[The heart and hyperkalemia]

Hyperkalaemia is a common and serious clinical condition in medical and surgical intensive care units. It is mainly encountered in patients with overt or latent cardiac and/or renal failure, and often aggravated by dietetic and therapeutic mismanagement. Hyperkalaemia depresses cardiac contractility, automaticity, conductivity and excitability, leading to ECG changes which must be recognized before clinical cardiovascular deterioration occurs if treatment is to be given to reverse an irremediably fatal evolution: ST-T changes and widening of the QRS with axial deviation shortly precede sinoatrial, intraatrial and atrioventricular block, the characteristic appearances of atrial standstill and ventricular and junctional hyperexcitability. The ECG changes faithfully follow the rise in serum potassium with few exceptions, such as associated electrolytic and acid-base disturbances (usually acidosis). Treatment must be administered as soon as a rise in potassium is observed. It may be administered intravenously (hypertonic glucose and insulin, calcium gluconate, furosemide, buffer solution and, above all, sodium bicarbonate or hypertonic saline) or orally (cation exchange resin). Renal dialysis may be required secondarily.