Final answer:
If you are unable to contact the dispatcher at the scene of a motor vehicle crash, you should administer first aid to the critically injured patients.
Step-by-step explanation:
If you are at the scene of a motor vehicle crash and you are unable to contact the dispatcher with your portable radio, it is important to take immediate action to ensure the critically injured patients receive the necessary help. In this situation, you should administer first aid to the critically injured patients. Providing immediate medical assistance can be crucial in saving lives and preventing further harm.