Final answer:
The nurse should assess the patient and the electrical leads first. If the patient is found to be in a critical condition, then life support measures including the use of an AED should be initiated.
Step-by-step explanation:
When a monitor alarms showing a wavy baseline without a PQRST complex, it indicates that the patient's ECG is abnormal and may suggest a severe cardiac event such as ventricular fibrillation. However, the first action a nurse should take is to assess the patient and the electrical leads to ensure that the alarm is not a false positive due to technical issues like loose electrodes. If the patient is found to be unresponsive and without a pulse, then life support measures like CPR and the use of a defibrillator should be initiated, following advanced cardiac life support (ACLS) guidelines. Automated external defibrillators (AED) are available in many public places and are designed to be used by nonmedical personnel, providing verbal instructions for use in life-threatening situations.