Hypomagnesemia

From Dog

Hypomagnesemia is defined as a serum magnesium levels below the normal canine reference range of 0.7 - 1.1 mmol/L.

The converse is hypermagnesemia.

Hypomagnesemia is commonly observed with:

Magnesium is a co-factor for all enzyme reactions that involve ATP. most notably the sodium-potassium ATPase pump. Therefore, magnesium deficiency can lead to potassium wastage from the body and the resultant hypokalemia may be refractory to appropriate potassium replacement therapy.

Magnesium deficiency inhibits PTH secretion from the parathyroid gland, resulting in hypocalcemia, as well as causing the resting membrane potential of myocardial cells to be decreased and leads to Purkinje fibre excitability, with the consequent generation of arrhythmias.

Hypomagnesemia may predispose dogs to a variety of cardiovascular, neuromuscular and metabolic complications.

Many dogs remain asymptomatic but several nonspecific signs may be evident, including lethargy, anorexia, muscle weakness (including dysphagia and dyspnea), muscle fasciculations, seizures, ataxia and coma.

ECG testing usually shows atrial fibrillation, supraventricular tachycardia, ventricular tachycardia and/or ventricular fibrillation.

Concurrent hypokalemia, hyponatremia and hypocalcemia commonly occur in dogs with hypomagnesemia.

Diagnosis can usually be confirmed on blood electrolyte testing and ECGs, which show prolonged PR intervals, widened QRS complexes, depressed ST segment and peaked T waves.

Treatment is usually achieved with oral magnesium sulfate or magnesium chloride supplementation (1 - 2 mEq/kg daily). With life-threatening ventricular arrhythmias, a dose of 0.15 - 0.3 mEq/kg intravenously over 10 - 15 minutes is usually restorative to myocardial contractility.

References

  1. Dossin O & Lavoué R (2011) Protein-losing enteropathies in dogs. Vet Clin North Am Small Anim Pract 41(2):399-418