Hypokalemia

At normal blood pH, the normal potassium concentration in the serum can mask the actual total deficiency in the body( up to 200 mmol).The decrease in serum potassium concentration for each 1 mmol / l corresponds, as a rule, to a general deficit of about 350 mmol. The concentration of potassium in the serum below 2 mmol / l indicates a general deficiency in the body, exceeding 1000 mmol. The following situations lead to hypokalemia.

■ Loss of gastrointestinal fluids, concomitant chloride loss deepens metabolic alkalosis.

■ Prolonged treatment with osmotic diuretics or saluretics( mannitol, furosemide), as well as diabetic glucosuria.

■ Stress conditions accompanied by increased adrenal activity, Cushing's disease.

■ Decreased potassium consumption in the postoperative and post-traumatic periods in combination with sodium retention in the body( yatrogenic hypokalemia).

■ Prolonged acidosis or alkalosis, as a result of which the kidney function is disrupted and there is potassium.

■ Previous potassium deficiency caused by a severe chronic illness and reinforced with a postoperative period.

■ Continuous use of HA.

■ Dilution hypokalemia in the rehydration phase after acute or chronic dehydration.

■ CRF.

■ Bartter's syndrome.

■ Low-grade hyperaldosteronism.

All four causes of hypokalemia are based on four main mechanisms: decreased potassium intake, increased potassium transfer from extracellular fluid into the cell, reduced potassium yield from the cell, and increased loss of potassium. Nevertheless, the main mechanism of hypokalemia is an increased loss of potassium, which occurs in two ways - through the gastrointestinal tract and the kidneys( hypokalemia of "exhaustion").Intestinal and biliary fistulas, as well as extensive burns, are two secondary ways of losing potassium. The most massive losses of potassium occur with repeated vomiting( in this connection, hyperkaliemia is often absent in patients with acute renal failure), intestinal obstruction, as well as in all diseases accompanied by diarrhea.

The main causes of increased potassium transfer from the extracellular space into the cell include the administration of insulin( or the presence of insulinoma), thyrotoxicosis, alkalosis. Hypokalemia associated with alkalosis is due, first, to the fact that potassium passes from the extracellular fluid( plasma) to the intracellular fluid in exchange for hydrogen ions entering to lower the pH of the blood;secondly, there is increased excretion of potassium in the urine, while potassium is lost, and hydrogen ions are reabsorbed to correct alkalosis.

A decrease in potassium intake is possible in patients with reduced diet( with alcoholism, anorexia), as well as with prolonged intravenous administration of non-potassium solutions.

Symptoms of potassium deficiency - nausea, vomiting, muscle weakness( including respiratory muscles - shallow breathing), atony of the intestine and bladder, heart weakness. At a serum potassium concentration below 3 mmol / l, ECG indicates changes that indicate impaired and decreased excitability and conduction in the heart muscle. In some cases, the relationship between the concentration of potassium in the blood and the occurrence of such serious consequences as a violation of the rhythm of the heart, do not follow.