Final answer:
A flatline on an EKG indicates a lack of heart electrical activity, and the nurse's first priority is to assess the patient and begin CPR if there's no pulse or responsiveness, following ACLS protocols.
Step-by-step explanation:
When a nurse sees a flatline on an EKG (electrocardiogram), the first priority is to assess the patient to confirm the absence of a heartbeat and check for responsiveness.
If the patient is unresponsive and has no pulse, the situation is considered a code and requires immediate medical intervention, typically starting with cardiopulmonary resuscitation (CPR). The flatline, medically referred to as asystole, represents a lack of electrical activity in the heart and is a critical medical emergency.
The healthcare professionals would follow established advanced cardiac life support (ACLS) protocols, which include administering CPR and potentially using medications or an automated external defibrillator (AED) if indicated and available.