소아과학 개론

소아과학 개론 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 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 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 anatomy Fetal vs Neonatal Placental Circulation Ductus Arteriosus Ductus Venosus Foramen Ovale Pulmonary Vasculature Myocardium FETAL CIRCULATION Normal Anatomy PLACENTAL CIRCULATION interruption 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 VASCULATURE Fetal  Very High PVR Early in Gestation  Progressive Rise in PAP  Rise in QP (3-10%) thru gestation PULMONARY VASCULATURE Newborn  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 PHYSIOLOGY Fetal 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 MECHANICS Immature 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 MECHANICS Contractile Proteins  Troponin I - inhibits Actin- Myosin interactions  Troponin T- binds troponin complex to thin fillament MYOCARDIAL MECHANICS Immature  Myofibril number: fetus < newborn < adult  ATPase increases with maturation  ATPase determines velocity of muscle shortening MYOCARDIAL MECHANICS Energy 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 MECHANICS Calcium Metabolism  SR poorly formed in immature  Ca uptake by SR is depressed  Function of SR increases with maturation SUMMARY Anatomy  Changes re-route blood  Flow to adapt to extra-uterine environment SUMMARY Physiology  Changes (most notably in PVR) permit the circulation to sustain life as maturation progresses SUMMARY Myocardial 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 →↑IWL 2)↑BSA→↑IWL 3)↑Skin Thickness → IWL 4)↑G.A.→ IWL 5)↑Postnatal Age → IWL 1)↑Humidity→ IWL 2)↑Temp & Temp→↑IWL 3) Overhead heater→↑IWL 4) Bililights→↑IWL