At what magnesium level does cardiac arrest typically occur?

Cardiac arrest can result from significantly elevated magnesium levels, particularly in the case of hypermagnesemia. At levels around 25 mEq/L, magnesium has profound effects on cardiovascular function, leading to potentially life-threatening complications such as cardiac arrest. At this high concentration, magnesium acts primarily as a muscle relaxant, not only affecting the skeletal muscles but also leading to depression of the myocardium’s excitability. This can result in various arrhythmias and ultimately cardiac arrest.

Patients with such high levels of magnesium may present with lethargy, loss of deep tendon reflexes, hypotension, and bradycardia, which can escalate to cardiac arrest if not managed promptly. While lower levels of magnesium may be associated with some cardiovascular changes, the synthesis of cardiac arrest is predominantly seen at significantly elevated concentrations, reinforcing the understanding that a magnesium level of 25 mEq/L represents a critical threshold for this serious condition.