Hypokalaemia

Clinical Cases

Causes of HYPOkalaemia

  • Definition: Serum potassium <3.5mEq/L
  • Implication: Nerves and muscles mostly affected, especially the heart

1) Decreased intake

  • Geophagia (Clay ingestion)
  • Anorexia nervosa
  • Alcoholism

2) Increased loss

  • GIT loss
    • Vomit, NGT (Associated with renal loss secondary to aldosterone secretion to respond to hypovolaemia)
    • Diarrhoea (Infection, adenoma, enteritis) – Direct K loss in stool
    • Fistula, malabsorption
  • Renal loss
    • Drugs (Diuretics very common cause) – K-losing diuretics (Thiazide and loop)
      • Sodium penicillin, amphotericin
      • Licorice
    • Osmotic diuresis
      • Hyperglycaemia, Mannitol
    • Aldosterone excess (increased collecting duct excretion)
      • Primary hyperaldosteronism (Conn’s)
      • Secondary hyperaldosteronism (CCF, cirrhosis, hypoproteinaemia)
    • Mineralocorticoid excess
      • Cushing’s syndrome, steroid use, Fanconi’s
    • Congenital
      • Bartter’s, Liddle’s, Gitelman’s (renal ion transport deficit)
    • Renal artery stenosis

3) Transcellular shift

  • Alkalosis
  • Hypomagnesaemia, Hypernatraemia
  • Dextrose/insulin infusion

4) Other

  • AML and pernicious anaemia (increased new cell uptake of potassium)

5) Drugs causing hypokalaemia

  • Diuretics (Loop and Thiazides), mannitol
  • Penicillin, amphotericin, steroids(Renal loss)
  • Gentamicin, cisplatin, amphotericin (Associated with hypomagnesemia)
  • Insulin and Beta agonists, adrenaline, salbutamol, lithium (Na/K ATPase increase)

Clinical

  • Weakness
  • Fatigue
  • Paralysis and rhabdomyolysis
  • Respiratory difficulty
  • Constipation/ileus
  • Leg cramps

Complciations

Cardiac Arrhythmia and ECG changes

  • Flat T waves
  • U waves
  • Prolonged QT and PR
  • Broadening QRS
  • Arrhythmia and PEA

Hypokalemia exacerbates Digoxin toxicity

Correction

  • Minimise further K loss (commonest is GI loss and drugs)
  • Give potassium replacement
  • Correct magnesium and phosphate deficiencies
    • Oral K
      • Chlorvescent (K 14mmol, Cl 8mmol)
      • Span K (KCL 8 mmol) – nteric coated, delayed release
    • Intravenous
      • Maximum 20mEq/hr unless imminent cardiac arrest
      • CVL required if > 10mmol/hr
      • Requires ECG monitoring
      • Dextrose free solution to minimise insulin stimulation (worsen hypokalaemia)
      • Paediatric maximum dose 0.4 mmol/kg/hr
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