Introduction
Hypokalaemia is a condition where there is a low Potassium level in the plasma. It is a plasma potassium less than 3.5 millimoles per Litre.
Normal plasma potassium level is any value between 3.5-5 millimoles per litre.
Hypokalaemia is the most common electrolyte abnormality in hospitalised patients; mostly caused by drugs and GI disease.
Causes
Things mostly associated with increase in potassium loss
Increased renal loss:
- Diuretics and salt-waste and secondary hyperaldosteronism
- Increased distal delivery of non reabsorbable anions (vomiting, DKA, renal tubular acidosis)
- Amphotericin B
- Cushing’s syndrome,
- Bartter’s syndrome
Increased non-renal loss:
- GIT loss (diarrhoea, integumentary sweat)
- Redistribution into cells: Metabolic alkalosis
- Drugs:
- Insulin
- β-adrenergic agonists
- α-adrenergic antagonists
- Decreased intake: Starvation
Clinical features
Vary between patients and depend on the level of potassium loss
Serum K<3mmoles/Litre:
- Fatigue
- Myalgia
- Weakness of the lower extremities
More severe hypokalaemia results in
- Progressive weakness
- Hypoventilation
- Complete paralysis
- ECG changes are due to ventricular depolarisation
- Flattening/inversion of the T wave
- Aprominent Uwave
- ST segment depression
- Prolonged QT interval
- Severe depletion results in prolonged PR interval
- Decreased voltage and widening of the QRS complex
Investigations
- Electrocardiography
- Electrolytes, Urea and Creatinine
- Acid-base status
- Identifying the underlying disease
Treatment objectives
- Correction of potassium deficit
- Minimize/stop on-going loss
Drug treatment
(Oral route preferred)
Potassium chloride
- Doses depend on deficits, on-going losses and renal status
Intravenous potassium (given in an infusion)
- Do not exceed 20 mmoles/L
- Add daily requirement of potassium and correct over 3 days
Calculation of potassium requirement
- = Deficit × body weight (kg) × 0.4
Caution
- Oral potassium supplements should be
taken in an erect position or sitting upright and with plenty of water to avoid
oesophageal erosions