Final answer:
An important action prior to returning a patient's blood using the hand crank in the event of power failure is to ensure the correct bloodlines are connected.
Step-by-step explanation:
An important action prior to returning a patient's blood using the hand crank in the event of power failure is to ensure the correct bloodlines are connected. This is important to prevent any complications or risks associated with incorrect bloodlines. Confirming the correct connections helps ensure that the patient receives the appropriate blood and avoids any potential harm or adverse reactions. It is always crucial to double-check and verify the correct setup in order to maintain patient safety.