Final answer:
After a patient has received more than 2 units of Type O Rh- blood, it is important to consider the presence of Rh antibodies and potential problems caused by introducing antibodies against A and B antigens. Pretransfusion blood testing and cross matching should be performed to ensure future transfusions are compatible.
Step-by-step explanation:
After a patient has received more than 2 units of Type O Rh- blood, several factors should be considered to direct future transfusions. These include checking for the presence of Rh antibodies in the patient's blood due to prior exposure to Rh antigen. If Rh- individuals receiving blood have had prior exposure to Rh antigen, antibodies for this antigen may be present in the blood and trigger agglutination. Additionally, introducing Type O blood into an individual with Type A, B, or AB blood will introduce antibodies against both A and B antigens, which may cause problems for the recipient. Therefore, when considering future transfusions, it is important to perform pretransfusion blood testing and cross match the patient's blood to ensure compatibility.