June 26, 2024

REBEL Core Cast 125.0 – Hyperkalemia

7 minutes

Take Home Points

Always obtain an EKG in patients with ESRD upon presentation

Always obtain an EKG in patients with hyperkalemia as pseudohyperkalemia is the number one cause

If the patient with hyperkalemia is unstable or has significant EKG changes (wide QRS, sine wave) rapidly administer calcium salts

In patients who are anuric, early mobilization of dialysis resources is critical

REBEL Core Cast 125.0 – Hyperkalemia

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Definition: A serum potassium level > 5.5 mmol/L

Epidemiology

Common electrolyte disorder

10% of hospitalized patients (Elliott 2010)

Causes

Pseudohyperkalemia: extravascular hemolysis

Renal failure (potassium is primarily eliminated by the kidneys)

Acidosis

Massive cell death (tumor lysis syndrome, rhabdomyolysis, burns, crush injuries, hemolysis)

Drugs: ACEI, ARBs, Spironalactone, NSAIDs, Succinycholine

Clinical Manifestations

Mild hyperkalemia often asymptomatic

Cardiac Effects

Increased potassium raises the resting membrane potential of cardiac myocytes

Slows ventricular conduction

Decreases length of action potential

Increases cardiac myocyte excitability

Cardiac effects can manifest in lethal dysrhythmias

Neuromuscular Effects

Paresthesias

Weakness

Flaccid paralysis

Depressed or absent deep tendon reflexes

Diagnosis

Suspect hyperkalemia in ALL patients with renal impairment, especially end-stage renal disease (ESRD)

Serum potassium

Can be artificially elevated by extravascular hemolysis

Blood gas results may differ from standard metabolic panels by up to 0.5mmol/L

12-Lead EKG

Screening test that can rapidly detect severe cardiac manifestations of hyperkalemia

A normal EKG with a significant serum potassium elevation should raise concerns for spurious results (extravascular hemolysis)

Sensitivity of EKG to detect hyperkalemia is poor (Wrenn 1991, Aslam 2002, Montague 2008)

Classic EKG findings

PR prolongation

Peaked T waves

Loss of P waves

Widening of QRS complex

Sine wave

Ventricular Fibrillation

Asystole

Note: Hyperkalemia can present with a number of “non-classic” EKG findings including AV blocks and sinus bradycardia (Mattu 2000)

Note: Hyperkalemic EKG changes do not necessarily occur in order (i.e. patients can jump from peaked T waves to sine wave)

Management

Basics: ABCs, IV, O2, Cardiac Monitor and, 12-lead EKG

Identify + treat underlying cause of hyperkalemia (i.e. rhabdomyolysis -> hydration)

Remove inciting factors (i.e. stop ACEI, NSAIDs etc)

Asymptomatic Patients without EKG Changes

Eliminate potassium from the body

Binding agents (SPS, Sodium zirconium cyclosilicate etc)

Enhance renal elimination

Intravenous hydration if volume depleted

Consider potassium wasting loop diuretics (i.e. furosemide)

Dialysis for anuric patients (i.e. ESRD)

Symptomatic Patients or Significant EKG Changes

Stabilize cardiac myocytes with calcium salts

Mechanism: Recreates the electrical gradient leading to rapid reversal of cardiac effects and rapid stabilization

Two Options: CaGluconate, CaCl2

No difference in time to onset (1st pass metabolism is a myth)

Dose: 1 ampule CaCl2 (270 mg Ca2+) = 3 ampules CaGluconate (90 mg Ca2+/ampule)

Onset of action: seconds to minutes

Duration: 20-30 minutes

Shift potassium into intracellular space (temporary)

Insulin (Moussavi 2021)

Mechanism: Activation of the Na-K-ATPase

Dose: 5-10 units IV

Onset of Action: < 15 min

Effect: Lowers potassium by about 0.6 mmol

Duration of action: 30-60 min

Give with dextrose (0.5 – 1 g/kg) unless hyperglycemia present

Caution: Duration of action of insulin may outlast administered dextrose. Be vigilant for hypoglycemia

Beta-adrenoreceptor agonists (i.e. albuterol)

Mechanism: Activation of beta receptors

Dose: 10-20 mg inhaled (4-8 standard ampules)

Onset of Action: < 15 min

Effect: Lowers potassium by about 0.6 mmol

Duration of action: 30-60 min

Additive effect with insulin (Allon 1990)

Note: Unlikely to have effect in patients taking beta-adrenoreceptor blocker medications

Sodium Bicarbonate (NaHCO3)

Evidence for the efficacy of NaHCO3 to lower serum potassium is scant and contradictory (Elliott 2010, Weisberg 2008)

Eliminate potassium from the body (see above)

Asymptomatic Patients with Minor EKG Changes

Minimal recommendations on managing this clinical entity

Eliminate potassium from the body (see above)

Consider calcium salt administration: patients can rapidly progress through EKG changes and calcium administration may prevent this from occurring. However, the effects of calcium are temporary and offer no long-term protection

Consider medications to shift potassium intracellularly while waiting for elimination

Take Home Points

Always obtain an EKG in patients with ESRD upon presentation

Always obtain an EKG in patients with hyperkalemia as pseudohyperkalemia is the number one cause

If the patient with hyperkalemia is unstable or has significant EKG changes (wide QRS, sine wave) rapidly administer calcium salts

In patients who are anuric, early mobilization of dialysis resources is critical

References

Elliott MJ et al. Management of patients with acute hyperkalemia. CMAJ 2010; 182(15): 1631-5. PMID: 20855477

Wrenn K et al. The ability of physicians to predict hyperkalemia from the ECG. Ann Emerg Med 1991; 20(11): 1229-32. PMID: 1952310

Aslam S et al. Electrocardiography is unreliable in detecting potentially lethal hyperkalaemia in hemodialysis patients. Nephrol Dial Transplant 2002; 17: 1639-42. PMID: 12198216

Montague BT et al. Retrospective review of the frequency of ECG changes in hyperkalemia. Clin J Am Soc Nephrol 2008; 3:324–330. PMID: 18235147

Mattu A et al. Electrocardiographic manifestations of hyperkalemia. Am J Emerg Med 2000; 18: 721-9. PMID: 11043630

Allon M, Copkney C. Albuterol and insulin for treatment of hyperkalemia in hemodialysis patients. Kidney Int 1990; 38:869–872. PMID: 2266671

Weisberg LS. Management of hyperkalemia. Crit Care Med 2008; 36: 3246-51. PMID: 18936701

Moussavi K et al. Reduced alternative insulin dosing in hyperkalemia: a meta-analysis of effects on hypoglycemia and potassium reduction. Pharmacotherapy 2021; 41(7): 598-607. PMID: 33993515

Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter/X: @srrezaie)

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