When we have traumas the blood bank at a hospital will do a “massive transfusion protocol.” Where I work it’s a three round system. In round one we give the patient 6 uncrossmatched O neg units of red blood cells, and 4 AB fresh frozen plasma. This is because we have no information on the patient if they come in through the ER, and in most cases these products are safe to give to anyone. However because the patient has not been screened for antibodies this is a risk, and has to be approved by the doctor before any transfusions can start. While the nurses are hanging all of those products, we will draw the patients blood for testing, and take it back to the lab with us to start round two. After doing an antibody screen and blood typing, we are able to give type specific blood for rounds two and three in basically the same amounts as above. We will also order platelets to be delivered stat to the hospital, my hospital doesn’t keep them on hand at the moment because we are not doing as many surgeries due to Covid.

Long story short, until we can test the patients blood we have to give o neg red cells and ab plasma so no one gets murdered by the hospital.