Electrolytes — Calcium

Current · V5 (2025) → F1.v Historical · V4 (2023) → I1.iii 1 exam appearance

2011A Q04

Exam question

Outline the role of calcium in the body (70% of marks). Outline the differences between calcium chloride and calcium gluconate solutions (30% of marks).

CICMWrecks answer

Master answer

Calcium

Total body stores of calcium = 25,000mmol (400mmol/kg)
Distribution
- 99% in poorly exchangeable pool (bone, teeth)
- 1% in readily exchangeable pool, majority of this is plasma
  - 2.15-2.65mmol/l in plasma
Absorbed from gut (increased with calcitriol)
Homeostasis maintained
- Short-term by distal tubular resorption, under control of PTH and calcitriol
- Long-term by bone osteoclast activity, influenced by PTH, calcitriol and calcitonin

Role of Calcium

Intracellular:
- Myocyte excitation-contraction coupling
- Required for cross bridge cycling
- Regulates mitotic function
- Intracellular second messenger for enzyme activation
Cell membrane:
- Flow of calcium is responsible for automaticity in SA and AV nodes
- Calcium channels are involved in membrane excitation
Extracellular:
- Forms part of the mineral matrix giving bone and teeth strength
- Involved in fibrinolysis
- Factor IV in the clotting cascade, required for binding of other clotting factors to phospholipids
- Required for the complement cascade

Ca Gluconate vs Ca Chloride

	Calcium gluconate	Calcium chloride
Chemical structure	2 gluconate ions 1 Ca²⁺ ions	2 chloride ions 1 Ca²⁺ ions
Dose	10ml of 10%	10ml of 10%
Potency	2.2mmol in 10ml	6.8mmol in 10ml
pH	6.0-8.2	5.5-7.5
Difference in adverse effects	Somewhat irritant to veins	Very irritable to veins
Administration	Can be safely given through peripheral IV cannulae	Best through CVC Can use in PIVC in resuscitation

Mooney 2016

Answer by Mooney

Past papers

Exam appearances

1 appearance

Exam	Exact exam wording	Candidate success
2011A Q04	Outline the role of calcium in the body (70% of marks). Outline the differences between calcium chloride and calcium gluconate solutions (30% of marks).	33%