Hypokalemia

Introduction Hypokalemia, when the concentration of potassium in human plasma is lower than 3.5 mEq/L, it is called hypokalemia. Common causes are decreased intake and excessive loss, such as diarrhea, vomiting, etc., and potassium ions are transferred from extracellular fluid to intracellular fluid. liquid. When the body's hypokalemia occurs, it will affect the heart's blood vessels, central nervous system, digestion, urinary and muscle systems. The physiological functions of potassium are mainly manifested in: 1 involved in cell metabolism, such as potassium involved in the synthesis of intracellular glycogen and glucose oxidation, potassium involved in protein synthesis. When the intracellular synthesis process is enhanced, extracellular potassium will enter the cell, and potassium also activates the enzyme involved in cell synthesis. 2 regulate the body's osmotic pressure and acid-base balance. 3 maintain the stress function of nerves and muscle cells, the ratio of potassium concentration inside and outside the cell is the determinant of the transmembrane resting potential. The establishment of resting potential is the basis of nerve and muscle impulse transmission, generating action potential, therefore, potassium Changes in the content will still affect the stress of nerves and muscle cells.

Cause

Potassium in the human body depends on the outside world. The daily intake of potassium from food is about 50-100mmol, and 90% is absorbed by the small intestine. The kidney is the main organ for potassium excretion and potassium balance regulation. The potassium in the glomerular filtrate is completely absorbed in the proximal renal tubules. Later, the distal tubular cells and collecting duct cells secrete excess potassium from the urine. Discharge, so that potassium maintains balance in the body. However, when the body's intake of potassium is insufficient, the kidneys can not significantly reduce potassium excretion, so that potassium remains in the body, so it is easy to cause potassium deficiency. The serum potassium concentration was 3.5-5.5 mmol/L with an average of 4.2 mmol/L. Usually with serum potassium hypokalemia. However, the decrease in serum potassium does not necessarily mean that potassium deficiency in the body can only indicate the concentration of potassium in the extracellular fluid, and serum potassium does not necessarily decrease when the body is deficient in potassium. Therefore, clinical analysis should be combined with medical history and clinical manifestations.

an examination

Related inspection

Serum potassium electrocardiogram

Laboratory examinations must be based on the objective materials and physical examination of the objective materials to be summarized and analyzed. Serum potassium determination of blood K +, ECG examination, more sensitive to reflect hypokalemia, the main performance of ECG is QT The period is extended, the ST segment is lowered, the T wave is low, widened, biphasic, inverted or U wave appears.

Differential diagnosis

The diagnosis should be differentiated from the following symptoms:

Metabolic low potassium

Potassium in the human body depends on the outside world. The daily intake of potassium from food is about 50-100mmol, and 90% is absorbed by the small intestine. The kidney is the main organ for potassium excretion and potassium balance regulation. The potassium in the glomerular filtrate is completely absorbed in the proximal renal tubules. Later, the distal tubular cells and collecting duct cells secrete excess potassium from the urine. Discharge, so that potassium maintains balance in the body. However, when the body's intake of potassium is insufficient, the kidneys can not significantly reduce potassium excretion, so that potassium remains in the body, so it is easy to cause potassium deficiency. The serum potassium concentration was 3.5-5.5 mmol/L with an average of 4.2 mmol/L. Usually with serum potassium hypokalemia. However, a decrease in serum potassium does not necessarily mean a deficiency of potassium in the body.

2. Excessive potassium discharge

Excessive potassium excretion in the kidney is common in long-term use of diuretics or excessive use. Long-term use of thiazide diuretics may lead to water and electrolyte imbalance, resulting in low sodium, low chlorine and hypokalemia.

3. Hypokalemia

The total potassium reserves in the body are 3-4 mol (equivalent to 130-160 g), 98% is distributed in the cells, and extracellular fluid only accounts for 2%. The intracellular fluid K+ is 140 mmol / L, and the extracellular fluid K+ concentration is equivalent to 1 / 30 of the intracellular fluid. Normal serum potassium concentration is 3.5-5.5 mmol / L. Serum potassium should be constantly exchanged with intracellular potassium. This exchange is restricted by many conditions, and the exchange takes a certain time. Therefore, the serum potassium level does not always reflect the actual content in the body. Many diseases can be accompanied by changes in blood potassium. The safe range of changes in blood potassium is very small. Whether it is hypokalemia or hyperkalemia, it can cause serious dysfunction of the body, and even the heart stops, which is an important factor in the death of many diseases. One.

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