Objectives
Since the beginning of the COVID-19 pandemic in Austria, occupancy of ICU beds has been a key indicator for proxying the burden of the Austrian health care system. Subsequently, the risk of hospital overburdening has been cited as justification for lockdowns in the epidemic law, and ICU occupation and projected ICU occupation with COVID patients have been implemented as indicators for risk assessment by the Austrian Corona Commission.
This paper scrutinizes this justification by analysing the consequences of high ICU occupancy on outcomes of COVID and non-COVID patients both in the ICU and in normal wards. Specifically, we test the hypotheses that high COVID ICU occupancy is associated with higher mortality inside and outside the ICU in COVID and non-COVID patients.
Methods
Our analysis is based Austrian DRG data which contains patient-level data from inpatient stays up to November 2021. COVID-specific ICU capacity and occupancy rates by federal state are published in the weekly reports of the Austrian Corona Commission.
We regress three patient outcomes, in-hospital mortality, admission to the ICU and in- or post-ICU mortality, on the set of patient-level (age, gender, comorbidities), hospital-level (type and size of hospital) and spatio-temporal (region, pandemic phase) covariates. COVID-specific ICU occupancy is the primary variable of interest.
Results
Preliminary analyses show that high ICU occupancy is associated with lower ICU admission rates and higher in-hospital and in- or post-ICU mortality in COVID patients after controlling for patient-level, hospital-level and spatio-temporal covariates. Sensitivity analysis reveals that the reduced probability of ICU admission is insignificant for patients below the age of 70.
For non-COVID patients, high COVID-specific ICU occupancy is also associated with higher in-hospital and in- or post-ICU mortality with no significant effect on ICU admission rates.
We find that these effects are also significant, albeit small, at intermediate levels of COVID-specific ICU occupancy (10–33%).
Discussion
Our findings are in line with the literature on consequences of high ICU occupancy on patient outcomes. Since treatment of COVID-patients places above-average burden on ICU staff, high COVID-specific ICU occupancy leads to relevant adverse consequences for patients.
Monitoring of ICU occupancy projections and public health interventions that limit ICU admission, such as vaccinations or NPI, are therefore critical elements of the strategic response to the Coronavirus pandemic.