每日一题_2022.09.26

A 28-year-old man sustained severe brain injury from hypoxia-ischemia after cardiac arrest due to hypoxic respiratory failure in the setting of a heroin overdose. He undergoes a trial of targeted temperature management (TTM) to hypothermia (core temperature of 33°C [91.4°F]) in the ICU; shivering is managed with infusions of fentanyl, meperidine, midazolam, and cisatracurium. After 24 hours, he is re-warmed to a core temperature of 37°C (98.6°F). His renal and liver functions are deteriorating. On day two, the family requests a formal evaluation for prognosis and determination of neurologic function. His vital signs are: blood pressure 148/98 mm Hg, heart rate 78 beats/min, respiratory rate 16 breaths/min per ventilator and oxygen saturation 98% (fraction of inspired oxygen 0.5, positive end-expiratory pressure 8 cmH20). On examination, he is comatose, with a Glasgow Coma Scale score of 3. No motor responses are seen. Corneal, pupillary, oculocephalic, cold caloric, gag, and cough reflexes are absent. Sodium is 148mEq/L, blood urea nitrogen 108 mg/dL, creatinine is 4.2 mg/dL, bicarbonate is 18 mEq/L, aspartate aminotransferase is 2818 IU, and alanine aminotransferase is 3245 IU. Neuron-specific enolase is 44 μg/L.

Which of the following is the best approach to determine brain death in this patient, on the basis of neurologic criteria?

A. Begin renal replacement therapy to clear the cisatracurium.

B. Obtain an EEG.

C. Await clearance of sedatives and reevaluate after 72 hours after TTM.

D. Obtain an immediate cerebral blood flow scan.

答案解析：

脑死亡的临床检查是神经病学中最明确的。它应该小心和准确地执行。在体温过低的时代，有证据表明，在提供预后信息之前，最好的方法是在复温后等待 72 小时。如果患者在器官功能障碍的情况下接触镇静剂和麻痹剂，这一点尤其重要，这可能会混淆临床检查。美国神经病学学会实践参数建议通过病史、药物筛选、使用药物半衰期的五倍计算清除率（假设肝肾功能正常）来排除中枢神经系统 (CNS) 抑制药物作用的存在，或者，如果可能，药物血浆水平低于治疗范围。先前使用低温（心脏骤停心肺复苏后）也可能延迟药物代谢。如果存在这两种情况，则可能需要更长的观察时间。脑电图可能会误导患有中枢神经系统抑制剂持续影响的患者。神经元特异性烯醇化酶不能诊断脑死亡，但在与其他变量（如临床检查）一起使用时可以提供预后信息。如果医生在合理的观察期后无法准确评估神经功能，则血流扫描将有助于确定脑死亡，但在这种情况下可能为时过早。

正确答案：C