Final answer:
The first choice for rapid extrication after a motor vehicle accident is through the door of the vehicle. In critical emergencies where blood type is unknown, type O negative blood is transfused as it is universally compatible.
Step-by-step explanation:
Your first choice for rapid extrication of a patient in a motor vehicle accident in front of your ambulance would be through the door. This is typically the fastest and safest way to remove a patient, especially if the door can be opened normally or with the use of extrication tools. If the door is not an option, alternative methods such as removing the patient through a window or using the 'roof flap' technique may be considered.
In critical situations where immediate blood transfusion is required and the patient's blood type is unknown, type O negative blood is used. O negative blood is considered the universal donor and can be transfused to patients of any blood type without causing an adverse reaction, which is critical in life-threatening emergencies. This is due to the absence of A, B, or Rh antigens on the red blood cells.