How does fluctuation in potassium levels in the blood affect the heart?
Both high potassium and low potassium levels in the blood are bad for the heart. Electrical transmission of signals within the conduction system of the heart and the heart muscle are highly dependent on blood potassium levels. Potassium concentration within cells is much higher than that in the blood. Blood level of potassium has only a narrow normal range. When it goes above normal, electrical conduction within the heart slows down, ultimately leading to stoppage of the heart (cardiac arrest). Heart muscle function also ceases when blood potassium levels are high. In fact, heart surgeons use fluids with high levels of potassium to stop the heart temporarily during open heart surgery and later reverses it to restart the heart. Low levels of potassium in the blood leads to dangerous abnormalities in heart rhythm which can also finally lead to cardiac arrest. Prior the extreme form, ECG changes are noted in both high and low potassium states, the changes being different for different levels of potassium.
It may be noted that the laboratory value actually measured is serum potassium (blood is allowed to clot, the clot removed and the remaining fluid is known as serum).
How can potassium levels change in blood?
High potassium levels can occur when the kidney function is poor as kidney has a very important role in maintaining the normal potassium level in circulation. Certain medications and foods can also increase the potassium levels. Citrous fruits (e.g. lime) and tender coconut water can increase blood potassium levels. Uncontrolled diabetes (high blood sugar) can also increase blood potassium levels. Vice versa, controlling high blood sugar levels with insulin can bring down blood potassium levels. Medications which increase excretion of urine (diuretics) decrease the potassium levels.