高血压患者脊柱手术俯卧位后发生低血压的研究进展
王 琳1 陈 丽2▲
1.山西医科大学麻醉学系,山西太原 030000;2.山西医科大学第二临床医学院麻醉科,山西太原 030000
[摘要]在目前的临床麻醉工作中,全身麻醉下行俯卧位脊柱手术的患者合并高血压病的情况明显增多。俯卧位后因腹腔和胸腔受压,下腔静脉回流减少,心室顺应性下降,每搏输出量减少可导致低血压;高血压患者长期服用降压药物,使得自主神经功能抑制,血压调节能力受损,全身麻醉的交感抑制和血管扩张作用可进一步加重低血压。低血压使重要脏器的血流及灌注减少,引起相关并发症,延长患者的住院时间甚至增加死亡率。高血压患者多合并心、脑、肾等重要靶器官的损害,更不易耐受低血压的发生。发生低血压时可通过补液、减浅麻醉及使用升压药予以纠正。目标导向液体治疗及α1肾上腺素能受体激动剂的应用为麻醉医生更好地维持术中血流动力学稳定,实现患者的快速康复提供了保障。本文就高血压患者脊柱手术俯卧位后发生低血压的原因、对机体的影响及预防和处理的方法进行综述。
[关键词]高血压病;ACEI/ARB类药物;俯卧位;低血压;α1肾上腺素能受体激动剂
[中图分类号]R544.1 
[文献标识码]A 
[文章编号]1674-4721(2018)6(b)-0024-05
▲通讯作者
Research progress of hypotension after prone position in patients w ith hypertension during spinal surgery
WANG Lin1CHEN Li2▲
1.Department of Anesthesiology,Shanxi Medical University,Shanxi Province,Taiyuan 030000,China;2.Department of Anesthesiology,the Second Hospital of Shanxi Medical University,Shanxi Province,Taiyuan 030000,China.
[Abstract]In the current clinical anaesthesia work,the incidence of hypertensive disease has significantly increased in patients with general anesthesia underwent prostrate spine surgery.The inferior vena cava is reduced because of the abdominal and thoracic compression in the prone position,and the ventricular compliance is decreased which resulted in the decline of the SV that leading to the hypotension.Antihypertensive drugs which taken by the chronic hypertensive patients cause the autonomic nervous function inhibition and blood pressure regulation impaired,and the sympathetic inhibition and vascular dilatation of general anesthesia further aggravate the hypotension.Hypotension can reduce the blood flow and perfusion of important organs,cause related complications,prolong hospital lengths of stay and even increase mortality.Hypertensive patients are more likely to be organ damaged,and are less resistant to the occurrence of hypotension.When hypotension occurs,it can be corrected by using intravenous infusion and vasoactive agents,or decreasing the level of anesthesia.The application of goal-directed fluid therapy and α1adrenergic receptor agonist ensure the stability of hemodynamic during surgery and make the patient recover quickly.In this paper,the causes of hypotension occurred in patients with hypertensive during spine surgery are reviewed,as well as the effects on organism and how to prevent and treatment.
[Key words]Hypertension;ACEI/ARBs drugs;Prone position;Hypotension;Isolated α1adrenergic receptor agonist
高血压病是临床工作中最常见的慢性疾病,目前我国约有2.5亿高血压患者,且患病率随年龄增高而上升,手术患者中合并高血压病的情况也明显增多。高血压患者行脊柱手术时,俯卧位后可发生明显的血压下降,需要麻醉医生及时处理,以保证重要脏器及组织的灌注,减少相关并发症。本文主要从高血压患者俯卧位后发生低血压的原因、对机体的影响以及预防和处理三方面进行综述,旨在为这类手术的临床麻醉及循环管理提供一些参考。
1 高血压患者俯卧位后发生低血压的原因
1.1 高血压患者的病理生理改变
高血压患者全身的细小动脉硬化,弹性减退,管壁增厚,管腔狭窄,长期作用可引起心、脑、肾等重要靶器官的损害[1],导致机体的代偿能力下降。高血压患者长期服用降压药物,抑制自主神经功能,使血压的调节能力受损[2],对全身麻醉、低血容量及体位改变等的耐受性降低,易发生剧烈的循环波动。
1.2 降压药物的使用
高血压患者服用的降压药物主要包括利尿剂、β受体阻滞剂、钙通道阻滞剂、血管紧张素转换酶抑制剂(ACEI)和血管紧张素Ⅱ受体拮抗剂(ARB)。长期服用β受体阻滞剂和钙通道阻滞剂的患者手术当天应继续使用[3-5],利尿剂易引起水电解质平衡紊乱,建议术前停止使用[4-5],而ACEI/ARB类药物是否停用一直存在争议。长期服用ACEI/ARB类药物,抑制肾素-血管紧张素-醛固酮系统(RASS),使血管的收缩能力下降[2],在全身麻醉的交感抑制和血管扩张作用下可导致严重的低血压,当与利尿剂联合使用时则更易发生[6],因此建议术前停用ACEI/ARB类药物以减少术中低血压的发生[7],降低术后心血管事件的发生率及术后死亡率[8]。但有研究提出ACEI/ARB类药物有其特殊的心脏保护作用,停用后又可因交感神经系统激活而引起高血压,不建议术前停用[9]。最近有研究显示ACEI/ARB类药物术前停用,与术中和术后高血压的发生并没有明显的相关性[10]
2017年美国高血压病指南建议术前可考虑停用ACEI/ARB类药物,2014年ESC/ESA非心脏手术指南建议高血压患者术前应停用ACEI/ARB类药物,但对于合并心力衰竭及心脏疾病的患者需继续使用[3]。Mc Clendon等[11]对208位行脊椎手术的患者(融合节段≥5个)进行研究,发现术前使用ACEI/ARB类药物(手术当天停用)的患者,术后肌钙蛋白明显升高,并且住院时间延长,对于术前是否应更换药物治疗或暂停手术还需要进一步的讨论。
1.3 麻醉及容量因素
全身麻醉诱导时抑制交感神经系统并使外周血管扩张,可发生低血压,持续5~10 min,在此阶段改变体位则可使血压进一步下降。足够的循环血容量是形成血压的重要因素,术前长时间禁饮食及麻醉的血管扩张作用使机体的有效循环血量减少,俯卧位后可发生严重的低血压。
1.4 俯卧位后体位性的低血压
脊柱手术改变为俯卧位后可出现血压下降,有研究使用经食道超声观察5种不同俯卧位体位下发生的循环变化,其中使用俯卧位垫和Wilson脊柱架表现为心输出量(CO)下降,膝-胸位体位表现为前负荷下降,三种体位的心指数(CI)和每搏输出量(SV)均下降,而使用Jackson脊柱床和纵向支撑垫引起的循环变化最小[12]。在此研究的基础上,使用对循环影响最小的Jackson脊柱床,并用BioZ.com无创血流动力学监测仪进行观察,发现俯卧位后发生低血压的原因主要是SV和CI的降低[13]。俯卧位时因腹部受压,下腔静脉回流受阻,回心血量减少,同时胸廓受压且在机械通气状态下,胸腔内压力升高,心室顺应性下降,导致每搏输出量减少[14],引起血压下降。对于心脏功能不佳的患者,如既往有心肌梗死病史或冠心病病史,俯卧位后引起的循环改变更加严重[15]
2 高血压患者俯卧位后发生低血压对机体的影响
2.1 对心脏的影响
在非心脏手术中,当平均动脉压(MAP)<65mmHg的时间≥13 min,或即使MAP<55 mmHg出现很短的时间,均可使术后心肌损伤和急性肾损伤(AKI)发生的风险增加[16-17]。高血压患者的大动脉弹性减退,管壁硬化,表现为收缩压升高,舒张压下降,长期作用可使心室肥厚,心脏的舒张功能减退[5],导致冠脉供血减少;又因多合并冠状动脉粥样硬化性病变,发生低血压时冠脉的血流和灌注进一步减少,心肌细胞缺血、缺氧加重,使术后心肌损伤/心律失常和心肌梗死的发生率明显增加。
2.2 对肾脏的影响
在择期非心脏手术中,当MAP<60 mmHg>20 min或MAP<55 mmHg>10 min时,可使术后AKI发生的风险增加[18]。高血压患者的肾小球内囊压力升高,肾小球纤维化、萎缩,肾小动脉硬化,长期作用可使肾实质缺血和肾单位不断减少,导致慢性肾功能不全。当发生低血压时,肾脏的血流和灌注进一步减少,肾小球滤过率下降,血肌酐升高,导致术后AKI的发生率增加。
2.3 对脑功能的影响
当MAP下降>30%时,术后10 d内发生缺血性脑卒中的风险增加,且低血压每持续1 min,脑卒中发生的风险增加1.3%[19]。高血压患者的脑血流自身调节右移,脑动脉粥样硬化,发生低血压时脑组织的血流和灌注减少,更易导致术后缺血性脑卒中或脑梗死的发生。虽然术中低血压和术后谵妄并没有明显的相关性,但防止术中血压的剧烈波动对减少术后谵妄及认知功能障碍的发生具有重要意义[20]
2.4 其他影响
俯卧位和低血压都是导致术后视力丧失的主要危险因素[21],高血压患者的视网膜动脉硬化,血压下降可进一步降低眼的灌注压,导致严重的并发症[22]。有研究显示,当术中收缩压<70 mmHg持续时间≥5 min时,可使术后30 d的死亡率增加[23],而高血压患者若出现这样的低血压,则预后更加不好。
3 高血压患者俯卧位后发生低血压的预防及处理
3.1 液体治疗
麻醉诱导后的低血压反应通常是由于血容量相对减少和心肌抑制及血管扩张共同作用的结果,因此术前需要适当地补液扩容,尤其对于高血压患者,诱导前的容量补充更加重要,以减少诱导后低血压的发生。在改变为俯卧位前适当补液[24],提高机体的有效循环血量,可减少俯卧位后低血压的发生。但补液过多又可在高血压患者恢复为仰卧位后,因容量负荷增加而导致心力衰竭以及术后肺水肿和恶心、呕吐的发生。建议术中使用脉压变异率(PPV)[25]或每搏输出量变异率(SVV)监测进行目标导向液体治疗,为器官和组织提供有效的灌注及氧合,减少术后呼吸系统的并发症,加快胃肠道功能的恢复[26]
3.2 麻醉诱导和维持
由于麻醉药物和抗高血压药物之间的相互作用,宜适量减少麻醉药物用量和减慢注射速度,为机体发挥代偿作用留有充裕的反应时间,选用对循环影响较小的依托咪酯进行分次、缓慢诱导,减少低血压的发生。术中发生低血压时可适当减浅麻醉深度。有研究显示,MAP<75 mmHg,BIS<45 可使术后 90 d 的死亡率增加[27],但一味地减浅麻醉又可因麻醉过浅而导致高血压的发生,因此术中应维持适当的麻醉深度,若仍伴有低血压的发生,可使用血管活性药物以维持血流动力学的稳定。
3.3 血管活性药物的使用
3.3.1 最常使用的药物——麻黄碱麻黄碱通过激动α受体和β受体,使血压升高,心率加快,同时增强心肌收缩力,使心输出量增加,在俯卧位后发生低血压时使用效果明确,且优于去氧肾上腺素[28],但麻黄碱多次使用易产生快速耐药反应,对于维持术中血流动力学的平稳作用有限。
3.3.2 去氧肾上腺素(PE)和去甲肾上腺素(NE) PE属于α1肾上腺素能受体激动剂,在升高血压的同时心脏的后负荷增加,CO下降,而静脉收缩又可使回心血量增加,CO变化不明显[29]。有研究显示,PE对CO的影响与心脏的前负荷有关,当前负荷足够时,PE使CO下降,而当前负荷欠佳时,PE使CO增加,但持续泵注PE时CO下降[30]。NE可同时激动α受体和β受体,使血压升高,心率加快,CO增加[31-32],相比PE,俯卧位后发生低血压时持续泵注NE能更好地维持循环稳定,保证重要器官及组织的灌注;但对于NE最大的顾虑是不能经外周静脉注射,而PE可以。最新的研究显示,在全身麻醉发生低血压时,经外周静脉注射等效剂量的PE和NE,NE引起的动脉弹性变化和SV下降的程度比PE小[33]。还有研究显示,在血容量充足的情况下,持续泵注PE和NE,两者引的血流动力学变化并没有明显差异[34]
3.3.3 甲氧明 高血压患者多合并冠状动脉粥样硬化性病变,使用PE或NE时冠脉收缩,冠脉的血流减少,心肌细胞缺血、缺氧加重,易发生心肌损伤。甲氧明主要作用于α1A-AR和α1B-AR,对冠脉几乎没有作用;血压升高不仅使冠脉的血流和灌注增加,同时使心肌的氧供增加,而反射性的心率减慢,使心肌的氧耗减少,起到保护心脏的作用。甲氧明的作用温和,与PE和NE相比,较少引起心率的显著减慢[35],在膝关节置换手术中持续泵注甲氧明可使老年高血压患者的血流动力学保持平稳[36],而能否预防和处理高血压患者俯卧位后发生的低血压还需要进一步的研究。
4 总结
高血压患者俯卧位脊柱手术的循环管理至关重要,在麻醉诱导前适当补液扩容能够提高有效循环血量,减少俯卧位后低血压的发生,术中使用血管活性药物可以维持血流动力学的平稳,保证重要器官和组织的灌注,减少相关并发症。但对于术前ACEI/ARB类药物是否停用及术中使用甲氧明是否更具优势,还需要进一步的研究。
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(收稿日期:2018-01-23
本文编辑:祁海文)