Causes and Etiology
The development of potassium deficiency is associated with three key groups of factors:
- Inadequate intake: daily consumption drops below 10 mEq due to starvation or strict exclusion of plant-based and dairy foods.
- Excessive loss:
- Gastrointestinal: profuse diarrhea and recurrent vomiting, provoking hypovolemia and secondary hyperaldosteronism.
- Renal: action of osmotic diuretics and nephrotoxic antibiotics.
- Intracellular shift: rapid redistribution of potassium from the blood into cells due to excess insulin, catecholamines, or cell division stimulation during megaloblastic anemia treatment.
Other factors include diabetic ketoacidosis and inherited disorders such as Bartter and Liddle syndromes.
Clinical Presentation
Symptoms affect several vital body systems:
- Neuromuscular system: marked muscle weakness progressing to paralysis, arteriolar hypotension, and a drop in blood pressure. Severe deficiencies can lead to rhabdomyolysis and myoglobinuria.
- Cardiovascular system: predisposition to arrhythmias and life-threatening cardiac arrest in diastole.
- Gastrointestinal tract: decreased motor function, gastric and intestinal hypokinesia.
- Psychiatric: apathy, drowsiness, and generalized asthenia.
Pathogenesis and ECG Changes
At the cellular level, extracellular potassium deficiency triggers a compensatory movement of hydrogen ions into cells, leading to intracellular acidosis. This disrupts tissue respiration, glycolysis, and causes dystrophic changes in the myocardium, kidneys, liver, and intestinal wall.
Electrocardiography in Hypokalaemia demonstrates characteristic changes:
- Prolongation of the $P-Q$ and $Q-T$ intervals.
- Widening and flattening of the $T$ wave, even becoming inverted (negative).
Principles of Management
Treatment is based on two main approaches:
- Aetiological therapy: eliminating the underlying cause that led to the electrolyte loss.
- Replacement therapy: correcting the deficit via parenteral administration of salts. Potassium chloride is the drug of choice because potassium deficiency is frequently accompanied by hypochloremia.