Which electrolyte, when at abnormal levels, can cause cardiac arrhythmias and even death?

Potassium is a crucial electrolyte that plays a significant role in maintaining the electrical balance of the heart and other muscles. When potassium levels are abnormal—especially when they are elevated, a condition known as hyperkalemia—it can disrupt the normal electrical impulses that control heart rhythms. This can lead to serious cardiac arrhythmias, which can significantly increase the risk of life-threatening situations, including cardiac arrest.

The normal functioning of the heart relies on a delicate balance of electrolytes, and potassium is particularly important for the repolarization phase of cardiac action potentials. In individuals with impaired kidney function, as commonly seen in those undergoing hemodialysis, potassium can accumulate in the blood because the kidneys are unable to excrete it effectively. Additionally, sudden changes in potassium levels—whether increased from dietary intake, cellular release due to injury, or inadequate removal during dialysis—can have immediate and severe effects on heart rhythm.

While bicarbonate, chloride, and sodium also play important roles in bodily functions and maintaining homeostasis, their imbalances are generally less directly associated with acute life-threatening cardiac events compared to potassium.