Optimizing Patient Placement in Normal Care Units: An Instrumental Causal Forest Approach Minimizing Mortality

Abstract: Normal care units (NCU) placement affects health outcomes. NCUs in a hospital have different specialisations. There are patients that can potentially stay in multiple different NCUs. On a given day the NCUs are on different utilisation levels, which also affects health outcomes. Our approach uses instrumental variable causal forests, with emergency admission as an instrument, to estimate how the effect of NCU placement varies across patients and utilisation levels. The results show a clear trade-off between specialisation and utilization. Based on these findings, we design a minimax regret placement policy, using frequentist, Balke-Pearl and Manski bounds, that lowers mortality without capacity expansion. The policy reallocates patients according to their individualized average treatment effects, showing that data-driven patient placement can improve outcomes by using existing resources more efficiently.