Renal System >
Hyperkalaemia

“A high serum potassium K+ >5.5mmol/L”

Risk Factors & Aetiology
  • M – Medications: ACE inhibitors, NSAIDs
  • A – Acidosis: Metabolic and respiratory
  • C – Cellular destruction: Burns, traumatic injury
  • H – Hypoaldosteronism, haemolysis
  • I – Intake: Excessive e.g. supplements
  • N – Nephrons, renal failure
  • E – Excretion: Impaired e.g. AKI, CKD
Pathophysiology
  • Ineffective K+ renal elimination
    • ↓ GFR and tubular flow = ↓ urine output = ineffective elimination and raised serum K+ levels
  • Medications that interfere with urinary excretion
    • Inhibit RAAS (ACEi, ARBs, β-blockers, calcineurin inhibitor immunosuppressants e.g. Ciclosporin, Tacrolimus), K+ sparing diuretics (e.g. Amiloride prevents excretion into urine and Spironolactone competitively inhibits the action of aldosterone)
  • NSAIDs (Ibuprofen, Naproxen, Celecoxib)
    • ↓ prostaglandin synthesis → ↓ renin and aldosterone production ↑ K+ retention
  • Mineralocorticoid deficiency or resistance can contribute
  • ↑ Cell breakdown (rhabdomyolysis/ burns/tumour lysis syndrome)
    • rapid tissue necrosis → release intracellular K+ into blood → ↑ serum levels of K+
  • Metabolic acidosis
    • ↑H+ ions → K+ displacement from cells
  • Insulin deficiency
    • prevents K+ uptake into cells
  • Hyperglycaemia
    • ↑ osmolarity of extracellular fluid → diffusion of K+ into the extracellular compartment
Clinical Presentation
  • Most patients asymptomatic and symptoms are non-specific (muscular/cardiac)
  • Nervous system: cells are constantly depolarised so hard to become repolarised which leads to decreased contractility (flaccid paralysis, weakness, fatigue, paraesthesia, decreased deep tendon reflex)
  • Palpitations or chest pain
  • Nausea and vomiting, diarrhoea
Investigations
  • Bloods:
    • Urea and Electrolytes – Creatinine, Urea and eGFR
    • Potassium Levels – Check multiple values
  • Imaging: n/a
  • Special:
    • ECG
      • Tall Peaked T waves
      • Flattening or absence of P waves
      • Broad QRS (normally 0.42s or <3small squares)
        • (pinch the top of the T wave and pull it up – this will broaden QRS and flatten P)
      • In severe hyperkalaemia – sinusidal waves
Electrocardiography showing precordial leads in hyperkalemia.
Credit: Mikael Häggström / Public domain via Wikipedia Commons
Management
  • Potassium <6mmol/L
    • No urgent treatment
    • Change diet and medications
  • Potassium >6mmol/L
    • Insulin and dextrose infusion with IV calcium gluconate
      • K+ move into cells and dextrose given to prevent hypocalcaemia, calcium gluconate stabilises cardiac muscle cells to reduce risk of arrhythmia
  • Other options to reduce serum potassium:
    • Nebulised Salbutamol – temporarily drives potassium into cells
    • IV fluids – to increase urine output – encourages K+ loss from Kidneys
    • Oral calcium resonium – draws K+ out of the gut and into stools
    • Sodium Bicarbonate – in acidotic patients with renal failure will drive potassium into cells as acidosis is corrected
    • Dialysis – in severe cases / renal failure
Complications
  • Cardiac Arrhythmias
  • Ventricular Fibrilation

Leave a Reply

Search Our Notes

Get Updates

Get updates direct to your inbox as we post more notes!

Our Latest Notes