Hyperkalemia

Background

• Defined as >5.5 mEq/L
• Consider pseudohyperkalemia (e.g. from hemolysis)
• Potassium secretion is proportional to flow rate and sodium delivery through distal nephron
  • Thus, loop & thiazide diuretics cause hypokalmia

Medication Causes

Alter transmembrane potassium movement

• β blockers
• Digoxin
• Potassium-containing drugs
• Potassium supplements
• Salt substitutes
• Hyperosmolar solutions (mannitol, glucose)
• Suxamethonium
• Intravenous cationic amino acids
• Stored red blood cells (haemolysis releases potassium)
• Herbal medicines (such as alfalfa, dandelion, horsetail, milkweed, and nettle)

Reduce aldosterone secretion

• ACE inhibitors; Angiotensin II receptor blockers
• NSAIDs
• Heparin
• Antifungals (ketoconazole, fluconazole, itraconazole)
• Ciclosporin
• Tacrolimus

Block aldosterone binding to mineralocorticoid receptors

• Spironolactone
• Eplerenone
• Drospirenone
• Potassium sparing diuretics (amiloride, triamterene)
• Trimethoprim
• Pentamidine

Clinical Features

Typically non-specific

• Muscle weakness
• Lethargy, fatigue
• Parathesias
• Nausea and Vomiting
• Difficulty breathing
• Palpitations, chest pain

Differential Diagnosis

Peaked T-waves

• MI (hyperacute T waves)
• Hyperkalemia
• Benign Early Repolarization
• De Winter's T waves (acute LAD occlusion)

Wide-complex tachycardia

Assume any wide-complex tachycardia is ventricular tachycardia until proven otherwise (it is safer to incorrectly assume a ventricular dysrhythmia than supraventricular tachycardia with abberancy)

• Regular
  • Monomorphic ventricular tachycardia
  • PSVT with aberrant conduction:
    • PSVT with bundle branch block^
    • PSVT with accessory pathway
    • Atrial flutter with bundle branch block^
  • Sinus tachycardia with bundle branch block^
  • Accelerated idioventricular rhythm (consider if less than or ~120 bpm)
  • Metabolic
    • Hyperkalemia
    • Digoxin toxicity
    • Severe metabolic acidosis
• Irregular
  • Atrial fibrillation/atrial flutter with variable AV conduction AND bundle branch block^
  • Atrial fibrillation/atrial flutter with variable AV conduction AND accessory pathway (e.g. WPW)
  • Atrial fibrillation + hyperkalemia
  • Polymorphic ventricular tachycardia
    • Torsades de pointes
    • Nonsustained ventricular tachycardia

^Fixed or rate-related

Evaluation

ECG

Changes NOT always predictable and sequential

• 6.5 - 7.5 mEq/L: peaked T waves, prolonged PR interval, shortened QT interval
• 7.5 - 8.0 mEq/L: widened QRS interval, flattened P waves
• 10 - 12 mEq/L: sine wave, ventricular fibrillation, heart block

Management

Stabilize cardiac membranes

Indicated if there are any ECG changes or evidence of arrhythmias. Consider if K >7 mEq/L

• Either one of the following:
  • Calcium gluconate: Give 10ml of a 10% solution over 10 mins
    • Only 1/3 the calcium compared to calcium chloride
    • Can cause hypotension due to osmotic shift
  • Calcium chloride 1 gram IV
    • Give over 1 - 2 minutes
    • Extravasation is bad: use a good IV
    • Usually given in code situations
• Takes effect in 15-30 minutes
  • (If given for hyperkalemic cardiac arrest, need to continue resuscitation for at least 30 minutes)
• Duration of action: 30 - 60 minutes
• Use caution in patients taking Digoxin although risk of Stone heart may be unsubstantiated
• Do serial ECGs to track progress: may need to give multiple doses

Shift K+ intracellularly

• Intravenous insulin + dextrose
  • Give 10 units regular insulin intravenously with 25 to 50 grams (1 - 2 50 mL ampules) of 50% dextrose (D50)
    • May withhold dextrose if blood sugar >300mg/dl (>17 mmol/L)
    • Duration of effect: 4 - 6 hours
    • Consider mixing in 10 cc NS syringe to ensure small volume of 10 units insulin fully administered via IV
    • Insulin cleared renally, be careful about inducing hypoglycemia (ESRD patients).
      • In a small 2017 retrospective cohort study, researchers found that giving 5 units of insulin instead of 10 units reduced serum potassium to the same extent as 10 units, with a lower rate of hypoglycemia.
• Nebulized albuterol 5 - 20mg
  • Response is dose-dependent
  • Peak effect: 30 minutes
  • Duration of effect: 2 hours
• Intravenous sodium bicarbonate 50ml of 8.4% solution (1 ampoule) given over 5 minutes
  • Duration of effect: 1 - 2 hours
  • Generally not required, unless pH <7.1

Remove K+ from body

• Intravenous furosemide (Lasix) 40 - 80mg
  • Ensure adequate urine output first
• Sodium polystyrene sulfonate (Kayexylate): 30 gm oral or per rectum
  • Very Controversial, High Risk of Bowel Perforation, see: EBQ: Use of Kayexylate in Hyperkalemia
• Sodium zirconium cyclosilicate
  • Potassium binder, similar to Kayexylate
• Intravenous normal saline solution for volume expansion if dehydrated, rhabdomyolysis, diabetic ketoacidosis or other acidosis
• Hydrocortisone if suspicious for adrenal insufficiency
• Definitive treatment is hemodialysis

Disposition

• Consideration for ICU for frequent electrolyte checks and close cardiac monitoring

See Also

• Electrolyte abnormalities
• Acute kidney injury
• Hemodialysis/Hemoperfusion
• Crush syndrome

External Links

• ECG Weekly -Hyperkalemia