Page 1149 - Clinical Small Animal Internal Medicine

119 Disorders of Phosphorus and Magnesium 1087

Hypomagnesemia has also been reported in associa­
Box 119.4 Common clinical conditions associated
VetBooks.ir with hypomagnesemia tion with a number of endocrine conditions, for exam­
ple, in cats with hyperthyroidism, diabetes mellitus, and
Gastrointestinal loss
●
of these associations is still uncertain and a study evalu­
– Anorexia diabetic ketoacidosis. However, the clinical significance
– Malabsorption/severe diarrhea ating magnesium concentrations in dogs with diabetes
– Short bowel syndrome mellitus did not find an association.
Renal loss Hypomanesemia may be identified in lactating bitches
●
– Diabetes mellitus/diabetic ketoacidosis although is rarely clinically significant in the healthy
– Chronic kidney disease bitch. The prevalence of hypomagnesemia in bitches
– Renal tubular acidosis with eclampsia has been reported to be 44%.
– Drugs: loop diuretics
– Renal transplantation Treatment of Hypomagnesemia
Miscellaneous Magnesium supplementation should be considered
●
– Eclampsia when a patient’s clinical signs are attributable to
– Redistribution hypomagnesemia. Supplementation may also be indi­
○ Severe pancreatitis cated in those patients with refractory hypokalemia or
○ Sepsis hypocalcemia despite appropriate potassium and cal­
○ Refeeding syndrome cium supplementation respectively.
○ Catecholamine excess (pheochromocytoma) Intravenous magnesium supplementation is usually
○ Large‐volume resuscitation with magnesium‐ provided as magnesium sulfate or magnesium chloride.
replete fluid Typical dosages reported are 0.03–0.04 mEq/kg/h
administered as a CRI diluted in 5% dextrose or 0.9%
saline. Magnesium salt concentrations >20% should not
potassium such that hypomagnesemia and hypokalemia be administered and magnesium salt solutions are not
occur simultaneously. Clinical signs in this situation usu­ compatible with calcium‐ or bicarbonate‐containing flu­
ally reflect hypokalemia but potassium deficiency may ids. Careful monitoring should be performed during
prove refractory to therapy until magnesium levels have administration to avoid inadvertent overdosage and sup­
also been corrected. Hypocalcemia has also been plementation continued until low normal concentrations
reported in conjunction with hypomagnesemia. have been achieved and maintenance magnesium
In human patients, magnesium deficiency has been requirements can be provided via the patient’s daily die­
reported to contribute to the development and severity tary intake. Caution should be exercised when providing
of atrial fibrillation, supraventricular tachycardia, and magnesium supplementation, particularly in those
ventricular tachyarrhythmias. Information regarding patients with reduced renal function where risk of devel­
hypomagnesemia in dogs and cats with cardiac disease opment of hypermagnesemia is increased. The value of
is limited and the clinical importance is therefore uncer­ chronic supplementation is uncertain in veterinary med­
tain. However, certain drugs commonly used in cardiac icine but oral supplementation with magnesium oxide
patients such as digoxin and loop diuretics increase (1–2 mEq/kg/day) has been reported.
magnesium loss. Patients with cardiac disease that Reports of magnesium supplementation in the veteri­
develop hypomagnesemia may be at risk of cardiac nary literature have also included patients with tetanus
arrhythmias, decreased cardiac contractility, and refrac­ where supplemental magnesium may aid in reducing
tory hypokalemia. Consideration could therefore be muscle spasm and sedative requirements, and in patients
given to assessment of magnesium concentrations in with cardiac arrhythmias where hypomagnesmia is
these situations. deemed contributory.
Magnesium deficiency due to reduced dietary intake is
unlikely, particularly if commercial diets are being fed, Hypermagnesemia
but could occur in patients with prolonged anorexia or
severe gastrointestinal disease such as chronic diarrhea, The kidney excretes excess magnesium. Hyperm­
malabsorptive disease, and short bowel syndrome. agnesemia may occur with any marked reduction in
Hypomagnesemia has previously been reported in dogs GFR. It is rare for dogs and cats to demonstrate clinical
with protein‐losing enteropathy (PLE) and as a compo­ signs associated with mild to moderate hypermagne­
nent of refeeding syndrome when increased cellular semia. Clinical signs reported with severe hypermagne­
demand occurs in addition to chronic depletion second­ semia can include depression, weakness, lethargy, flaccid
ary to prior anorexia. paralysis, and decreased reflexes. Hypotension may be