pediatric anatomy, physiology & pharmacology

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1、PediatricAnatomy,Physiology&Pharmacology848thFSTIntroductionOfprimaryimportancetothepediatricanesthesiaprovideristherealizationthatinfantsandchildrenarenotsimplyasmalladult.Theiranestheticmanagementdependsupontheappreciationofthephysiologic,anatomicandpharmacologicdifferencesbetw

2、eenthevaryingagesandthevariableratesofgrowth.Alsoofimportanceisageneralknowledgeofthepsychologicaldevelopmentofchildrentoenabletheanesthetisttoprovidemeasurestoreducefearandapprehensionrelatedtoanesthesiaandsurgery.DefinitionsPretermorPrematureInfant:<37weeksTermInfant:38-42weeksg

3、estationPostTermInfant:>42weeksgestationNewborn:upto24hoursoldNeonate:1-30daysoldInfant:1-14monthsoldChild:14monthstopuberty(~12-13years)BodySizeThemostobviousdifferencebetweenchildren&adultsissizeItmakesadifferencewhichfactorisusedforcomparison:anewbornweighing3kgis1/3thesizeofan

4、adultinlength1/9thebodysurfacearea1/21theweightBodysurfacearea(BSA)mostcloselyparallelsvariationsinBMR&forthisreasonBSAisabettercriterionthanageorweightforcalculatingfluid&nutritionalrequirementsBodySizeFetalDevelopmentThecirculatorysystemisthefirsttoachieveafunctionalstateinearly

5、gestationThedevelopingfetusoutgrowsitsabilitytoobtain&distributenutrientsandO2bydiffusionfromtheplacentaThefunctioningheartgrows&developsatthesametimeitisworkingtoservethegrowingfetusAt2monthsgestationthedevelopmentoftheheartandbloodvesselsiscompleteIncomparison,thedevelopmentofth

6、elungbeginslater&isnotcompleteuntilthefetusisneartermFetalCirculationPlacentaGasexchangeWasteeliminationUmbilicalVenousTensionis32-35mmHgSimilartomaternalmixedvenousbloodResult:O2saturationof~65%inmaternalblood,but~80%inthefetalumbilicalvein(UV)LowaffinityoffetalHgb(HgF)for2,3-DPG

7、ascomparedwithadultHgb(HgA)Lowconcentrationof2,3-DPGinfetalbloodO2&2,3-DPGcompetewithHgbforbinding,thereducedaffinityofHgFfor2,3-DPGcausestheHgbtobindtoO2tighterHigherfetalO2saturationFetalCirculationP50is27mmHgforadultHgb,butonly20mmHgforfetalHgbThiscausesaleftshiftintheO2dissoci

8、ationcurveBecausethebridgebetween