The Basics

• 98% is intracellular
• Serum range 3.5 – 5 mmol/L
• K⁺ and H⁺ tend to vary together
• Most body secretion is in urine – from distal tubules

Shifts K+ INSIDE cells

• Insulin
• Aldosterone
• β-adrenergic stimulation
• Alkalosis

Shifts K+ OUTSIDE cells

• Addison’s disease
• β-blockade
• Acidosis
• Cell lysis

Hypokalaemia

ΔΔ

• Usually due to Excess Losses

1. GI losses
   1. Diarrhoea
   2. Vomiting
2. Renal losses
   1. Diuretics
   2. Excess mineralocorticoids
3. Intracellular shift
   1. β₂– adrenergic stimulation
   2. Insulin
   3. Alkalosis

Signs  & Symptoms

1. Muscular dysfunction
   1. Weakness
   2. Cramping
   3. Fasciculation
   4. Tetany
2. ECG changes
   1. T wave depression
   2. ST sagging
   3. U wave prominence
   4. Prolonged P-R interval

Management

• Correct any potential cause e.g. diuretics
• Mild   – Oral K⁺ supplements
  • routine K⁺ replacement is not needed in most patients on diuretics
• Severe – Cautious IV K⁺
  • Must be:      < 20mmol/h and < 40 mmol/L

Hyperkalaemia

ΔΔ

1. Renal
   1. Oliguric renal failure
   2. K⁺ sparing diuretics
2. Metabolic acidosis
3. Adrenal Insufficiency – e.g. Addison’s
4. Drugs
   1. ACE-inhibitors
   2. B- blockers
   3. NSAIDS
   4. Iatrogenic K⁺
5. Rhabdomyolysis
6. Artefact – Haemolysis

Signs & Symptoms

1. ECG changes
   1. Tall Tented T waves (TTT)
   2. Small P waves
   3. Wide QRS complexes
   4. Ventricular Fibrillation!!!
2. Weakness
   1. Occasional paralysis
   2. Usually death first

Management

• Correct any potential cause e.g. beta-blockers
• If mild simply reduce intake

1. Calcium Gluconate (10ml-10%)
   1. IV over 2 mins
   2. Repeat as necessary (stabilises the heart)
2. Insulin & Glucose IV
   2. Drives K⁺ into cells

3. Nebulised Salbutamol

1. Polystyrene sulfonate resin (trade name- Calcium resonium)
   1. Orally or enema if N&V

5. Dialysis?

References

1. Guyton & Hall. Textbook of Medical Physiology
2. The Merck manual
3. Oxford Handbook of Clinical medicine.
4. Patient.co.uk

References

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