王琳 陳麗
[摘要]在目前的臨床麻醉工作中,全身麻醉下行俯臥位脊柱手術的患者合并高血壓病的情況明顯增多。俯臥位后因腹腔和胸腔受壓,下腔靜脈回流減少,心室順應性下降,每搏輸出量減少可導致低血壓;高血壓患者長期服用降壓藥物,使得自主神經(jīng)功能抑制,血壓調節(jié)能力受損,全身麻醉的交感抑制和血管擴張作用可進一步加重低血壓。低血壓使重要臟器的血流及灌注減少,引起相關并發(fā)癥,延長患者的住院時間甚至增加死亡率。高血壓患者多合并心、腦、腎等重要靶器官的損害,更不易耐受低血壓的發(fā)生。發(fā)生低血壓時可通過補液、減淺麻醉及使用升壓藥予以糾正。目標導向液體治療及α1腎上腺素能受體激動劑的應用為麻醉醫(yī)生更好地維持術中血流動力學穩(wěn)定,實現(xiàn)患者的快速康復提供了保障。本文就高血壓患者脊柱手術俯臥位后發(fā)生低血壓的原因、對機體的影響及預防和處理的方法進行綜述。
[關鍵詞]高血壓?。籄CEI/ARB類藥物;俯臥位;低血壓;α1腎上腺素能受體激動劑
[中圖分類號] R544.1 [文獻標識碼] A [文章編號] 1674-4721(2018)6(b)-0024-05
Research progress of hypotension after prone position in patients with hypertension during spinal surgery
WANG Lin1 CHEN Li
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 α1 adrenergic 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 α1 adrenergic receptor agonist
高血壓病是臨床工作中最常見的慢性疾病,目前我國約有2.5億高血壓患者,且患病率隨年齡增高而上升,手術患者中合并高血壓病的情況也明顯增多。高血壓患者行脊柱手術時,俯臥位后可發(fā)生明顯的血壓下降,需要麻醉醫(yī)生及時處理,以保證重要臟器及組織的灌注,減少相關并發(fā)癥。本文主要從高血壓患者俯臥位后發(fā)生低血壓的原因、對機體的影響以及預防和處理三方面進行綜述,旨在為這類手術的臨床麻醉及循環(huán)管理提供一些參考。
1高血壓患者俯臥位后發(fā)生低血壓的原因
1.1高血壓患者的病理生理改變
高血壓患者全身的細小動脈硬化,彈性減退,管壁增厚,管腔狹窄,長期作用可引起心、腦、腎等重要靶器官的損害[1],導致機體的代償能力下降。高血壓患者長期服用降壓藥物,抑制自主神經(jīng)功能,使血壓的調節(jié)能力受損[2],對全身麻醉、低血容量及體位改變等的耐受性降低,易發(fā)生劇烈的循環(huán)波動。
1.2降壓藥物的使用
高血壓患者服用的降壓藥物主要包括利尿劑、β受體阻滯劑、鈣通道阻滯劑、血管緊張素轉換酶抑制劑(ACEI)和血管緊張素Ⅱ受體拮抗劑(ARB)。長期服用β受體阻滯劑和鈣通道阻滯劑的患者手術當天應繼續(xù)使用[3-5],利尿劑易引起水電解質平衡紊亂,建議術前停止使用[4-5],而ACEI/ARB類藥物是否停用一直存在爭議。長期服用ACEI/ARB類藥物,抑制腎素-血管緊張素-醛固酮系統(tǒng)(RASS),使血管的收縮能力下降[2],在全身麻醉的交感抑制和血管擴張作用下可導致嚴重的低血壓,當與利尿劑聯(lián)合使用時則更易發(fā)生[6],因此建議術前停用ACEI/ARB類藥物以減少術中低血壓的發(fā)生[7],降低術后心血管事件的發(fā)生率及術后死亡率[8]。但有研究提出ACEI/ARB類藥物有其特殊的心臟保護作用,停用后又可因交感神經(jīng)系統(tǒng)激活而引起高血壓,不建議術前停用[9]。最近有研究顯示ACEI/ARB類藥物術前停用,與術中和術后高血壓的發(fā)生并沒有明顯的相關性[10]。
2017年美國高血壓病指南建議術前可考慮停用ACEI/ARB類藥物,2014年ESC/ESA非心臟手術指南建議高血壓患者術前應停用ACEI/ARB類藥物,但對于合并心力衰竭及心臟疾病的患者需繼續(xù)使用[3]。Mc Clendon等[11]對208位行脊椎手術的患者(融合節(jié)段≥5個)進行研究,發(fā)現(xiàn)術前使用ACEI/ARB類藥物(手術當天停用)的患者,術后肌鈣蛋白明顯升高,并且住院時間延長,對于術前是否應更換藥物治療或暫停手術還需要進一步的討論。
1.3麻醉及容量因素
全身麻醉誘導時抑制交感神經(jīng)系統(tǒng)并使外周血管擴張,可發(fā)生低血壓,持續(xù)5~10 min,在此階段改變體位則可使血壓進一步下降。足夠的循環(huán)血容量是形成血壓的重要因素,術前長時間禁飲食及麻醉的血管擴張作用使機體的有效循環(huán)血量減少,俯臥位后可發(fā)生嚴重的低血壓。
1.4俯臥位后體位性的低血壓
脊柱手術改變?yōu)楦┡P位后可出現(xiàn)血壓下降,有研究使用經(jīng)食道超聲觀察5種不同俯臥位體位下發(fā)生的循環(huán)變化,其中使用俯臥位墊和Wilson脊柱架表現(xiàn)為心輸出量(CO)下降,膝-胸位體位表現(xiàn)為前負荷下降,三種體位的心指數(shù)(CI)和每搏輸出量(SV)均下降,而使用Jackson脊柱床和縱向支撐墊引起的循環(huán)變化最小[12]。在此研究的基礎上,使用對循環(huán)影響最小的Jackson脊柱床,并用BioZ.com無創(chuàng)血流動力學監(jiān)測儀進行觀察,發(fā)現(xiàn)俯臥位后發(fā)生低血壓的原因主要是SV和CI的降低[13]。俯臥位時因腹部受壓,下腔靜脈回流受阻,回心血量減少,同時胸廓受壓且在機械通氣狀態(tài)下,胸腔內壓力升高,心室順應性下降,導致每搏輸出量減少[14],引起血壓下降。對于心臟功能不佳的患者,如既往有心肌梗死病史或冠心病病史,俯臥位后引起的循環(huán)改變更加嚴重[15]。
2高血壓患者俯臥位后發(fā)生低血壓對機體的影響
2.1對心臟的影響
在非心臟手術中,當平均動脈壓(MAP)<65 mmHg的時間≥13 min,或即使MAP<55 mmHg出現(xiàn)很短的時間,均可使術后心肌損傷和急性腎損傷(AKI)發(fā)生的風險增加[16-17]。高血壓患者的大動脈彈性減退,管壁硬化,表現(xiàn)為收縮壓升高,舒張壓下降,長期作用可使心室肥厚,心臟的舒張功能減退[5],導致冠脈供血減少;又因多合并冠狀動脈粥樣硬化性病變,發(fā)生低血壓時冠脈的血流和灌注進一步減少,心肌細胞缺血、缺氧加重,使術后心肌損傷/心律失常和心肌梗死的發(fā)生率明顯增加。
2.2對腎臟的影響
在擇期非心臟手術中,當MAP<60 mmHg>20 min或MAP<55 mmHg>10 min時,可使術后AKI發(fā)生的風險增加[18]。高血壓患者的腎小球內囊壓力升高,腎小球纖維化、萎縮,腎小動脈硬化,長期作用可使腎實質缺血和腎單位不斷減少,導致慢性腎功能不全。當發(fā)生低血壓時,腎臟的血流和灌注進一步減少,腎小球濾過率下降,血肌酐升高,導致術后AKI的發(fā)生率增加。
2.3對腦功能的影響
當MAP下降>30%時,術后10 d內發(fā)生缺血性腦卒中的風險增加,且低血壓每持續(xù)1 min,腦卒中發(fā)生的風險增加1.3%[19]。高血壓患者的腦血流自身調節(jié)右移,腦動脈粥樣硬化,發(fā)生低血壓時腦組織的血流和灌注減少,更易導致術后缺血性腦卒中或腦梗死的發(fā)生。雖然術中低血壓和術后譫妄并沒有明顯的相關性,但防止術中血壓的劇烈波動對減少術后譫妄及認知功能障礙的發(fā)生具有重要意義[20]。
2.4其他影響
俯臥位和低血壓都是導致術后視力喪失的主要危險因素[21],高血壓患者的視網(wǎng)膜動脈硬化,血壓下降可進一步降低眼的灌注壓,導致嚴重的并發(fā)癥[22]。有研究顯示,當術中收縮壓<70 mmHg持續(xù)時間≥5 min時,可使術后30 d的死亡率增加[23],而高血壓患者若出現(xiàn)這樣的低血壓,則預后更加不好。
3高血壓患者俯臥位后發(fā)生低血壓的預防及處理
3.1液體治療
麻醉誘導后的低血壓反應通常是由于血容量相對減少和心肌抑制及血管擴張共同作用的結果,因此術前需要適當?shù)匮a液擴容,尤其對于高血壓患者,誘導前的容量補充更加重要,以減少誘導后低血壓的發(fā)生。在改變?yōu)楦┡P位前適當補液[24],提高機體的有效循環(huán)血量,可減少俯臥位后低血壓的發(fā)生。但補液過多又可在高血壓患者恢復為仰臥位后,因容量負荷增加而導致心力衰竭以及術后肺水腫和惡心、嘔吐的發(fā)生。建議術中使用脈壓變異率(PPV)[25]或每搏輸出量變異率(SVV)監(jiān)測進行目標導向液體治療,為器官和組織提供有效的灌注及氧合,減少術后呼吸系統(tǒng)的并發(fā)癥,加快胃腸道功能的恢復[26]。
3.2麻醉誘導和維持
由于麻醉藥物和抗高血壓藥物之間的相互作用,宜適量減少麻醉藥物用量和減慢注射速度,為機體發(fā)揮代償作用留有充裕的反應時間,選用對循環(huán)影響較小的依托咪酯進行分次、緩慢誘導,減少低血壓的發(fā)生。術中發(fā)生低血壓時可適當減淺麻醉深度。有研究顯示,MAP<75 mmHg,BIS<45可使術后90 d的死亡率增加[27],但一味地減淺麻醉又可因麻醉過淺而導致高血壓的發(fā)生,因此術中應維持適當?shù)穆樽砩疃?,若仍伴有低血壓的發(fā)生,可使用血管活性藥物以維持血流動力學的穩(wěn)定。
3.3血管活性藥物的使用
3.3.1最常使用的藥物——麻黃堿 麻黃堿通過激動α受體和β受體,使血壓升高,心率加快,同時增強心肌收縮力,使心輸出量增加,在俯臥位后發(fā)生低血壓時使用效果明確,且優(yōu)于去氧腎上腺素[28],但麻黃堿多次使用易產(chǎn)生快速耐藥反應,對于維持術中血流動力學的平穩(wěn)作用有限。
3.3.2去氧腎上腺素(PE)和去甲腎上腺素(NE) PE屬于α1腎上腺素能受體激動劑,在升高血壓的同時心臟的后負荷增加,CO下降,而靜脈收縮又可使回心血量增加,CO變化不明顯[29]。有研究顯示,PE對CO的影響與心臟的前負荷有關,當前負荷足夠時,PE使CO下降,而當前負荷欠佳時,PE使CO增加,但持續(xù)泵注PE時CO下降[30]。NE可同時激動α受體和β受體,使血壓升高,心率加快,CO增加[31-32],相比PE,俯臥位后發(fā)生低血壓時持續(xù)泵注NE能更好地維持循環(huán)穩(wěn)定,保證重要器官及組織的灌注;但對于NE最大的顧慮是不能經(jīng)外周靜脈注射,而PE可以。最新的研究顯示,在全身麻醉發(fā)生低血壓時,經(jīng)外周靜脈注射等效劑量的PE和NE,NE引起的動脈彈性變化和SV下降的程度比PE小[33]。還有研究顯示,在血容量充足的情況下,持續(xù)泵注PE和NE,兩者引的血流動力學變化并沒有明顯差異[34]。
3.3.3甲氧明 高血壓患者多合并冠狀動脈粥樣硬化性病變,使用PE或NE時冠脈收縮,冠脈的血流減少,心肌細胞缺血、缺氧加重,易發(fā)生心肌損傷。甲氧明主要作用于α1A-AR和α1B-AR,對冠脈幾乎沒有作用;血壓升高不僅使冠脈的血流和灌注增加,同時使心肌的氧供增加,而反射性的心率減慢,使心肌的氧耗減少,起到保護心臟的作用。甲氧明的作用溫和,與PE和NE相比,較少引起心率的顯著減慢[35],在膝關節(jié)置換手術中持續(xù)泵注甲氧明可使老年高血壓患者的血流動力學保持平穩(wěn)[36],而能否預防和處理高血壓患者俯臥位后發(fā)生的低血壓還需要進一步的研究。
4總結
高血壓患者俯臥位脊柱手術的循環(huán)管理至關重要,在麻醉誘導前適當補液擴容能夠提高有效循環(huán)血量,減少俯臥位后低血壓的發(fā)生,術中使用血管活性藥物可以維持血流動力學的平穩(wěn),保證重要器官和組織的灌注,減少相關并發(fā)癥。但對于術前ACEI/ARB類藥物是否停用及術中使用甲氧明是否更具優(yōu)勢,還需要進一步的研究。
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(收稿日期:2018-01-23 本文編輯:祁海文)