Final answer:
Magnesium is indicated for use in cardiac arrest when the patient has pulseless ventricular tachycardia associated with torsades de pointes, to help stabilize the heart's electrical activity.
Step-by-step explanation:
The indication for the use of Magnesium (Mg) in cardiac arrest specifically relates to cases involving pulseless ventricular tachycardia (VT) associated with torsades de pointes. There are different reasons someone may experience cardiac arrest, but when it comes to the use of Mg, the correct answer is C. Pulseless VT associated with torsades de pointes. This type of ventricular tachycardia is characterized by a unique 'twisting' pattern on an EKG and can progress to ventricular fibrillation (VF), leading to cardiac arrest. Mg is used in this scenario to stabilize the heart's electrical activity and reduce the likelihood of recurrent arrhythmias.