Hypokalemia is a decrease in plasma potassium levels below 3.5 mmol/L (mEq/L). The main cause of this condition is excessive loss of potassium through the kidneys or gastrointestinal tract. Symptoms include general muscle weakness, increased urination. The greatest danger is the development of cardiac arrhythmias. In addition to determining the concentration of potassium in the serum, the diagnostic search should be aimed at establishing the cause of the electrolyte imbalance. For treatment, potassium deficiency is replenished and the pathology that caused it is treated.
Potassium is the main intracellular macronutrient. Inside the cells is about 90% of all potassium ions in the body. Such a large difference between intra- and extracellular concentration is necessary to maintain the membrane potential of cells, their ability to excite and transmit a nerve impulse. Precise data on the overall prevalence of hypokalemia are not available. It is only known that it is detected in 3-20% of patients undergoing inpatient treatment. Somewhat more often this disorder is observed in patients of the cardiological, gastroenterological departments.
With regard to the physiological and benign cause of hypokalemia, profuse sweating during sports, an alimentary factor, i.e. insufficient intake of potassium from food (strict diets, monotonous nutrition), can be considered. Pathological hypokalemia has a greater number of causes, differing in the mechanism that causes a decrease in the content of potassium in the body:
Hypokalemia leads to hyperpolarization of cell membranes, as a result of which the threshold for the occurrence of an action potential rises (up to its complete blocking), which worsens the excitability of neurons and myocytes. The transmission of a nerve impulse in the neuromuscular synapses, the conduction system of the heart, is disrupted. The tone of the skeletal muscles, smooth muscle walls of blood vessels, and internal organs decrease. This is the cause of most of the symptoms.
The motility of the gastrointestinal tract slows down. The sensitivity of arterioles to the vasoconstrictor effect of angiotensin II decreases. Hypokalemia contributes to the appearance in the heart of ventricular ectopic rhythms, a violation of the concentration ability of the kidneys (increased excretion of water). The secretion of insulin in the pancreas and aldosterone in the adrenal glands is suppressed.
The depletion of K+ reserves leads to the accumulation of hydrogen in the cell and intracellular acidosis. As a result, the processes of tissue respiration and glycolysis are suppressed. Pathological anatomical examination reveals dystrophic changes in almost all internal organs (especially in the heart, kidneys, and liver).
Most often in clinical practice, it is customary to divide hypokalemia into:
Separately, pseudohypokalemia is distinguished, which has no symptoms and does not require treatment. A false test result can be obtained if the patient has a very high level of leukocytes (leukocytes actively absorb K +). This happens, for example, with leukemia or a severe infection. Also, falsely high values are possible if the concentration of K + is determined in blood stored for a long time at room temperature.
In some patients, hypokalemia may occur without any symptoms. The clinical picture, its severity is determined to a greater extent not by the concentration of K +, but by the rate of its decrease. Muscle weakness is one of the first symptoms. Sometimes there are muscle twitches (fasciculations), tetanic convulsions (spasms). Inhibition of the excitability of CNS neurons leads to the development of symptoms of psychasthenia (drowsiness, apathy, deterioration in concentration).
Due to the slow motility of the gastrointestinal tract during meals, a feeling of fullness sets in very quickly, heaviness in the epigastrium worries. Constipation is characteristic. The conducting system of the heart is especially sensitive to a decrease in K + - tachycardia appears, interruptions in the work of the heart. Due to hypotension, dizziness begins. In primary hyperaldosteronism, on the contrary, symptoms of arterial hypertension (heaviness and pain in the back of the head, tinnitus) are always observed. Also, patients are concerned about an increase in diuresis and a constant feeling of thirst.
The most formidable complication of this electrolyte disorder is considered to be heart rhythm disturbances - ventricular tachycardia, ventricular fibrillation, which, without urgent treatment, very often lead to death. Also, hypokalemia increases sensitivity to cardiac glycosides, which increases the risk of glycosidic (digitalis) intoxication.
Some patients develop respiratory failure due to severe weakness of the diaphragm and intercostal muscles. Possible dynamic intestinal obstruction. A very rare complication of severe hypokalemia is rhabdomyolysis (destruction of muscle tissue). Prolonged depletion of potassium ions can lead to the appearance of cysts in the kidneys, chronic renal failure.
Patients with this electrolyte disorder are treated by doctors of different specialties, depending on what caused it to develop. Most often these are gastroenterologists, nephrologists, endocrinologists. Find out what medications the patient is taking. On examination, the identification of symptoms such as muscle hypotension, arrhythmic pulse is of the greatest importance. An additional examination is scheduled, which includes:
The differential diagnosis should be made primarily with hyperkalemia, as these conditions share similar clinical symptoms. Also, hypokalemia should be distinguished from neuromuscular diseases (myasthenia gravis, Guillain-Barré syndrome, muscular dystrophies), diseases that occur with incipient syndrome (diabetes, diabetes insipidus). Acute paralysis requires the exclusion of stroke.
The department in which patients are treated is determined by the pathology that caused the decrease in K + (nephrology, gastroenterology, etc.). Patients in serious condition must be transferred to the intensive care unit. To begin with, all drugs that can lead to hypokalemia are canceled. The main and primary task is to normalize the concentration of K +, stopping life-threatening rhythm disturbances.
Hypokalemia is a serious pathology that, without timely treatment, can be fatal. Arrhythmias (SVT, VF) are the most common cause of death. Less often, patients die from paralysis of the diaphragm, acute renal failure due to massive rhabdomyolysis. Prevention is reduced to the treatment of diseases, against which the level of K + in the blood decreases, the addition of potassium-sparing diuretics to conventional diuretics, the use of foods rich in potassium (bananas, dried fruits, vegetables).