Among women at risk for the development of hemolytic disease of the fetus and newborn (HDFN), Rhesus D (RhD)-negative red blood cell (RBC) products should be the first choice if resuscitation is required, according to a review published recently in BMJ Military Health.
The authors evaluated the latest models of D-alloimmunization following the transfusion of RhD-positive RBCs to injured female service personnel of childbearing potential (WCBPs) and the ensuing rates of HDFN-related adverse events. In addition, they assessed some surveys in which the transfusion preferences of WCBPs in emergencies have been described.
Based on their status as having universal recipient compatibility, the RBC and low-titer group O whole blood units that are used for transfusions among individuals on the battlefield are group O. Because around 15% of those in Western populations are known to be RhD antigen–negative, a supply restriction with this blood type exists, thus necessitating the utilization of RhD-positive blood products in some situations.
Read more about the prognosis of HDFN
In fact, dependence on group O RhD-negative blood products in the military setting may rapidly exhaust the resources available. The “current transfusion dogma” might result, in turn, in hesitancy to utilize RhD antigen–positive RBC products in WCBPs because of the potential risk for developing HDFN.
Certain RhD-negative patients might generate an antibody to the RhD protein if they are exposed to RhD-positive blood products. This can lead to a process known as alloimmunization, in which the anti-D antibody might cause hemolysis when an RhD-positive blood transfusion is administered in the future.
Notably, according to current information, an injured patient who is transfused with antigen-incompatible RBC units, such as an individual with anti-D who receives RhD-positive RBCs, is not likely to develop hemolysis. This is due possibly to “the immunosuppression that accompanies trauma.”
HDFN occurs when maternal anti-D enters the fetal circulation and causes destruction of the fetus’s RBCs. Because the severity of HDFN can vary from mild to severe, the benefits associated with the transfusion of RhD-positive RBCs needs to be balanced against their potential risk of causing future harm—in particular, HDFN.
Based on several simple HDFN risk prediction models, eight steps are needed for HDFN to occur following an RhD-positive RBC transfusion to an injured woman:
- She is of current or future childbearing age
- Her status is RhD-negative
- She has survived a trauma
- She becomes D-alloimmunized
- She produces a high anti-D antibody titer
- She becomes pregnant
- Fetal status is RhD-positive
- Fetus/neonate experiences an adverse outcome linked to HDFN
It is of key importance to consider the possibility of an injured girl becoming pregnant in the future if she survives her trauma.
The authors emphasize that “Traditional paradigms of risk overestimated the danger of HDFN” and the risk for alloimmunization following RhD-positive blood to service WCBPs is considerably lower than previously thought.
They concluded that “Fear of potential future consequences should not be a barrier to providing life-saving transfusion[s] for WBBP[s] if RhD[-]negative blood products are not available. Deployed clinicians should be well versed in the low risk [for] HDFN to ensure life-saving transfusions are not delayed.”
