Red Book - Calcium

Question 1

Normal serum Ca

Answer 1

2.2 to 2.6 mmol/L

Question 2

Total body calcium

Answer 2

1kg, 99% in bone and teeth

Question 3

Average daily calcium need

Answer 3

0.1mmol/kg/day

Question 4

Absorbed by

Answer 4

Kidney

Bone

Small bowel

Question 5

Excretion

Answer 5

Secreted in GI tract

Renal excretion (calcitonin prevents absorbtion)

Bone deposition

Question 6

Role of Ca

Answer 6

Bone mineralisation

Neuronal function

Coagulation

2nd messenger in signal transduction

Muscle contraction

Bind troponin for contraction

Question 7

Calcium exists in what forms?

Answer 7

Free ions

Ions bound to plasma protein (40-50%)

Diffusible complexes 10%

Question 8

What increases/decreases ion/protein binding

Answer 8

reduced by metabolic acidosis

Increased by resp alkalosis

Question 9

Role of PTH

Answer 9

Form parathyroid glands

acts in response to hypocalcaemia

1) calcium released from bone (osteoclastic)

2() increased reabsorption from DCT

3). Reduced phosphate reabsorption (increased Ca as less phosphate to complex with)

Question 10

Role of vitamin D3

Answer 10

PTH acts on it to convert to 1,25 dihydorxy vitamin D3 —> increases gut Ca absoption

Question 11

Role of calcitonin

Answer 11

C cells of the thyroid

Due to HYPERcalcaemia

Opposes PTH

1) inhibit Ca absorption from GI tract
2) Inhibit osteoclasts
3) stimulate osteoblasts
4) inhibit tubular reabsorption BUT also stops phosphate absorption in DCT

Question 12

Define hypercalcaemia

Answer 12

Ca > 2.6

Question 13

Presentation of hypercalcaemia

Symptoms/Signs/ECG changes

Answer 13

Symptoms:
Groans - abdominal pain, constipation, N&V
Bones - bony pain
Moans - psychosis
Stones - renal
Polyuria/polydipsia

Signs - Dehydration
Calcified skin/cornea

ECG changes
SHORT QTc, broad T-waves
Cardiac arrest if >3.75mmol/L

Question 14

Causes of hypercalcaemia

Answer 14

Malignancy - deposits in bone, myeloma, ectopic PTH

Endocrine - primary hyperparathyroid (adenoma, MEN)
hyperthyroidism
tertiary hyperparathyroid

Granulomatous - TB, sarcoid

Drugs - Lithium, Aminophyline, Vitamin D, Thiazides

Other - milk alkali syndrome, renal failure

Question 15

Treatment

Answer 15

ABCDE and treat

1) iv 0.9% saline, to diurese
2) pamidronate 60-90mg
3) Consider furosemide
4) stop meds contributing (calcium, Vit D, thiazides)
5) Consider calcitonin, RRT

Question 16

ECG features of hypercalcaemia

Answer 16

Short QTc

Prolonged PR interval

Wide QRS

Wide T waves

AV block and arrest

Question 17

What is hypocalcaemia

Answer 17

Less than 2.2mmol/l

Severe < 1.9mmol/l

Question 18

Causes hypocalcaemia in critical care

Answer 18

Hypoalbuminaemia
Hyperventilation
Transfusion of citrated blood

Question 19

Causes of hypocalcaemia generally

Answer 19

Endocrine - primary hypoparathyroid
Congenital - DiGeorges
Pseudohypopara (PTH resistance)
Vit D deficiency

Malnutrition - osteomalacia, poor intake

Drugs - furosemide, calcitonin, bisphos, phenytoin, gent

Misc - hyperphosphataemia, TLS, rhabo, acute renal failure, pancreatitis

Question 20

ECG in hypocalcaemia

Answer 20

Prolongd QTc
AV block
Torsades

Question 21

Treatment

Answer 21

Replace with 10mls 10% gluconate or chloride

Chloride - 6.8mmol vs Gluconate 2.2

Question 22

Features of hypocalcaemia

Answer 22

Altered mental state

Neuromusc:
Tetany
Chvosteks (facial nerve)
Trousseaus (carpopedal spasm)

Seizures