Hyperkalemia : Causes, Symptoms, Diagnosis & Treatment

• Causes Of Hyperkalemia
• Pathogenesis
• Classification
• Symptoms Of Hyperkalemia
• Complications
• Diagnostics
• Treatment Of Hyperkalemia
• Forecast And Prevention

Hyperkalemia is an increase in the level of potassium in the blood serum above 5.5 mmol / l or mEq / l. The reason is an increased intake of potassium in the body, its release from cells or a slowdown in excretion. The main clinical symptoms include general muscle weakness, severe cardiac arrhythmias. Diagnosis is made by measuring the concentration of potassium in the blood. As measures of treatment, potassium intake is maximally limited, some drugs are canceled, calcium, glucose, and insulin preparations are used. In severe hyperkalemia, hemodialysis is performed.

Hyperkalemia is a pathological condition characterized by high levels of potassium in the blood. Potassium is predominantly an intracellular cation providing the membrane potential of cells, mainly muscle cells and neurons. The difference in the concentration of potassium on the inner and outer surface of the cell membrane determines the cell's ability to excite. This macronutrient enters the human body with food, is excreted mainly with urine, as well as with feces and sweat. Hyperkalemia is diagnosed in approximately 10% of patients hospitalized in the intensive care unit, in men it occurs somewhat more often than in women. More accurate information about the prevalence of this condition is not available.

Causes of hyperkalemia

There are many reasons for high potassium levels. Hyperkalemia is almost always a polyetiological condition, i.e. it develops under the simultaneous influence of several factors affecting different stages of potassium metabolism. Depending on the mechanism of action, the causes of hyperkalemia can be:

• Violation of the excretion of potassium in the urine . A decrease in the excretion of a macroelement due to a slowdown in blood flow in the renal glomeruli occurs in acute and chronic renal failure. Also, a deterioration in potassium excretion is observed with aldosterone deficiency (adrenal insufficiency), the use of drugs (ACE inhibitors, potassium-sparing diuretics, non-steroidal anti-inflammatory drugs).
• Enhanced exit from cells . Any disease or pathological condition, accompanied by damage or accelerated tissue catabolism, leads to hyperkalemia. These include hemolytic anemia, tumor decay syndrome during chemotherapy, malignant hyperthermia. A sharp increase in potassium levels occurs in the syndrome of prolonged compression due to massive rhabdomyolysis.
• Violation of intracellular transport . The transition of potassium into the cell from the intercellular space is disturbed with metabolic acidosis, insulin deficiency (type 1 diabetes mellitus), taking medications (beta-blockers, cardiac glycosides, muscle relaxants).
• Increased exogenous intake . Parenteral administration of a large amount of potassium chloride, potassium salts of antibiotics can lead to hyperkalemia. With long-term storage of donated blood, erythrocytes are destroyed, potassium is released from them, so the transfusion of such blood can cause hyperkalemia in the recipient.

The development of hyperkalemia predisposes to a diet containing foods rich in potassium (dried apricots, prunes, chocolate), taking dietary supplements with potassium. The likelihood of hyperkalemia is higher in young children and the elderly, which may be due to the physiological imperfection of the excretory function of the kidneys. Also, risk factors include diseases that require treatment with drugs that cause an increase in potassium - arterial hypertension, chronic heart failure (CHF).

Pathogenesis

Regardless of the cause, hyperkalemia has the same pathogenesis. An increase in the concentration of potassium in the extracellular fluid reduces the membrane potential, which increases the difference between the resting potential of the cell and the critical level of depolarization. This leads to a decrease in the excitability of the cell, in which a nerve impulse arises and propagates worse. This is especially strongly reflected in the function of skeletal muscle cells, cardiomyocytes of the conduction system of the heart and neurons.

Classification

Separately, the so-called false, or pseudohyperkalemia, which is a laboratory artifact, is isolated. Its occurrence is associated with the release of potassium from formed elements during the formation of a clot in a test tube after blood sampling for analysis. Often this phenomenon is observed with thrombocytosis more than 90 thousand, leukocytosis above 7 thousand. Pseudohyperkalemia has no symptoms and does not require treatment. According to the level of potassium increase (in mmol / l), three degrees of hyperkalemia are traditionally distinguished:

• Light - from 5.5 to 6.
• Moderate - from 6.1 to 6.9.
• Heavy - more than 7.

The following classification is considered more practical in terms of prognosis and determination of treatment tactics:

• Life-threatening hyperkalemia - a level above 6.5 in combination with the presence of changes on the electrocardiogram characteristic of hyperkalemia.
• Non-life-threatening hyperkalemia - concentration below 6.5 mol / l, there are no specific ECG signs.

Symptoms of hyperkalemia

Clinical symptoms and their severity are largely determined not so much by the degree of hyperkalemia as by the speed of its onset. For example, in many patients suffering from chronic renal failure for several years, hyperkalemia increases very slowly. Therefore, they often do not have any symptoms due to adaptation to ionic imbalance.

The main symptoms of hyperkalemia include muscle weakness, rapid onset of fatigue, and difficulty in breathing due to weakness of the respiratory muscles. Muscle pain may occur during exercise. Sometimes muscle hypotonia is so pronounced that it is difficult for the patient to get out of bed. Neurological symptoms are usually limited to drowsiness, paresthesias (tingling sensations, crawling sensations) of the fingers and toes.

Hyperkalemia has a particularly toxic effect on the heart. The main cardiological symptoms are a slowing of the pulse, sometimes bouts of palpitations. Some patients develop chest pain resembling a myocardial infarction. Atony of the muscles of the gastrointestinal tract is manifested by a feeling of heaviness in the epigastric region, a feeling of fullness in the stomach, and constipation.

Complications

Life-threatening arrhythmias are considered the most frequent and dangerous complications of elevated potassium levels, which, without urgent treatment, lead to the death of the patient in about 40% of cases. Such arrhythmias include complete atrioventricular block, ventricular fibrillation, asystole (cardiac arrest). Severe hypotension of the respiratory muscles (diaphragm and intercostal muscles) can cause respiratory failure and respiratory arrest. Atony of the digestive tract in rare cases contributes to the development of dynamic intestinal obstruction.

Diagnostics

A doctor of any specialty can supervise a patient with hyperkalemia, but nephrologists and resuscitators are most often involved in such patients. When collecting an anamnesis, it is specified what medications, biological supplements the patient takes. During a physical examination, symptoms such as weakening or inhibition of tendon reflexes, tachypnea (more than 2 breaths per minute), bradycardia (less than 6 beats per minute) are revealed. Further examination should be aimed not only at diagnosing hyperkalemia and its consequences, but also at finding the cause of its development. This is essential for effective treatment.

• Laboratory tests . In the hemogram, the content of formed elements (erythrocytes, platelets, leukocytes), hemoglobin is determined. In a biochemical blood test, the level of glucose, creatine phosphokinase, and sodium is assessed. Indicators of acid-base balance are measured. If the patient has symptoms of adrenal insufficiency, a serum cortisol test, an ACTH test, and a renin-aldosterone ratio are performed.
• Assessment of kidney function . Particularly important in the diagnosis is the assessment of renal function. The concentration of creatinine, urea, the total amount and specific gravity of urine is determined. The glomerular filtration rate is calculated. The transtubular potassium gradient (THC) is recognized as a specific indicator that allows one to draw a conclusion about the ability of the kidneys to excrete potassium. To calculate it, you need to know the osmolarity of urine and serum, the concentration of potassium in the urine, in serum.
• Electrocardiography. ECG is the main instrumental method for diagnosing hyperkalemia, with the help of which the following changes are detected: sinus bradycardia, high peaked T waves, expansion of the QRS complex. Also on the cardiogram, there is a shortening of the QT interval, lengthening of the PQ interval, flattening, expansion, and sometimes the disappearance of the P wave.

Differential diagnosis of hyperkalemia should be carried out with diseases, the clinical picture of which is dominated by symptoms of muscle weakness and hypotension. Such diseases are hereditary muscular dystrophies, neuromuscular pathologies (myasthenia gravis, Guillain-Barré syndrome), thyrotoxic periodic paralysis. Acute paralysis requires a differential diagnosis with botulism.

Treatment of hyperkalemia

Patients are subject to hospitalization for treatment in a hospital, and in case of life-threatening hyperkalemia - in the intensive care unit. The first condition for successful treatment is the abolition of all medications that can lead to hyperkalemia (potassium-sparing diuretics, ACE inhibitors, NSAIDs, etc.), stopping the administration of potassium salts. Respiratory failure may require connection to a ventilator. Specific treatment of hyperkalemia involves several areas:

• Stabilization of cardiomyocyte membranes . With high life-threatening hyperkalemia, for the treatment and prevention of severe cardiac arrhythmias, calcium salts are administered intravenously, which has an antagonistic effect on potassium and improves myocardial contractility. It is preferable to use calcium gluconate, since calcium chloride, when it enters the subcutaneous tissue or muscle tissue, causes their necrosis.
• Movement of potassium into cells . For this, the administration of insulin with glucose, beta-adrenergic agonists (salbutamol) is used. For the same purpose, metabolic acidosis is corrected by the introduction of sodium bicarbonate (soda solution).
• Accelerated excretion of potassium . Loop diuretics (furosemide) are very effective in stimulating the excretion of potassium ions in the urine. To remove potassium through the intestines, enterosorbents, cation exchange resins (sodium polysterol sulfonate) are prescribed. With the development of hyperkalemia against the background of adrenal insufficiency, hormonal preparations (fludrocortisone, hydrocortisone) are necessarily used for treatment.
• Hemodialysis . This is an emergency way to remove potassium from the body. Such treatment is resorted to either with the ineffectiveness of the above measures, or immediately with a very high concentration of potassium. It is preferable to use a bicarbonate-buffered dialysate.

Forecast and prevention

Hyperkalemia is a severe (and sometimes urgent) pathological condition. The success of treatment directly depends on timely diagnosis. The frequency of deaths from hyperkalemia ranges from 2 to 41%. The probability of death is determined not only by the level of potassium, but also by the disease against which hyperkalemia developed. The main cause of death is dangerous arrhythmias. Prevention consists in the abolition of dietary supplements containing potassium, limiting potassium-rich foods in patients with chronic kidney disease. The simultaneous use of drugs that cause hyperkalemia should be avoided, and if they are prescribed, the level of potassium in the blood should be regularly monitored.