ICM - 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 tractRenal 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 acidosisIncreased by resp alkalosis

Question 9

Role of PTH

Answer 9

Form parathyroid glandsacts in response to hypocalcaemia1) calcium released from bone (osteoclastic)2() increased reabsorption from DCT3). 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 hypercalcaemiaSymptoms/Signs/ECG changes

Answer 13

Symptoms:Groans - abdominal pain, constipation, N&VBones - bony painMoans - psychosisStones - renalPolyuria/polydipsia

Signs - DehydrationCalcified skin/corneaECG 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 PTHEndocrine - primary hyperparathyroid (adenoma, MEN) hyperthyroidism tertiary hyperparathyroidGranulomatous - TB, sarcoidDrugs - Lithium, Aminophyline, Vitamin D, ThiazidesOther - milk alkali syndrome, renal failure

Question 15

Treatment

Answer 15

ABCDE and treat1) iv 0.9% saline, to diurese2) pamidronate 60-90mg3) Consider furosemide4) 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/lSevere < 1.9mmol/l

Question 18

Causes hypocalcaemia in critical care

Answer 18

HypoalbuminaemiaHyperventilationTransfusion of citrated blood

Question 19

Causes of hypocalcaemia generally

Answer 19

Endocrine - primary hypoparathyroid Congenital - DiGeorges Pseudohypopara (PTH resistance) Vit D deficiencyMalnutrition - osteomalacia, poor intakeDrugs - furosemide, calcitonin, bisphos, phenytoin, gentMisc - hyperphosphataemia, TLS, rhabo, acute renal failure, pancreatitis

Question 20

ECG in hypocalcaemia

Answer 20

Prolongd QTcAV blockTorsades

Question 21

Treatment Hypocalcaemia

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 stateNeuromusc: Tetany Chvosteks (facial nerve) Trousseaus (carpopedal spasm)Seizures