What is Hypokalemia?

The serum potassium (K ⁺ ) concentration ranged from 3.5 to 5.5 mmol / L with an average of 4.2 mmol / L. Hypokalemia is usually called when serum potassium is less than 3.5mmol / L. However, a decrease in serum potassium does not necessarily indicate a lack of potassium in the body, but only a decrease in the concentration of potassium in extracellular fluid, and a decrease in serum potassium does not necessarily decrease when the body is deficient in potassium. Therefore, the clinical history and clinical manifestations should be analyzed and judged.

Basic Information

English name

hypopotassaemia

English alias

Visiting department

Internal medicine

Common causes

Coma, fasting, severe diarrhea, and vomiting are common

Common symptoms

Numbness in the limbs, followed by weakness, muscle weakness and paroxysmal palsy

Causes of hypokalemia

1. Reduced potassium intake

The general diet is rich in potassium. Therefore, as long as you can eat normally, the body will not be deficient in potassium. Patients with gastrointestinal obstruction, coma, and fasting for a long period of time after surgery. If these patients are not fed with potassium at the same time or the potassium supplement is insufficient, it can lead to potassium deficiency and hypokalemia. However, if inadequate intake is the only cause, the degree of potassium deficiency in a certain period of time may not be very serious due to the potassium-retaining function of the kidney.

2. Excessive potassium excretion

(1) Potassium loss through the gastrointestinal tract This is the most important cause of potassium loss in children. It is often found in patients with severe diarrhea, vomiting, etc. who have a large amount of digestive fluid loss. During severe vomiting, the loss of gastric juice is not the main cause of potassium loss. A large amount of potassium is lost through the kidneys with urine, because metabolic alkalosis caused by vomiting can increase renal excretion of potassium, and blood volume reduction caused by vomiting can also be passed Increased secondary aldosterone promotes renal potassium excretion.

(2) Loss of potassium through kidney This is the most important cause of potassium loss in adults. Common factors that cause increased potassium excretion in the kidney are: long-term continuous use or excessive use of diuretics; certain kidney diseases; excessive adrenal corticosteroids; anions that are not easily reabsorbed in the distally curved tubules increase; magnesium deficiency ; alkali poisoning.

(3) Transdermal potassium loss Sweat contains only 9mmol / L of potassium. Under normal circumstances, sweating does not cause hypokalemia. However, when performing heavy physical work in a high temperature environment, a large amount of sweating can also lead to the loss of potassium.

3. Extracellular potassium transfer to intracellular

When extracellular potassium is transferred into cells, hypokalemia can occur, but the total potassium content of the body does not decrease as a result.

(1) Extracellular potassium is transferred into cells during the onset of hypokalemic periodic paralysis , which is a familial disease.

(2) The intracellular H + of alkalosis is moved to the outside to compensate, and the extracellular K + enters the cell.

(3) Excessive insulin Hypokalemia occurs when diabetic ketoacidosis is treated with large doses of insulin.

(4) Barium poisoning is caused by barium poisoning, such as barium acetate, barium carbonate, barium chloride, barium hydroxide, barium nitrate, and barium sulfide.

4.Raw raw cotton oil poisoning

In the past two or three decades, a hypokalemia paralysis has appeared in some cotton producing areas in China, and it is also called "soft disease" in some provinces.

Clinical manifestations of hypokalemia

The severity of clinical manifestations depends on the degree of potassium deficiency inside and outside the cell and the rate of potassium deficiency. The symptoms of acute hypokalemia are more severe than chronic hypokalemia with the same level of potassium deficiency.

Neuromuscular system

Common symptoms are myasthenia gravis and paroxysmal palsy. The latter may be preceded by myasthenia gravis. Although the onset is related to the absolute level of plasma K +, it is more closely related to the K + gradient inside and outside the cell. The larger the threshold potential difference, the lower the muscle excitability. Paralysis can also occur when plasma K + increases, and more often at night and after exertion. The affected muscles are most common in the limbs, and the head and neck muscles are generally not affected, but can be Dyspnea occurs when the respiratory muscles are involved. Before the attack, there may be numbness in the extremities, followed by fatigue, and finally the voluntary movement completely disappears. Generally, the proximal muscles are slightly milder than the distal muscles. The patient cannot stand, walk, sit or squat and cannot stand. In light, the lighter person can stand up by holding the support firmly and unable to stand up on their own. Painful spasms or twitching of the hands and feet can also occur. Most of the central nervous system is normal and conscious, with indifferent expressions, depression, sleepiness, memory and orientation. Mental symptoms such as power loss or loss, the brain nerve is rarely involved, the superficial nerve reflex weakens or completely disappears, but the deep tendon reflex and the abdominal wall reflex are less affected .

2. Cardiovascular system

Low potassium can reduce myocardial stress and various arrhythmias and conduction blocks. Mild patients have sinus tachycardia, atrial or ventricular preconstriction, and atrioventricular block; in severe cases, paroxysms occur. Atrial or ventricular tachycardia, or even ventricular fibrillation, potassium deficiency can aggravate digitalis and antimony poisoning, which can lead to death, peripheral peripheral blood vessels dilate, and blood pressure can decrease; decreased myocardial tension can cause the heart to enlarge, and in severe cases Heart failure, changes in the electrocardiogram appear U waves, often suggest that potassium loss in the body is at least 500mmol / L.

3. Urinary system

Long-term hypokalemia can cause damage to renal tubules and cause potassium-deficient nephropathy. Concentrated renal tubules, ammonia synthesis, hydrogen absorbing and chloride reabsorption functions can be reduced or enhanced, and sodium excretion function or sodium reabsorption function can also be decreased. As a result, it results in metabolic low potassium and low chlorine alkalosis.

4. Endocrine and Metabolic System

Hypokalemia may have impaired glucose tolerance, children with chronic potassium deficiency have delayed growth and development, and patients with hypokalemia have decreased urinary potassium excretion (24 hours), but are caused by renal tubular acidosis and acute renal failure, Increased urinary potassium excretion (> 40mmol / 24 hours).

5. Digestive system

Potassium deficiency can slow down bowel movements. People with mild potassium deficiency can only have appetite deficiency, abdominal distension, nausea and constipation; severe potassium deficiency can cause paralytic intestinal obstruction.

Hypokalemia test

Blood test index

The serum potassium concentration decreased, L, the blood pH value was at the normal high limit or> 7.45, and the sodium ion concentration was at the normal low limit or <135mmol / L.

2. Urine test index

Urinary potassium concentration decreases, urine pH is acidic, and urine sodium excretion is high.

3. ECG examination

The earliest manifestations are ST-segment depression, T-wave depression, widening, upside-down, waves appear, QT time is prolonged, and the above changes can be improved after potassium supplementation.

Hypokalemia diagnosis

The diagnosis of hypokalemia includes determining the cause of hypokalemia and determining the cause of hypokalemia.

1. Determine hypokalemia

According to: serum potassium is less than 3.5mmol / L; ECG examination has low potassium images; clinical manifestations consistent with hypokalemia.

2. Determine the cause of hypokalemia

Including: Detailed inquiry of medical history such as food intake, gastrointestinal symptoms, urination and nocturia and diuretics, laxatives and drinking history; laboratory tests in addition to potassium, sodium, chlorine, blood calcium, magnesium Hypocalcemia, hypomagnesium, and acidosis can worsen hypokalemia.

Hypokalemia Treatment

Acute hypokalemia

Urgent measures should be taken for treatment; as long as the serum potassium is not less than 3mmol / L, the cause can be checked first, and then the cause can be treated.

Potassium supplement

It should be determined based on blood potassium levels. Those with blood potassium of 3.5 4mmol / L do not need additional potassium supplementation. They only need to encourage patients to eat more potassium-containing foods, such as fresh vegetables, fruit juices and meat foods. When the blood potassium is 3.0 3.5mmol / L, it is necessary to determine whether to supplement potassium according to the specific situation of the patient. Patients who have had arrhythmia, congestive heart failure, heart failure being treated with digitalis, ischemic heart disease and a history of myocardial infarction should receive potassium supplements. Patients who are generally in good condition can only encourage eating potassium-containing foods, or oral potassium preparations. Those whose blood potassium is lower than 3.0mmol / L should supplement potassium.

For minor cases, only oral potassium is needed, and 10% potassium chloride is the first choice. Blood potassium should be monitored during oral potassium preparations. If blood magnesium is below 0.5mmol / L, 50% magnesium sulfate should be injected intramuscularly. Can also be taken orally with 10% magnesium sulfate.

Severe patients (including arrhythmia, rapid ventricular rate, severe cardiomyopathy, familial periodic paralysis) should be intravenously infused with potassium preparations, and the commonly used preparation is also potassium chloride. Blood potassium should be monitored during infusion or by electrocardiogram. For those with combined acidosis or without hypochloremia, 31.5% potassium glutamate solution 20ml should be replenished into 5% glucose solution, slowly intravenous drip, potassium chloride should not be used at this time.

3. Correct water and other electrolyte metabolism disorders

Many of the causes of hypokalemia can cause the loss of water and other electrolytes such as sodium and magnesium at the same time. Therefore, it should be checked in time, and once found, it must be actively addressed. As mentioned earlier, if hypokalemia is caused by magnesium deficiency, potassium supplementation alone is not effective without magnesium supplementation.