Predictors of pre-icu duration and its association with mortality in COVID-19 infection: A secondary analysis of the stop-covid registry

Rationale: High patient volume and limited ICU resources associated with the COVID-19 pandemic have exacerbated ICU capacity strain, leading to longer pre-ICU lengths-of-stay (LOS). We examined the patient- and hospital-level predictors of pre-ICU LOS, and the association of pre-ICU LOS on in-hospital mortality for patients with COVID-19. Methods: Data were derived from the Study of the Treatment and Outcomes in Critically Ill Patients with COVID-19 (STOP-COVID), a multicenter cohort study of critically ill adults with COVID-19 admitted to 68 US hospitals. All patients had a minimum of 28-day follow-up;those discharged from hospital were presumed alive. The primary outcome was pre-ICU LOS, dichotomized into brief (≤1 day) vs. prolonged (>1 day). We constructed a multivariate mixed effects model, adjusting for patient factors (e.g., demographics, comorbidities, and pre-hospital symptom duration) and hospital factors (pre-COVID ICU beds number, countylevel case rates of COVID-19 (number of cases per 100,000 residents), and the hospital site itself) to determine predictors of pre-ICU LOS. Using 1:3 propensity score matching for pre-ICU period, we used multivariate mixed effect modelling to examine the association between pre-ICU LOS and in-hospital mortality. Results: A total of 4738 patients with complete data were admitted to the ICU, 36.6% were female, with median age 62 years (IQR 52-71). The majority (85.5%) were admitted from the ED or wards, with 62.5% classified as having a brief pre- ICU LOS. While demographics and co-morbidities (cancer, diabetes, and end-stage renal disease) were not associated with pre-ICU LOS, pre-existing lung disease (OR 1.33, 95% CI 1.02-1.74) was a patient-level predictor of a brief pre-ICU LOS as compared to a prolonged LOS. Having more available ICU beds (>100 vs. 0-48 ICU beds, OR 1.41, 95% CI 1.03-1.92) was a hospital-level predictor of a brief pre-ICU LOS. More patients were intubated at the time of ICU arrival in the prolonged pre-ICU LOS group, compared to the brief LOS group (64.6% vs. 59.2%, p≤0.001). In the mixed model, propensity matched for pre-ICU LOS, and adjusted for patient/hospital characteristics, differential pre-ICU LOS was not predictive of in-hospital mortality (OR 1.22, 95%CI 0.81-1.87), though oxygen support modality was associated with mortality. Conclusion: Patient- and hospital-level factors, such as ICU capacity, had an impact on pre-ICU duration, with more patients requiring a higher level of oxygen support at ICU arrival if admitted later in their course. However, once adjusting for clinical and hospital factors, pre-ICU LOS was not associated with in-hospital mortality.