Hypermagnesemia Clinical Manifestations

Neurological Manifestations

Muscular weakness and flaccid paralysis develop as magnesium interferes with neuromuscular transmission, leading to a progressive spectrum of neurological symptoms, in patients with serum magnesium levels >2.2 mEq/L, according to the American Heart Association 1
Drowsiness, confusion, and depressed level of consciousness progressing to coma occur with severe elevations of magnesium levels, in patients with hypermagnesemia 1
Ataxia (loss of coordination) may be present in patients with elevated magnesium levels, as a result of neuromuscular transmission interference 1

Vasodilation and hypotension occur even at moderately elevated magnesium levels, in patients with hypermagnesemia, due to the effect of magnesium on blood vessels 1
ECG changes, including prolonged PR interval, prolonged QRS duration, and prolonged QT interval, occur at magnesium levels of 2.5-5 mmol/L, according to the American Heart Association 2
Bradycardia develops as conduction slows, in patients with hypermagnesemia, due to the effect of magnesium on the cardiac conduction system 1, 2
Atrioventricular nodal conduction block occurs at severely elevated magnesium levels (6-10 mmol/L), in patients with hypermagnesemia, according to the American Heart Association 2
Cardiac arrhythmias and ultimately cardiac arrest can occur at extreme elevations of magnesium levels, in patients with hypermagnesemia, due to the effect of magnesium on the cardiac conduction system 1, 2

Hypoventilation develops as respiratory muscles weaken, in patients with hypermagnesemia, due to the effect of magnesium on neuromuscular transmission 1
Cardiorespiratory arrest may occur at extremely high magnesium levels, in patients with hypermagnesemia, according to the American Heart Association 1

The American Heart Association provides specific magnesium level correlations with clinical findings, including ECG changes (prolonged PR, QRS, QT intervals) at 2.5-5 mmol/L, and atrioventricular block, bradycardia, hypotension, and cardiac arrest risk at 6-10 mmol/L 2

Renal dysfunction is the primary risk factor for hypermagnesemia, as the kidneys are responsible for magnesium excretion, according to the American Heart Association 1
Pregnant women receiving magnesium for preterm labor are at risk of iatrogenic overdose, according to the American Heart Association 2