The Impact of Hyperkalemia on the Heart

Written by Chen Li Ping
Endocrinology
Updated on October 20, 2024
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Typically, when serum potassium exceeds 5.5 mmol/L, it is referred to as hyperkalemia. The manifestations of hyperkalemia on the cardiovascular system usually include bradycardia and arrhythmias, but generally do not lead to congestive heart failure. Sometimes, there may be cardiac enlargement and diminished heart sounds, with characteristic changes on an electrocardiogram. Finally, when serum potassium reaches 12 mmol/L, some parts of the myocardium may be excited and recover, while others have not yet depolarized, making it very easy to cause tachycardia, flutter, ventricular fibrillation, and even cardiac arrest, leading to death. Therefore, hyperkalemia is also a major cause of sudden cardiac death. Some patients with hyperkalemia may only exhibit arrhythmias and show no neuromuscular symptoms before death, thus a rapid diagnosis is crucial. The severity of hyperkalemia is generally assessed by both the measured serum potassium concentration and changes in the electrocardiogram.

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Hyperkalemia is seen in which diseases?

When serum potassium levels exceed 5.5 millimoles per liter, it is referred to as hyperkalemia. Elevated serum potassium does not reflect an overall increase in body potassium, but due to limitations in testing methods, the clinical diagnosis of hyperkalemia still relies on combining serum potassium levels with electrocardiogram history. The causes of hyperkalemia are complex and commonly include: First, decreased renal potassium excretion, seen in acute kidney failure or insufficiency in adrenal cortical hormone synthesis and secretion, or long-term use of potassium-sparing diuretics; Second, shifts of potassium from inside the cells, often due to hemolysis, tissue damage, large-scale necrosis of tumors and inflammatory cells, shock, burns, excessive muscle contractions, acidosis, or injection of hypertonic saline or mannitol, which causes dehydration inside cells and leads to potassium leakage, resulting in hyperkalemia; Third, excessive intake of potassium-containing medications, such as high doses of potassium penicillin; Fourth, transfusion of stored blood can lead to hyperkalemia; Fifth, digitalis poisoning can cause hyperkalemia.

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What should be noted in the diet for hyperkalemia?

In cases of hyperkalemia, it is important to avoid eating foods high in potassium, such as corn, lettuce, carp, eel, lamb, beef, pork, as well as dates, bananas, and others. These foods are rich in potassium and should be consumed less or not at all. Additionally, a diet high in sugar and fat should be provided, or some intravenous nutrition may be used, to ensure sufficient caloric intake and prevent the release of potassium from metabolic breakdown, which could lead to an increase in blood potassium levels. Also, it is important to avoid certain medications high in potassium, such as traditional Chinese medicines. (Medication use should be under the guidance of a professional doctor.)

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Does hyperkalemia cause a fast or slow heart rate?

Hyperkalemia often causes a slowed heart rate and is associated with various arrhythmias. When serum potassium is between 6.6 to 8.0 mmol/L, tented T-waves may be observed. When serum potassium levels rise rapidly, it can lead to ventricular tachycardia or even ventricular fibrillation. On the other hand, a slow increase in serum potassium can cause conduction blocks, and in severe cases, may lead to cardiac arrest. These are the heart rate changes caused by hyperkalemia, which typically result in a slower heart rate.

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How is hyperkalemia treated?

For hyperkalemia, commonly used clinical treatments include firstly diuretics, which increase the excretion of potassium, thus increasing its discharge from the body. Additionally, hypertonic glucose with insulin is used intravenously to facilitate the movement of potassium from outside to inside the cells. Sodium bicarbonate can also be used to correct acidosis, which can likewise reduce blood potassium levels. When hyperkalemia causes ventricular arrhythmias, calcium injections should be administered immediately to counteract the cardiac toxicity of high potassium. If these treatments do not result in significant effects and the condition is critical, emergency hemodialysis or peritoneal dialysis can be performed to lower blood potassium levels. (Medication should be administered under the guidance of a doctor.)

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How to rescue hyperkalemia

Hyperkalemia must be dealt with immediately once it occurs. The usual treatments in clinical settings include promoting potassium excretion using furosemide or other loop diuretics to maximize renal potassium excretion, or using oral or rectal potassium-eliminating agents. For life-threatening hyperkalemia with serum potassium levels greater than 6.5 mmol/L, hemodialysis is necessary. Another approach is to facilitate the shift of potassium into cells, which is done through the administration of insulin with glucose, or sodium bicarbonate along with calcium gluconate that helps protect the myocardium, thus providing treatment and protective measures for hyperkalemia.