
Pediatric Anesthesia. Greg Gordon MD. 13 Mar 09. Objectives. Participants will be able to explain the implications for anesthesia care of selected characteristics unique to our pediatric patients in the areas of: . Preop preparation Fluids and electrolytes Cardiopulmonary physiology
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Participants will be able to
explain the implications for anesthesia care
of selected characteristics unique to our
pediatric patients in the areas of:
Ref: MetroHealthAnesthesia.com/edu/ped/peds1.htm
Pediatric anesthesia is a family affair.
Psychological preparation involves stress reduction
The two most important sources of stress are: 1. Fear of the unknown 2. Fear of separation
These stresses are best dealt with by:
1. Simple, honest communication,
colored by positive suggestion
modified according to age In other words:
tell 'em just what's gonna happen,
in a positive, supportive way.
2. Maintain parental presence during induction of anesthesia
in selected cases.
Approach depends on age of patient:
Early infancy (neonate to about 7 months of age):
Parents are the primary focus
Comfortable separation in preop holding area usual
Later infancy to about 3 years:
Separation anxiety major
Surgery ought be outpatient
Selected parental presence
3 to 6 years: Child becomes primary focus.
Explain exactly what will happen; what you will do
Then do it that way. (Be trustworthy!)
6 years to adolescent: Increasing involvement of patient.
From 3 of 4 years through adolescence:
Give child choices
Parental presence often helpful
Guidelines apply to healthy patients undergoing elective proceures.
They do not guarantee complete gastric emptying.
Reference: Anesthesiology 90:896-905, 1999
Offer clear liquids up to 2 hours before induction:
INFANT CHILD ADULT
Total Water (%) 75 70 55-60 ECF 40 30 20
ICF 35 40 40
Fat 16 23 30
immature function at birth:
Newborn kidney has limited
capacity to compensate for
volume excess or
volume depletion
• limited hepatic glycogen stores
risk of hypoglycemia
provide 5%-10% dextrose maintenance
supplemental insulin prn
greater BSA:mass ratio
other factors:
radiant warmers
fever
illness
injury
thin, immature skin
4:2:1 Rule
4 ml/kg/hr 1st 10 kg +
2 ml/kg/hr 2nd 10 kg +
1 ml/kg/hr for each kg > 20
Term Newborn (ml/kg/day)
Day 1 50-60 D10W
Day 2 100 D10 1/2 NS
>Day 7 100-150 D5-D10 1/4 NS
Older Child: 4-2-1 rule
Perioperative Fluid Management
Perioperative Fluid Management
Choice of Fluids
Isotonic Crystalloids
• best replacement fluid
Hypotonic Fluids - DANGER
• can cause hyponatremia
Is intraoperative glucose necessary?
maybe, sometimes
patients at risk for hypoglycemia:
• neonates and young infants
• debilitating chronic illness
• patients on parenteral nutrition
• neonates of diabetic mothers
• Beckwith-Wiedemann syndrome
• nesidioblastosis
Infant comes to OR with D10 infusing at 10 ml/hr.
What to do intraop?
Continue D10, but at
reduced rate (e.g., reduce by 50% to 5 ml/hr)
to compensate for hyperglycemic surgical stress;
And add by piggy-back or second IV line
an infusion of isotonic crystalloid (LR or NS)
Brief Procedures ( myringotomy, PET)
replacement may be unnecessary
1-2 hr Procedures
IV placement after inhalation induction
replace 10-20 cc/kg + EBL 1st hour
Longer and Complex Procedures
4-2-1 rule
hypovolemia: 10-20 cc/kg LR / NS
Glucose IF hypoglycemic risk
III. Pediatric cardiopulmonary physiology
In utero circulation
placenta ->
umbilical vein (UV)->
ductus venosus (50%) ->
IVC ->
RA ->
foramen ovale (FO) ->
LA ->
Ascending Ao ->
SVC ->
RA ->
tricuspid valve ->
RV (2/3rds of CO) ->
main pulmonary artery (MPA) ->
ductus arteriosus (DA) (90%) ->
descending Ao ->
umbilical arteries (UAs)->
III. Pediatric cardiopulmonary physiology
Transitional circulation
Placenta Out and Lungs In
PVR drops dramatically
(endothelial-derived NO and prostacyclin)
FO closes
DA closes
10-12 hours to 3 days to few weeks
prematures: closes in 4-12 months
PFO potential route for systemic emboli
DA and PFO routes for R -> L shunt in PPHN
III. Pediatric cardiopulmonary physiology
Neonatal myocardial function
Contractile elements comprise 30% (vs 60% adult) of newborn myocardium
Alpha isoform of tropomyosin predominates
more efficient binding for faster relaxation at faster heart rates
Relatively disorganized myocytes and myofibrils
Most of postnatal increase in myocardial mass due to
hypertrophy of existing myocytes
Diminished role of relatively disorganized sarcomplasmic reticulum (SR)
and greater role of Na-Ca channels in Ca flux so
greater dependence on extracellular Ca
may explain:
Increased sensitivity to
calcium channel blockers (e.g. verapamil)
hypocalcemia
digitalis
III. Pediatric cardiopulmonary physiology
Normal aortic pressures
Wt (Gm) Sys/Dias mean
1000 50/25 35
2000 55/30 40
3000 60/35 50
4000 70/40 50
Age (months) Sys/Dias mean
1 85/65 50
3 90/65 50
6 90/65 50
9 90/65 55
12 90/65 55
III. Pediatric cardiopulmonary physiology
Adrenergic receptors
Sympathetic receptor system
Tachycardic response to isoproterenol and epinephrine
by 6 weeks gestation
Myocyte β-adrenergic receptor density
peaks at birth then
decreases postnatally
but coupling mechanism is immature
Parasympathetic, vagally-mediated responses are mature at birth
(e.g. to hypoxia)
Babies are vagotonic
III. Pediatric cardiopulmonary physiology
Normal heart rate
Age (days) Rate
1-3 100-140
4-7 80-145
8-15 110-165
Age (months) Rate
0-1 100-180
1-3 110-180
3-12 100-180
Age (years) Rate
1-3 100-180
3-5 60-150
5-9 60-130
9-12 50-110
12-16 50-100
III. Pediatric cardiopulmonary physiology
Newborn myocardial physiology
Type I collagen (relatively rigid) predominates (vs type III in adult)
Neonate Adult
Cardiac output HR dependent SV & HR dependent
Starling response limited normal
Compliance less normal
Afterload compensation limited effective
Ventric interdependence high relatively low
So:
Avoid (excessive) vasoconstriction
Maintain heart rate
Avoid rapid (excessive) fluid administration
Pediatric Respiratory Physiology
Perinatal adaptation
First breath(s)
up to 40 to 80 cmH2O needed
to overcome high surface forces
to introduce air into liquid-filled lungs
adequate surfactant essential for smooth transition
Elevated PaO2
Markedly increased pulmonary blood flow ->
increased left atrial pressure with
closure of foramen ovale
Pediatric Respiratory Physiology
Infant lung volume small in relation to body size
VO2/kg = 2 x adult value
=> ventilatory requirement per unit lung volume is increased
less reserve
more rapid drop in SpO2 with hypoventilation
Pediatric Respiratory Physiology
Infant and toddler
more prone to severe obstruction of upper and lower airways
absolute airway diameter much smaller that adult
relatively mild inflammation, edema, secretions
lead to greater degrees of obstruction
Pediatric Respiratory Physiology
Central apnea
apnea > 15 seconds or
briefer but associated with
bradycardia (HR<100)
cyanosis or
pallor
rare in full term
majority of prematures
Pediatric Respiratory Physiology
Postop apnea in preterms
Preterms < 44 weeks postconceptional age (PCA): risk of apnea = 20-40%
most within 12 hours postop(Liu, 1983)
Postop apnea is reported in prematures as old as 56 weeks PCA
(Kurth, 1987)
Associated factors
extent of surgery
anesthesia technique
anemia
postop hypoxia
(Wellborn, 1991)
44-60 weeks PCA: risk of postop apnea < 5% (Cote, 1995)
Except: Hct < 30: risk remains HIGH independent of PCA
Role for caffeine (10 mg/kg IV) in prevention of postop apnea in prematures?
(Wellborn, 1988)
Pediatric Respiratory Physiology – Pulmonary and Thoracic Receptors
Laryngospasm
Sustained tight closure of vocal cords
by contraction of adductor (cricothyroid) muscles
persisting after removal of initial stimulus
More likely (decreased threshold) with
light anesthesia
hyperventilation with hypocapnia
Less likely (increased threshold) with
hypoventilation with hypercapnia
positive intrathoracic pressure
deep anesthesia
maybe positive upper airway pressure
Hypoxia (paO2 < 50) increases threshold (fail-safe mechanism?)
So: suction before extubation while
patient relatively deep and
inflate lungs and maybe a bit of PEEP at time of extubation
Pediatric Respiratory Physiology – Assessment of Respiratory Control
CO2 response curve
Pediatric Respiratory Physiology – Assessment of Respiratory Control
Effects of anesthesia on respiratory control
Shift CO2response curve to right
Depress genioglossus, geniohyoid, other phayrngeal dilator muscles ->
upper airway obstruction (infants > adults)
work of breathing decreased with
jaw lift
CPAP 5 cmH2O
oropharyngeal airway
LMA
Active expiration (halothane)
Pediatric Respiratory Physiology – Lung Volumes and Mechanics of Breathing
= 60 ml/kg infant
after 18 months
increases to
adult 90 ml/kg
by age 5
=
50% of TLC
may be only 15% of TLC in
young infants under GA
plus muscle relaxants
= 25% TLC
Pediatric Respiratory Physiology – Lung Volumes and Mechanics of Breathing
Under general anesthesia, FRC declines by
10-25% in healthy adults with or without muscle relaxants and
35-45% in 6 to 18 year-olds
In young infants under general anesthesia
especially with muscle relaxants
FRC may = only 0.1 - 0.15 TLC
FRC may be < closing capacity leading to
small airway closure
atelectasis
V/Q mismatch
declining SpO2
Pediatric Respiratory Physiology – Lung Volumes and Mechanics of Breathing
General anesthesia, FRC and PEEP
Mean PEEP to resore FRC to normal
infants < 6 months 6 cm H2O
children 6-12 cm H2O
PEEP
important in children < 3 years
essential in infants < 9 months
under GA + muscle relaxants
(increases total compliance by 75%)
(Motoyama)
Pediatric Respiratory Physiology – Dynamic Properties
Poiseuille’s law for laminar flow:
where R resistance
l length
η viscosity
R = 8lη/πr4
For turbulent flow: Rα1/r5
Upper airway resistance
adults: nasal passages: 65% of total resistance
Infants: nasal resistance 30-50% of total
upper airway: ⅔ of total resistance
NG tube increases total resistance up to 50%
Pediatric Respiratory Physiology
Oxygen transport
If SpO2 = 91
then = PaO2 =
Adult 60
6 months 66
6 weeks 55
6 hours 41
Pediatric Respiratory Physiology
Oxygen transport
P50 Hgb for equivalent tissue oxygen delivery
Adult 27 8 10 12
> 3 months 30 6.5 8.2 9.8
< 2 months 24 11.7 14.7 17.6
Implications for blood transfusion
older infants may tolerate somewhat lower Hgb levels at which
neonates ought certainly be transfused
Pediatric Respiratory Physiology – Selected Summary Points
Basic postnatal adaptation lasts until 44 weeks postconception,
especially in terms of respiratory control
Postanesthetic apnea is likely in prematures, especially anemic
Formation of alveoli essentially complete by 18 months
Lung elastic and collagen fiber development continues through age 10 years
Young infant chest wall is very compliant and
incapable of sustaining FRC against lung elastic recoil when
under general anesthesia, especially with muscle relaxants
leading to airway closure and
‘progressive atalectasis of anesthesia’
Mild – moderate PEEP (5 cmH2O) alleviates
Hemoglobin oxygen affinity changes dramatically first months of life
Hgb F – low P50 (19)
P50 increases, peaks in later infancy (30)
implications for blood transfusion
IV. Induction - premedication options
http://metrohealthanesthesia.com/edu/ped/pedspreop6.htm
IV. Induction - premedication options
Pharmacologic premedication options
When awake separation of child from parent
before induction is planned
midazolam (Versed)
PO: 0.5 to 1.0 mg/kg up to 10 mg max.
Peak sedation by about 30 minutes
Mix with grape concentrate or
aetaminophen syrup or
ibuprofen suspension (10 mg/kg)
Mother may administer to child
Volume should not exceed 0.5 ml/kg (NPO!)
http://metrohealthanesthesia.com/edu/ped/pedspreop6.htm#premeds
IV. Induction - premedication options
ketamine
PO: 6 to 10 mg/kg
IM: 3 to 4 mg/kg for sedation;
6 to 10 mg/kg for induction of GA
midazolam + ketamine : PO
0.4 + 4 mg/kg respectively
PO induction of GA: 0.8 + 8 mg/kg
EMLA cream
Eutectic mixture of lidocaine and prilocaine
For cutaneous application one hour preop
http://metrohealthanesthesia.com/edu/ped/pedspreop6.htm#ketamine
"Infants should preferably be anesthestized in the mother's or nurse's arms. Care should be taken in anesthestizing children to make the operation as informal as possible... Mental suggestion here plays a great part, as well as gentleness in voice and movement..."
-Gwathmey J: Anesthesia 1914
http://metrohealthanesthesia.com/edu/ped/induction1.htm
http://metrohealthanesthesia.com/edu/ped/induction1.htm
Inhalational induction tips
“Try on your mask” test
Timely praise & positive reinforcement
One monitor: YOU
Think but DON’T TALK about breathing
Talk boring soothing bedtime story talk
Slowly bring mask near patient from below
Start with 70%N2O in O2
Slowly add/increase major inhaled agent
http://metrohealthanesthesia.com/edu/ped/induction5.htm#inhalational
IM induction
Useful back-up plan
10% ketamine
4 mg/kg in deltoid (or thigh)
22 gauge needle
Onset within 4 minutes
http://metrohealthanesthesia.com/edu/ped/induction6.htm#im
V. Technical Considerations - Airway differences – infant vs adult
epiglottis and tongue relatively larger
glottis more superior, at level of C3 (vs C4 or 5)
cricoid ring narrower than vocal cord aperture
until approx 8 years of age
4.5 mm in term neonate
11 mm at 14 years
http://metrohealthanesthesia.com/edu/ped/pedAir.htm
The appropriate uncuffed ETT size (age in years):
4 + (1/4)(age)
Subtract 0.5 for the appropriate cuffed ETT
E.g.: 4-year-old: uncuffed ETT = 4 + (1/4)4 = 5, so
cuffed ETT = 4.5
The appropriate depth of ETT insertion (cm) :
Over one year of age:
oral: 13 + (1/2)age
nasal: 15 + (1/2)age
Infants (weight in kg):
oral: 8 + (1/2)(weight)
nasal: 9 + (1/2)(weight)
Alternative Intubation Technics
Blind Nasotracheal Intubation
Digital Assisted Intubation
Fiberoptic Intubation
GlideScope Video Laryngoscope
Gum Elastic Bougie Assisted Intubation
LMA Assisted Fiberoptic Intubation
Retrograde Intubation
Wuscope Intubation
http://metrohealthanesthesia.com/edu/airway/difAir4.htm#intTechnics
LMA and LMA-Fiberoptic Technic Sizes
http://metrohealthanesthesia.com/edu/ped/lmatable.htm
Pediatric Anesthesia
check out the lessons and quizzes at
http://metrohealthanesthesia.com/edu/ped/peds1.htm