Equine Electrolyte Disorders Flashcards
what are the common causes of hypocalcemia?
pseudohypocalcemia: hypoproteinemia
lactation
sweat
anorexia
diarrhea
systemic inflammation
what is parathyroid hormone stimulated by?
hypocalcemia
what are the mechanisms of parathyroid hormone mobilizing calcium?
rapid bone phase: bone fluid
slow bone phase: bone matrix
increased renal absorption of calcium
increased active intestinal absorption via active vitamin D3
what do you commonly see with hypocalcemia in horses?
muscle fasciculations
synchronous diaphragmatic flutter
tetany
what happens in synchronous diaphragmatic flutter?
increased irritability of phrenic nerves
fire when atria depolarize
diaphragm contracts
what is neuromuscular irritability proportional to? equation
[Na][K]/[Ca][Mg][H]
neuromuscular irritability increases as calcium concentrations ______________
decrease
how can you have decreased intake of calcium?
low Ca diet
anorexia
how can you have altered parathyroid hormone function?
endotoxemia
hypoparathyroidism (rare)
what can a high calcium diet result in?
suppression of vitamin D activity
which horses are at higher risk for hypocalcemia when lactating?
draft horses
how do endurance horses lose electrolytes?
in sweat
high risk hypocalcemia
what is the short-term therapy for hypocalcemia in horses?
IV calcium: calcium gluconate
125 ml per 5-liter bag of IV fluids
why does renal hypercalcemia occur?
renal failure: would normally have high level of calcium excretion in urine
which bones are affected first in primary hyperparathyroidism?
thinnest bones
what can cause hypophosphatemia?
decreased intake: anorexia
refeeding syndrome: rare
what are the main pathogenic mechanisms in refeeding syndrome?
hypophosphatemia
decreased 2,3-DPG
ischemic heart disease
what serum electrolyte values become lowered in refeeding syndrome?
phosphate
calcium
magnesium
what do red blood cells become deficient in in refeeding syndrome?
ATP
2,3-DPG
what is the short-term therapy for hypophosphatemia?
intravenous fluids with phosphates
phosphite solutions do not help
when is hyperphosphatemia normal?
young animals
improperly stored blood
how is phosphorous filtered out of the body?
through glomerulus
what are the common causes of hypomagnesemia?
decreased intake: anorexia
increased loss in sweat
endotoxemia
how can you diagnose hypomagnesemia?
low plasma Mg concentration (routine chem)
low urine fractional clearance of Mg
what can cause hypermagnesemia?
iatrogenic overzealous administration of magnesium sulfate laxative to horses with large colon impactions
what are the rare and very rare causes of hypocalcemia?
rare: blister beetle toxicosis
very rare: hypoparathyroidism
is it common to see paresis or recumbency in horses with hypocalcemia?
no
what does hypocalcemia cause in muscles?
inactivation gates stay open too long
Na into cell, K out of cell, resting membrane potential too high
rapid firing and myotonia
eventual weakness
how can you have increased losses of calcium?
lactation
sweating
diarrhea
what is a common cause of mild hypocalcemia in hospitalized patients?
anorexia
what can cause endotoxemia that leads to hypocalcemia?
colitis
enteritis
peritonitis
pleuropneumonia
what is stage 1 of parturient paresis in cows?
hyperexcitability, ear twitching
what is the long term therapy for hypocalcemia in horses?
calcium in diet
calcium carbonate
dicalcium phosphate
acidify diet if possible
what is the most common cause of hypercalcemia in horses?
renal failure
how common are hypercalcemia of malignancy and primary hyperparathyroidism in horses?
rare
how do horses excrete calcium in urine?
calcium carbonate
what does primary hyperparathyroidism look like?
phosphate low or normal
osteopenia
shifting leg lameness
fibrous osteodystrophia
thinnest bones affected first
enlarged head
what is the long term management of hypophosphatemia?
adjust phosphorous content of ration
add trace minerals to diet
what can cause hyperphosphatemia that is not normal?
decreased glomerular filtration rate
nutritional secondary hyperparathyroidism: rare
normal in growing and if improperly stored blood
is secondary renal hyperparathyroidsim seen in horses?
not yet
what can cause nutritional secondary hyperparathyroidism?
dietary Ca:P imbalance
high grain diets- especially bran high in phosphorous
oxalate toxicity
can lactation and vitamin D toxicosis cause hypomagnesemia?
occasionally lactation
vitamin D toxicosis rare- camelids
how can you treat hypomagnesemia in horses?
magnesium-containing calcium fluids
offer endurance horses electrolyte replacement solutions
when has hypermagnesemia been seen in horses?
iatrogenic overzealous administration of magnesium sulfate laxative to horses with large colon impactions
