- Purpose: IV calcium does not lower potassium; it stabilizes cardiac membranes within minutes and buys time for potassium-shifting/removal therapies.
- Common adult dose: Many US algorithms start with 1 g calcium gluconate (≈10 mL of 10% solution) and repeat if ECG changes persist. Some European/UK pathways target a larger elemental calcium dose and therefore use 30 mL of 10% calcium gluconate (≈3 g) or 10 mL of 10% calcium chloride. Follow your local protocol.
- Onset & duration: Onset within minutes; effect lasts ~30–60 min—so reassess ECG and redose if needed.
Why calcium in hyperkalemia?
Dangerously high serum potassium (often K⁺ ≥ 6.0–6.5 mmol/L or any K⁺ with ECG changes) can precipitate lethal dysrhythmias. IV calcium raises the myocardial threshold potential, counteracting hyperkalemia-related conduction abnormalities (peaked T waves, wide QRS, sine wave, bradyarrhythmias). It doesn’t lower K⁺; it stabilizes the myocardium while you shift/remove potassium.
When to give it
Give IV calcium immediately for:
- Severe hyperkalemia with ECG changes, or
- Peri-arrest or unstable rhythms in suspected hyperkalemia.
Recheck the ECG in ~5 minutes; repeat calcium if the QRS remains wide or instability persists.
Dosing: why you’ll see 10 mL in some places and 30 mL in others
Elemental calcium equivalence matters
- 10% Calcium chloride (CaCl₂): ~6.8 mmol elemental Ca²⁺ in 10 mL.
- 10% Calcium gluconate: much less elemental Ca²⁺ per mL; to deliver ~6.8 mmol you need 30 mL.
UK regulators highlighted the risk of underdosing when substituting gluconate for chloride; many EU/UK algorithms therefore specify 30 mL of 10% calcium gluconate (or 10 mL of 10% CaCl₂) over ~5 min, with ECG reassessment and possible repeat.
North American quick dose (and repeat)
Practical takeaway: Know your hospital’s algorithm. If it targets a fixed elemental calcium dose, you’ll often see 30 mL of 10% calcium gluconate (or 10 mL of 10% CaCl₂). If it uses a titrate-to-ECG approach, you may see 1 g (10 mL) gluconate, reassessed and repeated.
Administration tips
- Route/line: Calcium gluconate is less irritating and safe via peripheral IV; calcium chloride is caustic and usually reserved for central lines (or true peri-arrest).
- Rate: Give over 2–5 minutes (some protocols say up to 5–10 minutes), ideally through a large peripheral vein. Avoid mixing with bicarbonate/phosphate solutions due to precipitation.
- Reassessment: Continuous ECG monitoring; repeat ECG 5–10 minutes after the bolus. Redose if dangerous ECG changes persist.
What to do next (calcium buys you time)
Calcium is step one. Immediately start therapies that shift or remove potassium:
- Insulin + dextrose: e.g., 10 units regular insulin IV with dextrose; monitor glucose closely (check at 15 & 30 minutes, then hourly for several hours).
- Beta-agonist nebulization (salbutamol/albuterol) as adjunct.
- Bicarbonate (select cases with metabolic acidosis).
- Potassium binders (e.g., sodium zirconium cyclosilicate or patiromer) when appropriate.
- Urgent dialysis for refractory or severe cases (especially in renal failure).
Special situation: suspected digoxin toxicity
Historically calcium was avoided (“stone heart” myth). Modern evidence is mixed:
- A widely cited retrospective series found no increase in dysrhythmias or mortality after IV calcium in digoxin-toxic patients; others, including recent consensus, caution that calcium is not helpful and may be harmful in severe digoxin toxicity. Definitive therapy is digoxin immune Fab.
Bottom line: If digoxin toxicity is strongly suspected, many references advise avoiding IV calcium and prioritizing digoxin immune Fab (plus standard hyperkalemia management). Follow your toxicology/cardiology guidance.
Safety and adverse effects
- Extravasation/necrosis risk (especially with CaCl₂), hypotension, bradycardia, and hypercalcemia in repeated dosing. Keep the patient on a monitor and use a reliable IV.
Frequently asked questions (SEO)
Does calcium lower potassium?
No—it stabilizes the heart while other therapies shift or eliminate potassium.
How fast does it work and how long does it last?
Onset is within minutes; effect lasts ~30–60 min. Reassess ECG and repeat dosing if needed.
Is 30 mL of 10% calcium gluconate too much?
Not if your protocol targets ~6.8 mmol elemental calcium—that’s why some systems use 30 mL of gluconate or 10 mLof CaCl₂. Others use 1 g (10 mL) gluconate with repeat dosing. Match your local guideline.
Peripheral line or central line?
Gluconate: peripheral OK. Chloride: prefer central due to tissue injury risk.
How often should I check glucose after insulin?
At 15 and 30 minutes, then hourly for several hours (institutional specifics vary).
Implementation checklist (for clinicians)
- Confirm hyperkalemia +/− ECG changes
- Give IV calcium per local dosing algorithm
- ECG: continuous monitoring; repeat in 5–10 min
- Start insulin + dextrose (and consider beta-agonist, bicarbonate if acidotic)
- Order binder and evaluate for dialysis
- Glucose monitoring: 15, 30 minutes, then hourly
- Consider digoxin toxicity pathway if relevant