Why is the urine acidic in hypokalemia?

Written by Gan Jun
Endocrinology
Updated on December 24, 2024
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When hypokalemia occurs, the concentration of potassium ions in the extracellular fluid decreases, causing potassium ions to shift from the inside to the outside of the cell. Meanwhile, two sodium ions and one hydrogen ion from the extracellular fluid move into the cell, decreasing the concentration of hydrogen ions outside the cell, thus resulting in metabolic alkalosis. At the same time, due to the reduction of blood potassium, the potassium-sodium exchange in the renal tubules is reduced. The renal tubule cells exchange more hydrogen ions and sodium ions, thus increasing the reabsorption of bicarbonate ions and raising the pH value. This type of metabolic alkalosis increases the number of hydrogen ions inside cells, while the kidney secretes more hydrogen, thereby producing acidic urine, also known as paradoxical aciduria.

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Written by Gan Jun
Endocrinology
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What are the clinical manifestations of hypokalemia?

When patients present with hypokalemia, the first symptoms often include significant muscle weakness and episodic flaccid paralysis. Additionally, there may be a decrease in the stress tolerance of cardiac myocytes, leading to arrhythmias or an increased heart rate. Hypokalemia can also cause damage to the renal tubules, leading to a decline in kidney excretion functions. The most crucial manifestation is endocrine disorder, which can lead to kidney failure. The primary treatment for hypokalemia is potassium supplementation. For mild hypokalemia, it is advisable to consume foods high in potassium, such as oranges, bananas, and other fruits and vegetables. In cases of severe hypokalemia, potassium can be administered intravenously or orally, and blood potassium levels should be dynamically monitored.

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Written by Wei Shi Liang
Intensive Care Unit
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What medicine should be taken for hypokalemia?

The treatment of hypokalemia primarily involves addressing the underlying disease. Symptomatic treatment should avoid excessive potassium supplementation, which can lead to hyperkalemia. The principle of potassium supplementation is as follows: for mild hypokalemia, such as in patients showing clinical signs, oral potassium can be administered at 40-80 millimoles per day. For patients with severe hypokalemia, or those whose gastrointestinal tract cannot utilize potassium, with potassium levels less than 2.0 millimoles per liter, intravenous potassium can be provided. An initial supplementation rate of 10-20 millimoles per hour is relatively safe. In cases of severe hypokalemia with life-threatening clinical signs, a rapid increase to 40-80 millimoles can be achieved in a short period, but close monitoring is necessary.

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Written by Wang Li Bing
Intensive Care Medicine Department
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How to replenish potassium for hypokalemia

After the occurrence of hypokalemia, we usually adopt oral potassium supplementation or intravenous potassium supplementation. Oral potassium supplementation is the safest method clinically, and patients can also be advised to consume potassium-rich fruits or vegetables, etc. On the other hand, there is intravenous potassium supplementation, which must be decided based on the patient's urine output. Generally, potassium supplementation can be carried out only when the patient's urine output is more than 500 milliliters per day. However, the concentration of potassium must be diluted and not administered undiluted to prevent arrhythmias and so on.

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Written by Wang Li Bing
Intensive Care Medicine Department
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How to treat hypokalemia?

After the occurrence of hypokalemia, there are generally two methods of potassium supplementation clinically. The first is oral potassium supplementation, which is relatively safe, and one can also eat fruits or vegetables rich in potassium. The second method is intravenous potassium supplementation. The first thing to note with intravenous supplementation is the patient's urination status. If the patient’s urination is normal, potassium chloride can be administered intravenously but must be diluted. In clinical practice, the concentration of intravenous potassium chloride generally does not exceed 0.3%, so we must pay attention to the concentration during potassium supplementation.

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Written by Wei Shi Liang
Intensive Care Unit
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Clinical manifestations of hypokalemia

The clinical manifestations of hypokalemia are diverse, with the most life-threatening symptoms affecting the cardiac conduction system and the neuromuscular system. Mild hypokalemia on an electrocardiogram presents as flattened T waves and the appearance of U waves, while severe hypokalemia can lead to fatal arrhythmias such as ventricular tachycardia and ventricular fibrillation. In the neuromuscular system, the most prominent symptoms of hypokalemia are skeletal muscle flaccid paralysis and sustained smooth muscle tension, which can involve the respiratory muscles and lead to respiratory failure. Hypokalemia can also cause insulin resistance or hinder insulin release, leading to significant glucose tolerance abnormalities. Reduced potassium excretion decreases the kidney's ability to concentrate urine, resulting in polyuria and urine with low specific gravity.