Hypermagnesemia E83.4

Hypermagnesemia is defined as a serum magnesium level > 1 mmol/l (see magnesium below).

Hypermagnesemia only becomes clinically relevant at a concentration of > 1.6 mmol/l.

Elevated magnesium levels are found in acute and chronic renal insufficiency, in magnesium substitution as well as in hypothyroidism and Addison's disease.

At levels > 2 mmol/l, the cardiac conduction system and the transmission of excitation at the neuromuscular endplate are blocked (prolongation of the PQ time, widening of the QRS complex). The result is hypotension, hyporeflexia, nausea, vomiting, constipation and flaccid paralysis.

If the level rises above 3.5 mmol/l, respiratory insufficiency develops; even higher levels can lead to respiratory paralysis and diastolic cardiac arrest.

In parenteral overdose of magnesium, calcium acts as an antidote. In case of hypermagnesemia /hyperkalemia due to terminal renal insufficiency: dialysis.