소아과학 개론

1. 소아과학 개론 삼성서울병원 소아청소년과 장 윤 실

2. 소아과학의 특징 • 임신-청소년기 • 성장과 발달 • “The child is not a little man” • 발육단계

3. 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

4. 소아인구의 동태

5. 영아 사망률

6. 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

7. 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

8. Newborn Infant

9. 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

10. The fetal to neonatal metabolic transition Function Before After • Temperature Uterine Brown fat • Gas exchange Placenta Lung • Waste Placenta Kidney • Activity Do nothing Eat and move • Energy Maternal glucose Fat & CHO • Environment Peace & Quiet Stress & Strain

11. Succes in transition • Ca. 10% : require some assistance • 1% : need extensive resuscitation • 90% : transition witout difficulty

12. 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

13. 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

14. 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)

15. 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

16. Circulation anatomyFetal vs Neonatal Placental Circulation Ductus Arteriosus Ductus Venosus Foramen Ovale Pulmonary Vasculature Myocardium

17. FETAL CIRCULATION Normal Anatomy

19. PLACENTAL CIRCULATIONinterruption of flow Immediate Decrease in Pre-load Immediate Increase in After-load

20. DUCTUS VENOSUS Mechanism of Closure not well understood Probably Passive

21. 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

22. PULMONARY VASCULATUREFetal • Very High PVR Early in Gestation • Progressive Rise in PAP • Rise in QP (3-10%) thru gestation

23. PULMONARY VASCULATURENewborn • Increased media:lumen Ratio • Immediate Rapid Fall in PVR • Slower Further Fall in PVR

24. FORAMEN OVALE Passive Closure due to increased left atrial flow and resultant increase in pressure

25. MYOCARDIUM Immature • Myocyte division only in fetus and early newborn • Smaller percentage of contractile proteins and mitochondria

26. PHYSIOLOGYFetal vs Neonatal • Pressure • Flow • Resistance • Contractility

27. RESISTANCE CHANGES • Decrease in PVR • Increase in SVR

28. PRESSURE CHANGES • Decrease in PAP due to decrease in PVR • Increase in LAP due to increase in PBF

29. FLOW CHANGES • PDA flow changes to L to R • FO flow changes to Lto R and dimishes rapidly

30. CONTRACTILITY • Immature Myocardium • High Resting Tension • Diminished Active Response

31. MYOCARDIAL MECHANICSImmature vs Mature • Contractile Proteins • Energy Utilization • Calcium Metabolism

32. MYOCARDIAL MECHANICS • Contractile Proteins • Myosin Heavy Chain* • Myosin Light Chain • Actin • Tropomyosin* • Troponin C • Troponin I* • Troponin T*

33. MYOCARDIAL MECHANICSContractile Proteins • Troponin I - inhibits Actin- Myosin interactions • Troponin T- binds troponin complex to thin fillament

34. MYOCARDIAL MECHANICSImmature • Myofibril number: fetus < newborn < adult • ATPase increases with maturation • ATPase determines velocity of muscle shortening

35. 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

36. MYOCARDIAL MECHANICSCalcium Metabolism • SR poorly formed in immature • Ca uptake by SR is depressed • Function of SR increases with maturation

37. SUMMARYAnatomy • Changes re-route blood • Flow to adapt to extra-uterine environment

38. SUMMARYPhysiology • Changes (most notably in PVR) permit the circulation to sustain life as maturation progresses

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

40. 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!

41. 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

42. Clothing ◆Clean scrub suit or gown when holding newborn ◆Hats. shoe covers, masks not routinely required

43. 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

44. 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

45. 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

46. Neonatal Concentrating Ability • Neonate cannot concentrate urine as well as adult Adult maximum 1200 - 1400 mosm/L Newborn maximum 600 - 700 mosm/L

47. 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.

48. 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.

49. 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.

50. FLUID BALANCE • Fluid Balance = Intake - Output • Output -Urine -GI -Skin -Lungs