早期营养支持对于重症患者是标准的治疗方式，而这同样需要医生对营养支持的时机、提供方式以及营养成分进行复杂的计算，毕竟所有这些都可能影响预后。而究竟此时是采用肠内营养还是肠外营养的问题，许多荟萃分析鉴于样本量较小、缺乏强有力的质量控制以及营养成分的差异等因素，并不能得到有足够说服力的答案。
英国国家重症监护审查与研究中心（ICNARC）、盖伊和圣托马斯医院、伦敦帝国学院、伦敦国王学院、伦敦大学学院发表在美国《新英格兰医学杂志》（NewEnglandJournalofMedicine）的重症患者早期营养支持途径选择临床试验（CALORIES）展示了一项大型、多中心、随机对照研究，探索了肠内及肠外营养的方式对于其预后、合并症等的影响。
研究以非预期进入33个英国重症监护病房（ICU）的患者为研究对象，之后将这类患者随机分为肠内营养组及肠外营养组，在患者进入ICU的36小时内开始营养支持，持续至5天的时间。研究终点定义为30天内各种原因导致的死亡。
研究纳入了2400个患者，其中2388例（99.5%）患者进入随访（肠外营养组1191例；肠内营养组1197例）。在30天内，1188个肠外营养组的患者中393例（33.1%）发生死亡，而1195个肠内营养组的患者中409例发生死亡（34.2%），统计学并未发现显著差异（P=0.57）。而在肠外营养组中，低血糖及呕吐的发生率明显低于肠内营养组（44例[3.7%]比74例[6.2%]，P=0.006；100例[8.4%]比194例[16.2%]，P＜0.001），而感染发生率（0.22vs.0.21=0.72）、90天死亡率（442of1184patients[37.3%]vs.464of1188patients[39.1%],P=0.40）、并发症及总能量摄入方面两组间并无显著差异。
当然，既往也有一些研究表明早期采用肠外营养支持的方式会增加感染的发生几率，且并不利于预后，这可能并非是采用哪种途径导致的问题。本研究采用非常严格的试验监控系统，加强了对肠外营养支持的血糖监测，从而并未发现肠内及肠外两组之间感染发生率的差异。因此，肠内或肠外的途径并非真正导致感染发生差异的原因，而应进一步加强医疗系统对于重症患者的血糖监管。
研究表明，对于重症患者的早期营养支持方式，肠内营养及肠外营养对预后的影响并无显著差异，而肠内营养组患者发生肠道反应及低血糖的几率要高于肠外营养组。
N Engl J Med. 2014 Oct 1. [Epub ahead of print]
Trial of the Route of Early Nutritional Support in Critically Ill Adults.
Harvey SE, Parrott F, Harrison DA, Bear DE, Segaran E, Beale R, Bellingan G, Leonard R, Mythen MG, Rowan KM; the CALORIES Trial Investigators.
Clinical Trials Unit, Intensive Care National Audit and Research Centre (S.E.H., F.P., D.A.H., K.M.R.)
Departments of Nutrition and Dietetics (D.E.B.) and Adult Critical Care (D.E.B., R.B.), Guy's and St. Thomas' NHS Foundation Trust
Department of Intensive Care, Imperial College Healthcare NHS Trust (E.S., R.L.)
Division of Asthma, Allergy and Lung Biology, King's College London (R.B.)
National Institute for Health Research Biomedical Research Centre, University College London Hospitals NHS Foundation Trust and University College London (G.B., M.G.M.)
Department of Surgery and Cancer, Imperial College London (R.L.)
Background: Uncertainty exists about the most effective route for delivery of early nutritional support in critically ill adults. We hypothesized that delivery through the parenteral route is superior to that through the enteral route.
Methods: We conducted a pragmatic, randomized trial involving adults with an unplanned admission to one of 33 English intensive care units. We randomly assigned patients who could be fed through either the parenteral or the enteral route to a delivery route, with nutritional support initiated within 36 hours after admission and continued for up to 5 days. The primary outcome was all-cause mortality at 30 days.
Results: We enrolled 2400 patients; 2388 (99.5%) were included in the analysis (1191 in the parenteral group and 1197 in the enteral group). By 30 days, 393 of 1188 patients (33.1%) in the parenteral group and 409 of 1195 patients (34.2%) in the enteral group had died (relative risk in parenteral group, 0.97; 95% confidence interval, 0.86 to 1.08; P=0.57). There were significant reductions in the parenteral group, as compared with the enteral group, in rates of hypoglycemia (44 patients [3.7%] vs. 74 patients [6.2%]; P=0.006) and vomiting (100 patients [8.4%] vs. 194 patients [16.2%]; P<0.001). There were no significant differences between the parenteral group and the enteral group in the mean number of treated infectious complications (0.22 vs. 0.21; P=0.72), 90-day mortality (442 of 1184 patients [37.3%] vs. 464 of 1188 patients [39.1%], P=0.40), in rates of 14 other secondary outcomes, or in rates of adverse events. Caloric intake was similar in the two groups, with the target intake not achieved in most patients.
Conclusions: We found no significant difference in 30-day mortality associated with the route of delivery of early nutritional support in critically ill adults.
Funded by the United Kingdom National Institute for Health Research; CALORIES Current Controlled Trials number, ISRCTN17386141.
PMID: 25271389
DOI: 10.1056/NEJMoa1409860
