Final answer:
A nurse should place a client with fatal injuries in the expectant triage category during mass casualty triaging. O negative blood is used for emergency transfusions when the recipient's blood type is unknown. Agglutination with both anti-A and anti-B antibodies indicates AB blood type.
Step-by-step explanation:
A nurse triaging clients following a mass casualty event should place a client who has sustained fatal injuries in the expectant triage category. This category is used for individuals with extensive injuries who are not expected to survive given the severity of their injuries and the resources available. In these situations, the focus is on providing pain relief and comfort rather than extensive medical intervention.
Regarding the matter of blood transfusion in an emergency where the patient's blood type is unknown, the universally transfused blood type is O negative (O-). This is because O- blood is considered the universal donor type and is the safest option for transfusion when the recipient's blood type is unknown, as it lacks antigens that would typically cause a recipient's body to reject the blood.
In a routine blood typing test where a patient's blood agglutinates with both anti-A and anti-B antibodies, this indicates the patient has AB blood type. Agglutination with both antibodies means the patient's blood has both A and B antigens, which is characteristic of type AB blood. This is a normal response and does not indicate an error.