Final answer:
In emergencies where there's no time to type a patient's blood, O negative blood is used for transfusions due to its universal donor status and compatibility with all blood types.
Step-by-step explanation:
When a patient is in critical condition following a motor vehicle accident with multiple traumatic injuries and severe bleeding, there is no time to determine the patient's blood type. In such emergency situations, O negative blood is transfused. This is because O negative blood is considered the universal donor and is most likely to be compatible with all other blood types, reducing the risk of adverse transfusion reactions. In critical emergencies, it is vital to stabilize the patient quickly, and using O negative blood can provide lifesaving volume and oxygen carrying capacity to the patient's circulation.