中华急诊医学杂志  2023, Vol. 32 Issue (4): 505-517   DOI: 10.3760/cma.j.issn.1671-0282.2023.04.012
新型冠状病毒感染住院患者肠外肠内营养支持策略循证建议(2023)
江华1,2,3 , 陈伟1,3 , 曾俊1,2     
1. 四川省急危重症临床医学研究中心,成都 610072;
2. 四川省医学科学院·四川省人民医院,电子科技大学附属医院,成都 610072;
3. 北京协和医院临床营养科, 北京 100730
1 概述与方法学

自2019年底新型冠状病毒感染(coronavirus disease 2019, COVID-19) (以下简称新冠感染)在全球范围内爆发以来,因其传播速度快、致病性强的特性,造成了破坏性的医疗、经济和社会负担。自2022年以来奥密克戎变异株已经成为全球主要毒株[1]。其传播性更强、发生免疫逃逸的可能性更大,感染者除出现咽部不适、咳嗽和发热等主要症状外,还可能伴有恶心、腹泻、胃纳减退等消化道症状[2],严重者快速进展为急性呼吸窘迫综合征、脓毒症休克和多器官功能衰竭[3]。其中,老年、合并慢性基础性疾病和免疫力低下的感染者更易进展为重症。部分患者会因消化道症状导致营养素摄入不足或吸收障碍而引发营养不良。对于重症患者而言,大量炎性因子的释放引发免疫-内分泌-代谢的瀑布级联反应,造成代谢功能严重失调,加重营养不良的发生发展[4-5]。国家卫生健康委员会最新公布的《新型冠状病毒感染诊疗方案(试行第十版)》指出,应当加强支持治疗,保证充分能量摄入[3]。医学营养治疗应当贯穿新冠感染的预防、治疗和恢复全过程。

疫情发生以来,国际和国内医学界对新冠感染者肠外肠内营养支持治疗的循证医学证据不断出现,但是由于新冠感染对机体造成的广泛影响,及其病理生理机制迄今仍有诸多未明之处。为响应国家科学、精准开展疫情处置工作的号召,更好的治疗各种住院、尤其是重症感染住院患者,落实推进优化措施、改善治疗效果,我们组织全国相关领域专家启动《新型冠状病毒感染住院患者肠外肠内营养支持策略循证建议(2023)》的编写工作。我们参考世界卫生组织(World Health Organization, WHO)的《WHO指南编写指南》等权威机构的方法学原则[6-9],同时结合新冠感染医学营养治疗的具体工作内容,邀请了循证医学、肠外肠内营养、急诊医学领域工作的专家共同合作,制定了本文件。由于疫情发展迅速,需要在较短时间内尽可能全面和完整的完成证据检索和提取,我们首次引入人工智能技术,将人工检索与智能检索相结合。本文件作为第一版,还将根据疾病的演变、临床使用情况和临床证据的变化进行实时更新。

1.1 文献检索策略

文献检索结合人工检索与智能文献检索两种方法。人工检索主要由支持小组工作人员按照相关方法完成,智能检索见1.2节。

1) 检索文献为2010年及后发表文献。

2) 二级数据库:Guideline Clearing House, Cochrane Library, Sum Search; 一级数据库:Medline,EMBASE,Web of Science, 中国生物医学文献数据库、中国知网。限定条件见表 1

表 1 证据检索——数据库和关键词
检索时限 2010年1月1日至2023年1月10日(部分涉及重症患者营养的主题可上溯至更早)
语言 英语,汉语
数据库 二级数据库:Guideline Clearing House, Cochrane Library, Sum Search, Clinical Key
  一级数据库:Medline,EMBASE,Web of Science, 中国生物医学文献数据库
筛选项目 人类
文献出版类型 有效性:指南,Meta分析,系统评价,随机对照试验,观察研究,病例报告,共识意见
  安全性:指南,Meta分析,系统评价,随机对照试验,不良反应报告,共识意见
主要检索词 COVID-19, SARS-CoV-2, enteral nutrition, parenteral nutrition, nutritional risk, critical illness

3) 统一的推荐分级: 以GRADE协作网的指南分级标准进行分级。

1.2 利用自然语言处理技术不断更新证据

自然语言处理(natural language processing, NLP)是人工智能(artificial Intelligence, AI)的一个分支,其目的是让计算机有能力以与人类相同的方式理解文本和口头语言。目前基于中文论文的预训练模型在学术论文的自动总结、整理和自动标记方面已经取得了一定成果,但是尚未将上述成果用于临床医学特定话题、研究热点的自动追踪和总结。本文件制定过程中,首创性地引入了该工具进行快速自动临床证据检索。

1.3 证据级别与推荐意见分级标准

采用GRADE工作组(Grading of Recommendations Assessment, Development and Evaluation)的证据分级和推荐强度分级系统对证据进行评估并形成循证推荐意见[10],主要推荐意见均按照“临床问题-推荐意见(证据级别,推荐级别)-证据简述”的基本框架进行阐述。关键临床问题部分按照PICO格式,即患者类型(patient),干预措施或诊断试验(intervention)、对照/替代措施(comparison)、结局(outcome)进行描述和评价。推荐意见根据对关键临床问题的证据合成的总结,并充分考虑卫生经济学效应后作出结论。当一项干预措施的益处超过其风险且经济上可负担时,推荐意见为“强推荐”,当获益减弱或风险增加时,推荐意见降级为“弱推荐”。每一推荐意见后附证据质量分级。如“证据质量A,强推荐级”。

1.4 编写委员会构成

由全国肠外肠内营养、急诊医学、重症医学、循证医学等相关领域专家组成编委会。所有参与本文件编写的人员均基于志愿工作。

指导专家:杨桦、吕传柱、孙鑫

主编:江华、陈伟、曾俊

编委(按姓氏拼音排序)

陈伟、邓磊、黄河、江华、刘明、李增宁、彭谨、孙明伟、王雯、王宇、汪志明、尤丕聪、姚颖、赵彬、曾俊、朱明炜、周平、周业平、庄则豪

编委会秘书:王宇、王璐、张建成、马伟、张驰、袁婷、岳汉阳、王栋、杨广宇、张瑞鹏

1.5 利益冲突声明

所有参编人员均声明:未接受任何利益相关公司的赞助。未持有任何与本指南建议涉及领域的专利。

1.6 注册

本循证建议已通过国际实践指南注册与透明化平台注册,注册号:PREPARE-2023CN006。

2 主要推荐意见

推荐意见1  所有收治入院的新冠感染患者,均应在入院24-48 h内使用营养风险筛查2002(the nutritional risk screening 2002,NRS-2002)完成风险筛查;(证据等级A, 强推荐)对于NRS-2002评分<3分的患者,应注意监测体重、进食量变化,7 d后重新进行营养风险筛查(证据等级A, 强推荐);条件允许时可进一步使用全球领导人营养不良倡议(Global Leadership Initiative on Malnutrition, GLIM)进行营养不良诊断。

新冠感染会对多系统造成损害,尤其是呼吸系统和消化系统,感染者除出现咽部不适、咳嗽和发热等主要症状外,还可能伴有恶心、腹泻、胃纳减退等消化道症状[11]。由于病毒的攻击和继发感染,导致大量炎症因子释放,患者代谢功能严重失调,促使营养不良发生发展[12-13]。一项大样本系统评价和Meta分析发现,在新冠住院患者中,营养不良发生率高达49.11% (95% CI 31.67~66.54),存在营养不良的新冠感染患者相较于无营养不良的患者总体病死率增加近10倍[14];另一项研究发现,在入ICU的新冠感染患者中营养不良的发生率高达92.2%[15]。因此,对新冠感染患者进行营养风险的筛查与营养不良的诊断显得尤为重要。若患者NRS-2002评分<3分则提示目前患者尚无营养不良风险,应做好营养健康宣教工作[10, 27]。由于新冠肺炎的进展很快,患者的营养代谢状态也可能迅速变化,医生应密切监测新冠肺炎患者体重、进食量的变化,并在7 d后对患者再次进行营养风险筛查[28-29]。NRS2002的筛查内容和结果判断可参见中华人民共和国卫生行业标准《临床营养风险筛查》(WS/T 427-2013)。

常用的营养风险筛查工具NRS-2002是2002年欧洲肠外肠内营养学会(European Society for Parenteral and Enteral Nutrition,ESPEN)制定的[16]。Alikiaii等[17]的研究表明,NRS2002评分与新冠肺炎住院患者病死率有很强的相关性。Silva等[18]的研究表明NRS2002在评估老年新冠感染患者入院时的营养风险和预测住院时间方面有显著作用。新冠病毒肺炎老年患者的医学营养支持专家意见同样推荐使用NRS2002对老年新冠病毒感染者进行营养风险筛查[19]

2016年提出的GLIM为营养不良的诊断制定了统一的标准[20]。近年来,大量研究验证了GLIM在临床所具有的较强可行性[21-25]。有证据表明,在新冠感染患者中GLIM标准也具有良好的适用性[26]

推荐意见2  对于经口摄食量减少无法完全满足每日营养需要量的患者可提供口服营养补充(oral nutritional support, ONS),可首选整蛋白型肠内营养制剂,提供不低于500 kcal/d的补充能量(证据等级A, 强推荐)。对于合并糖尿病或应激性高血糖的患者,可选用糖尿病专用型肠内营养制剂(证据等级C, 弱推荐)。

2020年发表的7项多中心横断面研究以及1项Meta分析(n=3 515),报道了约有一半(50%~61%)的住院新冠感染患者在入院时存在胃肠道紊乱,包括厌食、腹泻、恶心、呕吐和腹痛等[30-37]。与此相似,于2022年发表的一项多中心横断面研究发现,63.6%的新冠感染患者入院时有消化道症状,以厌食居多(44%)[38]。另有一项研究评估了ONS对于患者临床结局的影响,发现需要并接受ONS的患者与不需要ONS的患者出院率相近(91.9% vs. 92.2%,P = 1.000),表明ONS可以帮助新冠感染患者从疾病中恢复[39]。因此,对于新冠感染的住院患者若有胃肠道功能障碍,影响正常进食,应早期给予ONS。

在住院的新冠感染患者中,高血糖是不良预后因素[40-41]。Miguelez等[42]2021年发表的队列研究报道,64例死亡患者中,60例合并有高血糖(93.8%)(P < 0.001)。因此建议合并有糖尿病和应激性高血糖的新冠感染患者,密切监测血糖,可使用糖尿病专用型肠内营养制剂。

推荐意见3  对于ONS无法满足患者营养需求或无法接受ONS的患者,推荐管饲肠内营养(证据等级C, 弱推荐);管饲途径首选经鼻胃管途径(证据等级B, 弱推荐)

目前已发表的各个指南均将肠内途径作为新冠感染患者营养治疗的首选途径。经营养评估后需要接受营养治疗的患者应首选ONS。当患者ONS无法达到目标量的50%或无法耐受ONS时,应尽快启动管饲营养治疗[43]。在选择管饲方式时首选快捷、操作方便的鼻胃管方式[44],以利于营养治疗的尽快实施[45-48]。一项大规模随机对照试验(randomized controlled trial, RCT)发现,早期接受鼻胃管饲和小肠管饲的患者在住院时长、肺炎发病率及营养物质输送效率上没有明显差异[49]

推荐意见4  无法经口进食的患者,应该尽早进行管饲(证据等级A,强推荐);对于接受机械通气,尤其是俯卧位通气的管饲患者,如果存在胃排空障碍或存在高误吸风险,有床旁插管条件(内镜下引导、超声引导或磁引导),推荐经鼻空肠喂养途径进行管饲(证据等级B, 弱推荐)

重症新冠感染患者往往需要接受有创机械通气。2022年,Ojo等[50]发表的meta分析显示,肠内营养能显著降低新冠感染患者的死亡风险(P = 0.04)。亚组分析结果显示通过早期肠内营养,新冠感染患者病死率的相对风险降低了11%。2021年有研究发现,肠内营养组患者的28 d病死率远低于肠外营养组[51],另一项研究[52]比较了早期肠内营养(early enteral nutrition,EEN,起始时间≤2 d)和晚期肠内营养(late enteral nutrition,LEN, 起始时间≥3 d)对重症新冠感染患者的疗效。结果显示,接受肠内营养治疗后第3天,EEN组患者的炎症因子浓度较LEN组患者显著降低(P < 0.05),且EEN组患者整体住院时间和ICU住院时间显著缩短(P < 0.0001)。

幽门后管饲喂养可能减少高危患者吸入性肺炎的发生[44],其在重症患者中的有效性已在多项meta分析中得到证明[53-54]。对于接受机械通气的患者,尤其是俯卧位通气的管饲患者,由于普遍存在的胃扩张,经胃喂养发生胃潴留甚至误吸的风险增加。2015年,Wan等[55]发表的一项纳入70例患者的RCT证实,采用鼻空肠途径肠内营养能够显著改善机械通气患者的营养状况并减少其并发症,鼻空肠途径组的反流和肺炎发生率、机械通气时间、ICU平均住院时间和营养支持费用都明显低于鼻胃喂养途径组(P < 0.01)。Ge等[56]针对鼻空肠喂养途径对呼吸机相关肺炎(ventilator-associated pneumonia, VAP)进行的一项RCT显示,鼻空肠喂养途径组患者的VAP发生率较鼻胃喂养途径组显著降低(P < 0.05),同时,其ICU住院时间和呼吸机使用时长也较鼻胃喂养途径组显著缩短(P < 0.05),与孔祥伟等[57]、孙慧等[58]及谢美婵等[59]的研究结论相似。

推荐意见5  应根据病情分阶段实施目标导向的营养治疗,即在炎症高峰期接受短期允许性低能量喂养,能量目标15~20 kcal/(kg·d);对于接受俯卧位通气的患者可适当下调,不低于10 kcal/(kg·d),蛋白质目标1.0~1.2 g/(kg·d),允许性低摄入的时间一般不超过1周(证据等级C, 弱推荐);炎症高峰期后,能量目标25~30 kcal/(kg·d),蛋白质目标1.2~1.5 g/(kg·d)(证据等级C, 弱推荐)

2022年一项研究表明,重症新冠感染者相较于普通重症患者更容易出现能量的负平衡,尤其是长期住院者的能量债累积[60]。准确的预估新冠感染住院患者的目标能量需求(energy expenditure, EE)是实施合理营养支持治疗的前提。间接测热法(indirect calorimetry, IC)是目前测定能量代谢率的金标准。美国肠外肠内营养学会(American Society for Parenteral and Enteral Nutrition, ASPEN)和ESPEN在其重症指南中均将其作为首选[43, 61]。考虑到间接测热法所需的设备要求较高,且目前大量的患者在短时间内就诊造成医疗资源的紧张,故本指南不推荐IC法作为首选。使用预测公式估算每日能量需求也是临床工作中较为常用的方法,但是,目前的系统评价和大量的临床研究表明,预测公式测定的EE相较于IC法差异较大[62-68],且不能显著改善患者的临床结局[43, 69-70]。因此,也不推荐在紧急条件下使用该方法。

为了能够快速评估患者的能量需求,在相对较短时间内指定合理的营养支持治疗方案,且便于在各级医疗机构推广,依据国内外权威临床营养指南[43, 61, 71-72],我们推荐25~30 kcal/(kg·d)作为目标能量,但应分阶段实施。国内外的权威指南(见表 2)大多推荐患者在最初接受营养支持治疗时的能量和蛋白质供给量均应从小剂量开始,随病情稳定逐步过渡到全量喂养。据报道重症新冠感染者住院3 d累积能量债为(2 171.2±945)kcal,蛋白质的累积赤字为(114.9±49.2)g;住院7 d的累积能量债和累计蛋白赤字为(2 586.4±1 151)kcal和(133.3±60.4)g。这表明在实践中,大多数患者接受了允许性低摄入的营养支持策略[84]。有大型研究表明早期摄入量为患者静息能量消耗(resting energy expenditure, REE)的70%~80%时,患者的死亡风险最小[70, 85]。因此,本指南推荐在患者入院早期采用允许性低摄入策略,能量摄入量为15~20 kcal/(kg·d)。考虑到接受俯卧位通气的患者发生误吸和反流的风险较大,故对于接受俯卧位通气患者的早期能量目标可进一步适度下调,不低于10 kcal/(kg·d)。待患者病情好转,代谢紊乱得到相应的纠正后,可逐步过渡到25~30 kcal/(kg·d)的目标量,以避免长期的能量摄入不足。同时,考虑到重症感染者早期强烈的炎症反应,过高的蛋白质摄入可能会加剧这种情况;此外,若患者伴有肝肾功能不全,人体对蛋白质的代谢利用能力下降,蛋白质的供给量应当适当减少。故本指南推荐在感染早期蛋白质摄入量不超过1.0~1.2 g/(kg·d)[5]

表 2 新冠感染临床营养指南关于蛋白质和能量的主要推荐意见
指南 能量 蛋白质
ASPEN[45] 第1周:15-20 kcal/(kg·d) 1.2-2.0 g/(kg·d)
ESPEN[48] IC法可及:
  前3 d:<70%MREE
  3-7 d:逐步过渡到80-100%MREE
预测公式法:
  第1周<70% 目标量
逐步增至1.3g/(kg·d)
ANSISA (Italian)[77] 20-25 kcal/(kg·d) 1.2-2.0 g/(kg·d)
AuSPEN[46] 前5 d:50mL/h,1.25kcal/mL
6+ d:逐步增量至20-30 kcal/(kg·d)
≥1.2 g/(kg·d)
BRASPEN[78] 1-4 d:15-20 kcal/(kg·d)
5+ d:25 kcal/(kg·d)
1-2 d:<0.8 g/(kg·d)
3-5 d:08-1.2 g/(kg·d)
6+ d:>1.5 g/(kg·d)
IDA[79] 第1周:15-20 kcal/(kg·d) 1.3-1.5 g/(kg·d),依据代谢需求可逐步增量至2 g/(kg·d)
ATID [80] 1-2 d:<25 kcal/(kg·d)的70%
3-7 d:25 kcal/(kg·d)
7+ d:25-30 kcal/(kg·d)
1-2 d:>1.3 g/(kg·d)的70%
3-7 d:>1.3 g/(kg·d)
7+ d:1.5-2.0 g/(kg·d)
老年患者:1.5-2.0 g/(kg·d)
TDA [81] 25-30 kcal/(kg·d) 1.2-2.0 g/(kg·d)
中华医学会肠外肠内营养学分会[82] 15-30 kcal/(kg·d) 1.2-2.0 g/(kg·d)
上海市临床营养质量控制中心[83] 25-30 kcal/(kg·d)
低剂量起始,3-7 d达目标量
1.2-2.0 g/(kg·d)
新型冠状病毒肺炎老年患者的医学营养支持专家意见[19] 轻型和普通型:
  83.6-125.4kJ/(kg·d)
重症:
  83.6-104.5kJ/(kg·d),初期可考虑较低能量供给,建议62.7-83.6 kJ/(kg·d),应激状态缓解后可恢复至目标全量。
轻型和普通型:
  1.0-1.5 g/(kg·d)
重型:
  无肾功能障碍1.2-2.0 g/(kg·d)
    注:ASPEN:American Society for Parenteral and Enteral Nutrition;美国肠外肠内营养学会;ESPEN:European Society for Parenteral and Enteral Nutrition,欧洲肠外肠内营养学会;ANSISA:Italian association of medical specialists in dietetics and clinical nutrition, 意大利膳食学与临床营养医学专家协会;AuSPEN, Australasian Society of Parenteral and Enteral Nutrition,澳大利亚肠外肠内营养学会;BRASPEN:Brazilian Intensive Care Medicine Association, 巴西重症监护医学协会;IDA:Indian Dietetic Association, 印度膳食协会;ATID, The Israeli Dietetic Association, 以色列膳食协会;TDA, Turkish dietetic association, 土耳其膳食协会;MREE:Measured Resting Energy Expenditure, 测得的静息能量消耗

新冠感染后机体处于应激状态,同时,尿氮排出量明显增加,机体处于负氮平衡[60]。2022年美国成人重症营养治疗指南仍然延续了1.2~2.0 g/(kg·d)蛋白质供应的推荐意见[61];而2018年ESPEN的指南中推荐1.3 g/(kg·d)。目前的系统评价和RCT表明[73-74],蛋白质的剂量高低对患者病死率没有显著影响,但较高剂量的蛋白质摄入组中营养不良发生率显著低于低剂量组(6.9% vs. 27.6%,P<0.05)[74]。此外,目前大型的临床研究表明,强化蛋白质供给量,即蛋白质供应量大于1.5 g/(kg·d)并未显著改善患者预后[75-76]。基于此,本指南推荐患者的蛋白质供给量为1.2~1.5 g/(kg·d)。

推荐意见6  管饲喂养方式,建议采用容量为基础的泵输注喂养(volume-based feeding, VBF)(证据等级A, 强推荐);进行VBF应常规给以甲氧氯普胺(没有锥体外系反应或颅脑损伤的患者)或红霉素(有甲氧氯普胺禁忌证的患者)(证据等级A, 强推荐);肠内营养管饲启动后,应遵循由慢到快的原则,在2~3 d内逐渐达到目标量(证据等级B,弱推荐);

在危重患者,尤其是机械通气患者的肠内营养治疗中,喂养不足始终是主要挑战之一。其中,在进行肠内营养过程中发生的输注中断(enteral nutrition interruption, ENI)(如患者因外出检查、接受治疗等情形,必须暂停肠内营养)是阻碍营养达标的最重要因素之一[86]。研究发现,有近70%的患者在ICU中经历了ENI,与没有ENI的患者相比,每天的能量输送比例减少了19%[87]。临床证据表明,ENI时间越长,危重患者的热量不足程度越高[88]。Heyland等首次提出了容量为基础的泵输注喂养[89-94]。2021年Wang等[95]发表的Meta分析显示VBF方案能够显著提高危重患者肠内营养的输注,且不会增加危重症患者腹泻[RR=1.17, 95% CI (0.91, 1.50), P=0.23]、呕吐[RR=0.80, 95% CI (0.42, 1.55), P=0.51]及喂养不耐受[RR=0.97, 95% CI (0.64, 1.48), P=0.90]等并发症的发生率。同年,Heyland等[96]再次发表研究强调了ENI在机械通气的危重患者中的重要性。近两年,更多的研究证明了VBF在改善机械通气患者的肠内营养输注中的优越性[97-98]。VBF的实施可参考以下方案:即按能量推荐意见计算出当日喂养总量(mL)后,将其除以预计的输注时间,得到每小时喂养量;若在喂养过程中,出现ENI,记录ENI的时间及其在此时间段内没有输注的营养液总量,在重新开始喂养时,将因ENI未能输入的营养液量加入当日剩余的营养液量中,除以当日剩余的喂养时间,重新开始喂养,以避免出现能量蛋白质供应不足。

新冠感染患者大多以呼吸道症状为主,但越来越多的研究显其很容易伴随胃肠道症状(约9%,在插管、深度镇静或处于俯卧位的患者中占比高达26%),其中胃肠道动力不足的患者高达37%[36, 45, 99-104]。2020年,Kaafarani等[105]的一项观察性研究发现,超过50%的重症新冠感染患者在临床或影像学证据中出现了与胃肠道运动不足有关的并发症。ESPEN的指南[43, 106]和中国成年患者营养治疗通路指南[44]中均推荐,在患者伴随胃肠道运动不足时建议首先使用甲氧氯普胺、红霉素等促动力药以增强患者胃肠道蠕动的能力。多项RCT表明[107]甲氧氯普胺(10 mg,静脉注射,1次/12 h)的平均吸收停留时间、达药物浓度高峰的时间与开始吸收的时间,均显著短于西沙比利(10 mg,静脉注射,1次/12 h)和红霉素(200 mg,静脉注射,1次/12 h)。且能显著减少胃残留量(gastric residual volume, GRV) [108-109, 111],系统评价也有类似发现[110]。本指南推荐胃复安用量10 mg,静脉注射,1次/12 h或1次/8 h, 红霉素用量200 mg,静脉注射,2次/d。

推荐意见7  对高误吸风险的患者,每日喂养前或喂养中监测胃残留量(gastric residual volume, GRV),若GRV≤250 mL,可以继续喂养,若GRV>250 mL,应暂停喂养,寻找可能导致GRV增加的原因(如PEEP过高、鼻饲管末端移位等),若在消除上述因素后,GRV下降,可继续喂养;若GRV>300 mL,应考虑停止管饲,GRV的监测方法可采用床旁B超(证据等级B,弱推荐)

新冠感染的重症患者,因为接受机械通气(尤其是俯卧位通气),易发生胃排空障碍并可能出现较高的误吸风险,因此,需要对GRV进行监测。Kar等[112]总结了评估胃排空测定的各种方法,认为闪烁成像法(scintigraphy)为金标准。近年来,随着床旁超声的推广应用,其在评估GRV中展现出独特的优势。超声的优点是无创,无辐射且简便易行。GRV可以使用二维或三维超声测量。利用二维超声,胃排空通常通过测量胃窦横截面积或直径随时间的变化来表征。三维超声则能获得更为精确的测量结果(包括近端体积),其已被报道与闪烁成像法的测量结果非常相近[113]。目前,有证据表明认为当GRV>250 mL时,发生胃排空障碍的风险增加[114-117]。对于GRV的监测频次,目前尚不统一,一些研究认为应每4~6 h测量一次,另一些则认为应每12~48 h测量一次[118-120]

推荐意见8  重症患者应用肠外营养的适用情况:

1)对于接受管饲,但因各种原因无法达到60%目标喂养量且持续3 d以上,可考虑接受补充性肠外营养支持治疗(supplemental parenteral nutrition, SPN)以补足患者的能量蛋白质缺口,推荐使用剂型适宜的肠外营养多腔袋(证据等级C,弱推荐);

2)对于有肠内营养禁忌证(肠麻痹、完全性机械性肠梗阻、高流量小肠瘘、重度肠功能损伤-AGI Ⅲ级等)方可考虑全肠外营养(TPN),肠外营养的能量和蛋白质目标量参照推荐意见5(证据等级C, 弱推荐)

3)使用PN应遵循“全合一”的使用原则,不推荐单独输注脂肪乳或氨基酸注射液,对于有特殊代谢需要的患者可以个体化配置肠外营养液(证据等级A, 强推荐)

根据我国一项关于ICU患者营养治疗实施状况的横断面调查发现,如果仅给予肠内营养,2周内很少有患者能实现营养支持达标率够[121]。最近对危重症患者早期肠内与肠外营养的比较表明,早期肠外营养没有增加感染风险,病死率也没有差异,这表明早期肠外营养是安全可行的[122-123]。新冠肺炎相关的呼吸衰竭常需用到非侵入式正压通气(NIPPV)以及俯卧位通气,而对这类患者,实施全量肠内营养存在很大挑战[5, 101, 124]。因此,与其他危重患者群体相比,如果新冠感染患者需要达到目标喂养量,肠内营养加SPN可能是较好的选择。

本建议纳入并比较了7项权威国际性或全国性循证指南(美国、欧洲、中国、澳大利亚、以色列、印度、爱尔兰、巴西)对肠外营养的适应证的推荐[46, 48, 77-80, 45, 125-126],发现具有较高的一致性,即肠内营养存在禁忌证/无法耐受或因各种原因肠内营养未达到能量目标的患者。而上述指南及研究关于肠外营养开始的时间稍有不同,综合上述研究后,笔者推荐建议对存在高营养风险、营养不良或预计ICU住院时间长的患者,应尽早启动肠外营养,低营养风险患者3 d后仍不能达到目标喂养量的60%,则应考虑SPN。一项在ICU中的RCT[127]发现,对肠内营养不能达到目标喂养量60%时,第4~8天给予SPN以提供近100%的能量目标,与继续肠内营养组相比,SPN组的28 d院内感染率显著降低。

肠外营养安全性管理中国专家共识[126]指出,多瓶串输及单瓶输注会增加肠外营养液的浓度和渗透压,而“全营养混合液”输注更符合人体生理代谢需求,不仅能使得营养素更好吸收,减少代谢并发症,还能降低感染率及病死率。此外,RCT及系统评价也均显示三腔袋比多瓶串输以及“全营养混合液”的成本更低,且更安全[128-129]。因此,不推荐单独输注常规脂肪乳、氨基酸,优先推荐使用工业化三腔袋,也可使用医院配制的“全营养混合液”。

推荐意见9  Omega-3多不饱和脂肪酸制剂的临床应用:静脉输注omega-3多不饱和脂肪酸可以降低炎性细胞因子风暴水平,改善细胞免疫功能,并可能改善临床结局,对于有高炎症反应风险或继发性免疫缺陷(CD4 T淋巴细胞<350/μl)且无禁忌证患者,推荐应用5~7 d(证据等级C, 弱推荐)。对于接受肠内营养的患者可采用含omega-3的肠内营养制剂(证据等级D, 弱推荐)。

细胞因子风暴是新冠感染相关肺炎的突出特征,表现为循环系统中细胞因子水平的持续增高,免疫细胞功能的过度激活以及继发的多器官系统持续损伤,可对机体造成持续伤害,影响临床结局[130]。omega-3多不饱和脂肪酸在免疫调节和抗炎的功效已得到长期的验证[5],且omega-3多不饱和脂肪酸改善氧合的作用得到了专家和指南的认可[48],最新的RCT对重症新冠感染住院患者静脉输注omega-3多不饱和脂肪酸的应用场景进行了评估,提供了无不良事件发生的一致证据,且观察到静脉输注omega-3多不饱和脂肪酸降低重症新冠住院患者病死率以及下调C反应蛋白水平[131-132]。一项meta分析观察到:新冠感染重症患者外周血淋巴细胞亚群计数明显下降,尤以CD4、CD8 T淋巴细胞变化最为明显。该研究发现外周血淋巴细胞亚群计数的显著下降可作为新冠感染患者转危的早期预警指标,且CD4、CD8 T淋巴细胞数量的下降与新冠感染患者的不良结局显著相关[133]。而一项RCT和meta分析提供了一致的证据:补充omega-3多不饱和脂肪酸后淋巴细胞计数有所增加[134-135]。综合国际指南、随机对照实验和meta分析,对有高炎症反应风险或继发性免疫缺陷病(CD4 T淋巴细胞<350/μL)的新冠感染患者,推荐早期尝试使用静脉输注omega-3多不饱和脂肪酸10 g/d,使用5~7 d。对于接受肠内营养的患者,推荐使用添加omega-3的制剂。

推荐意见10  住院患者适度补充维生素D和锌元素可能缩短味觉和嗅觉丧失的时间(证据级别C,弱推荐)

Pereira等[136]基于27个研究的meta分析发现,维生素D缺乏增加新冠感染患者病死率和住院率。Lakkireddy等[137]的研究表明,将维生素D的水平提高到80~100 ng/mL,可显著降低新冠感染者的炎症水平。Villasis-Keever等[138]发现,每天口服4 000 IU维生素D能够降低新冠感染的风险(RR: 0.23; 95% CI: 0.09~0.55)。补充维生素D有助于改善新冠感染患者在康复过程中的健康状况和生活质量,缩短患者咳嗽和味觉丧失的恢复时间[139-140]

锌在免疫调节、止血、促进组织修复等生理过程中具有重要作用[141-143]。一项纳入了28个RCT的Meta分析(n=5 446)发现,锌可以预防急性呼吸道病毒感染的症状,缩短病程[144]。一项纳入33名新冠感染患者的RCT发现锌治疗安全、可行[145]。一项纳入5个新冠感染患者研究的Meta分析(n=1 506)发现,补充锌可显著降低患者的死亡风险[146]。临床研究还发现,补充锌有助于新冠感染患者的嗅觉恢复[147]

推荐意见11  需要透析的新冠感染住院患者,能量建议按照25~35 kcal/(kg·d)给予。蛋白质推荐量为1.0-2.0 g/(kg·d),持续性肾脏替代治疗(Continuous renal replacement therapy,CRRT)患者最高可至2.5 g/(kg·d) (证据级别D,弱推荐),必要时补充乳清蛋白粉(证据级别C,弱推荐)。存在维生素摄入不足风险的患者,需要适量补充(证据级别D,强推荐)。应关注血电解质和透析间期体重增加等情况并给予相应饮食指导;高磷高钾血症患者的肠内营养可选择低磷低钾的肾病专用型全营养制剂。(证据级别C,强推荐)。

2020年美国肾脏基金会肾病预后质量倡议(Kidney Disease Outcome Quality Initiative, KDOQI)对血液透析患者的能量推荐范围为25~35 kcal/(kg·d),蛋白质推荐量为1.0~1.2 g/(kg·d) [148]。新冠感染合并透析更容易发生蛋白质能量消耗(protein energy consumption,PEW),因此蛋白质推荐量为1.2~2.0 g/(kg·d);CRRT每日从透析液中丢失的氨基酸约10~15 g。有研究表明2.5 g /(kg·d)蛋白质摄入有助于达到正氮平衡,而大于2.5 g/(kg·d)的蛋白质摄入没有显示出明显优势,且可能增加尿素氮的产生[10, 45, 149-150]。一项多中心RCT表明,乳清蛋白粉能有效地使腹膜透析营养不良患者的蛋白质摄入量达标[151],另一项单中心研究表明,乳清蛋白除了能使新冠感染的ICU患者蛋白质摄入达标,还能缩短机械通气时间,改善炎症状态和提高生存率[152]。对存在维生素摄入不足风险的患者,需要适量给予补充,特别是补充叶酸、维生素B12、维生素C和维生素D [148]。一项新冠感染疫情期间对191名持续性血液透析患者的调查问卷结果显示,60%的患者观察到血磷升高,72%的患者透析间期体重增加[153]。另外一项涉及15家血液净化中心156名透析患者的前瞻性队列研究表明,远程电话饮食指导能显著改善患者的血磷血钾水平和营养状况[154]

为了方便临床操作,笔者将主要推荐意见绘制成流程图,见图 1

图 1 新冠感染住院患者营养支持治疗流程图
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