Final answer:
A triage officer should immediately perform a triage assessment on all patients to prioritize their treatment needs. Critical patients are often given red tags and must receive medical attention first. In an emergency without time for blood typing, O negative blood is used because it's the universal donor type.
Step-by-step explanation:
When assigned as a triage officer at a multiple crash pileup, the correct immediate action is to perform a triage assessment on all patients. This is essential in order to determine the severity of injuries and prioritize treatment correctly.
The main objective of the triage officer is to quickly categorize patients based on the urgency of their medical needs. Priority and critical patients should be identified, with those sustaining life-threatening injuries or conditions marked with red tags, signifying immediate care is required, while those with less serious conditions are tagged accordingly to receive attention after critical patients have been stabilized.
In the specific scenario where a patient arrives in the emergency department with multiple traumatic injuries and severe bleeding, without time to determine the blood type, O negative blood is transfused. This is because O negative blood is the universal donor type and can be given to patients of any blood type without risk of transfusion reaction, making it crucial in emergencies where there is no time for blood typing tests.