Hypokalaemia

Clinical Cases

• What is potassium?
• Hypokalemia and Metabolic Acidosis

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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