rev bras hematol hemoter. 2017;39(2):100–101
w w w . r b h h . o r g
Revista
Brasileira
de
Hematologia
e
Hemoterapia
Brazilian
Journal
of
Hematology
and
Hemotherapy
Scientific
Comment
Tides
within
ourselves:
how
posture
can
affect
blood
volume,
blood
cells
and
clinical
reasoning
夽
Erich
Vinicius
De
Paula
∗UniversidadeEstadualdeCampinas(UNICAMP),Campinas,SP,Brazil
Over120yearsago,ErnestStarlingdemonstratedthatfluids andothermoleculesmovebackandforwardfrombloodtothe extravascularspace,andthatthismovementisdeterminedby thebalancebetweenhydrostaticandoncoticpressuresacting withincapillariesandinterstitialspaces.1Thefirst
measure-mentoftheeffectoftheseforcesonbloodvolumes(plasma and cells) was published in 1928 in a 32-page long paper intheJournalofClinicalInvestigation.Thispaperelegantly demonstratedthattotalplasmavolumedecreasesonaverage 11%after30minstandingstill,comparedtotherecumbent position,andthathematocritincreasedproportionally, indi-cating no significant changes in total blood cell volume.2
Theauthors interpreted their findings asthe result ofthe passageofwaterandotherdiffusiblesolutesthroughthe cap-illarywall,duetoanincreaseinhydrostaticpressurewithin blood vessels.Nearlythirty yearslater,using radionuclide-labeledredbloodcellsandacolordyethatbindstoalbumin, FawcettandWynnevaluatedtheimpactofthesemovements onparametersofthecompletebloodcount(CBC)inhealthy individualsand inpatients withclinicaledemaand/orlow albumin concentrations.3 The standard experimental
pro-cedure consisted in subjects remaining in the horizontal positionfor12h,andthenstandingupfor1h(slowwalking wasallowedduringthisperiod).Bloodwascollected15and 60minafterrising.Thehorizontalpositionwasthenresumed, andadditionalsampleswereobtainedafterthesame time-pointstoevaluatewhetherchangeswerereversible.Thestudy confirmedameandecreaseinplasmavolumeof10.8% (equiv-alenttoaround500mLina70kgadult)after15min,which
DOIoforiginalarticle:http://dx.doi.org/10.1016/j.bjhh.2017.01.004.
夽
SeepaperbyLima-Oliveiraetal.inRevBrasHematolHemoter.2017;39(2):127–32.
∗ Correspondenceto:UniversidadeEstadualdeCampinas(UNICAMP),CentrodeHematologiaeHemoterapia,RuaCarlosChagas,480,
13104-184Campinas,SP,Brazil. E-mailaddress:erich@unicamp.br
remainedstableafteronehour.Thischangewascompletely reversedafterlyingdownagain,withameanincreaseintotal plasmavolumeof12.5%inhealthysubjects.Theseshiftsof totalplasmavolumewereaccompaniedbyinversechangesin hematocrit,whichincreased6.6%afteronehourofstanding, and decreased7.0%afterresumingthehorizontalposition. Interestingly, the magnitude of these changes were much higherinpatientswithedemaorhypoproteinemia,inwhom the meandecreaseintotalplasmavolumewas15.7%after onehour standing,andthe meanhematocrit increasewas 12.3%. Of note, while the change in hematocrit was com-pletely reversedafter returning tothe recumbent position, the behavioroftotalplasma volumewassomewhat differ-ent,in thatagreater increase intotalplasma volumewas observed afterlyingdown, witha mean valueof21% that reachinga30%increaseinsomepatients.3In1988,Leppanen
and Grasbeckevaluatedtheeffectofshiftingposture(from supine toseated to standing in differentorders; 15minin eachposition)in22healthywomen.Observedchangeswere moreevidentwhencomparingthesupinetostanding posi-tion,andstatisticallysignificantincreaseswereobservedin redbloodcellcount,hemoglobin,hematocrit,andwhiteblood cell(WBC)andplateletcounts.Inregardtothemagnitudeof thesechanges(meanvalues),hemoglobinvariedfrom12.8gto 13.5g/dL,hematocritfrom40.6to42.6%,plateletcountsfrom 297to320×109/L,andWBCcountsfrom7.37to7.62×109/L.4 Inthis issueofthe BrazilianJournalofHematologyand Hemotherapy, Lima-Oliveira et al.5 report the findings of
a study performed in 19 healthy volunteers that aimed
http://dx.doi.org/10.1016/j.bjhh.2017.03.007
revbrashematolhemoter.2017;39(2):100–101
101
to evaluatethe impact of posture changes in CBC values, withfocus on platelet and differential WBCcount. Similar resultswere obtainedconcerningredbloodcellparameters and platelet counts compared to the 1988 study. In addi-tion, increases in neutrophil and lymphocyte counts were alsodemonstrated,withmeanvaluesinsupineand stand-ing positions varyingfrom 3.2to 3.7×109/L forneutrophil countandfrom1.7to1.9×109/Lforlymphocytecount.These results confirm and extend previous reports,3,4,6,7
suppor-tingthe importance ofstandardizing samplecollection for laboratoryevaluations, asalreadyestablishedbymostCBC collectionguidelines.Whiletheclaimforclinicalsignificance ofthechangesreportedbyLima-Oliveiraetal.cancertainly bedisputed,oneshouldconsiderthatthemagnitudeofthese changescanalsobeinfluencedbyothervariablessuchas tem-perature,previousexercise,tourniquetuseandevenfainting duringsamplecollection,asrecentlyreviewed.8Accordingly,
the final bias caused by posture variations could be even higherin thereal world. Evenmoreimportant, the results ofFawcettandWynnshowingthatposture-inducedchanges intotal plasmavolume tendtobehigher inpatients than inhealthyindividualshighlightstheimportanceof consider-ingthesevariationsinourclinicalevaluations.Asaspecialty dealingwithpatientswhoseStarlingequationrarelyequals zeroandwhosesamplesarefrequentlyobtainedundervery diverseconditions,knowledgethatupto30%ofvariationsin totalplasmavolumecanbeattributedsolelytolyingdown shouldcertainlyinfluenceourpostureandourreasoning dur-ingclinicalevaluations.
Conflicts
of
interest
Theauthordeclaresnoconflictsofinterest.
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1.StarlingEH.Ontheabsorptionoffluidsfromtheconnective tissuespaces.JPhysiol.1896;19(4):312–26.
2.ThompsonWO,ThompsonPK,DaileyME.Theeffectofposture uponthecompositionandvolumeofthebloodinman.JClin Invest.1928;5(4):573–604.
3.FawcettJK,WynnV.Effectsofpostureonplasmavolumeand somebloodconstituents.JClinPathol.1960;13:304–10.
4.LeppänenEA,GräsbeckR.Experimentalbasisofstandardized specimencollection:effectofpostureonbloodpicture.EurJ Haematol.1988;40(3):222–6.
5.Lima-OliveiraG,GuidiGC,SalvagnoGL,DaneseE,Montagnana M,LippiG.Patientpostureforbloodcollectionby
venipuncture:Reopenthequestionofstandardizationafter28 years.RevBrasHematolHemoter.2017;39(2):127–32.
6.MawGJ,MackenzieIL,TaylorNA.Redistributionofbodyfluids duringposturalmanipulations.ActaPhysiolScand.
1995;155(2):157–63.
7.WaterfieldRL.Theeffectsofpostureonthecirculatingblood volume.JPhysiol.1931;72(June(1)):110–20.
