Makindo Medical Notes

Related Subjects:Hyperkalaemia |ECG - Hyperkalaemia |Hypokalemia |Hyperkalaemic and Hypokalaemic Periodic Paralysis |Resuscitation - Advanced Life Support |Action Potential

Introduction

Rapid IV infusions of potassium (K⁺) can be harmful and must be administered in a controlled and monitored setting. Infusion rates should not exceed 40 mmol in 1 L over 4-6 hours unless there is a life-threatening arrhythmia or profound hypokalaemia. Such cases should be managed in an HDU/CCU environment.

Aetiology

• Potassium (K⁺) is the primary intracellular cation, with 98% located in cells at a concentration of 140-150 mmol/L and only 2% in extracellular fluid (3.5-5 mmol/L).
• Factors such as insulin, beta agonists (salbutamol/albuterol), and alkalosis promote K⁺ entry into cells.
• A fine balance between intracellular and extracellular potassium is crucial for maintaining membrane voltage, with acute changes potentially leading to life-threatening events.

Causes

Clinical Features

• Weakness, palpitations, lethargy
• Severe cases: arrhythmias (torsades de pointes), heart failure
• Potential for rhabdomyolysis, diaphragmatic weakness

Investigations

• FBC: usually normal
• U&E: normal K⁺ range 3.5-5.0 mmol/L; moderate hypokalaemia 2.5-3.0 mmol/L; severe < 2.5 mmol/L
• Additional tests as indicated: Ca²⁺, Mg²⁺, venous HCO₃, ECG for characteristic changes

Management

• ABC assessment and IV fluids as needed; treat any underlying cause and provide telemetry if severe.
• Mild to Moderate Hypokalaemia: Oral KCl replacement (e.g., Sando-K 2 tablets TDS).
• Severe Hypokalaemia with arrhythmias (K⁺ < 2.5 mmol/L): Consider IV potassium infusion in CCU/HDU if very severe. Use a central vein for administration.
• In cases of sympathetic states (e.g., theophylline overdose), propranolol may assist in correcting hypokalaemia.

References

• Management of Hypokalaemia (GGC Medicines)