Page 230 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

220 ELECTROLYTE DISORDERS

BOX 8-1 Causes of Magnesium common finding in hospitalized dogs and cats that are
admitted to a critical care unit.
Deficiency 39,100,126,182 The reported incidence of concurrent electrolyte
abnormalities in these patients does not mirror that found
Gastrointestinal in humans, however. In dogs, it was common to see con-
Reduced intake/starvation/malnutrition current hypokalemia. 41,82,188 However, only one study
Chronic diarrhea reported concurrent hypocalcemia in dogs (Chew, DJ,
Gastric suction unpublished data). Abstracts that retrospectively
Malabsorption syndromes analyzed a large database of laboratory submissions for
Short bowel syndrome evaluation of calcium disorders suggest that ionized mag-
Gastric bypass surgery
nesium concentrations do differ among dogs and cats
Colonic neoplasia 145,146
with various calcium disorders. Unexpectedly,
Familial or inherited
two studies in dogs reported concurrent abnormalities
Renal in sodium. 99,188 In two of the feline studies, hypokalemia
Diabetes mellitus/diabetic ketoacidosis and hypocalcemia were reported, but there was not suffi-
Diuretics (except potassium-sparing agents) cient information available to determine the significance
Osmotic agents (including hyperglycemia) (Chew, DJ, unpublished data). 41 In the published feline
Intrinsic renal causes of diuresis
study, no concurrent association with other electrolyte
Postobstructive 163
disturbances was reported. Although several studies
Polyuric acute failure
Hyperaldosteronism reported mortality statistics, it is extremely difficult to
Hyperthyroidism interpret these findings without benefit of illness scoring
Renal tubular acidosis systems (e.g., APACHE II).
Concurrent electrolyte disorders Numerous veterinary researchers have also reported
Hypokalemia their findings of the prevalence of serum hypomagnese-
Hypercalcemia/hyperparathyroidism mia in specific disease conditions. Prospective studies of
Hypophosphatemia gastric dilation-volvulus syndrome and parvoviral enteri-
Drugs tis, respectively, in dogs reported no significant
Gentamycin abnormalities of serum magnsesium. 17,96 A prospective
Carbenicillin study of King Charles Cavalier spaniels with myxomatous
Ticarcillin
mitral valve disease reported significant serum hypomag-
Cyclosporin 114
nesemia in affected dogs. A prospective study of cats
Cisplatin
with diabetes mellitus or diabetic ketoacidosis (DKA)
Postrenal transplantation
reported a point prevalence of ionized hypomagnesemia
Familial or inherited
of 62% of diabetic and 57% of DKA cats. 110 A prospective
Miscellaneous study of 14 feline renal transplant patients documented a
Excessive loss from 189
period prevalence of ionized hypomagnesemia of 94%.
Sweat
Interestingly, concurrent hypocalcemia and hypokalemia
Lactation
were documented in the majority of cats with magnesium
Redistribution
deficiency in this study. A prospective study of cats with
Acute myocardial infarction
chronic renal failure documented ionized hypomagnese-
Acute pancreatitis
Insulin mia, hypercalcemia, and elevated parathyroid levels
Catecholamine excess (Chew, DJ, unpublished data). One case report and
Idiopathic one case series of five dogs have reported hypomagnese-
mia and hypocalcemia in dogs with protein-losing enter-
point prevalence of hypomagnesia in a group of opathy. 27,83 The significance of these studies cannot be
hospitalized dogs that were not necessarily confined to overlooked, and they lend strong support to the central
a critical care unit as 6.1% of 3102 dogs. 82 Abstracts for concept that magnesium deficit in ill and hospitalized
three additional studies in critically ill dogs and cats report dogs and cats is common. Currently, there is insufficient
a period prevalence of 33.6% of 70 animals (50 dogs and evidence to know whether a magnesium deficit
20 cats), a point prevalence of 50% of 101 dogs and a contributes to mortality in this population of patients.
point prevalence of 39% of 65 animals (42 dogs and 23 As a result, we cannot also answer the question of whether
cats) (Chew, DJ, personal communication). 41,188 Based treatment with magnesium contributes a significant
on these reports, it appears that hypomagnesemia is a very benefit to survival or outcome.