What does calcium gluconate do in hyperkalemia and what is the recommended adult dose?

Mechanism and Dosing of Calcium Gluconate in Hyperkalemia

Calcium gluconate does NOT lower serum potassium—it stabilizes cardiac membranes by protecting against life-threatening arrhythmias through restoration of conduction velocity, not by restoring resting membrane potential as traditionally believed. 1, 2

Mechanism of Action

Cardioprotective Effect (Not "Membrane Stabilization")

• Calcium gluconate works by restoring conduction velocity through calcium-dependent propagation in cardiac tissue, rather than by restoring resting membrane potential 2
• The protective effect begins within 1–3 minutes but lasts only 30–60 minutes, requiring concurrent potassium-lowering measures 1
• Calcium does not reduce total body or serum potassium levels—it only provides temporary cardiac protection while definitive therapies take effect 1, 3, 4
• The mechanism involves L-type calcium channel-mediated conduction rather than sodium-dependent conduction, which explains why it reverses QRS widening and sine-wave patterns without normalizing action potential duration 2

Limited Efficacy Profile

• Calcium gluconate is effective primarily for main rhythm disorders (e.g., bradycardia, heart blocks, ventricular arrhythmias) caused by hyperkalemia 5
• It is not effective for non-rhythm ECG changes such as peaked T waves, flattened P waves, or prolonged PR intervals when these occur without frank arrhythmias 5
• The therapeutic benefit is most pronounced when hyperkalemia produces abnormalities of conduction (QRS prolongation, sine-wave pattern) 2

Adult Dosing Recommendations

Standard Dosing

• Calcium gluconate 10%: 15–30 mL (1.5–3 grams) IV over 2–5 minutes is the first-line dose for cardiac membrane stabilization 1, 3
• Calcium chloride 10%: 5–10 mL (500–1000 mg) IV over 2–5 minutes may be used if central venous access is available, as it provides higher ionized calcium concentrations 1, 3
• Repeat the calcium dose if the ECG does not improve within 5–10 minutes 1, 3

Administration Considerations

• Administer calcium immediately when ECG changes (peaked T waves, widened QRS, prolonged PR interval) or arrhythmias are present—do not wait for repeat potassium results 1, 3
• Continuous cardiac monitoring is mandatory during and for 5–10 minutes after calcium administration 1, 3
• Stop injection if symptomatic bradycardia occurs during infusion 3
• Calcium chloride should be given through a central venous catheter when possible, as extravasation through peripheral IV can cause severe tissue injury 3

Critical Contraindications and Precautions

• Never administer calcium through the same IV line as sodium bicarbonate—precipitation will occur 6, 3
• Use calcium cautiously in patients with elevated phosphate levels (e.g., tumor lysis syndrome), as it increases the risk of calcium-phosphate precipitation in tissues and obstructive uropathy 6, 3
• In patients with malignant hyperthermia and hyperkalemia, calcium should only be used in extremis as it may contribute to calcium overload of the myoplasm 7

Clinical Algorithm for Calcium Use

Step 1: Verify Indication

• Confirm hyperkalemia with ECG changes (peaked T waves, widened QRS, prolonged PR, sine-wave pattern) or arrhythmias 1, 3
• Exclude pseudo-hyperkalemia from hemolysis or improper sampling before initiating aggressive therapy 3, 7

Step 2: Immediate Calcium Administration

• Give calcium gluconate 10%: 15–30 mL IV over 2–5 minutes (or calcium chloride 10%: 5–10 mL if central access available) 1, 3
• Monitor ECG continuously for 5–10 minutes 1, 3

Step 3: Repeat Dosing if Needed

• If no ECG improvement within 5–10 minutes, administer a second dose of 15–30 mL calcium gluconate IV over 2–5 minutes 1, 3

Step 4: Simultaneous Potassium-Lowering Therapies

• While calcium provides temporary protection, immediately initiate:
  • Insulin-glucose: 10 U regular insulin IV + 25 g dextrose (50 mL D50W) 1, 3
  • Nebulized albuterol: 10–20 mg in 4 mL over 10–15 minutes 1, 3
  • Sodium bicarbonate: 50 mEq IV over 5 minutes only if pH < 7.35 and bicarbonate < 22 mEq/L 1, 3

Step 5: Definitive Potassium Removal

• Hemodialysis for severe hyperkalemia (>6.5 mEq/L), oliguria, ESRD, or refractory cases 1, 3
• Loop diuretics (furosemide 40–80 mg IV) if eGFR > 30 mL/min and non-oliguric 1, 3
• Potassium binders (sodium zirconium cyclosilicate or patiromer) for sub-acute management 1, 3

Common Pitfalls to Avoid

• Do not delay calcium administration while waiting for repeat potassium levels when ECG changes are present—ECG abnormalities indicate urgent need regardless of the exact potassium value 1, 3
• Do not rely on calcium alone—it is a temporizing measure only; failure to initiate concurrent potassium-lowering therapies will result in recurrent life-threatening arrhythmias within 30–60 minutes 1, 3, 2
• Do not assume calcium will normalize all ECG changes—it primarily reverses conduction abnormalities (QRS widening) but does not restore action potential duration or correct peaked T waves without arrhythmias 5, 2
• Do not use calcium as monotherapy—it provides no potassium removal and its effect is transient 1, 3, 4

Special Populations

Pediatric Dosing

• Calcium gluconate: 100–200 mg/kg/dose (or calcium chloride: 20 mg/kg [0.2 mL/kg of 10%]) via slow IV infusion with ECG monitoring for bradycardia 6, 3

Tumor Lysis Syndrome

• Use calcium cautiously at 50–100 mg/kg IV for symptomatic hypocalcemia, but avoid if phosphate levels are elevated due to precipitation risk 6, 3