What is the primary concern when a patient's potassium level is 2.5 mEq/L?

A potassium level of 2.5 mEq/L is an indication of severe hypokalemia, which can significantly affect the heart's electrical activity. The heart relies on a balance of electrolytes, including potassium, to maintain a stable rhythm. When potassium levels drop to such a low level, it can lead to life-threatening cardiac arrhythmias. These can manifest as changes on an electrocardiogram (ECG), including a prolonged QT interval, T wave changes, and potentially lethal arrhythmias such as ventricular tachycardia or fibrillation.

Maintaining normal potassium levels is crucial for both cardiac and neuromuscular function. While low potassium can indeed impact muscle function and may cause muscle weakness or cramps, the most urgent and life-threatening complication involves the cardiovascular system. Therefore, among the listed options, the primary concern when encountering a potassium level this low is the potential for cardiac arrhythmias.