Anatomy & Physiology

Question 1

Premature Infant

Answer 1

Less then 37 weeks gestational age

Question 2

Neonate

Answer 2

Less then 30 days old

Question 3

Infant

Answer 3

1 month to 1 year old

Question 4

Children

Answer 4

1 to 12 years old

Question 5

Adolescent

Answer 5

13 to 18 years old

Question 6

Gestational Age

Answer 6

Preterm = < 37 weeks
Term = 38 weeks
Post term = 42 weeks

Question 7

Brain Development:

Answer 7

25% neuronal cells present at birth
@ 1 yo cortex and brain stem nearly mature
brain weight doubles @ 6mo, triple @ 1 yo
Myelination not complete until 3 yo
BBB immature until 1 yo

Question 8

Spinal Cord Development:

Answer 8

nerve cell maturation until 6-7 yo
SC ends @ L3 at birth, L1 at 1 yo
Dural sac ends @ S3-4 at birth, S1-2 at 1 yo

Question 9

Autonomic Nervous System

Answer 9

Innervation to heart and blood vessels has vagal predomincance
SNS is immature, SNS innervation more developed and functional by 4-6 months

Question 10

Reasons for neonatal bradycardia

Answer 10

1 is hypoxia / drugs (succs, sevo, neostigmine), med error / acidosis, hypercarbia, hypoglycemia, hypothermia, hypovolemia, apneic periods, intubation, OCR, celiac

Question 11

Pain Response

Answer 11

Pain pathways present at birth
Response are behavioral and neuro-endocrine
Become tachycardic and HTN –> poss IVH/ICH
May have re-wiring of neuronal pain pathways with excessive/rept noxious stimuli

Question 12

Cranium Characteristics

Answer 12

Circum incr by 10cm by 1 yo
Supple and expansive w/ suture lines and fontanelles, allow assessment of hydration and ICP
Anterior - closes at 9-18 months
Posterior - closes at 4 months

Question 13

Upper Airway Characteristics

Answer 13

Tongue - large relative to oral cavity
Epiglottis - short, stiff, 45* posterior aim
Larynx - cephalad and anterior, at acute angle from tongue base to glottis - Prem @ C3, Infant @ C4, Adult @ C5-6
VC - concave shape/u-shaped (omega-shaped), vs adult rigid v shape

Question 14

Cricoid and Trachea Characteristics

Answer 14

Cricoid - narrowest part of pediatric airway, conical shape, creates risk of subglottic edema post extubation
Reaches adult shape/size at 12 yo
Trachea - shorter in pediatric pt (<1 yo 5-9cm), softer and easily compressed, R/L mainstem with similar angles

Question 15

Respiratory Muscles

Answer 15

Type 1 = slow twitch, resist fatigue, for sustained activity
Type 2 = fast twitch, fatigue easy
Diaphragm = Prem - 10% type 1, NB = 25% type 1, adult = 55% type 1
Intercostals - primarily type 2 fibers until 2 months
NB are diaphragmatic breathers

Question 16

Pulmonary Mechanics

Answer 16

Large abdo hinders diaphragm mvmt
All major airway tubes liable to be compressed d/t incr compliance (trachea, larynx, cricoid)
Neonates lung compliance less than adults, incr with age

Question 17

Thoracic Cage

Answer 17

Ribs extend horizontally, decr thorax expansion with respiration, soft and cartilaginous
Neonates chest wall 20-40x more compliant, decr with age
Retraction and small airway collapse d/t less mechanical support from rib cage,

Question 18

Lung Volumes

Answer 18

Neonates - decr TLC
Vt and Vd = to adults
Peds FRC < adults
Closing volume/CC - small caliber and decr elasticity contributes to early airway closure, CC occurs in Vt breathing, CC incr with Peds vs adults

Question 19

Induction Issues with Ventilation

Answer 19

Decr FRC (most in neos) + Incr CC + Incr BMR = mandatory supportive ventilation throughout induction, shortened apnea time
Decr compliance = care Vt/PC ventilation parameters, keep PAP low
Decr sensitivity of chemoreceptors, easily atelectatic, high O2 needs, reduced resp effort/compensation ability
Easily apneic once anesthetized with remaining paradoxical abdo/diaphragm breathing = incr Vd = V/Q mismatch

Question 20

Resp Control

Answer 20

Incr BMR = Incr MVe
Decr chemoreceptor responsiveness, poorly sustained compensation, depressed by hypoxemia/hyperoxemia
Hypoglycemia, hypothermia, anemia = resp depressants

Question 21

Surfactant

Answer 21

Two phospholipids = lecithin, sphingomyelin
Produced by type 2 pneumocytes, begins at 22 weeks, sharp incr @ 35-36 weeks
Decreased alveoli surface tension - P=2T/R (Laplace)
Role - incr compliance, stents alveoli/prevents collapse, promote gas exchange interface, decr WOB, keep alveoli dry

Question 22

Causes of Apnea

Answer 22

Anemia, hypothermia, hypoglycemia, acidosis, sepsis, physio stress, congenital anomolies

Question 23

Fetal Circulation Pathway

Answer 23

(+oxy blood) Placenta –> One Umb v. –> Liver/Ductus Venosis 50/50 –> IVC –> RA –> FO –> LA –> LV –> AscAo –> Upper body/brain
(-oxy blood) Upper body/brain –> SVC –> RA –> RV –> PA –> DA/Pulm –> DescAo –> lower body –> Two Umb a. –> placenta

Question 24

Unique Fetal Circ shunts/etc

Answer 24

Placenta - o2/co2 exchange, nutrients, wastes
Ductus Venosus - allows oxy blood to bypass liver to IVC
FO - intra atrial, allows oxy blood to bypass pulmo circ to AscAo
DA - allow blood to bypass fetal lungs to DescAo and placenta

Question 25

HD changes in transitional circulation

Answer 25

Inflated lungs --> decr PVR, decr RH pressures, assists in FO closure, incro PO2, increases LAP Placental loss --> incr SVR and Ao pressure, incr LH pressures, assists in FO closure DA with reversed flow with incr Ao pressure, Decr RH pressure, incr PO2 all assist with closure

Question 26

Shunt Closures

Answer 26

DA - fxnl @ 15h - 4days, anatomical 1 month FO - fxnl @ few hours, anatomical 1 year Delayed by patho factors that maintain fetal circ

Question 27

Persistent Fetal Circulation causes

Answer 27

hypoxia, acidosis, prematurity, congenital heart disease, prolonged physio stress, hypothermia, sepsis, mecon aspiration Pulmo vaso constriction from patho maintains incr RH to LH pressures, flows cont thru FO and DA, contributing to venous shunting and persistent hypoxia

Question 28

Neonatal cardiac output

Answer 28

7ml/kg/min vs adult of 3.9 ml/kg/min, maintained by HR, is vagally mediated system so incr HR is desirable Compliance is poor, undesirable location on F-S curve, poor contractile structure/organization, cells immature in Ca handling

Question 29

HR ranges, Hypotension Defined

Answer 29

``` Neos/NB = 85-205, BP < 60 1m-1yr = 100-190, BP <90 ```

Question 30

Blood Volumes

Answer 30

``` Neo - dependent on cord blood given, BP = circ volume PreNB = 90-100 ml/kg FTNB = 80-90 ml/kg 3m-3yr = 75-80 ml/kg 3-6yr = 70-75 ml/kg 6yr + = 65-70 ml/kg ```

Question 31

ECF:ICF proportions

Answer 31

Neo/Inf has increased amounts of ECF compared to ICF, which doesnt vary with age, ECF as %BW decr with age, TBW decr accordingly with EBV decr per age

Question 32

Hematopoetic Issues

Answer 32

Physio Infant anemia - d/t decr epo levels p/ birth with loss of hypoxic environment, h/h lowest 3-4m, h/h = 9-11/30-40

Question 33

Hemoglobin and oxy Curve

Answer 33

HbF - less responsive to 2-3DPG, shifted oxy curve to L, 2 alpha/gamm vs HbA 2 alpha/beta and incr resp to 2-3DPG NeoNatal Hb is 60-90% F, 3-4mo HbF/A is 50/50 P50 - NB = 20, 3mo = 30, adult = 27

Question 34

Glucose Levels, Tx of hypoglycemia

Answer 34

Prem = 20-65, Neo = 40-100, Inf/Child = 60-115 | Tx: 1-2 cc/kg D50 diluted to D10 (too hypertonic --> IVH)

Question 35

Neos At risk for hypoglycemia / signs and symptoms

Answer 35

Overall Neo with immature liver and limited glycogen stores. At risk: born from DM mothers, hyperalimentation, SGA, prolonged fasting, premature resp distress, apnea, tachy-bradycardia, lethargy, cyanosis, tremors, diaphoresis, hypotension

Question 36

Hepatic Drug Metabolism

Answer 36

Decr d/t decr liver blood flow and decr CP450 enzyme conc and function. Enzymes fully active at 2-3mo, mature/adult at 2-3yr

Question 37

Hyperbilirubinemia

Answer 37

Occurs during first week, primarily d/t excess bili from RBC bkdown (physio jaundice), limited hepatic uptake of bili, and decr hepatic conjugation. Pathological hemolysis of NB with Rh incompatibility.

Question 38

Renal Issues

Answer 38

Neonate has decr renal function d/t low renal blood flow and decr GFR. At risk for fluid overload with rapid admin, unable to excrete excess lytes/fluid, drugs. Tend to loose sodium and water. Limited responses to aldosterone and ADH. Overall low GFR, decr Na retention and drug excretion.

Question 39

GI Issues

Answer 39

High risk for aspiration with decr LES tone, increase incidence of GERD <1yr. Poor breathing/swallowing coordination.

Question 40

Thermoregulation: Factors that increase heat loss

Answer 40

Large BSA to weight, decr subQ tissue, thin skin.

Question 41

NonShivering Thermogenesis

Answer 41

Increases core temp by metabolism of brown adipose tissue in mediastinum, kidneys, adrenals, neck and scapula. Hypothermia --> catecholamines --> triglycerides metab to FA and glycerol --> rls heat. Byproducts contribute to acidosis, pulm/peri vasoconstriction, hypoxia and r->l shunting.

Question 42

Mechanisms for Heat Loss

Answer 42

``` #1 - Radiation, heat loss from body to environment, gradient = patient --> environment #2 - Convection, heat loss from body by ambient cool current air = patient --> air, rises, replaced by cool air #3 - Evaporation, heat loss from vapor press difference between body surface and environment = sensible and insensible loss, prep solutions (skin and lungs, 20% of heat loss) #4 - Conduction, heat loss from exposed body to cooler surface = patient --> table/blanket/fluids ```

Question 43

Methods to Prevent Hypothermia

Answer 43

Incr room temp / heating blankets / sterile drapes / radiant heat / heated fluids/irrigation / covering head (loose 60% of heat) /HME / low gas flows Most Eff way to maintain normothermia = warm OR Most Eff way to rewarm hypothermia = forced air warmer

Question 44

Core Temp Monitoring Sites

Answer 44

Esophageal, tympanic likely to produce most accurate, simplest core temps. Also consider nasopharyngeal if correctly placed