重症患者营养支持概述营养支持的演变危重病状态下的代谢特点糖代谢变化高分解代谢Randomizedtrialshavenotshownabenefitfromapproachesthattrytocounteractthenaturalcatabolicstatethatoccursintheacutephaseofcriticalillness(i.e.,forcingpatientstoreachtheircalculatedcaloricgoals,throughcombinationsofentericandparenteralfeedings).营养需要量正常人体所需的营养素正常人体能量的需求正常成人蛋白质需求不一样年龄精细能量消耗量应激时能量日需要量（正常倍数）蛋白与电解质的日需要量危重症的营养支持危重病人营养支持目的危重病人营养支持原则营养支持途径营养支持途径营养支持途径选择原则危重病人能量补充原则经验性估计：轻度应激：20～30kcal/天/Kg；中度应激：30～40kcal/天/Kg；重度应激：40～50kcal/天/Kg；特殊病例（严反复合伤、大面积烧伤、严重感染等）：60～80kcal/天/Kg。肠外营养支持（PN）应用指征应用指征应用指征肠外补充的重要营养素碳水化合物脂肪乳剂脂肪乳剂氨基酸/蛋白质水、电解质的补充维生素与微量元素肠外营养支持途径肠内营养（EN）与全胃肠外营养(TPN)Enteralnutritionispreferabletototalparenteralnutrition,whichisassociatedwithnosocomialinfections.Ameta-analysisof6randomizedtrials(n=498)comparingenteralwithparenteralnutritionsuggestedTPNalmostdoubledtheinfectionratecomparedtotubefeedings.JPENJParenterEnteralNutr.Sep-Oct;27(5):355-73.Manycriticallyillpatientshavereducedgutmotilityandfailtotolerateenteralfeedingsintheamountscalculatedtomeettheirtheoreticalcaloricneeds.Forthesepatients,thereappearstobenobenefittostartingtotalparenteralnutritioninthefirstweekafterimpairedgutmotilityoccurs,anddoingsomayincreasetheriskfornosocomialinfection.ProvidingnonutritionalsupportordextroseinfusionsareasgoodorbetterthanearlyTPNforcriticallyillpatientswhocan’ttoleratetubefeedings.Thatbeingsaid,earlyparenteralnutritionhasneverbeenshowntoincreasemortalityfromcriticalillness.Ifapatientcan'ttolerateenteralliquidfeedingsviaatube,whatwouldyoudo？Ahugetrial(n=4,640)publishedinNEJMinshowednobenefitandpotentialharmfromprovidingTPNatday3,ratherthanday8offailingentericfeeds.NEnglJMed.Aug11;365(6):506-17AlargeobservationaltrialalsodidnotshowanyclinicalbenefitamongthosegivenearlyTPNnutritionvsenteralnytritionalone(high60-daymortalityandlowalivedischargedrate).CritCareMed.Dec;39(12):2691-9AnotherhugeRCT(n=1372)inJAMAinshowedno60-daymortalityandnewinfectiondifferencesbetweenearlyPNgroup(mean44min,36to55min)andlateENorPNgroup(mean