The estimated risk for hemolytic disease of the fetus and newborn (HDFN) due to pre-hospital use of Rhesus D (RhD)–positive low-titer group O whole blood (LTOWB) transfusions is low in Finland, according to results of the Finnish Prehospital Whole Blood (FinnPHWB) study recently published in the journal Transfusion.
The utilization of pre-hospital LTOWB transfusions offers the benefits of cold-stored hemostatically active platelets with decreased bacterial contamination, along with lower diluted coagulation factor activity levels, compared with transfusions of red blood cells (RBCs) and plasma.
In an effort to enhance the availability of type O RhD-negative RBCs for emergency situations, LTOWB for prehospital utilization is typically RhD-positive. Transfusion of RhD-positive LTOWB carries with it the possibility of RhD alloimmunization in RhD-negative recipients, which can lead to the development of HDFN.
The researchers sought to estimate the increase in occurrence of HDFN associated with RhD-positive LTOWB transfusions in a Finnish population compared with national data regarding pregnancy-linked anti-D immunizations. They obtained data on recipients of blood products from helicopter emergency medical service (EMS) units located in the areas of Helsinki University Hospital and Tampere University Hospital. These two areas represent approximately 40% of the total population of Finland.
Read more about HDFN symptoms and risks
The data included the number and the sex of the individuals who had been transfused with any prehospital blood product, the date of the transfusion and the number of females under 45 years of age who had received a transfusion. Calculations were made with respect to the number of females of childbearing potential who might become RhD-alloimmunized after implementation of group O RhD-positive LTOWB transfusions in prehospital EMS units and the number of pregnancies that might be impacted by severe HDFN.
A 24% mean rate of reported alloimmunization rates in trauma studies and a higher reported rate of 42.7% in trauma patients 13 to 50 years of age were used to estimate the risk for HDFN, which was then extrapolated to the entire country of Finland.
Results of the study showed that based on the current prehospital transfusion rates in Finland, an estimated one to three patients with severe HDFN attributable to prehospital LTOWB transfusions every 10 years would be reported. In fact, fetal deaths due to HDFN linked to LTOWB transfusions were estimated to be less than one over a period of 100 years.
“[T]he estimated risk [for] serious HDFN due to prehospital LTOWB transfusion in the Finnish population is similar to previously published estimates,” the authors noted. “We consider it unethical to withhold a potentially lifesaving intervention from females of childbearing potential to avoid the slight risk [for] serious HDFN in a potential future pregnancy.”
