Final answer:
In an emergency where the patient's blood type is unknown, O negative blood is used because it is the universal donor type, presenting no risk of reaction to the recipient.
Step-by-step explanation:
In the medical scenario described where a patient is involved in a motor vehicle accident (MVA) with severe bleeding and critical injuries, there is no time to determine the patient's blood type.
In such emergencies, O negative blood is transfused. This is because O negative blood is considered the universal donor type and can be received by individuals of any blood type without the risk of an immune reaction.
In an emergency where the patient’s blood type is unknown, this is the safest option to prevent transfusion reactions.
Regarding the second situation, when agglutination occurs in the presence of both anti-A and anti-B antibodies, this indicates that the patient has AB positive blood.
This is a normal response for individuals with type AB blood, suggesting the presence of both A and B antigens on the surface of their red blood cells and no error was made by the technician.