 2020 – 1 April 2022. Main outcome measures: Primary outcome: in-hospital mortality; secondary outcomes: ICU and hospital lengths of stay and frequency of selected complications. Results: Of 5207 people with records in the SPRINT-SARI Australia database at 1 April 2022, 328 (6.3%) had been transferred between hospitals, 305 (93%) during the third pandemic wave. Compared with patients not transferred, their median age was lower (53 years; interquartile range [IQR], 45–61 years v 60 years; IQR, 46–70 years), their median body mass index higher (32.5 [IQR, 27.2–39.0] kg/m² v 30.1 [IQR, 25.7–35.7] kg/m²), and fewer had received a COVID-19 vaccine (22% v 44.9%); their median APACHE II scores were similar (14.0; IQR, 12.0–18.0 v 14.0; IQR, 10.0–19.0). Bacterial pneumonia (64.7% v 29.0%) and bacteraemia (27% v 8%) were more frequent in transferred patients, as was the need for more intensive ICU interventions, including invasive mechanical ventilation (71.2% v 38.1%) and extra-corporeal membrane oxygenation (26% v 1.7%). Crude ICU (19% v 14.9%) and in-hospital mortality (19% v 18.4%) were similar for patients who were or were not transferred; median lengths of ICU (20.0 [IQR, 11.2–40.3] days v 4.6 [IQR, 2.1–10.1] days) and hospital stay (29.7 [IQR, 18.1–49.6] days v 12.3 [IQR, 7.3–21.0] days) were longer for transferred patients. In the multivariable regression analysis, in-hospital mortality risk was lower for transferred patients (risk difference [RD], –5.0 percentage points; 95% confidence interval [CI] –10 to –0.03 percentage points), but not in the propensity score-adjusted analysis (RD, –3.4 [95% CI, –8.9 to 2.1] percentage points). Conclusions: Among people with COVID-19 admitted to ICUs, patients transferred from another hospital required more intense interventions and remained in hospital longer, but were not at greater risk of dying in hospital than the patients who were not transferred.