Calcium in Emergency Medicine
Calcium plays a critical role in cardiac contractility, vascular tone, neuromuscular function, and coagulation. In emergency situations, intravenous calcium may be needed to correct life-threatening hypocalcemia, counteract the effects of certain toxins, or support cardiac function. Two formulations are available: calcium chloride and calcium gluconate. Understanding their differences and indications is important for advanced EMS providers.
Calcium Chloride vs. Calcium Gluconate
The key difference between these formulations is the amount of elemental calcium they deliver:
- Calcium chloride 10%: 1 gram provides 272 mg (13.6 mEq) of elemental calcium. It delivers approximately three times more ionized calcium per gram than calcium gluconate.
- Calcium gluconate 10%: 1 gram provides 93 mg (4.65 mEq) of elemental calcium. It is gentler on veins and less likely to cause tissue necrosis if it extravasates.
Calcium chloride is preferred in critical situations where a rapid increase in serum calcium is needed (cardiac arrest, severe hyperkalemia). Calcium gluconate is preferred for less urgent situations and when peripheral IV access is the only route available, because calcium chloride can cause severe tissue necrosis if it infiltrates from a peripheral line.
Prehospital Indications
Hyperkalemia with Cardiac Effects
Calcium stabilizes the cardiac membrane against the effects of elevated potassium. It does not lower the potassium level but protects the heart from arrhythmias while other treatments (albuterol, sodium bicarbonate) work to shift potassium intracellularly.
Calcium Channel Blocker Overdose
High-dose calcium can partially overcome the competitive blockade of calcium channels in overdose situations, improving cardiac contractility and blood pressure.
Hydrofluoric Acid Exposure
Calcium gluconate gel applied topically or calcium gluconate administered IV can bind fluoride ions and prevent systemic toxicity from hydrofluoric acid burns.
Cardiac Arrest
Calcium is indicated in cardiac arrest caused by hyperkalemia, hypocalcemia, or calcium channel blocker overdose. It is not routinely recommended for other causes of cardiac arrest.
Administration Considerations
Administer calcium chloride slowly (over 5 to 10 minutes in non-arrest situations) through a large-bore IV, preferably in a large vein. Monitor for bradycardia, hypotension, and arrhythmias during infusion. Do not mix calcium with sodium bicarbonate in the same IV line, as they will precipitate. Flush the line between these medications.