一位心臟衰竭病人正在服用呋塞米（Furosemide）。護理師最擔心哪種電解質失衡？

呋塞米（Furosemide，商品名 Lasix）是一種強效的環利尿劑（loop diuretic），常用於治療心臟衰竭、水腫和高血壓。其主要作用機制是抑制亨利氏環粗上升支（thick ascending limb of the loop of Henle）上的鈉-鉀-氯共同轉運蛋白（Na-K-2Cl cotransporter），從而減少鈉、氯和鉀的再吸收，導致這些電解質和水分大量排出。由於鉀離子會隨尿液排出，因此服用呋塞米的病人最常見且最需擔心的電解質失衡是低鉀血症（hypokalemia）。 低鉀血症會增加心律不整（cardiac arrhythmias）的風險，特別是對於心臟衰竭病人而言，這可能導致危及生命的併發症。護理師必須密切監測病人的血清鉀離子水平，並評估是否有低鉀血症的臨床症狀，例如肌肉無力、疲勞、便秘或心電圖（ECG）變化，並適時補充鉀離子。

Furosemide (brand name Lasix) is a potent loop diuretic commonly used to treat heart failure, edema, and hypertension. Its primary mechanism of action is inhibition of the Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, which decreases reabsorption of sodium, chloride, and potassium and produces marked excretion of these electrolytes and water. Because potassium is lost in the urine, the most common and concerning electrolyte imbalance in clients taking furosemide is hypokalemia. Hypokalemia increases the risk of cardiac arrhythmias, which can be life-threatening complications, particularly in clients with heart failure. The nurse must closely monitor the client's serum potassium level and assess for clinical signs of hypokalemia such as muscle weakness, fatigue, constipation, and ECG changes, and provide potassium replacement as appropriate.