護理師準備為低血鉀病人靜脈輸注氯化鉀。開始輸注前最關鍵的評估指標為何？

核心概念：靜脈輸注氯化鉀（Potassium Chloride）的安全性考量。 為何正確答案對： B. 腎臟是排除鉀離子的主要途徑。若病人腎功能不全或尿量不足（通常定義為每小時少於 30 mL 或 0.5 mL/kg/hr），靜脈輸注的鉀離子將無法有效排出體外，迅速蓄積於血液中，導致高血鉀（Hyperkalemia）。嚴重高血鉀會引發致命性的心律不整（如心室纖維顫動、心跳停止）。因此，在給予靜脈鉀離子輸注前，確認病人有足夠的尿量是確保安全的最高優先事項。 為何其他選項錯： A. 血壓（Blood Pressure）雖然是重要生命徵象，但相較於腎臟排泄功能對鉀離子代謝的直接影響，其重要性次之。若發生嚴重高血鉀，可能進一步影響血壓，但尿量不足是導致高血鉀的根本風險。 C. 血鎂（Serum Magnesium）水平對鉀離子平衡有間接影響，但並非靜脈補鉀前最關鍵的直接評估項目。 B. 周邊靜脈（Peripheral IV site）的完整性很重要，以防滲漏，但相較於腎臟排泄功能對全身鉀離子平衡的決定性影響，其優先級較低。一旦發生滲漏，可立即停止輸注並更換部位，但若腎臟無法排泄，即使通路良好，也會造成全身性危險。

Core concept: Safety considerations for intravenous potassium chloride infusion. Why the correct answer is right: B. The kidneys are the primary route for excreting potassium. If a client has renal impairment or inadequate urine output (typically defined as less than 30 mL/hour or 0.5 mL/kg/hr), intravenously infused potassium cannot be effectively excreted and rapidly accumulates in the blood, causing hyperkalemia. Severe hyperkalemia triggers fatal arrhythmias (such as ventricular fibrillation or cardiac arrest). Therefore, before giving IV potassium, confirming adequate urine output is the highest safety priority. Why the other options are wrong: A. Blood pressure is an important vital sign, but compared with the kidney's direct role in potassium metabolism, its importance is secondary. Severe hyperkalemia may eventually affect blood pressure, but inadequate urine output is the root cause of hyperkalemia. C. Serum magnesium has an indirect influence on potassium balance, but is not the most critical immediate assessment before IV potassium replacement. D. The integrity of a peripheral IV site is important to prevent extravasation, but compared with renal excretion's decisive role in body-wide potassium balance, it is a lower priority. Extravasation can be addressed by stopping the infusion and changing sites; in contrast, if the kidneys cannot excrete potassium, even a patent line is dangerous.