Renal System >
Hypokalaemia

“A low serum potassium of <3.5mmol/L”

Risk Factors
  • Eating Disorders
  • AIDS
  • Alcoholism
  • Bariatric Surgery
Aetiology
  • Increased Potassium uptake
  • Increased Potassium excretion
  • Decreased Potassium intake
  • Increased Potassium shift from extracellular to intracellular
Pathophysiology
  • Increased Potassium Excretion (loss)
    • Drugs – diuretics (thiazides, loop), laxatives, glucocorticoids, fludrocortisone, penicillin, amphotericin, aminoglycosides
    • GI losses – diarrhoea, vomiting, ileostomy, intestinal fistula
    • Renal – renal tubular acidosis, diuretics, increased mineralocorticoid activity, polyuria, dialysis
    • Endocrine disorders – hyperaldosteronism, Cushing’s syndrome
  • Increased Potassium Uptake
    • Insulin/glucose therapy
    • Increase in beta-adrenergic activity e.g. salbutamol, theophylline, head injury
    • Metabolic alkalosis
    • Hypothermia
    • Increased blood cell production
    • Toxins
  • Decreased Potassium Intake
    • Diet
  • Increased sweat loss – Magnesium depletion associated with increased renal potassium loss
Clinical Presentation
  • Most patients asymptomatic and symptoms are non-specific (muscular/cardiac)
  • Nervous system – cells are unable to become depolarised due to increased RMP (flaccid paralysis, weakness, muscle cramps)
  • Constipation
  • Respiratory difficulties
Investigations
  • Bloods:
    • Urea and Electrolytes – Creatinine ratio
    • Potassium Levels – Check multiple values
  • Imaging: n/a
  • Special:
    • Urinary Potassium
      • To establish urinary loss vs transcellular shift
      • >30mmol = inability of kidney to concentrate potassium
    • ECG
      • ST segment depression
      • T wave flattering
      • U waves
Electrocardiography showing U waves
Management
  • Mild Hypokalaemia
    • Potassium supplements
    • Potassium-sparing diuretics (Spironolactone)
  • Severe Hypokalaemia
    • Oral and IV KCl administration with normal saline at 10mmol/hr
Complications
  • Cardiac Arrhythmias
  • Rhabdomyolysis
  • Ascending Paralysis

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