每日一题_2022.10.03

A 19-year-old woman is brought to the emergency department (ED) by her friends for altered mental status while at a party. At one point during the evening, her friends noticed that she was not responding. When she did not wake up a few hours later, they brought her to the ED. They report that she was fine before they left for the party, and she had not been ill. They admit that there was alcohol at the party, but become evasive when asked about illicit substances. On examination, she is well-developed and well-nourished. She is not in respiratory distress and is unarousable to stimuli. On sternal rub, she groans but does not wake up. Heart rate is 94 beats/min, respiratory rate 18 breaths/min, blood pressure 142/70 mm Hg, and temperature 38.1°C (100.6°F). Pupils are dilated and reactive. Oral membranes are dry. Jaw is clenched. Neck is supple. Cardiac, pulmonary and abdominal examinations are unrevealing. No peripheral edema is present. She has normal reflexes. Her skin is warm and dry; no needle marks are noted. During the examination, she has a tonic-clonic seizure that responds to IV lorazepam. Laboratory blood results are: sodium 110 mEq/L, potassium 3.0 mEq, BUN 11 mg/dL, creatinine 0.5 mg/dL, lactate 1.1 mg/dL. Hepatic panel is within normal limits. White blood cell count 59 103/mm3, normal differential, hemoglobin 14.2 g/dL, platelet count 223 103/mm3, INR 1.0. Chest radiograph is unrevealing. ECG shows normal sinus rhythm with a rate of 94 beats/min and no ST-T wave abnormalities. Urine toxicology screen is negative for benzodiazepines, opiates, cocaine metabolites, and cannabinoids. Blood toxicology shows alcohol level of 22 mg/dL (mildly increased), and negative for salicylates and acetaminophen. Head CT shows no acute infarct, bleeding, or mass.

Which of the following is the most likely cause of her altered mental status?

A. 3,4-methylenedioxymethamphetamine (MDMA)

B. Heroinoverdose

C. Alcoholpoisoning

D. Acute bacterial meningitis

答案解析：

3, 4-亚甲二氧基甲基苯丙胺 (MDMA) 是一种苯丙胺衍生物，据说可引起欣快感并降低抑制作用。副作用包括口干、磨牙症、咬紧牙关、焦虑、惊恐发作、心动过速、高血压、体温过高和过度口渴。更严重的副作用包括血清素综合征、横纹肌溶解症、蛛网膜下腔出血、暴发性肝功能衰竭、昏迷和严重的低钠血症，这可能与癫痫发作有关。据估计，首次使用 MDMA 的死亡风险在 20,000 分之一到 50,000 分之一之间。

MDMA引起低钠血症的原因被认为是由于抗利尿激素不当综合征与过量饮水的综合作用。抗利尿激素增加导致游离水重吸收增加，降低血清钠水平。然后，由于 MDMA 引起的过度口渴感导致的水摄入量增加，钠含量进一步下降，从而加剧了这种情况。体力活动增加导致出汗过多也会导致盐分流失。急性低钠血症会导致脑水肿，并可能导致癫痫发作，就像这个病人一样。

海洛因，也称为二乙酰吗啡，是一种具有很高成瘾潜力的麻醉剂。海洛因过量的迹象包括精神状态改变、呼吸抑制和瞳孔缩小。海洛因过量通常与 IV 给药途径有关。呼吸抑制可导致心肺骤停和死亡。纳洛酮用于逆转海洛因的作用。在这名精神状态改变的患者中，呼吸频率正常、瞳孔散大、没有注射痕迹和尿液毒理学筛查阴性表明海洛因过量服用。 （值得注意的是，许多静脉注射吸毒者使用不显眼的部位，因此找不到注射部位并不排除注射使用。）低钠血症通常与海洛因过量无关。

震颤性谵妄是因大量摄入酒精而导致的乙醇中毒。它可能导致低钠血症。该患者的酒精水平升高，表明饮酒，但水平不足以导致这种程度的低钠血症。

急性细菌性脑膜炎可导致发烧患者的精神状态改变。缺乏病史和她的病程使诊断不太可能。在检查时，临床医生会寻找畏光和颈部僵硬。瞳孔反应从迟缓到扩张，并且是非特异性的。虽然可能会发生低钠血症，但通常不会那么严重。正常的白细胞计数也反对感染。在该患者中，进行腰椎穿刺以排除急性细菌性脑膜炎并非不合理，但由于缺乏其他提示脑膜炎的发现，因此不太可能进行诊断。

正确答案：A