Hypocaloric enteral nutrition - Deranged Physiology

"The generally accepted definition of trophic feeding is a small volume of balanced enteral nutrition insufficient for the patient's nutritional ... Breadcrumb DerangedPhysiology RequiredReading Endocrinology,MetabolismandNutrition   Hypocaloricenteralnutrition ByAlexYartsev-Jun26,2017 LastupdatedSat,07/08/2017-18:43 Topic:EndocrinologyMetabolismandNutrition Previouschapter:Managementofinadequatenutritionandfeedintolerance Nextchapter:Immunonutritionandpharmaconutrition AllSAQsrelatedtothistopic Allvivasrelatedtothistopic Question23 fromthefirstpaperof2017askedforasubstantialamountofdetailwithregardstopermissiveundefeeding,hypocaloricentralnutrutionandtrophicfeeding.Havingdiscussedtheimportanceofgoodnutritionover manychapters,theauthoracknowledgesthatthereisanargumenttobemadeforintentionallyunderfeedingICUpatients.  Inbriefsummary: Hypocaloricnutrition isdefinedasnutritionwhichintentionallydeliverslessnonprotein nutrientsthanwouldberequired fordailyenergyexpenditure. Trophic feedingisdefinedasfeedingatarateunder500kcal/day  Permissiveunderfeeding  isdefinedas asfeedingunder40-60%ofthecaloriesrequiredfordailyenergyexpenditure. Thedifferencebetween"trophic"and"permisive"hypocaloricnutritionisthattheintentionof"permissiveunderfeeding"istointentionallyprovideless nutrition,whereas"trophic"feedingdoesnothave nutritionasitsgoalandinsteadfocusesonmaintaininggutintegrity.  Goodreadingforthistopicshouldstartwith JoshFarkas'entryinPulmcrit,and-formostofus-itshouldfinish thereaswell.Toscrapetheworldliteratureformeaningfulinformationissomethingthetime-poorcandidatecannotafford,andFarkas'articlehasthebenefitofbeingwritteninhuman-readablelanguage.  Hypocaloricnutrition Hypocaloricnutritionisanutritionalstrategywhichintentionallyrestrictstheamountofintake.Specifically,theterm"hypocaloric" impliesthatonlyenergyintakeisdecreased,andproteinorfatmacronutrientsmaystillmeetmetabolicneeds.This isnotnew,noruniquetointensivecare.Itisa fashiontrendamongcritialcarenutritionexperts,which maybeareactiontothehypercaloricnutritionmuchinvogueduringthe1970sand1980s.Routineparenteral "hyperalimentation"waspracticed,withpatientsfrequentlybeingfedupto 200%oftheirrecommendedenergyrequirements;contemporaryrecommendationscalledfor40-50 kcal/kg/day(Spanieretal,1977) Theexpectationwasthat"inthedepletedpatientinfusionofcaloriesinexcessofthisamountresultsinarebuildingofthebodycellmass".  Fortunately,wenowknowthatthis approachisstupidanddangerous.Thependulumhasnowswungtowards underfeeding,withenthusiastsofhypocaloricnutritionplacing anemphasisonusingenteralnutrition foritsnon-nutritionalbenefits(eg."trophic"feeding,discussedbelow). Rationaleforhypocaloricnutrition Intheiranswerto Question23 fromthefirstpaperof2017,thecollegeofferalistofadvantagesinsupportofhypocaloricnutrition.Thislistcanbeexpandeduponwithreferences.  Inshort: Wedon'tknowhowmuchnutrientsthepatientsactuallyneed. Idealcalorictargetsforcriticallyillpatientsareunknown.Evencalorimetryfailsus(ittellsuswhattheyareusing,butnotwhattheyrequire foroptimalfunction).Inshort,withoutknowingwhat"eucaloric"feedingwouldlooklike,wecanjustifyfeedingatanintentionallyreducedrate-itmayactuallybetherequiredrate,forallweknow. Thereisatheoreticalimmunologicaladvantagetohypocaloricnutrition. Thecollegementionthat "calorie restrictionisassociatedwithincreasedlongevityinanimalmodels",whichisaninterestingthingtomention.Inthis,theexaminershavechosentoextrapolatetohumancriticalcaresuch experimentsasWeindruchetal(1986),whodemonstrated30-40%longerlifespansformicewhowerefedanincrediblypoordiet(~65%calorierestricted).Theunhappyrodentsledanexcruciatinglyprolongedexistancedevoidofcakeorbacon,generatingno envyfromthehappily gluttonouscontrolgroup(eventhoughtheirlifespans averaged53months whichaccordingtotheinvestigators "exceedsreportedvaluesforanymiceofanystrain"). Theeffectof100%nutritiononmusclebreakdownisunknown.Thatfullnutritionalsupportshouldpreventproteincatabolismincriticalillnessisawidelybelievedfact,butwehavelittletosupportthis.Streatetal(1987) fedtheirsepticpatientsaluxuriouslyrepletedietandfoundthattheybuiltmore fattytissue butlostmuscleanyway.  Thehypercatabolicresponsetocriticalillnessisadaptive,andworkingagainstitmaybecounterproductive.Disablingkeyautophagygenesleadstoincreasedsusceptibilitytocancerandinfectiousdiseases(Choietal,2013).Themeansofremovingdamagedorganellesanddigestingphagocytosedbacteriaareactivatedbystarvationandsuppressedbynutrients(VandeBergeetal,2012).Inthismanner, supplementationof100%ofgoalneedsmaydelayrecoveryfromorgansystemfailureandsepsis. Feedingatgoalratemayresultinfeedintolerance.Thisinturnleadstoaspiration,useofprokineticswithdangerousside-effects,gastricdistension,fluidoverloadandvariousothercomplicationsofenteralnutrition.Feedingbelowthegoalrateshouldtheoreticallypreventoramelioratetheseproblems. Permissiveunderfeeding Thedefinitionofpermissiveunderfeedingissomewhatnebulous.Forexample,thatiswhatthe PermiTtrial(Arabietal,2015)calledtheir40-60%goal(i.e40-60%oftheexpecteddailynutritionalrequirements). Jeejeebhoy(2004) didnotmakeanyattempttodefinetheterminhisreviewarticle.ThesystematicreviewbyOwaisetal(2010)revealsamassivevariationofhistoricaldefinitions,rangingthough13-14kcal/kg/day,<20kcal/kg/day, 1000kcal/day,  or<33%ofestimatedrequirement,or5,000-10,000kcal/week.Suchunconservativeproliferationof definitionsgivesrisetofrustrationandrageamongcriticalcaretrainees,particularlywherethedefinitionaccountsfor 40%ofafinalexamquestion.Thecollegeofferedthe40-60%goalfromArabietal astheircut-off,whichbecomesthedefinitivemark-scoringanswertothisdefinition. Evidenceforpermissiveunderfeeding Inshort,itisconflicting.Ifyouseparatethe"tropic"trials,thentherereallyisonlyonebigstudy,whichisthe the PermiTtrialby Arabietal.Theinvestigatorsrandomised894patients(mostlyintubated)toeitherreceive70-100%oftheircalculatedrequirements,or40-60%.Thegroupsendedupwellseparated(average835kcalvs.1299)andthiswasmaintainedfor14days.Nodifferenceinanyoftheprimaryoutcomemeasureswasfound. Apost-hocanalysis(Arabietal,2017)didnotfindanydifferenceevenamongpatientsdefinedasbeingatahighnutritionalrisk.Thishasbeenviewedasevidenceofsafety.Providedyougive100%oftheproteinrequirements,youcanenergy-restrictyourICUpatientsfortwoweekswithnoadverseconsequences. Trophicfeeding Intheiranswerto Question23 fromthefirstpaperof2017,thecollegedefinedtrophicfeedingas"feedingbelowtheminimumrequiredcaloricintake,withtheaimof maintaininggutintegrityratherthanmeetingpatient’snutritionalrequirements".Thiscloselyresembles Sondheimeretal(2004), who weremysourceforthedefinitionoftrophicfeeding asitisquoted: "Thegenerallyaccepteddefinitionoftrophicfeedingisasmallvolumeofbalancedenteralnutritioninsufficientforthepatient'snutritionalneedsbutproducingsomepositivegastrointestinalorsystemicbenefit." Thisarticleisactuallyaneditor'sperspectivefromtheworldofpaediatric(specificallypretermneonatal)intensivecare,whereapparentlyexistsan"almostreligious" attachmenttotheconceptofdeliveringasub-nutritivevolumeoffeeds.Thedefinitionalsocontainsacertaindailycaloric"target",i.e.onecannotcallone'sfeeds"trophic"ifonesuppliesmorethan25%ofthedailycaloricgoalsinthisway.Usingthestandardformula,thatwouldmeankeepingthetotalintakeunder 6.25kcal/kg/day. Foradults,thedefinitionoftrophicfeedingislargelybasedonthepapersby Riceetal(discussedbelow),whichusedarateof10-20cal/hr,uptoatotalof500cal/day(whichworksouttobeabout7kcal/kg/dayfora70kgpatient).Thecollegegivearangeof 10-30ml/hror15-25%ofcalculatedcaloricintake. Rationalefortrophicfeedingincriticalillness Theexpectedbenefitsofthispracticeare: Improvedfeedtolerance(reducedgastricresidualvolumes) Maintenanceofgastricandintestinalmucosalintegrity Preventionofbacterialovergrowthandbacterialtranslocation Preventionofexcessiveproteincatabolism(preventionofstarvation) Evidencefortrophicfeedingamongcriticallyilladults ThelargemulticentreEDENtrial(Riceet al,2012)followedanearliersingle-centre 2011studybythesameauthors intotheterritoryoftrophicfeedingforARDSpatients.Unfortunatelytheinvestigatorswereroundlypilloriedforundefeedingthepatientswithprotein(0.6g/kg/day)andenrolling patientswhichweredifficulttodescribeas"criticallyill"withastraightface.Theprimaryoutcomeswerecompletelyunaffectedbythetrophicdiet. Allthatcanbesaidisthatthelowervolumeoffeeds(around400cal/day)wasbettertoleratedthanfulldiet(i.e.theincidenceofhighgastricresidualvolumeswaslower)whichmakessomesortofcrudelogicalsense.Thiswashardlyagreatvictoryforpeoplewhoexpectedsomesortof positive effectsfromthisstrategy.However,itdidsuggestthatthereisprobablylittleharminthepractice,forwhateverthatisworth.Forfivedays,youcansafelyunderfeedyourICUpatientswithenergyinputofaround400calories.Additionally, isprobablyworthrememberingthatevery1mlof1%propofolcontains1.1caloriesofdelicioussoy-basedlipid,anditisquitepossibletosupplyadecentamountofenergy that form(i.e.15ml/hrfor24hrs=396kcal/day). Supportfromsocieties ASPENguidelines answeredthequestion,"ForwhichpopulationofpatientsintheICUsettingisitappropriatetoprovidetrophicENoverthefirstweekofhospitalization?" (McClaveetal,2016-p.169).TheyansweredusingresultsfromtheARDS-focusedtrialsbyToddW.Riceetal (2012and2011).Theexactphrasewas"WerecommendthateithertrophicorfullnutritionbyENisappropriate"forpatientswithacutelunginjury.  Previouschapter:Managementofinadequatenutritionandfeedintolerance Nextchapter:Immunonutritionandpharmaconutrition References Sondheimer,J.M."Acriticalperspectiveontrophicfeeding." Journalofpediatricgastroenterologyandnutrition 38.3(2004):237. McClave,StephenA.,etal."Guidelinesfortheprovisionandassessmentofnutritionsupporttherapyintheadultcriticallyillpatient:SocietyofCriticalCareMedicine(SCCM)andAmericanSocietyforParenteralandEnteralNutrition(ASPEN)." JournalofParenteralandEnteralNutrition 40.2(2016):159-211. 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