In an emergency department patient with severe hyperkalemia (serum potassium ≥6.5 mmol/L) and ECG changes, when and how should calcium gluconate be administered?

Calcium Gluconate Administration for Hyperkalemia in the Emergency Department

Immediate Indications for Calcium Gluconate

Administer IV calcium gluconate 10% (15-30 mL over 2-5 minutes) immediately for any patient with serum potassium ≥6.5 mmol/L OR any ECG changes attributable to hyperkalemia, regardless of the absolute potassium value. 1, 2

ECG Changes That Mandate Calcium Administration

• Peaked or tented T waves (earliest sign, typically appearing at K+ >5.5 mmol/L) 1, 2
• Flattened or absent P waves with prolonged PR interval (moderate hyperkalemia, ~6.0-6.4 mmol/L) 1, 2
• Widened QRS complex with deepened S waves (severe hyperkalemia, K+ >6.5 mmol/L) 1, 2
• Sine-wave pattern, idioventricular rhythms, ventricular fibrillation, or asystole (life-threatening, K+ ≥7-8 mmol/L) 1, 2

Mechanism and Timing

• Calcium does NOT lower serum potassium—it only stabilizes cardiac membranes by counteracting the depolarizing effects of hyperkalemia on myocardial conduction 1, 2, 3
• Onset of cardioprotective effect: 1-3 minutes 1, 2
• Duration of effect: 30-60 minutes only—this is a temporizing measure while other potassium-lowering therapies take effect 1, 2

Dosing and Administration Protocol

Standard Adult Dosing

• Calcium gluconate 10%: 15-30 mL IV over 2-5 minutes (preferred for peripheral IV access) 1, 2
• Calcium chloride 10%: 5-10 mL IV over 2-5 minutes (alternative when central venous access is available; more potent than gluconate) 1, 2

Pediatric Dosing

• Calcium gluconate: 100-200 mg/kg/dose via slow IV infusion with continuous ECG monitoring 1
• Calcium chloride: 20 mg/kg (0.2 mL/kg of 10% solution) over 5-10 minutes (reserve for central access due to tissue injury risk with extravasation) 1

Repeat Dosing

• Monitor ECG continuously for 5-10 minutes after the initial calcium dose 1, 2
• If no ECG improvement within 5-10 minutes, administer a second dose of 15-30 mL calcium gluconate IV over 2-5 minutes 1, 2
• The repeat dose can be given because the initial dose may have been insufficient or the cardioprotective effect is waning 1

Critical Monitoring Requirements

• Continuous cardiac monitoring is mandatory during and for at least 5-10 minutes after calcium administration 1, 2
• Stop the infusion if symptomatic bradycardia develops during calcium administration 1
• Obtain a repeat ECG after calcium administration to document resolution of hyperkalemic changes 1, 2

Important Contraindications and Precautions

Administration Precautions

• Never administer calcium through the same IV line as sodium bicarbonate—this causes precipitation of insoluble calcium salts 1, 2
• Use calcium cautiously in patients with elevated serum phosphate (e.g., tumor lysis syndrome, chronic kidney disease)—the combination increases risk of calcium-phosphate precipitation in tissues and vascular calcification 1, 2
• Calcium gluconate is preferred over calcium chloride for peripheral IV access because calcium chloride causes severe tissue necrosis if extravasation occurs 1

Special Population: Digoxin Toxicity

• In patients with suspected digoxin toxicity, calcium administration is controversial and should be used only in extremis, as it may theoretically worsen calcium overload in myocardial cells 1

Concurrent Therapies (Must Be Initiated Simultaneously)

Calcium is only a temporizing measure—failure to initiate concurrent potassium-lowering therapies will result in recurrent life-threatening arrhythmias within 30-60 minutes. 1, 2

Intracellular Potassium Shift (Administer All Three Together for Maximum Effect)

• Insulin 10 units regular IV + 25g dextrose (50 mL D50W) over 15-30 minutes—lowers K+ by 0.5-1.2 mEq/L within 30-60 minutes, lasting 4-6 hours 1, 2
• Nebulized albuterol 10-20 mg in 4 mL over 10-15 minutes—lowers K+ by 0.5-1.0 mEq/L within 30 minutes, lasting 2-4 hours; can be repeated every 2 hours 1, 2
• Sodium bicarbonate 50 mEq IV over 5 minutes ONLY if metabolic acidosis is present (pH <7.35, bicarbonate <22 mEq/L)—onset 30-60 minutes 1, 2

Definitive Potassium Removal

• Loop diuretics (furosemide 40-80 mg IV) if eGFR >30 mL/min and patient is non-oliguric 1, 2
• Hemodialysis is the most reliable method for severe hyperkalemia—absolute indications include K+ >6.5 mEq/L unresponsive to medical therapy, oliguria/anuria, ESRD, eGFR <15 mL/min, or ongoing potassium release (tumor lysis, rhabdomyolysis) 1, 2
• Continuous renal replacement therapy (CRRT) is preferred over intermittent hemodialysis in hemodynamically unstable patients 1

Common Pitfalls to Avoid

• Do NOT delay calcium administration while awaiting repeat potassium levels if ECG changes are present—ECG changes indicate urgent need regardless of the exact potassium value 1, 2
• Do NOT rely on calcium alone—it is a temporizing measure only and does not remove potassium from the body 1, 2, 3
• Do NOT give insulin without glucose—hypoglycemia can be fatal; monitor glucose every 30-60 minutes after insulin administration 1, 2
• Do NOT use sodium bicarbonate without documented metabolic acidosis—it is ineffective and wastes time 1, 2
• Recent evidence suggests calcium may be effective primarily for main rhythm disorders (e.g., bradycardia, heart block) rather than non-rhythm ECG changes (e.g., peaked T waves, widened QRS alone), though this remains controversial 4

Post-Administration Management

• Recheck serum potassium 1-2 hours after initiating shift therapies (insulin/glucose, albuterol) 1, 2
• Continue potassium monitoring every 2-4 hours until stable 1, 2
• Temporarily hold or reduce RAAS inhibitors (ACE inhibitors, ARBs, mineralocorticoid antagonists) when K+ >6.5 mEq/L 1, 2
• Initiate a potassium binder (sodium zirconium cyclosilicate 10g TID for 48h then 5-15g daily, or patiromer 8.4g daily) to enable eventual resumption of RAAS inhibitors at lower doses once K+ <5.0 mEq/L 1, 2