Equine Electrolyte Disorders

Question 1

what are the common causes of hypocalcemia?

Answer 1

pseudohypocalcemia: hypoproteinemia
lactation
sweat
anorexia
diarrhea
systemic inflammation

Question 2

what is parathyroid hormone stimulated by?

Answer 2

hypocalcemia

Question 3

what are the mechanisms of parathyroid hormone mobilizing calcium?

Answer 3

rapid bone phase: bone fluid
slow bone phase: bone matrix
increased renal absorption of calcium
increased active intestinal absorption via active vitamin D3

Question 4

what do you commonly see with hypocalcemia in horses?

Answer 4

muscle fasciculations
synchronous diaphragmatic flutter
tetany

Question 5

what happens in synchronous diaphragmatic flutter?

Answer 5

increased irritability of phrenic nerves
fire when atria depolarize
diaphragm contracts

Question 6

what is neuromuscular irritability proportional to? equation

Answer 6

[Na][K]/[Ca][Mg][H]

Question 7

neuromuscular irritability increases as calcium concentrations ______________

Answer 7

decrease

Question 8

how can you have decreased intake of calcium?

Answer 8

low Ca diet
anorexia

Question 9

how can you have altered parathyroid hormone function?

Answer 9

endotoxemia
hypoparathyroidism (rare)

Question 10

what can a high calcium diet result in?

Answer 10

suppression of vitamin D activity

Question 11

which horses are at higher risk for hypocalcemia when lactating?

Answer 11

draft horses

Question 12

how do endurance horses lose electrolytes?

Answer 12

in sweat
high risk hypocalcemia

Question 13

what is the short-term therapy for hypocalcemia in horses?

Answer 13

IV calcium: calcium gluconate
125 ml per 5-liter bag of IV fluids

Question 14

why does renal hypercalcemia occur?

Answer 14

renal failure: would normally have high level of calcium excretion in urine

Question 15

which bones are affected first in primary hyperparathyroidism?

Answer 15

thinnest bones

Question 16

what can cause hypophosphatemia?

Answer 16

decreased intake: anorexia
refeeding syndrome: rare

Question 17

what are the main pathogenic mechanisms in refeeding syndrome?

Answer 17

hypophosphatemia
decreased 2,3-DPG
ischemic heart disease

Question 18

what serum electrolyte values become lowered in refeeding syndrome?

Answer 18

phosphate
calcium
magnesium

Question 19

what do red blood cells become deficient in in refeeding syndrome?

Answer 19

ATP
2,3-DPG

Question 20

what is the short-term therapy for hypophosphatemia?

Answer 20

intravenous fluids with phosphates
phosphite solutions do not help

Question 21

when is hyperphosphatemia normal?

Answer 21

young animals
improperly stored blood

Question 22

how is phosphorous filtered out of the body?

Answer 22

through glomerulus

Question 23

what are the common causes of hypomagnesemia?

Answer 23

decreased intake: anorexia
increased loss in sweat
endotoxemia

Question 24

how can you diagnose hypomagnesemia?

Answer 24

low plasma Mg concentration (routine chem)
low urine fractional clearance of Mg

Question 25

what can cause hypermagnesemia?

Answer 25

iatrogenic overzealous administration of magnesium sulfate laxative to horses with large colon impactions

Question 26

what are the rare and very rare causes of hypocalcemia?

Answer 26

rare: blister beetle toxicosis
very rare: hypoparathyroidism

Question 27

is it common to see paresis or recumbency in horses with hypocalcemia?

Answer 27

no

Question 28

what does hypocalcemia cause in muscles?

Answer 28

inactivation gates stay open too long
Na into cell, K out of cell, resting membrane potential too high
rapid firing and myotonia
eventual weakness

Question 29

how can you have increased losses of calcium?

Answer 29

lactation
sweating
diarrhea

Question 30

what is a common cause of mild hypocalcemia in hospitalized patients?

Answer 30

anorexia

Question 31

what can cause endotoxemia that leads to hypocalcemia?

Answer 31

colitis
enteritis
peritonitis
pleuropneumonia

Question 32

what is stage 1 of parturient paresis in cows?

Answer 32

hyperexcitability, ear twitching

Question 33

what is the long term therapy for hypocalcemia in horses?

Answer 33

calcium in diet
calcium carbonate
dicalcium phosphate
acidify diet if possible

Question 34

what is the most common cause of hypercalcemia in horses?

Answer 34

renal failure

Question 35

how common are hypercalcemia of malignancy and primary hyperparathyroidism in horses?

Answer 35

rare

Question 36

how do horses excrete calcium in urine?

Answer 36

calcium carbonate

Question 37

what does primary hyperparathyroidism look like?

Answer 37

phosphate low or normal
osteopenia
shifting leg lameness
fibrous osteodystrophia
thinnest bones affected first
enlarged head

Question 38

what is the long term management of hypophosphatemia?

Answer 38

adjust phosphorous content of ration
add trace minerals to diet

Question 39

what can cause hyperphosphatemia that is not normal?

Answer 39

decreased glomerular filtration rate
nutritional secondary hyperparathyroidism: rare
normal in growing and if improperly stored blood

Question 40

is secondary renal hyperparathyroidsim seen in horses?

Answer 40

not yet

Question 41

what can cause nutritional secondary hyperparathyroidism?

Answer 41

dietary Ca:P imbalance
high grain diets- especially bran high in phosphorous
oxalate toxicity

Question 42

can lactation and vitamin D toxicosis cause hypomagnesemia?

Answer 42

occasionally lactation
vitamin D toxicosis rare- camelids

Question 43

how can you treat hypomagnesemia in horses?

Answer 43

magnesium-containing calcium fluids
offer endurance horses electrolyte replacement solutions

Question 44

when has hypermagnesemia been seen in horses?

Answer 44

iatrogenic overzealous administration of magnesium sulfate laxative to horses with large colon impactions