Hyperkalaemia

High-Yield Tips

• Always check Therapeutic Guidelines or your local guidelines prior to actually dosing a patient (as this information may be out of date by the time you read it)
• If serum [K] > 6.5, it is quite concerning
• Management
  • ECG
  • IV calcium gluconate
  • IV dextrose 50% + insulin (alternatively, salbutamol)
  • Resonium
  • IV sodium bicarbonate (if metabolic acidosis present)
  • 0.9% sodium chloride for rehydration

Definition

Serum potassium concentration > 5.2 mmol/L.

Normal range: 3.5-5.2 mmol/L

Classification

• Mild: 5.2 < serum [potassium] ≤ 6.0
• Moderate: 6.0 < serum [potassium] ≤ 7.0
• Severe: serum [potassium] > 7.0

Aetiology

Is it pseudohyperkalaemia or true hyperkalaemia?

• Pseudohyperkalaemia: falsely elevated serum [potassium]. Causes include:
  • Mechanical trauma during venepuncture → cell lysis → K release
  • Clotting (in a patient with thrombocytosis) → K moves out of platelets
  • Sample obtained from vein proximal to site of K infusion
• True hyperkalaemia causes:
  • ↑ K release from cells
    1. Metabolic acidosis (other than lactic acidosis or ketoacidosis)
       • Rare to see hyperkalaemia caused by respiratory acidosis too
    2. Insulin deficiency (+/- combined with hyperglycaemia and hyperosmolality)
       • Mechanism: (normally insulin promotes K entry into cells) in an insulin-deficient state with hyperglycaemia and hyperosmolality
         • → water moves by osmosis from within cells to ECF → raises intracelullar [K] → favourable gradient for passive movement of K to ECF
         • → body in 'fasting state' + insulin not able to inhibit β-oxidation → ketosis → ketoacidosis → H/K co-transporter shifts protons intracellularly in exchange for K to minimise extracellular acid-base disturbances → hyperkalaemia
    3. Other causes of ↓ insulin levels
       • Somatostatin (or analogues e.g. octreotide)
       • Fasting
    4. ↑ tissue catabolism
       • Trauma
       • Rhabdomyolysis
       • Tumour lysis syndrome
       • Severe hypothermia
    5. Other
       • Overdose of digitalis or related digitalis glycosides
       • Red cell transfusion
       • Succinylcholine
       • K absorption from GIT bleed
       • Hyperkalaemic periodic paralysis
  • ↓ urinary K excretion
    1. ↓ ALD secretion
    2. ↓ response to aldosterone (e.g. use of K-sparing diuretics aka aldosterone antagonists)
    3. ↓ distal sodium and water delivery 2° to hypovolaemia
    4. Acute and chronic kidney disease

Clinical Manifestations

• Muscle weakness or paralysis
• Cardiac conduction abnormalities and arrhythmias

ECG Changes

Changes usually progress as serum [K] increases.

• 5.5-6.5 mmol/L: Tall peaked T waves
• 6.5-7.5 mmol/L: Loss of P waves, prolonged PR interval
• 7.0-8.0 mmol/L: Widening of QRS complex
• 8.0-10.0 mmol/L: Sine wave, ventricular arrhythmia, asystole

Management

Emergency Management

1. Primary survey
2. ECG (or telemetry preferred for continuous monitoring)
3. IV calcium gluconate 10% 10mL IV over 2-3 mins into a large vein
   • Note: effect of this infusion is short-lived and dose may need to be repeated in 30-60 mins whilst simultaneously undertaking measures to reduce potassium
   • Purpose: stabilise cardiac membrane to prevent cardiac arrest
   • Indication: cardiac arrhythmia or severe ECG changes of acute hyperkalaemia
4. IV sodium bicarbonate 8.4% 50mL IV over 5-10 mins
   • Purpose: correction of volume depletion (if present) + any underlying metabolic acidosis
   • May be repeated in 60-120 mins
   • Fluid replacement may need to be continued with sodium chloride 0.9%
5. Glucose 50% 50mL IV over 5 mins + short-acting insulin (e.g. aspart 100 units/mL) 10 units IV bolus
   • Note: MUST give dextrose before insulin as dextrose can compromise cannula and if insulin is given first and subsequent glucose not given → hypoglycaemia
   • Glucose 50% may cause vascular irritation
   • Alternatively to above regimen of Glucose 50%, can give glucose 10% 250mL over 15 mins
   • Consider ongoing monitoring of BSL and need for further glucose + insulin
   • Effective in renal failure
6. Nebulised salbutamol e.g. 5mg neb q1-2h (max 10-20mg in 24h)
   • Can be given as an alternative to glucose + insulin to temporarily shift K intracellularly
   • 10 mg salbutamol may lower K by 0.5-1.0 mmol/L by 15-30 mins, with effect lasting ~ 2h
7. Cessation of any exacerbating medications e.g. potassium-sparing diuretics
8. Sodium polystyrene sulfonate 15g (suspended in 45-60mL of water) PO TDS or QID
   • Purpose: to reduce GIT potassium absorption
   • This treatment lowers the serum potassium concentration by 0.5 to 1 mmol/L over 1 to 6 hours.
   • Note: as sodium polystyrene can ↑ Na, consider calcium polystyrene sulfonate (same dose) instead
9. Situational treatment options:
   • Dialysis
   • Corticosteroid replacement (e.g. IV hydrocortisone) if aetiology is adrenal insufficiency and hypoaldosteronism + don't use insulin

Resources

1. LITFL: Hyperkalaemia
2. UpToDate: Causes and evaluation of hyperkalemia in adults
3. UpToDate: Clinical manifestations of hyperkalaemia in adults
4. Therapeutic Guidelines: Hyperkalaemia