What should be your immediate action if the casualty is unresponsive?

When a casualty is unresponsive, the most appropriate and immediate action is to check for pulse and breathing. This is critical because determining whether the casualty is breathing and has a pulse will guide the subsequent steps in emergency care. If the individual is breathing, you can provide further monitoring and supportive care. If there is no breathing or pulse, immediate initiation of cardiopulmonary resuscitation (CPR) is necessary to preserve brain function and increase chances of survival.

Attempting to awaken the casualty by shaking them may be a logical reaction in some situations, but it does not provide information about their vital signs and could delay potentially life-saving interventions. Similarly, assessing for visible injuries is important but should come after ensuring that the person is breathing and has a heartbeat. Applying a tourniquet without confirming the need for such an intervention can be dangerous and is typically reserved for severe hemorrhage that is evident. Therefore, checking for pulse and breathing takes precedence to establish the level of medical intervention required.