Pedi Anesthesia

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ariadne9
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265623
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Pedi Anesthesia
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2014-03-09 15:48:20
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BC Nurse Anesthesia
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Adv Principles
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  1. When does organogenesis occur in the fetus?
    first 8 weeks following conception
  2. When does the fetus develop organ function
    2nd trimester
  3. Prematurity
    Birth before 37 weeks gestation
  4. Postmaturity
    Birth after 42 weeks gestation
  5. Low birth weight
    < 2500 g
  6. T or F, infants that are premature, post mature, high BW, or low BW are more likely to have anesthesia issues
    T
  7. Avg newborn body weight
    3.5 kg
  8. Avg weight, 1 mo to 6 mo
    4 kg
  9. Avg weight, 1-2 yrs
    10 kg
  10. Formula to estimate child weight
    Age (years) x 2 + 9= wt in kilos
  11. Pressure difference between pulmonary and systemic circulation in the fetus vs. the adult
    • Adult- large pressure difference, avg PA pressure = 15, avg MAP= 100
    • Fetus- not a large pressure difference as the pulmonary circuit pressure is high due to to HPV
  12. What factors cause the DA and FO to close when the infant is born and takes a breath?
    Pressure difference, pulmonary vascular pressures decrease and the blood takes the path of least resistance.
  13. Describe the path of fetal circulation- well oxygenated blood
    • Oxygenated blood leaves the placenta via the umbilical vein
    • Half is shunted by the ductus venous and goes to the IVC
    • Other half passes thru the liver
    • Hence blood entering the IVC is mixed
    • Well oxygenated IVC blood enters the RA
    • Passes thru FA to LA
    • To LV and pumped into ascending aorta
    • This well oxygenated blood goes to: coronary arteries, upper body and brain (majority), and rest of fetal body
  14. Describe path of fetal circulation- poorly oxygenated blood
    • Poorly oxygenated blood comes from the IVC (after going thru the hepatic circulation) and from the SVC 
    • Enters the RA, goes to RV, to PA
    • Thru ductus arteriosus (low O2 tension of this blood increases PVR) 
    • Then to descending aorta
    • This blood supplies the lower extremities
    • Then goes to umbilical arteries back to placenta for gas exchange
  15. Risk factors for returning to pulmonary circulation in an infant
    • Stress
    • prematurity
    • infection
    • acidosis
    • pulmonary dz- hypercarbia or hypoxemia
    • Meconium aspiration
    • Hypothermia
    • CHD
  16. Why might hypoxia, hypercarbia, and anesthetic agents cause the infant to revert to fetal circulation
    • All increase PVR
    • PA may increase to systemic levels causing blood to be shunted thru DA and FO
  17. Why might hypoxic events be prolonged in infants?  Does supplemental O2 help?
    • Blood gets shunted via the fetal circulation
    • No, because there's a shunt
  18. How does the normal pedi heart differ from the adult heart?
    • Less contractile mass (not as strong)
    • Less compliant ventricles (stiffer)
    • Poor tolerance of increased after load (not that strong)
    • HR dependent CO
    • Underdeveloped compensatory mechanisms- can't compensate for hypotension with tachycardia
    • Increased O2 consumption
    • Lower BP
    • Fixed SV
  19. Normal O2 consumption in a newborn, child, adult
    • Newborn 5-8 ml /kg/ min
    • Child 4-6
    • Adult 3-5
  20. Avg newborn and infant HR
    • Newborn 133 bpm
    • Infant (6-12 mo) 120 bpm
  21. Avg newborn and infant SBP
    • Newborn- 80
    • Infant- 6 mo- 90
    • 12 mo- 96
  22. Avg HR 2 yo, 5 yo, 12 yo
    • 2 yo 105 bpm (+ / - 25)
    • 5 yo 90 bpm (+ / - 10)
    • 12 yo 70 bpm (+ / - 17)
  23. Avg SBP 2 yo, 5 yo, 12 yo
    • 2 yo 100 (+ / - 25)
    • 5 yo 100 (+ / - 14)
    • 12 yo 115 (+ / - 18)
  24. Describe the differences between the infant and adult pulmonary systems
    • Smaller airways- more rx to airflow
    • Poorly maintained negative intrathoracic pressure (can't take a large negative P breath)- higher closing capacity
  25. Infant RR and FRC compared to adults
    • RR- higher
    • FRC- lower
  26. T or F, infants have well developed hypoxic and hypercapneic drives?
    F, especially poorly developed in premies
  27. Pedi airway differences (4 major)
    • Large occiput (causes neck flexion when supine)
    • Large tongue size in relation to mouth size
    • Larynx is higher in neck (C3-4 vs C4-5 in adults)
    • Narrowest portion is at cricoid ring
  28. Narrowest point in the airway
    -adult
    -pedi
    • Adult- glottis
    • Pedi- cricoid
  29. What physiologic differences explains why infants experience respiratory fatigue faster than adults
    • Decreased number of type 1 muscle fibers (don't normalize until 2 years)
    • Underdeveloped intercostal muscles
  30. Why might an uncuffed ETT be preferable in peds < 6 yo?
    • Narrowest point is below the vocal cords
    • Risk of cuff inflation causing tracheomalacia
  31. Can a cuffed ETT be used in peds?
    Yes, use a size smaller
  32. Differences in TBW composition in preterm, vs term infants, vs 1 yr, vs adult ?
    What is the implication of this?
    • Preterm 85%
    • Term 80%
    • 1 yr 60%
    • Adult 50%
    • Water soluble drugs have a larger Vd
  33. Differences in fat composition in term infants, vs 1 yr, vs boy puberty, vs girl puberty?
    • Infant 12%
    • 1 yr 30%
    • Boy 10-15%
    • Girl 20-30%
  34. Differences in kidney function in peds
    • Kidney function is decreased in neonates and premies
    • Neonates have limited ability to conserve sodium and dilute / concentrate urine
    • Normal GFR after 1 year
    • Normal tubular function after 3 years
  35. How do the endogenous Ca++ stores of the infant compare to that of the adult?
    Decreased
  36. T or F, infants are at risk for large evaporative water losses, hyponatremia, hypoglycemia, and hypocalcemia?
    T!
  37. T or F, the half life of renal excreted meds is unchanged in infants
    F, it is prolonged
  38. Infant liver function
    Functional maturity is incomplete
  39. Is the infant's ability to metabolize drugs increased or decreased?  Why?
    Increased, due to increased hepatic blood flow and ability to induce C450 enzyme system with introduction of drug
  40. Is the infant's ability to conjugate drugs (phase 2 reaction) increased or decreased?  What is the implication of this?
    • Decreased, may reach adult activity by 1 yr
    • Increased drug half life of benzos and morphine
  41. T or F, the ability of the neonate to metabolize specific drugs is dependent on drug specific cytochromes and enzyme subfamilies?
    T
  42. Infant glycogen stores compared to adult, what are the implications of this?
    • Decreased glycogen stores
    • Risk of hypoglycemia, acidemia, inability to handle a large protein load
  43. glycogen
    Storage form of glucose
  44. T or F, GERD is uncommon in newborns and premies?
    F, many infants on GI prophylaxis
  45. GI pH
    1st day of life
    2nd day of life
    • 1st day- alkalotic
    • 2nd day- normal adult pH
  46. When does coordination of swallowing and respiration occur?
    4-5 mos
  47. Why are infants at risk for hypothermia?
    • Large ratio of surface area to body weight
    • Increased O2 consumption
    • Inability to shiver well
    • Increased metabolic rate for up to 12 hours post-op
  48. Non shivering thermogenesis
    -anesthetic agent effect on
    • Brown fat metabolism (premies have limited fat stores)
    • Anesthetic agents can inhibit this
  49. Protein binding ____ as age increases
    increases
  50. Premies have a ____ TBW content and a ____ fat content.
    • high
    • low
  51. MAC peaks at what age?
    • 6 mo
    • likely due to high fat content
  52. T or F, there is a narrow safety margin btw inadequate anesthesia and overdose in infants
    T due to functional immaturity of cardiac muscle and rapid rise in anesthetic levels
  53. MAC multiple
    amount of agent that can be delivered by the vaporizer divided by the MAC of the agent

    increased MAC multiple associated with potential OD in neonates
  54. What age groups are most vulnerable to OD from volatile anesthetics?  Why?
    • Premies and neonates
    • Due to immature cardiac muscle
    • This population experiences the least increase in HR and the most decrease in SBP
  55. What volatile is most commonly used in pedi?
    Sevo
  56. Profound myocardial depression seen in kids and infants with CHD is associated with what volatile agent?
    Halothane, this agent should be avoided in this population
  57. What volatile agent is typically used for induction
    sevo
  58. Iso is associated with ___ myocardial depression and preservation of ___.  Unfortunately, it is also associated with a higher incidence of ______.  
    • less
    • HR
    • airway events (laryngospasm and bronchospasm)
  59. Why is des not used commonly in pedi?
    • Higher incidence of emergence delirium due to rapid awakening
    • 50% incidence of laryngospasm on induction!
  60. Why are propofol induction doses increased for pedi?
    Due to higher fat content
  61. Propofol induction doses
    < 2 yo
    6-12 yo
    • < 2 yo- 2.9 mg / kg
    • 6-12 yo 2.2 mg / kg
  62. Only benzo approved for use in neonates
    midaz
  63. Is midaz water or fat soluble?
    water soluble
  64. Newborns have ___ clearance of morphine 
    • decreased
    • A lower dose results in decreased plasma values, longer elimination half time
  65. Most commonly used long acting opiate in peds
    morphine
  66. Succ is ___ soluble
    water
  67. Infant succ dose
    • 2 mg / kg
    • dose increased due to high TBW content
  68. Succ must be given with ___ 
    • atropine
    • give atropine first due to risk of bradycardia or cardiac arrest
  69. Infants are generally ____ sensitive to NDMR
    more
  70. Initial dosing of NDMR is ___ to that of adults, but the excretion is ___ and the effects are ____.
    • similar
    • slower
    • prolonged
  71. T or F, the DOA of vec is similar to that of panc in newborns
    T
  72. Neonate
    1st 30 days of life
  73. Newborn 
    1st 24 hours of life
  74. 3 major shunts
    • placenta
    • DA
    • FO
  75. When do the DA and FO permanently close?
    within the first few months of life
  76. How long does it take for PVR to decrease to normal levels?
    3-4 days
  77. Persistent pulmonary HTN patho
    • Hypoxia, acidosis, and inflammatory mediators  increase PA pressure, increased PVR occurs
    • Right to left shunt thru the DA and FO occurs
  78. Potential causes of persistent pulm Htn
    meconium aspiration, sepsis, PNA, respiratory distress, CDH
  79. Treatment of persistent pulmonary HTN
    • goal directed
    • surfactant
    • ventilation
  80. Enlarged ___ ventricle may occur with persistent pulmonary HTN
    right
  81. Bronchopulmonary dysplagia
    • Inflammation and scarring of lung parenchyma and small airways
    • Can result from long term ventilation 
    • Occurs in LBW and premie infants
    • Increased airway reactivity
    • Decreased lung compliance
    • V/Q mismatch
    • Hypoxia
  82. Management of bronchopulmonary dysplagia
    Managed like asthma
  83. RDS
    • Impaired gas exchange at alveolar level due to deficient levels of surfactant 
    • R to L shunting, metabolic acidosis, hypoxia
  84. Mature levels of surfactant are not present until __ weeks of age
    35
  85. Why does R to L shunting occur in RDS
    Due to increased PVR (no surfactant)
  86. S/sx RDS
    Tachypnea, IC and substernal retractions, nasal flaring, cyanosis
  87. RDS treatment
    • mechanical ventilation if PaO2 < 50 on 70-100% FiO2
    • maintain Hct at 40%
    • careful hydration (use albumin)
  88. Apnea
    cessation of breathing that lasts longer than 20 seconds or is accompanied by cyanosis or bradycardia
  89. Types of apnea
    • obstructive (neck flexion, pharyngeal instability)
    • central (immature control of respiratory function)
  90. Hct < __ is a risk for ___ regardless of gestational age
    • 30%
    • apnea
  91. Infants < ____ weeks post conceptual age are most at risk for apnea
    60
  92. Non essential surgeries should be postponed in infants < ___ weeks post conceptual age
    • 52
    • due to apnea risk
  93. Risk of apnea is ___ proportional to gestational age and post-conceptual age
    inversely
  94. Anesthetics (inhaled and IV) affect control of breathing for ___ post surgery
    up to 12 hours
  95. T or F, a 2 yo who was born premature with a h/o apnea is suitable to have outpatient surgery
    F!
  96. Examples of L to R shunts
    ASD, VSD, PDA, Eisenmenger's syndrome, endocardial cushion defect (trisomy 21)
  97. Examples of R to L shunts
    TOF, pulmonary atresia, tricuspid atresia, Ebstein's anomoly
  98. Anesthesia management of CHD
    • Avoid drops in SVR to prevent L to R shunt
    • Maintain IV volume
    • BB to control HR
    • R to L shunting may slow uptake of inhalation agents
    • Avoid acidosis
    • Maintain normal airway pressures
  99. What occurs in L to R shunts
    • SVR > PVR causes pulmonary blood flow to increase
    • Pulmonary congestion and CHF may result
    • Increased susceptibility to respiratory tract infection
    • Long standing shunt can lead to P HTN
  100. What occurs in R to L shunts
    • defect btw R and L heart
    • Resistance to pulmonary blood flow
    • Hypoxia and cyanosis result
  101. PDA beyond the ___ day of life is abnormal
    4th
  102. PDA can lead to __ to __ shunt
    L to R
  103. PDA medical treatment
    indocin (COX 2 inhibitor)
  104. Anesthesia considerations for PDA
    • Abx to prevent endocarditis
    • PPV is well tolerated 
    • Consider nipride post-op if SVR is elevated 
  105. Risks associated with surgical repair of PDA
    • IC hemorrhage
    • recurrent laryngeal nerve paralysis (in infants born < 28 weeks)
  106. Necrotizing enterocolitis
    • ulceration and necrosis of small bowel and colon
    • unknown cause
    • prematurity is a risk factor
  107. S/sx necrotizing enterocolitis
    feeding intolerance, abd distention, bloody stools
  108. Necrotizing enterocolitis tx
    NG decompression, holding oral feedings, IV, HD support, abx, possible surgical exploration
  109. Anesthesia implications of necrotizing enterocolitis
    • Pts are hypovolemic and have metabolic acidosis
    • Fluid and lyte deficiencies
    • IVF / blood products
    • Careful induction or awake intubation
    • Caution with agents that depress myocardial function due to potential sepsis
    • Mechanical ventilation post-op
  110. Hypertrophic pyloric stenosis
    • Interferes with emptying of gastric contents
    • High aspiration risk
    • Avoid use of LR (lactate gets metabolized to bicarb, these pts have metabolic alkalosis)
  111. Kernicterus
    Neuro d/o caused by toxic effects of unconjugated bilirubin in the brain stem nuclei and basal ganglia
  112. Anesthesia implications of kernicterus
    Avoid vec (contains benzyl alcohol- associated with IC hemorrhage)  
  113. FHgb vs adult Hgb
    • FHgb more likely to hold onto O2 (left shift)
    • FHgb is 2,3 DPG resistant (left shift)
  114. Premature infants < 55 weeks post conceptual age need a Hgb of at least ___ for elective surgery
    10 
  115. Preterm Hgb value
    13-15
  116. Neonate Hgb value
    17
  117. 3 mo Hgb value
    10-11
  118. 2-5 yo Hgb value
    12.5-13
  119. > 5 -10 years Hgb value
    14 g/ dl
  120. Retinopathy of prematurity
    • Associated with hyperoxia
    • Associated with premature infants < 1000 g
    • Retinal detachment and blindness may occur
  121. Anesthesia considerations to prevent ROP
    • PaO2 50-80
    • normocarbia
    • O2 sat 89-94%
  122. Infants undergoing peripheral retinal ablation have increased risk of both ___ and ___ 1-3 days post -op
    apnea and bradycardia
  123. IC hemorrhage
    • Inversely proportional to gestational age or birth weight
    • intraventricular hemorrhage is of the most significance
    • major complication of prematurity
    • due to incomplete auto regulation of blood flow and immaturity of cerebral capillary beds
  124. Anesthesia considerations to prevent IC hemorrhage
    • Avoid large swings in BP, esp. HTN
    • Slow volume expansion
    • normal BP is at low end of auto regulation limit
  125. Most common metabolic issue in newborns
    • hypoglycemia, due to inadequate glycogen stores and deficient gluconeogenesis
    • Highest in SGA infants
  126. Hypocalcemia
    • Infants have decreased levels of endogenous Ca stores
    • LBW infants, premies, and infants born to IDDM mothers are at risk
  127. Most common cause of neonatal seizures
    Hypocalcemia
  128. Pyloric stenosis
    • Palpable "olive" in RUQ
    • Hypertrophy of esophageal sphincter
  129. S/sx of pyloric stenosis
    • projectile vomiting
    • met alkalosis progressing to met acidosis
  130. Anesthesia management of pyloric stenosis
    • Awake intubation and IV induction, NO inhalation induction
    • NGT to sx prior to induction
    • Extubate fully awake
  131. Most common type of tracheal esophageal fistula
    • type C (90%)
    • upper esophagus ends in blind pouch, lower esophagus connects to trachea

    breathing causes gastric distention, feeding leads to aspiration PNA and choking
  132. VATER syndrome
  133. vertebral defects, anal atresia, TEF, radial dysplagia
  134. Anesthesia considerations of TEF
    • Avoid PPV 
    • Awake intubation
    • Keep spontaneously breathing with min assist until fistula is ligated
    • Ensure ETT is btw carina and fistula (visualize with FO scope)
    • Often dehydrated and malnourished (can't feed)
    • Frequent suctioning (copious secretions)
  135. CDH
    • Gut herniates into thorax during fetal development
    • Left sided is most common
    • Associated with pulmonary HTN
    • Pulmonary hypoplasia 
  136. Anesthesia implications of congenital diaphragmatic heria
    • NGT
    • Avoid high ventilation pressures (< 30 cm H20)
    • Awake intubation often without muscle relaxants
    • Caution with expansion of the ipsilateral lung
  137. Trisomy 21
    • Down's syndrome
    • short neck and large tongue= difficult airway
    • may be associated with CDH, VSD, subglottic stenosis, TEF, sz, chronic pulmonary infections
  138. Anesthesia considerations for trisomy 21
    • Possible difficult airway, esp during infancy
    • Use smaller ETT
    • Resp issues are common (stridor and apnea)
    • Neck flexion may result in A/O dislocation
    • Caution air in IV due to possibility of R to L shunts
  139. Diseases associated with micrognathia
    • Pierre Robin syndrome
    • Treacher collins syndrome
  140. Klippel feil syndrome
    • short neck
    • restricted c-spine mobility
    • fusion of C2-3 is common
    • prone to neuro damage
    • awake FOI!!
  141. Tetralogy of Fallot
    • 1) RV outflow obstruction (pulmonary stenosis)
    • 2) RV enlargement
    • 3) overriding aorta
    • 4) VSD
  142. Why is prostaglandin used in TOF
    • To keep PDA open
    • Neonate may decompensate with closure of PDA
    • Prevent severe L to R shunt
  143. Acute epiglottis
    • SUPRAglottic edema
    • a pre-emergency
    • bacterial infection
  144. S/sx acute epiglottis
    • Drooling 
    • Difficulty swallowing
    • Usually seen in kids ages 2-8
  145. Anesthesia considerations for acute epiglottitis
    • No MR
    • Intubate in OR (ER if emergent)
    • ENT should be aware (possible need for a trach)
    • Half to 2x smaller ETT 
    • Extubate when cuff leak demonstrated
    • Keep pt with mom, avoid stressing them
  146. Croup
    • laryngotracheobronchitis
    • SUBglottic edema that develops slowly over time in kids with a URI
    • rarely requires intubation
    • barking cough
  147. Kids at risk for OSA
    • craniofacial abn
    • neuromuscular d/o
    • obesity
    • adenotonsillar hypertrophy
  148. OSA anesthesia considerations
    • Higher sensitivity to respiratory depressant effects of narcotics (unregulated Mu receptors)
    • Narrowed upper airway
    • Propensity to upper airway collapse
    • Non narcotics or short acting narcotics
    • Steroids
    • regional or LA for post-op pain

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