When to use Speedup: An Examination of Intensive Care Units with Readmissions

Patient demand for critical care often exceeds bed availability. In such cases, current Intensive Care Unit (ICU) patients may be discharged in order to accommodate new, more urgent patients. Such a discharge increases the likelihood of physiologic deterioration resulting in readmission to the ICU. We model such an ICU as a state-dependent queueing network where patient service times and readmission probabilities depend on the ‘overloaded’ or ‘underloaded’ state of the ICU. We refer to the reduction in Length-of-Stay due to incoming critical patients during overloaded periods as ‘speedup’. We use a fluid model to examine how different definitions of ‘overload’ affect the steady-state behavior of the ICU and provide insight into capacity management of such systems. Readmissions can potentially increase the aggregate load on the ICU. We identify scenarios where speedup should never be used as well as scenarios where it can be helpful to temporarily alleviate congestion and increase access to ICU care. Additionally, our analysis provides approximations for the likelihood of patient speedup or readmission. Physicians and hospital administrators can determine how many beds are required in an ICU and when patient speedup should be utilized in order to meet performance targets for these various patient outcomes. Using data from 10 hospitals within a single hospital network, we verify that patient speedup occurs and investigate its impact on patient outcomes for ICUs of varying size. Using our state-dependent queueing model, we estimate how changes to the speedup policy would impact patient outcomes.