Hypocalcaemia

Question 1

Normal calcium level

Answer 1

2.2 to 2.7mmol/L

(= 8.5 to 10.5 mg/dL)

Question 2

Calcium level in different parathyroid conditions

Answer 2

• Primary hyperparathyroidism: High Ca
• Tertiary hyperparathyroidism: High Ca
• Secondary hyperparathyroidism: Low Ca
• Pseudohypoparathryroidism: Low Ca
• Primary hypoparathyroidism: Low Ca
• Pseudopseusohypoparathyroidism: Normal Ca

Question 3

How to reveal the cause of hypocalcaemia in majority of cases?

Answer 3

Clinical history + PTH (parathyroid hormone levels)

Question 4

Cause of hypocalcaemia

Answer 4

• Vitamin D deficiency (Osteomalacia) (Low PO_4, high ALP)
• Chronic renal failure (High ALP)
• Rhabdomyolysis (initial stages)
• Magnesium deficiency (due to end organ PTH resitance)
• Cisplatin (Low Mg causes low Ca; So, First correct low Mg, then low Ca)
• High NO levels
• Acute pancreatitis
• Cytotoxic agents (>>> Tumout lysis syndrome: TLS)
• Contamination of blood samples with EDTA (→ Falsely low calcium level)
• Hypoparathyroidism (e.g. post thyroid/parathyroid surgery) (Low PTH, High PO₄)
• Secondary hyperparathyroidism (usually due to CRF/CKD) (High PTH, but High PO₄)
• Primary hypoparathyroidism (Low PTH, High PO₄)
• Pseudohypoparathyroidism (target cells are insensitive to PTH) (High PTH, but High PO₄)

​N.B.

• Primary hyperparathyroidism has high calcium, high PTH, Low PO₄
• Tertiary hyperparathyroidism has high calcium, high PTH, high PO₄ (only here PO₄ is in the same direction of calcium; In all other cases, it goes opposite)

Question 5

Hypocalcaemia: ECG changes

Answer 5

Prolonged QT

Question 6

ECG changes: hypocalcaemia vs hypercalcaemia

Answer 6

• Hypocalcaemia: prolonged QT
• Hypercalcaemia: short QT

Question 7

Osteomalacia: findings

Answer 7

• Low vitamin D levels →
• Ca: Low (Hypocalcaemia)
• PO₄: Low (Hypophosphataemia)
• ALP: High

Question 8

ECF calcium conc. are important for - ?

Answer 8

Muscle and nerve function

Question 9

Hypocalcaemia: features

Answer 9

• Neuromuscular excitability >>>
  
  • Perioral paraesthesia
  • Tetany: = muscle twitching and spasm
• If chronic >>>
  
  • Depression
  • Cataracts
• ECG: Prolonged QT interval

Question 10

Prolonged QT in ECG >>> biochemical causes

Answer 10

• Hypocalcaemia
• Hypomagnesaemia
• Hypokalaemia

Question 11

Hypocalcaemia: specific signs

Answer 11

• Trousseau’s sign
• Chvostek’s sign

Question 12

Which sign is more sensitive and specific for hypocalcaemia?

Answer 12

Trousseau’s sign

Question 13

Trousseau’s sign: procedure and interpretation

Answer 13

• Steps: Inflate the blood pressure cuff → maintain pressure above systolic → brachial artery occluded
• Interpretation: wrist flexion + fingers drawn together (sign positive/present)

Question 14

Trousseau’s sign is seen in- ?

Answer 14

95% of patients with hypocalcaemia

1% of patients with normocalcaemia

Question 15

Chvostek’s sign: procedure and interpretation

Answer 15

• Step: Tap over parotid
• Interpretation: Facial muscles will twitch (sign present/positive)

Question 16

Chvostek’s sign is seen in-?

Answer 16

• 70% of patients with hypocalcaemia
• 10% of patients with normocalcaemia

Question 17

Hypocalcaemia: management

Answer 17

• ​Acute management of severe hypocalcaemia
  
  • TOC: ​IV calcium gluconate 10% 10ml over 10min
  • Less preferred: IV calcium chloride (As it causes local irritation)
• ​ECG monitoring
• Management of underlying cause

Question 18

Ca and K level: ECG and treatment contrast

Answer 18

• Hypocalcaemia and hypokalaemia both have long QT in ECG
• But Hypocalcaemia and hyperkalaemia (high K) have similar Tx: calcium gluconate