(湖北医药学院附属国药东风总医院麻醉科，湖北十堰442001)
[关键词]认知障碍；影响因素；综述文献doi:10.3969/j.issn.1007-3205.2021.04.025
1.5遗传因素遗传因素对POCD的发生也存在一定的作用，如携带载脂蛋白E4等位基因的男性在术后认知测试中表现较女性差，即使在调整了年龄、教育水平和共患病因素后也是如此[18]。不同血型患者发生POCD也存在差异，如老年A型血患者发生早期POCD的风险较高，而O型血患者发生早期POCD的风险较低，这可能与A型血患者对有害刺激引起的应激反应较强有关[19]。
2.3麻醉因素
2.3.2麻醉方式骨科手术在老年患者中较为普遍，研究比较老年患者在全身麻醉和区域麻醉下行膝关节置换术后POCD的发生情况，结果发现，行区域麻醉的患者术后第7天表现出较高的神经认知测试分数、较低的皮质醇和血糖水平、较高的胰岛素水平，与其更好的抑制应激反应有关[27]。然而，Mracek等[28]在颈动脉内膜剥脱术中却发现，与区域麻醉相比，全身麻醉患者仅在术后第1天出现了认知障碍，术后第6天恢复正常。这种差异可能与手术类型和POCD评估方法不同有关，关于麻醉方式对老年患者术后远期认知功能的影响仍有待进一步研究，而且可以将患者经历的麻醉次数考虑在其中。
2.3.3麻醉深度麻醉深度监测可以指导术中麻醉用药，避免麻醉过深或过浅而造成血流动力学波动，可防止术中知晓和麻醉药过量引起的术后恢复延迟。脑电双频指数(bispectralindex,BIS)常用于麻醉深度监测。但是，将BIS值控制在何种范围对POCD有益目前仍存在争议。有研究指出，与浅麻醉(BIS值45～60)相比，深麻醉(BIS值30～45)可减少老年患者腹部手术后短期POCD，抑制术中应激和炎症反应[29]。而且，深麻醉相比于浅麻醉更能够降低大脑对氧的需求，从而提高大脑对缺血缺氧的耐受。但另外一项研究得出了相反的结论，指出与深麻醉(BIS值40～50)相比，浅麻醉(BIS值55～65)更能降低全膝关节置换术后7d的POCD发生率[30]。各研究的手术类型不同、对深浅麻醉BIS值界定不一、麻醉药物的干扰和认知评估方法的不统一都有可能导致麻醉深度对POCD影响的差异，未来的研究还应着眼于麻醉深度对远期POCD影响的大样本研究。
疼痛作为第五大生命体征，日益受到患者和医务人员的重视，手术后患者会出现不同程度的疼痛，有些疼痛甚至转化为慢性疼痛，严重影响患者术后生活质量，与快速康复理念相违背。术后疼痛也是引起POCD的重要因素之一，动物研究发现术后疼痛会导致大鼠海马区与学习、记忆和疼痛有关的N-甲基-D-天门冬氨酸受体的2B亚单位表达降低，进而导致认知功能障碍[31]。术后疼痛也会导致术后睡眠障碍或使术前本存在的睡眠障碍进一步加重，而睡眠障碍本身也对认知功能有一定的影响[15]；而且研究表明，围术期睡眠剥夺增加了背根神经节Ⅰ型钙通道的表达和活性导致术后疼痛恢复延迟[32]。如果不给予适当的干预，可能造成疼痛和睡眠障碍之间恶性循环,进而可能诱发或加重POCD。王炯等[33]对肺癌根治术患者行胸椎旁神经阻滞明显减轻应激反应，缓解术后疼痛，改善术后早期认知功能。因此，围术期进行有效地镇痛干预对术后认知功能是有益的。
POCD的影响因素涉及围术期多个方面，术前因素如患者高龄、低教育水平及术前存在认知障碍、遗传因素和合并的某些疾病等虽然有的不可控或不可逆，但可以警示临床医师这些患者可能是发生POCD的高危人群，指导医师术中决策；术中麻醉药物和麻醉方式如何选择以及麻醉深度BIS值维持在何种范围对POCD最有益目前尚无绝对定论，有待多中心大样本临床研究进一步明确，但是术中加强监测如局部脑氧饱和度监测可优化术中管理和完善术后镇痛可能对术后认知功能有益。此外，由于POCD的影响因素众多，每例患者情况不同，未来POCD的防治可能需要个体化。
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[收稿日期]2020-05-06
[基金项目]十堰市科学技术局引导性科研项目(19Y85)
[作者简介]肖莹莹(1994-)，女，湖北襄阳人，湖北医药学院附属国药东风总医院医师，医学硕士研究生，从事临床麻醉学研究。