Background
Potassium ions play an important role in many biological processes, particularly in the generation of membrane and action potentials and electrical conduction in nerve cells and the heart. Potassium is 98% localized intracellularly. The primary active transporter Na+/K+-ATPase provides transport into cells. Two hormones maintain the deep extracellular potassium concentration. The first is insulin, produced in the pancreas, which promotes the uptake of potassium into cells, and the second is renin, produced in the cells of the juxtaglomerular apparatus of the kidney. Renin promotes the secretion of aldosterone at the zona glomerulosa of the adrenal gland, which in turn promotes potassium excretion at the kidney (Figure). Potassium is also excreted to a lesser extent via the colon.
Symptoms
Hypokalemia is said to occur when a blood serum potassium concentration of less than 3.5 mmol/L is measured. A mild reduction is often frequently asymptomatic (3.0 – 3.5 mmol/L). However, a more severe reduction of < 2.5 mmol/L can cause symptoms, some of them serious, such as general weakness, paralysis, cardiac arrhythmias (especially when taking digoxin), ECG changes, disintegration of striated muscles, alkalosis, renal disease, renal failure, and, in the worst cases, a fatal outcome.
Causes
Three processes promote the development of hypokalemia: reduced potassium intake, increased uptake of potassium into cells, and increased elimination. Increased loss via the kidneys and via the colon is the most common cause, usually as a result of diarrhea or use of loop diuretics or thiazides. Aldosterone promotes renal excretion of potassium ions. Since aldosterone itself is under the control of the renin-angiotensin system (RAS), any promotion of this system can lead to a decrease in potassium concentration. Aldosterone is produced in the adrenal gland, which is why diseases of the adrenal gland also cause hyperkalemia. 1. drugs:
- Diuretics: Thiazides, loop diuretics, carbonic anhydrase inhibitors.
- Glucocorticoids
- Antibiotics: Carbenicillin, gentamicin, clindamycin, amphotericin B.
- Licorice
- Azole antifungals
- Beta2-sympathomimetics
- Insulins
- Laxatives, abuse of laxatives
2. nutrition:
- A reduced intake of potassium, for example, malnutrition, alcoholism, fasting (less common).
3. diseases:
- An increased gastrointestinal potassium loss for example in diarrhea and vomiting.
- Primary or secondary hyperaldosteronism, increased secretion of glucocorticoids, renal disease, Bartter syndrome
- Impaired potassium transport
- Disturbed acid-base balance (alkalosis)
- Hypomagnesemia
Prevention
Adequate intake of potassium through the diet. Potassium is found, for example, in sea salt, bananas, avocados, raisins, melons, dried dates, apricots and dark green leafy vegetables.
Drug therapy
Drug therapy is usually based on potassium substitution with potassium salts (potassium chloride).
Things to know
A classic interaction occurs with concomitant use of furosemide (Lasix, generics) and digoxin (Sandoz / Streuli): furosemide can cause hypokalemia and digoxin can subsequently induce cardiac arrhythmias
