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Electrolyte Abnormalities
 
Electrolyte Abnormalities
 

Hypokalaemia

 
 
 
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Overview

Hypokalaemia, or a reduced serum potassium concentration of <3.5mmol/L, is associated with hyperpolarisation of cardiac myocytes. If severe, hypokalaemia causes abnormal ventricular automaticity which may result in ventricular arrhythmias.

Pathogenesis

  • Causes of Hypokalaemia

  • Inadequate intake
  • GI loss - vomiting, high NG output, diarrhoea, fistula, laxative abuse
  • Renal loss - Conns, Cushings, ectopic ACTH, loop diuretics, osmotic diuresis, corticosteroids, hypomagnesaemia, RTA
  • Compartmental shift - alkalaemia, insulin, refeeding, beta agonists

Manifestations

  • Clinical Features

  • Weakness
  • Hypotonicity
  • Depression
  • Constipation
  • Ileus
  • ECG Findings in Hypokalaemia

  • Moderate to Severe

  • PR prolongation
  • ST depression
  • T wave flattening or inversion
  • Prominent U wave (resulting in an apparent prolonged QT interval)
  • Life-Threatening

  • Torsade de pointes
  • Ventricular tachycardia
  • Ventricular fibrillation
  • Manifestations
     
ECG changes are not typically seen until the potassium concentration is <3.0.

Diagnosis

  • Severity of Hypokalaemia

  • Mild - 3.0 - 3.5 mmol/L
  • Moderate - 2.5 - 3.0 mmol/L
  • Severe - <2.5 mmol/L
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