Page 961 - Small Animal Internal Medicine, 6th Edition

CHAPTER 53 Electrolyte Imbalances 933

tablet supplement product to provide 1 to 2 mEq/kg body observation. Treatment aimed at improving renal function is
weight per day has been sufficient to maintain total magne- indicated in animals with concurrent chronic kidney disease
VetBooks.ir sium in the normal range in dogs in the experience of the (see Chapter 41). Saline diuresis and administration of loop
diuretics (e.g., furosemide) will accelerate renal magnesium
authors.
excretion. Administration of IV calcium gluconate is indi-
cated in dogs and cats with cardiac arrhythmias or signifi-
HYPERMAGNESEMIA cant hypotension (see Box 53.7).

Etiology
Hypermagnesemia is present if serum total and ionized mag- Suggested Readings
nesium concentrations are greater than 2.5 mg/dL and Bolliger AP, et al. Detection of parathyroid hormone-related protein
1.5 nmol/L, respectively, although reference ranges may vary in cats with humoral hypercalcemia of malignancy. Vet Clin
Pathol. 2002;31:3.
between laboratories. It is an uncommon clinical problem DiBartola SP, ed. Fluid, electrolyte and acid-base disorders in small
owing to the remarkable ability of the kidney to efficiently animal practice. ed 4. St Louis: Saunders Elsevier, 2006.
eliminate excessive magnesium. Hypermagnesemia may Fan TM, et al. Evaluation of intravenous pamidronate administra-
occur in dogs and cats with kidney disease and post–renal tion in 33 cancer-bearing dogs with primary or secondary bone
azotemia and iatrogenically after excessive intake of magne- involvement. J Vet Intern Med. 2005;19:74.
sium (e.g., IV administration). Because excess magnesium is Fincham SC, et al. Evaluation of plasma ionized magnesium con-
rapidly excreted by the healthy kidney, iatrogenic hyperma- centration in 122 dogs with diabetes mellitus: a retrospective
gnesemia usually occurs in animals with chronic kidney study. J Vet Intern Med. 2004;18:612.
disease. Hypermagnesemia has also been reported in cats Graham-Mize CA, et al. Absorption, bioavailability and activity
with thoracic neoplasia and pleural effusion and in dogs with of prednisone and prednisolone in cats. Adv Vet Dermatol.
hypoadrenocorticism, primary hyperparathyroidism, and 2005;5:152.
hypothyroidism. The mechanism involved in the develop- Holowaychuk MK, et al. Ionized hypocalcemia in critically ill dogs.
ment of hypermagnesemia in these cats and dogs is unknown. J Vet Intern Med. 2009;23:509.
Hostutler RA, et al. Uses and effectiveness of pamidronate diso-
Clinical Features dium for treatment of dogs and cats with hypercalcemia. J Vet
Intern Med. 2005;19:29.
Hypermagnesemia usually results in varying degrees of neu- Mellema MS, Hoareau GL. Hypomagnesemia in brachycephalic
romuscular blockade. Nonspecific clinical manifestations of dogs. J Vet Intern Med. 2014;28:1418.
hypermagnesemia include lethargy, weakness, and hypoten- Midkiff AM, et al. Idiopathic hypercalcemia in cats. J Vet Intern
sion. Loss of deep tendon reflexes and electrocardiographic Med. 2000;14:619.
changes, consisting of prolonged PR intervals, widening QRS Norris CR, et al. Serum total and ionized magnesium concentra-
complexes, and heart block, occur at higher serum magne- tions and urinary fractional excretion of magnesium in cats with
sium concentrations. Serious complications, including respi- diabetes mellitus and diabetic ketoacidosis. J Am Vet Med Assoc.
ratory depression, apnea, cardiac arrhythmias, and cardiac 1999;215:1455.
arrest, occur when serum magnesium concentrations exceed Ramsey IK, et al. Hyperparathyroidism in dogs with hyperadreno-
corticism. J Small Anim Pract. 2005;46:531.
12 mg/dL. At these high levels, magnesium acts as a nonspe- Savary KCM, et al. Hypercalcemia in cats: a retrospective study of
cific calcium channel blocker. 71 cases (1991-1997). J Vet Intern Med. 2000;14:184.
Diagnosis Schenck PA, et al. Prediction of serum ionized calcium concentra-
tion by serum total calcium measurement in dogs. Am J Vet Res.
Measurement of the serum magnesium concentration 2005;66:1330.
identifies hypermagnesemia. Unlike magnesium depletion, Sharp CR, et al. A comparison of total calcium, corrected calcium,
serum concentrations cannot be normal if there is an increase and ionized calcium concentrations as indicators of calcium
in magnesium stores. A correlation between increased serum homeostasis among hypoalbuminemic dogs requiring intensive
magnesium concentrations and the severity of total body care. J Vet Emerg Crit Care. 2009;19:571.
excess has not been reported. Silverstein DC, Hopper KK, eds. Small animal critical care medicine.
St Louis: Saunders Elsevier; 2009.
Treatment Stern JA, et al. Cutaneous and systemic blastomycosis, hypercalce-
mia, and excess synthesis of calcitriol in a domestic shorthair cat.
Treatment begins with discontinuation of all exogenous J Am Anim Hosp Assoc. 2011;47:116.
sources of magnesium. Additional treatment depends on Toll J, et al. Prevalence and incidence of serum magnesium abnor-
the severity of the hypermagnesemia, the clinical presen- malities in hospitalized cats. J Vet Intern Med. 2002;16:217.
tation, and the status of renal function. Most dogs and Whitney JL, et al. Use of bisphosphonates to treat severe idiopathic
cats with healthy kidneys require only supportive care and hypercalcemia in a young Ragdoll cat. J Fel Med Surg. 2011;13:129.