A prehospital protocol for transfusion of low-titer O-positive whole blood in patients with hemorrhagic shock in Los Angeles County: Modeling the risk of hemolytic disease of the fetus and newborn.

backgroundThe Los Angeles Development and Rapid Operationalization of Prehospital Blood (LA-DROP) pilot will protocolize prehospital administration of low titer O-positive whole blood (LTO + WB) to patients with hemorrhagic shock in Los Angeles County (LAC). We sought to quantify the risk of death from hemolytic disease of the fetus and newborn (HDFN) associated with RhD-negative alloimmunization in females of childbearing potential (FCPs) as a result of LA-DROP. STUDY DESIGN AND

methodsRetrospective data from LAC EMS databases were used in combination with estimates from published literature to assign probability distributions to each event in the sequence required for a transfusion of LTO + WB to result in a death from HDFN. Markov chain Monte Carlo simulation was used to derive risk estimates.

resultsWe estimated that the proposed prehospital transfusion strategy would result on average in one death from HDFN for every 10,000 transfusions in the overall population (95% confidence interval [CI] 6000-25,000) and for every 1800 transfusions in FCPs (95% CI 1000-4300). Based on the projected annual volume of transfusions under LA-DROP, this would result in one death due to HDFN approximately every 26 years (95% CI 15-64). DISCUSSION: The estimated per-transfusion risk of HDFN is similar to previously published work from other populations. The estimated frequency of deaths from HDFN associated with LA-DROP is lower than some previously published calculations, likely because of narrower eligibility criteria for transfusion.