Potassium

Potassium is an electrolyte (normal 3.5–5.0 mEq/L) essential for cardiac and skeletal muscle function. IV potassium is never given by push — it must always be diluted and infused on a pump — because rapid IV potassium can cause fatal cardiac arrest; oral forms are taken with food to limit GI irritation. Both hypokalemia and hyperkalemia cause life-threatening arrhythmias, so the level is watched closely.