Calcium/Phosphorus/Mg - Ex 4

Question 1

Total calcium =

Answer 1

Protein bound (40%) + ionized (50%) + complexed (10%)

Question 2

What does acidosis do to ionized Ca

Answer 2

increases ionized Ca++

Question 3

What does alkalosis do to ionized Ca

Answer 3

decreased ionized Ca++

Question 4

PTH effects

Answer 4

inc Ca and dec Pi

Question 5

Vit D effects

Answer 5

inc Ca and inc Pi

Question 6

Dairy cattle diet & Ca

Answer 6

Fed acidifying diet 3-5 weeks pre-partum –> acidosis promotes Ca release from bone, making Ca more available and increasing blood Ca levels at parturition and in the periparturient period

Question 7

What is the most common cause of apparent hypocalcemia

Answer 7

Hypoalbuminemia

Question 8

Hypocalcemia - Differentials (4)

Answer 8

1. Hypoalbuminemia (most common)
   - no CS
   - iCa is normal
2. Chronic renal failure
   - kidney can’t produce calcitriol –> reduced intestinal absorption of Ca and inc skeletal resistance to PTH
   - iCa is below the reference interval more often than total Ca
3. Acute Pancreatitis
   - release of lipase –> saponification
4. Periparturient hypocalcemia/Eclampsia
   - Small animals: usually small dog breeds with large litter; loss of Ca into milk during lactation
   - Lg animals: high lactating dairy cows

Question 9

Hypocalcemia - Diffs (less common) (5)

Answer 9

1. Nutritional hyperparathyroidism
   - low Vit D, low Ca and/or high Pi diet, inc PTH secretion (Ca level normal, but PTH leaches Ca from bones –> osteopenia)
2. Renal 2nd’y hyperparathyroidism
3. Primary hypoparathyroidism
4. Hypercalcitonism
5. Hypocalcemia in critical care pos

Question 10

CS of hypocalcemia

Answer 10

(occur when iCa is low!)

Tetany/mm tremors in most spp

Paresis in ruminants (milk fever)

Question 11

Tx of hypocalcemia

Answer 11

Usually only needed for cases of periparturient and acute hypocalcemia (following sx)

Question 12

“True” Hypercalcemia - Differentials

Answer 12

1. Paraneopastic (humoral hypercalcemia of malignancy) MOST COMMON
   - inc PTHrp, dec PTH
2. Hypoadrenocorticism - 2nd most common
3. Chronic renal failure
4. Vit D toxicoses
5. Primary hyperparathyroidism (rare)

Question 13

Most affected tissues - hypercalcemia

Answer 13

CNS, GI, heart, kidneys

severity of CS related to iCa levels

*all dogs respond differently to hypercalcemia and two dogs with the same levels may have very different degrees of CS

Question 14

Mineralization of soft tissue - hypercalcemia

Answer 14

most sever when the product of Ca and Pi is > 60 mg/dL

Question 15

Hypophosphatemia - Differentials (3)

Answer 15

1. Increased cellular uptake of phosphorus (maldistribution)
2. Increased loss (reduced renal reabsorption)
   - primary hyperparathyroidism: inc PTH –> dec Pi
   - renal tubular disorders
   - eclampsia (because PTH is high)
3. Dietary
   - Vit D deficiency

Question 16

Most common cause of hyperphosphatemia

Answer 16

Decreased excretion –> reduction in renal blood flow and dec GFR

Question 17

Hypoparathyroidism

Answer 17

can lead to hyperphosphatemia

Question 18

Hypomagnesemia - Diffs

Answer 18

1. Excessive loss from gut, mostly from malabsorption syndromes or diarrhea
2. Excessive loss from kidney, including fluid diuresis, diuretic therapy, or renal dz

Question 19

Hypomagnesemia - Ruminants

Two causes & CS

Answer 19

1. Milk tetany
   - calves fed milk-only diets (low in Mg)
2. Grass tetany
   - adults fed on lush, green pasture –> high K content in trash blocks normal Mg absorption from the rumen

Neuromuscular excitability, clonus, and contractors progressing to tetany may be observed
- acute death is possible

Question 20

Sequelae of hypomagnesemia

Answer 20

can lead to hypocalcemia and hypokalemia

Question 21

Hypermagnesemia

Answer 21

Clinically significant hypermagnesemia is most often seen when renal function and/or urinary elimination of excess Mg is compromised

CS rarely develop unless serum Mg exceeds approx 2 mmol/L, and are characterized by neuromuscular dysfunction (paresis or paralysis), cardiovascular depression, and Gi upset