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Flashcards in Pediatrics Deck (43)
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1

Neonatal period:

age

PGA calculation

What is considered low birth rate?

Extremely low gestational age?

  • Neonate is birth to 30 days old
  • PGA =(# weeks gestation at birth) + (current age in weeks)
    • post-op admission for pts <60 weeks PGA
  • Pre-term <37 weeks
  • Low birth rate <2500 grams
  • ELGAN = 23-27 weeks

2

All pre-term patients have potential for what problems?

(8)

  • respiratory distress
  • apnea
  • hypoglycemia
  • electrolyte disturbances (low mg and Ca)
  • infection
  • hyperbilirubinemia
  • polycythemia
  • thrombocytopenia

3

What are the risks for babies of normal gestation?

postmature?

former premature up to 60 weeks PGA?

  • Normal gestation: 37-40 weeks
    • congenital anomalies
    • viral infections
    • perinatal depression
    • fetal alcohol
    • thrombocytopenia
  • Postmature: >42 weeks (the above risks +...)
    • meconium aspiration
    • birth trauma if LGA
    • hypoglycemia (esp if mother is diabetic)
    • hyperbilirubinemia
  • Up to 60 weeks PGA
    • post-op apnea and bradycardia (often require 12 hour admission)

4

Describe fetal circulation

  • oxygenated blood leaves placenta via umbilical vein
  • blood bypasses the liver via the ductus venosus to go straight to the IVC
  • Portion of this blood "Jet streams" straight across Right atrium through Foramen ovale into left atrium to then be pumped through ventricle and aorta
  • *Remaining blood goes normal route to right ventricle and PA.  High pulmonary vascular resistance forces most of this blood through the Ductus arteriosus from PA to Aorta

5

What are the primary changes that occur to fetal circulation at birth?

(6)

  • ductus venosus closes
  • blood is now oxygenated via lungs
  • ductus arteriosus closes (d/t increased arterial O2 concentration)
  • pulmonary vascular resistance decreases
  • peripheral vascular resistance increases
  • foramen ovale closes
    • true closure is weeks later and 25-30% of adults have patent foramen ovale

6

What is transitional circulation and what causes it?

How can it be prevented?

  • occurs at birth and first several weeks of life
  • hypoxia, hypercapnia, or hypothermia can lead to increased pulmonary artery pressure, reversal of flow through the foramen ovale, re-opening of ductus arteriosus and shunting
    • hypoxia is #1 cause
  • Prevention with optimal oxygenation, correct acidosis, keep pt warm

7

How does the neonatal cardiovascular system differ?

  • Heart:
    • structurally immature
    • fewer myofibrils
    • sarcoplasmic reticulum immature
    • cardiac calcium stores reduced
  • Ventricles less compliant
    • CO is HR dependent
    • increased preload does not increase SV as much as in an older child
  • Baroreceptor reflex immature in the neonate causing inability to compensate for hypotension with reflex tachycardia
  • Parasympathetic dominance- tendency to brady

8

What is the resting CO for a neonate at birth?

infant?

adolescent?

  • neonate at birth: 400 ml/kg/min
  • infant: 200 ml/kg/min
  • adolescent:100 ml/kg/min

9

Neonates are vulnerable to problems caused by citrated blood products because __________.

 

__________ is the preferred treatment of badycardia and decreased cardiac output in pediatric patients.

they are dependent on ionized calcium

 

 

Epi

10

How does the neonatal pulmonary system differ?

 

  • Fewer and smaller alveoli- they increase in number and size up until 8 yo
  • Infants have a small airway diameter and increased resistance
  • Highly compliant airway and chest wall - easy to see retractions
  • Closing capacity is greater than FRC in very young and very old
    • airway closure can occure before end exhalation--leads to shunting and dead space
  • Early fatigue and diaphragmatic and intercostal muscles until age 2 b/c type 1 muscle fibers are not mature
    • neonates have 10%, 2 yr and greater have 55%
  • O2 consumption is 2-3x an adult

11

Describe the airway anatomy of an infant

(10)

  • larger tongue in smaller submental space
  • higher larynx (C2-C4)
  • short stubby (omega shaped) epiglottis
  • angles vocal cords (caudal slant)
  • funnel shaped larynx with narrowest region @ cricoid ring
  • obligate nasal breathers
  • large occiputs that affect sniffing position (use shoulder roll)
  • edentulous
  • short trachea (4-5 cm)
  • angulation of right mainstem bronchus

12

Airway differences comparing infant to adult

(table)

13

Compare between an adult and neonate: (table)

Oxygen consumption

alveolar ventilation

respiratory rate

TV

14

How does the pediatric airway affect gas flow?

 

A 50% reduction in radius increases the pressure ___-fold

  • young children have elevated airway resistance at baseline
    • swelling can have huge impact by increasing resistance
  • Turbulant airflow is present to 5th bronchial division
  • 32-fold

15

How does the pediatric neurological system differ?

O2 consumption

CBF

growth

other things...

 

  • Oxygen consumption and CBF is about 50% greatr in children than adults
    • adults: 3.5 ml blood flow/100 g brain mass
    • neonates: 5.5 ml/100g
  • Myelinization and synaptic connections not complete until age 3-4 years
  • Rapid brain growth in first 2 years
  • Conus medullaris at L3 at birth, migrates to L1 or L2 by 3 yo
  • Fontanels: anterior closed by 18 months, posterior closed by 2 mo

16

What does recent research say about anesthesia-induced developmental neurotoxicity?

 

  • Increased and accelerated neuroapoptosis occurs with virtually all anesthetics
  • Single exposures of short duration are usually of no consequence
  • Repeated and/or prolonged exposures at a young age (<3-4 years) may be associated with later behavioral and learning difficulties
  • ***evidence is inconclusive

17

What are differences you should consider with neuraxial in pediatrics?

  • The conus medullaris ends at L1 in adults and at the L2-L3 in neonates and infants
  • Iliac crest is even with L4-L5 or L5-S1 interspace (similar to adults) so it is still well below the conus medullaris
  • Dural sac terminates more caudally (S3) in neonates and infants than in adults (S1)
  • Infants have less lumbar lordosis leading to increased risk of high spinal with changes in positioning

18

How does the renal system change from infancy through childhood?

  • GFR is signifincantly impaired at birth but improves throughout the 1st year
    • premature infants will take longer to reach renal maturation
  • Renal tubular concentrating abilities do not achieve full capacity until about 2 yr
  • Half-life of medications excreted by glomerular filtration are prolonged in the very young
  • During childhood, renal clearance rate may be higher than adult clearance rates
    • drug half life is shorter that adults for kids >2yr

19

How is liver function different in pediatrics?

  • Enzyme systems are still developing up until 1 yr
  • At birth Phase I Cytochrome P450 system is 50% of adult values and Phase II (conjugation reactions) are impaired in neonates
    • Causes longer half life on BZD and morphine
    • deceased bilrubin breakdown d/t reduction in glucuronyl transferase (also affects tylenol metabolism)
  • Hepatic synthesis of clotting factors reach adult levels withing one week of birth
  • Lower levels of albumin and other proteins for drug binding in newborns--> causes larger proportion of unbound drug and increased effects
  • Minimal glycogen stores- prone to hypoglycemia

20

How does the GI system differ in pediatrics?

  • Coordination of swallowing with respiration is not mature until 4-5 months of age 
    • causes high incidence of reflux
  • Gastric juices are less acidic up to about 3 years
  • Absorption of oral medications is slower compared to adults
  • GI tract is slower (slower emptying time)

21

What is the significance of thermoregulation in pediatric patients?

< 3 months old?

factors that contribute?

  • They have large body surface area to weight ratio
  • lack subq tissue for an insulator
  • < 3 months:
    • inability to shiver
    • metabolize brown fat to increase heat production
    • can lead to metabolic acidosis and increased O2 consumption
  • Factors that contribute:
    • cold OR
    • anesthetic-induced vasodilation
    • room temp IV fluids
    • evaporative heat loss from surgical site
    • cold irrigating solutions
    • cold anesthetic gases

22

What are the ways heat is lost in the OR?

(pic)

  1. conduction
  2. evaporation
  3. convection
  4. radiation

23

How can you actively warm a pediatric patient?

  • warming mattress
  • incubator
  • cover with blankets
  • head coverings
  • transport in isolette
  • humidify gases
  • use plastic wrap on the skin
  • warm prep and irrigation solutions
  • change wet diapers and remove wet clothing
  • Forced air warming **most effective strategy for childre >1 yr**

24

How should you monitor temp?

How should you not?

What are some problems that hypothermia can cause?

  • Core temp is best (esophageal)
  • Axillary temp can recognize MH earlier
  • NO Forehead temp!  10 MH episodes unrecognized w/forehead temp
  • Hypothermia:
    • delayed emergence
    • reduced degradation of drugs
    • increased infection

25

How does body composition vary over the age spectrum?

(table)

*know trends, not actual numbers

26

How does the difference in body composition affect anesthesia?

  • Higher total body water:
    • Water sluble drugs have a larger volume of distribution
      • need a larger initial dose (sch, abx)
      • larger distribution can delay excretion
  • Neonates have less fat and muscle
    • drugs that depend on redistribution to fat for termination of action will have prolonged effects
  • Protein binding: <6 mo have less albumin and alpha-1 acid glycoprotein (AAG)
    • higher free-fraction of protein bound drugs
    • free fraction of local anesthetics will be higher (bind to AAG)

27

In general, most medications will have a _______ elimination half-life in pre-term and term infants, a _______ half-life in children older than 2 yrs up to early teen years, and a ________ of half-life in those approaching adulthood.

In general, most medications will have a prolonged elimination half-life in pre-term and term infants, a shortened half-life in children older than 2 yrs up to early teen years, and a lengthening of half-life in those approaching adulthood.

28

How do you calculate maximum allowable blood loss (MABL)?

29

How does fetal hgb differ from adult hgb?

Target hct for neonates?

  • Fetal Hgb has a lower P50 at 19 mmhg compared to 26 mmHg in adults
    • LEFT shift
  • Target HCT is higher in neonates d/t L shift and decreased CV reserve
    • minimum HCT of 40% instead of 30%

30

What is the expected hgb and hct for: (table)

newborn

3 mo***

6-12 mo

adult female

adult male

*** physiologic anemia at 2-3 mo