Maintenance treatment

1. 2 mmol/kg/day.⁴

• Oral replacement is the preferred method.
• Intravenous infusions – usual dose up to 0.2mmol/kg/hour.
  • Solution must be diluted to 1mmol/25ml if given via a peripheral line, or 1mmol/12.5ml via central line.

Acute treatment of symptomatic hypokalaemia

1. If renal function is adequate 0.5mmol/kg in an hour. Repeat as necessary.
2. Adjust maintenance potassium. Correct hypocalcaemia.

Indications

1. Prevention and treatment of hypokalaemia
2. Bradycardia secondary to hypokalaemia

Contraindications and Precautions

1. Hyperkalaemia
2. Caution in babies with severe renal impairment and oliguria and renal disease.
3. Caution in babies with severe haemolytic reactions.
4. Caution in babies with cardiac disease.
5. Caution in babies with systemic acidosis.
6. Caution in babies with digoxin intoxication in presence of conduction disturbances.
7. Caution in babies receiving potassium sparing diuretic.

Clinical Pharmacology

Potassium is the major intracellular cation.  Hypokalaemia in critically ill neonates is usually the result of diuretic therapy, inadequate intake or diarrhoea. Other causes include congenital adrenal hyperplasia and renal disorders.  However, serum potassium levels are a poor marker of total body stores of potassium, and a low serum potassium more often reflects redistribution than true deficit.  Alkalosis as well as insulin infusions will lower serum potassium concentrations by driving the ion intracellularly. Symptoms of hypokalaemia include neuromuscular weakness and paralysis, ileus, urine retention, and ECG changes, ST segment depression, low voltage T wave and appearance of U wave. Hypokalaemia increases digoxin toxicity. Renal mechanisms are of primary importance in maintaining both total body potassium and plasma concentration within narrow limits. Oral potassium preparations are completely absorbed.

Hyperkalaemia affects cardiac conduction. ECG changes include tall peaked T waves, heartblock with widening QRS complex, arrhythmia and cardiac arrest.

Potassium is excreted mainly by the kidneys and is secreted in the distal tubules where it is involved in the sodium-potassium exchange process. Some potassium is excreted in the stools and small amounts may also be excreted in the sweat, saliva, bile and pancreatic juice.

Possible Adverse Effects

1. Venous irritation, pain, soft tissue injury at the injection site.
2. Gastrointestinal disturbances common (diarrhoea, vomiting, bleeding, abdominal discomfort).
3. Altered sensitivity to digoxin.
4. Respiratory distress.
5. Hyperkalaemia, indicated by weakness, listlessness, flaccid paralysis, hypotension, cardiac arrhythmias including heart block and cardiac arrest.

Special Considerations

1. Administer IV slowly, maximum infusion rate, 0.5mmol/kg/hour.
2. Monitor electrolytes.
3. Dilute potassium before intravenous administration. The literature recommends dilution to 40mmol/L, i.e, 1mmol/25ml.⁴  As this may cause volume overload, in infants with central line access dilute to 1mmol/12.5ml ^1,2 and piggyback with IV fluids to achieve further dilution.
4. Adequate renal function must be confirmed.
5. Management of hyperkalaemia if K⁺>7mmol/L unhaemolysed.  Refer to hyperkalaemia guideline.