Purpose: Therapeutic hypothermia (TH) reduces mortality and neurodevelopmental impairment in infants born with hypoxic-ischemic encephalopathy (HIE). We used computer-based modeling techniques to determine the optimal number of TH devices as a function of birth volume.
Methods: We used discrete event simulation to create a model of HIE-affected births. Infants were born with inter-delivery times based upon institutional birth volume and HIE incidence, which varied randomly between 0.1% and 0.2%. Infants with HIE then entered a queue for a TH device. Infants underwent TH if a device was available within the 6-hour treatment window. Outcomes of interest were percent and number of infants not treated, and percent of time that all TH devices were in use.
Results: Mean HIE incidence across scenarios was 1.44 per 1000 births. In a hospital with 9000 annual births and only 1 TH device available, just over 1 HIE-affected infant each year was expected not to receive needed treatment because of device unavailability within the 6-hour window. Addition of a second TH device reduced this rate to less than 1 infant annually even in a 20000-birth hospital. Still, during 2% of the time, such a hospital would be at risk of no TH availability if one of their devices fails or another infant requires TH. The addition of a third TH device reduced these numbers even further for the 20000-birth hospital, so that less than 1 infant was expected not to receive TH every 10 years, and less than once a year would a backup device not be available. It should be noted, however, that the third device would not be used 99.8% of the time, or during more than 364 days of each year.
Conclusion: Our results demonstrate that the decision to have more than a single TH device available within a birth hospital significantly impacts care delivery. Even moderate-sized hospitals with NICU facilities would experience significant failure-to-treat rates due to device unavailability in the presence of a single TH unit. The quantitative nature of our analysis allows decision makers to determine the number of devices necessary to achieve a certain level of service given the birth volume of a particular institution. Such analytic techniques may be useful in informing decisions regarding system capacity necessary to treat other rare conditions.
Candidate for the Lee B. Lusted Student Prize Competition