소아과학 개론
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소아과학 개론. 삼성서울병원 소아청소년과 장 윤 실. 소아과학의 특징. 임신 - 청소년기 성장과 발달 “The child is not a little man” 발육단계. 소아기의 구분. 출생 전기 (prenatal period) 신생아기 (neonatal period) 생후 4 주간 ( 좁은 의미 생후 1 주간 ) Perinatal period ( 주산기 ): 재태 22 주 - 생후 1 주 사망과 장기 예후 관련 영아기 (infancy) : 1 개월 -1 년 (2 년 )

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소아과학 개론

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소아과학 개론

삼성서울병원 소아청소년과

장 윤 실


소아과학의 특징

  • 임신-청소년기

  • 성장과 발달

  • “The child is not a little man”

  • 발육단계


소아기의 구분

  • 출생 전기 (prenatal period)

  • 신생아기 (neonatal period)

    • 생후 4주간 (좁은 의미 생후 1주간)

    • Perinatal period (주산기): 재태 22주-생후 1주

      • 사망과 장기 예후 관련

  • 영아기 (infancy) : 1개월-1년 (2년)

  • 유아기 (preschool period or early childhood): 2세-5세

  • 학령기 (prepuberal period or late childhood): 6-10세

  • 사춘기(Puberty), 청소년기(Adolescence):11-20세, 개인차

    • 남자: 12-20년

    • 여자: 10-18년


소아인구의 동태


영아 사망률


사망의 원인

  • 1세 미만:

    • 주산기 질환-선천개형-미분류-호흡기계

  • 1-4세:

    • 불의의사고-신생물-선천기형-호흡기계

  • 5-9계:

    • 불의의 사고-신생물-신경계질한-타살-선천기형

  • 10-14계:

    • 불의의 사고-신생물-신경계 질환-자살-선천기형

  • 15-19세:

    • 불의의 사고-자살-신생물-신경계질환-순환기질환


성장과 발달

  • 장기별 성장 유형

    • 일반형: 키, 체중 호흡기

      • S자형 : 영아기, 사춘기 급성장

    • 신경형: 뇌, 척수, 시각기, 두위

      • 출생초부터 급성장하여 4세경에 이미 성인 수준

    • 림프형: 가슴샘, 림프절, 편도 등

      • 10-12세 성인의 2배, 이후 퇴축하여 18세경 성인수준

    • 생식형: 생식기, 유방, 음모, 자궁, 전립선

      • 사춘기부터 급성장 16-18세 성인수준


Newborn Infant


Definition of the Newborn

  • Infants below 28 days of life

  • Transition from dependent fetal period to non-dependent neonatal period

  • Most friable period of whole ages


The fetal to neonatal metabolic transition

FunctionBeforeAfter

  • Temperature UterineBrown fat

  • Gas exchangePlacentaLung

  • WastePlacentaKidney

  • ActivityDo nothingEat and move

  • Energy Maternal glucoseFat & CHO

  • EnvironmentPeace & QuietStress & Strain


Succes in transition

  • Ca. 10% : require some assistance

  • 1% : need extensive resuscitation

  • 90% : transition witout difficulty


Body Temperature Control

  • Easy to lose heat

    - Relatively large body surface area

    - Poor Insulation

  • Mechanisms of heat loss

    - Convection, Evaporation,

    Radiation, Conduction

  • Cold Stress :

    - Hypoxia, Hypoglycemia, Acidosis


Hematologic Values at Birth

  • Site of Sampling

    ·Capillary samples higher than venous

    -Especially if prematurity, hypotension, acidosis, anemia

  • Treatment of Umbilical Vessels

    ·Placental vessels contain 75-125 mls blood

    ·Can increase blood volume of newborn by 61%

    ·Placing infant below mother increases placental

    transfusion, completion within 30 sec

  • Blood Volume

    ·Term 85 ml/kg

    ·Preterm 90-105 ml/kg

    ·One month 75 ml/kg


Hemostasis in the Newborn

  • Platelet-vessel interaction

    ·Adhesion-Platelets bind exposed collagen via

    surface glycoprotein lb Von Willebrand

    factor interaction

    ·Aggregation-Platelets activated (by collagen

    binding)and expose fibrinogen binding sites

    (glycoproteins llb-llla)

  • Normal platelet cts, but decreased platelet aggregation in newborns

  • Bleeding time normal (modified template of lvy bleeding time device)


Hemostasis in the Newborn

  • Procoaqulant System

    ·Coagulation proteins synthesized by fetus

    ·Coagulation proteins do not cross placenta

    ·Appear by 10 weeks, increase t/o gestation

    ·Fibrinogen conc. slighly lower at birth

    ·Normal levels of V, VIII, and vWF

    ·"Physiologically" low levels of vit K

    dependent factors II, VII, IX and X


Circulation anatomyFetal vs Neonatal

Placental Circulation

Ductus Arteriosus

Ductus Venosus

Foramen Ovale

Pulmonary Vasculature

Myocardium


FETAL CIRCULATION

Normal Anatomy


PLACENTAL CIRCULATIONinterruption of flow

Immediate Decrease in Pre-load

Immediate Increase in After-load


DUCTUS VENOSUS

Mechanism of Closure not

well understood

Probably Passive


DUCTUS ARTERIOSUS

  • Functional Closure at 10-15 hr.

  • Constriction of Media due to O2

  • Obliteration may take weeks

  • Effect of Vasoactive Substances

    - less well defined


PULMONARY VASCULATUREFetal

  • Very High PVR Early in Gestation

  • Progressive Rise in PAP

  • Rise in QP (3-10%) thru gestation


PULMONARY VASCULATURENewborn

  • Increased media:lumen Ratio

  • Immediate Rapid Fall in PVR

  • Slower Further Fall in PVR


FORAMEN OVALE

Passive Closure due to

increased left atrial flow

and resultant increase

in pressure


MYOCARDIUM Immature

  • Myocyte division only in fetus

    and early newborn

  • Smaller percentage of contractile

    proteins and mitochondria


PHYSIOLOGYFetal vs Neonatal

  • Pressure

  • Flow

  • Resistance

  • Contractility


RESISTANCE CHANGES

  • Decrease in PVR

  • Increase in SVR


PRESSURE CHANGES

  • Decrease in PAP due to

    decrease in PVR

  • Increase in LAP due to

    increase in PBF


FLOW CHANGES

  • PDA flow changes to L to R

  • FO flow changes to Lto R

    and dimishes rapidly


CONTRACTILITY

  • Immature Myocardium

  • High Resting Tension

  • Diminished Active Response


MYOCARDIAL MECHANICSImmature vs Mature

  • Contractile Proteins

  • Energy Utilization

  • Calcium Metabolism


MYOCARDIAL MECHANICS

  • Contractile Proteins

  • Myosin Heavy Chain*

  • Myosin Light Chain

  • Actin

  • Tropomyosin*

  • Troponin C

  • Troponin I*

  • Troponin T*


MYOCARDIAL MECHANICSContractile Proteins

  • Troponin I - inhibits Actin-

    Myosin interactions

  • Troponin T- binds troponin

    complex to thin fillament


MYOCARDIAL MECHANICSImmature

  • Myofibril number:

    fetus < newborn < adult

  • ATPase increases with maturation

  • ATPase determines velocity of

    muscle shortening


MYOCARDIAL MECHANICSEnergy Utilization

  • Mitochondria are major source of

    high energy phosphate

  • Decreased number of MC in

    immature myocardium

  • Relative lack of enzyme for FFA

    transport into MC


MYOCARDIAL MECHANICSCalcium Metabolism

  • SR poorly formed in immature

  • Ca uptake by SR is depressed

  • Function of SR increases with

    maturation


SUMMARYAnatomy

  • Changes re-route blood

  • Flow to adapt to extra-uterine

    environment


SUMMARYPhysiology

  • Changes (most notably in PVR)

    permit the circulation to sustain

    life as maturation progresses


SUMMARYMyocardial Mechanics

Adaptation to extra-uterine condition is more gradual, probably because of the cellular and molecular processes involved


Infection Control - Basic Principles

  • Exclude ill personnel/visitors

    (often the source)

    - Respiratory Infection (RSV common)

    - Skin Infection

    - Diarhea

    - Fever

    - Cold Sores (Herpes Labialis)

  • Orient to Universal Precautions & Isolation Procedures

  • The usual problem is Poor Handwashing!


Handwashing

◆ 2 minute scurb at beginning of day

◆ 15 second wash before and after touching any patient

◆ A void self-contamination - touching eyes, face, nose, mouth, phone, other, objects not exclusive to the patient


Clothing

◆Clean scrub suit or gown when holding newborn

◆Hats. shoe covers, masks not routinely required


Renal Response to Sodium Load

  • Normal adult renal response to Na load is to increase Na excretion.

  • Newborn kidney able to respond to Na load but, not as well as adult.

    - proximal tubule decreases FRN

    - but distal nephron increases Na reabsorption

    more than adult

    - net result is less Na excretion in newborn

    than adult

  • Preterm infant < 36 weeks responds better to Na load than term infant


Excretion of K in Neonate

  • Mechanisms qualitatively similar in immature and mature kidney

  • Newborn cannot excrete K load as well as adult

    ↓K secretory ability of distal nephron

    ↓Distal Na-K-ATPase activity

    ?↓response to aldosterone

    ↓distal H2O & Na delivery (due to low GFR)

    permeability characteristics of cell membranes


Response to H2O Load

  • Newborns do not respond as well as adults to H2O load

    - Low GFR

  • Newborn can produce very dilute urine (50 mosm/L)

  • Fetus can and does produce dilute urine


Neonatal Concentrating Ability

  • Neonate cannot concentrate urine

    as well as adult

    Adult maximum 1200 - 1400 mosm/L

    Newborn maximum 600 - 700 mosm/L


Renal Glucose Handling

  • Glucose usually reabsorbed completely in proximal tubule

  • Maximum glucose reabsorption (TmG) lower in newborn than adult kidney

  • However, TmG/GFR equivalent in both groups

  • Renal threshold for glucose (level of plasma glucose at which glucose is excreted) lower in newborn than adult.


Glucose threshold

  • Glucose excreted at lower plasma glucose in younger animal

  • Thus newborn especially preterm infant more likely to spill glucose

  • Thus newborn prone to osmotic diuresis

  • Thus solute & H2O excretion increases & H2O intake requirements increase when glucose excreted.


Changes in Body H2O with Development

  • TBW (as % body weight) falls with development mostly in fetal, neonatal and early infant period.

  • Fall in TBW due to fall in ECF.


FLUID BALANCE

  • Fluid Balance = Intake - Output

  • Output-Urine

    -GI

    -Skin

    -Lungs


FACTORS AFFECTING IWL IN NEONATES

  • Environmental Factors

    Humidity

    Temperature

    Incubator vs Overhead Heater

    Bililights


FACTORS AFFECTING IWL IN NEONATES

  • Infant Factors

    - Minute ventilation (VE)

    - Body surface area

    - Skin thickness

    - Gestational Age

    - Postnatal Age


1) ↑ VE →↑IWL2)↑BSA→↑IWL3)↑Skin Thickness → IWL4)↑G.A.→ IWL 5)↑Postnatal Age → IWL


1)↑Humidity→ IWL

2)↑Temp & Temp→↑IWL

3) Overhead heater→↑IWL

4) Bililights→↑IWL


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