USMLE Prep - Medical Reference Library

Severe Hyperkalemia — ECG Changes, Membrane Stabilization, and Dialysis Triggers

System: Nephrology • Reviewed: Sep 1, 2025 • Step 1Step 2Step 3

Synopsis:

Hyperkalemia with ECG changes or K+ ≥6.5 mEq/L is a medical emergency. Stabilize the myocardium with IV calcium, shift potassium intracellularly with insulin/dextrose (± beta-agonists, bicarbonate if acidosis), and remove potassium via diuretics, binders, or hemodialysis. Identify and correct precipitants.

Key Points

  • Use the highest‑yield diagnostic test early; do not let testing delay time‑critical therapy.
  • Set objective targets and reassess frequently.
  • Plan definitive source control or disease‑specific therapy when indicated; document follow‑up and patient education.

Algorithm

  1. If ECG changes or K+ ≥6.5 → calcium IV immediately; place on monitor.
  2. Give insulin/dextrose; add albuterol and bicarbonate if acidotic; recheck K+ in 60 min.
  3. Initiate K+ removal: diuretics if euvolemic, K+ binders for adjunct, dialysis if severe/renal failure.
  4. Search/stop precipitants (medications, AKI); adjust RAAS inhibitors; counsel on diet.
  5. Observe until ECG normalizes and K+ safely reduced; arrange follow-up labs.

Clinical Synopsis & Reasoning

Hyperkalemia with ECG changes or K+ ≥6.5 mEq/L is a medical emergency. Stabilize the myocardium with IV calcium, shift potassium intracellularly with insulin/dextrose (± beta-agonists, bicarbonate if acidosis), and remove potassium via diuretics, binders, or hemodialysis. Identify and correct precipitants.


Treatment Strategy & Disposition

Stabilize ABCs. Initiate guideline‑concordant first‑line therapy with precise dosing and continuous monitoring. Escalate to advanced/procedural interventions based on explicit failure criteria. Define ICU, step‑down, and ward disposition triggers; involve specialty teams early.


Epidemiology / Risk Factors

  • Risk varies by comorbidity and precipitants; see citations for condition‑specific data.

Investigations

TestRole / RationaleTypical FindingsNotes
Repeat plasma potassium (non-hemolyzed) and ECGConfirm & risk stratifyPeaked T, widened QRS, sine-waveTreat on ECG, not number alone
BMP, glucose, venous blood gasEtiology/complicationsMetabolic acidosis, renal failure, hypoglycemia riskGuide adjuncts
Medication review & urine K+ (selected)CauseRAASi, K-sparing diuretics, NSAIDs, trimethoprimTailor plan

High-Risk & Disposition Triggers

TriggerWhy it mattersAction
ECG changes (peaked T, widened QRS) or K+ ≥6.5Impending dysrhythmiaImmediate calcium, temporizing shifts, ICU; consider dialysis
Refractory hyperkalemia or AKI on CKDPoor renal clearanceNephrology consult; dialysis prep
Beta-blocker use or insulin deficiencyReduced shift efficacyHigher insulin/adjuncts; glucose monitoring q30–60 min
Hemolysis suspected with symptomsFalse reassurance riskRepeat STAT plasma K+; do not delay treatment
Digitalis toxicity coexistenceCalcium controversyFavor cautious calcium gluconate; toxicology consult

Pharmacology

Medication/InterventionMechanismOnsetRole in TherapyLimitations
Calcium chloride 1 g IV (central) or calcium gluconate 3 g IV (peripheral)Membrane stabilizationMinutesImmediate QRS narrowing desiredRepeat if QRS not improved
Regular insulin 10 units IV + D10W 250 mL IV (or D50 25 g)Intracellular shiftMinutesFirst-line shift therapyMonitor glucose q30–60 min × 3–4 h
Nebulized albuterol 10–20 mgβ2-agonistMinutesAdjunct shiftTachycardia/tremor
Sodium bicarbonate 50–100 mEq IV (if acidosis)BufferMinutesHelps shift with metabolic acidosisLimited without acidosis
Loop diuretics, sodium zirconium cyclosilicate/patiromerEliminationHoursAdjunct removalNot for life-threatening scenarios
HemodialysisDefinitive removalImmediate when availableRefractory or renal failureNephrology consult

Prognosis / Complications

  • Outcome depends on timeliness of diagnosis and definitive therapy; monitor for complications.

Patient Education / Counseling

  • Provide red‑flag education, adherence guidance, and explicit return precautions; arrange timely specialty follow‑up.

References

  1. AHA ACLS & Nephrology reviews on hyperkalemia management — Link