護理師正監測一位因子癇前症接受靜脈硫酸鎂（Magnesium sulfate）輸注的病人。下列哪項發現應被視為鎂中毒的徵象？

硫酸鎂用於預防子癇前症病人的抽搐，但其安全治療區間狹窄。鎂中毒的首要徵兆包括深腱反射消失（DTRs absent/0+）和呼吸抑制。正常的呼吸速率應在 12-20 次/分，當呼吸降至 10 次/分時（B 選項），是嚴重的毒性警告，必須立即停藥並準備解毒劑（Calcium gluconate）。C 選項 2+ 是正常反射；D 選項尿量 40 mL/hr 高於警戒值（30 mL/hr），雖然鎂經由腎臟排泄，尿量減少會增加中毒風險，但 40 mL/hr 尚屬安全；A 選項血壓仍高，是子癇前症的表現而非鎂中毒徵象。護理師的監測重點在於「呼吸、反射、尿量」三劍客，其中呼吸抑制最為致命。這題考驗高風險藥物的毒性評估能力。

Magnesium sulfate is used to prevent seizures in patients with preeclampsia, but it has a narrow therapeutic window. The earliest signs of magnesium toxicity include absent deep tendon reflexes (DTRs 0+) and respiratory depression. The normal respiratory rate is 12-20 breaths/min; when it drops to 10 breaths/min (option B), this is a serious toxicity warning that requires immediate discontinuation of the infusion and preparation of the antidote (calcium gluconate). Option C's 2+ DTRs represent normal reflexes; in option D, urine output of 40 mL/hr is above the warning threshold (30 mL/hr) - although magnesium is excreted by the kidneys and decreased urine output increases the risk of toxicity, 40 mL/hr is still within a safe range. Option A shows persistently elevated blood pressure, which reflects the underlying preeclampsia rather than a sign of magnesium toxicity. The nurse's monitoring should focus on the triad of respirations, reflexes, and urine output, with respiratory depression being the most life-threatening. This question tests the assessment of toxicity from a high-risk medication.

在美國產科護理中，Magnesium sulfate 的滴定與監測有非常標準的 Flowsheet，護理師需每小時評估 DTRs 和 RR。台灣雖然也有監測規範，但在反射評估（DTRs）的精準度與執行頻率上，有時因護病比限制而不如美國嚴格。