Hyperkalemia

Introduction

Hyperkalemia is a condition where the serum or plasma potassium level is above the upper limits of normal, usually greater than 5.0 mEq/L to 5.5 mEq/L.

Actiology

  • Hyperkalemia usually occurs as a result of potassium release from cells.
  • Decreased renal excretion of K as in renal failure
  • Decreased potassium secretion
  • Impaired sodium reabsorption in
    • Primary hypoaldosteronism
    • Adrenal insufficiency
    • Secondary hypoaldosteronism
    • Medications such as ACE inhibitors, NSAIDs and heparin.
  • Enhanced chloride reabsorption (chloride shunt) as seen in Gordon’s syndrome

Clinical features

  • Weakness, flaccid paralysis, metabolic acidosis
  • ECG changes
  • Increased T wave amplitude
  • Peaked T waves
  • Prolonged PR intervals, QRS duration
  • Atrioventricular conduction delays
  • Loss of P waves
  • Ventricular fibrillation or asystole

Investigations

  • Serum Urea, Electrolytes and Creatinine
  • Other renal function tests
  • Acid base balance

Treatment objectives

  • Correction of hyperkalaemia
  • Preservation of cardiac function
  • Treatment of underlying cause(s)

Management

This depends on the degree of hyperkalaemia, associated physical features and ECG changes
The measures are aimed at:

  • Promoting potassium loss.
  • Limiting exogenous potassium intake
  • Discontinuation of anti-kaliuretic drugs
  • Shifting potassium into cells

Drug treatment

Calcium gluconate

  • 10 ml of 10% solution intravenously over 2-3 minutes

Insulin plus glucose infusion

  • 10-20 units of regular insulin plus 25 – 50 g of glucose given as 10 units in 100 ml of 50% glucose

Other alternatives to cause influx of
potassium:
Sodium bicarbonate

Or:

Parenteral/nebulised salbutamol (see
Bronchial asthma)

  • Removal of potassium with diuretics (loop plus thiazide diuretics in combination)
  • Sodium polysterene sulphonate (a cation exchange resin)
  • Administered as a retention enema of 50g of resin and 50 ml of 70% sorbitol mixed in 150 ml of tap water

Haemodialysis

  • The most rapid and effective way of lowering plasma potassium concentration
  • Reserved for patients in renal failure
    and those with severe hyperkalemia unresponsive to more conservative measures