Pediatric Anesthesia
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Pediatric Anesthesia. 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 Induction technics

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Pediatric Anesthesia

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Pediatric anesthesia

Pediatric Anesthesia


Pediatric anesthesia

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

  • Induction technics

  • Airway management technics

Ref: MetroHealthAnesthesia.com/edu/ped/peds1.htm


Pediatric anesthesia

I. Preop Preparation

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.


Pediatric anesthesia

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


Pediatric anesthesia

Useful for all of us, from infancy to old age!


Pediatric anesthesia

Minimum Fasting Periods:

Guidelines apply to healthy patients undergoing elective proceures.

They do not guarantee complete gastric emptying.

Reference: Anesthesiology 90:896-905, 1999


Pediatric anesthesia

  • Offer clear liquids up to 2 hours before induction:

  • reduces hunger, irritability

  • preserves hydration

  •  risk of hypoglycemia


Pediatric anesthesia

Preanesthesia Checklist

The only way to

definitely confirm readiness!USE A

PREANESTHESIA CHECKLIST


Pediatric anesthesia

II. Fluids and Electrolytes

INFANT CHILD ADULT

Total Water (%) 75 70 55-60 ECF 40 30 20

ICF 35 40 40

Fat 16 23 30


Pediatric anesthesia

Infant kidneys

immature function at birth:

  •  GFR (‘til 2 years old)

  •  concentrating capacity

  •  Na reabsorption

  • HCO3 /H exchange

  • free H2O clearance

  •  urinary loss of K+, Cl-


Pediatric anesthesia

What it means:

Newborn kidney has limited

capacity to compensate for

volume excess or

volume depletion


Pediatric anesthesia

Neonates:

• limited hepatic glycogen stores

risk of hypoglycemia

provide 5%-10% dextrose maintenance

supplemental insulin prn


Pediatric anesthesia

 fluid requirement

greater BSA:mass ratio

other factors:

radiant warmers

fever

illness

injury

thin, immature skin


Pediatric anesthesia

Hourly Maintenance Fluids

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


Pediatric anesthesia

Maintenance Fluid Therapy

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


Pediatric anesthesia

Perioperative Fluid Management

  • Maintenance Fluid

  • Replace Deficit

  • Replace Ongoing Losses


Pediatric anesthesia

Perioperative Fluid Management

Choice of Fluids

Isotonic Crystalloids

• best replacement fluid

Hypotonic Fluids - DANGER

• can cause hyponatremia


Pediatric anesthesia

Is intraoperative glucose necessary?

maybe, sometimes


Pediatric anesthesia

Effects of Intraop Glucose :

  • intraop hyperglycemia

  • hyperosmolality

  • osmotic diuresis

  • worsen neurologic outcome

  • after cerebral ischemia


Pediatric anesthesia

Intraop glucose exceptions:

patients at risk for hypoglycemia:

• neonates and young infants

• debilitating chronic illness

• patients on parenteral nutrition

• neonates of diabetic mothers

• Beckwith-Wiedemann syndrome

• nesidioblastosis


Pediatric anesthesia

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)


Pediatric anesthesia

Fluids - Summary

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


Pediatric anesthesia

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)->


Pediatric anesthesia

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


Pediatric anesthesia

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


Pediatric anesthesia

III. Pediatric cardiopulmonary physiology

Normal aortic pressures

Wt (Gm)Sys/Dias mean

1000 50/25 35

2000 55/30 40

3000 60/3550

4000 70/4050

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


Pediatric anesthesia

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


Pediatric anesthesia

III. Pediatric cardiopulmonary physiology

Normal heart rate

Age (days) Rate

1-3100-140

4-7 80-145

8-15110-165

Age (months) Rate

0-1100-180

1-3110-180

3-12100-180

Age (years) Rate

1-3100-180

3-5 60-150

5-9 60-130

9-12 50-110

12-16 50-100


Pediatric anesthesia

The Newborn Heart

  • Near peak of Starling curve

  • Stroke volume relatively fixed

  • C.O. relatively heart rate dependent


Pediatric anesthesia

III. Pediatric cardiopulmonary physiology

Newborn myocardial physiology

Type I collagen (relatively rigid) predominates (vs type III in adult)

NeonateAdult

Cardiac output HR dependentSV & HR dependent

Starling responselimitednormal

Compliancelessnormal

Afterload compensation limitedeffective

Ventric interdependencehighrelatively low

So:

Avoid (excessive) vasoconstriction

Maintain heart rate

Avoid rapid (excessive) fluid administration


Pediatric anesthesia

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 anesthesia

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 anesthesia

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 anesthesia

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 anesthesia

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 anesthesia

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 anesthesia

Pediatric Respiratory Physiology – Assessment of Respiratory Control

CO2 response curve


Pediatric anesthesia

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 anesthesia

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 anesthesia

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 anesthesia

Pediatric Respiratory Physiology – Lung Volumes and Mechanics of Breathing

General anesthesia, FRC and PEEP

Mean PEEP to resore FRC to normal

infants < 6 months6 cm H2O

children6-12 cm H2O

PEEP

important in children < 3 years

essential in infants < 9 months

under GA + muscle relaxants

(increases total compliance by 75%)

(Motoyama)


Pediatric anesthesia

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 anesthesia

Pediatric Respiratory Physiology

Oxygen transport

(Bohr effect)

= 27, normal adult(19, fetus/newborn)


Pediatric anesthesia

Pediatric Respiratory Physiology

Oxygen transport

If SpO2 = 91

then = PaO2 =

Adult 60

6 months66

6 weeks 55

6 hours 41


Pediatric anesthesia

Pediatric Respiratory Physiology

Oxygen transport

P50 Hgb for equivalent tissue oxygen delivery

Adult27 8 10 12

> 3 months30 6.5 8.2 9.8

< 2 months2411.714.717.6

Implications for blood transfusion

older infants may tolerate somewhat lower Hgb levels at which

neonates ought certainly be transfused


Pediatric anesthesia

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


Pediatric anesthesia

IV. Induction - premedication options

  • Parents and Toys

  • "Parents are often the best premedication." G. Gordon, MD

  • "The presence of the parents during induction has virtually eliminated the need for sedative premedication." -Fred Berry, MD, 1990

  • Parental presence is especially helpful for children older than 4 years who have calm parents.

  • Midazolam is more effective than parental presence. - Zeev Kain, 1998

  • Anxiety associated with oral midazolam administration was significantly reduced in children who had earlier received a toy to play with. - Golden et al, 2006

http://metrohealthanesthesia.com/edu/ped/pedspreop6.htm


Pediatric anesthesia

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


Pediatric anesthesia

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


Pediatric anesthesia

Induction

"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


Pediatric anesthesia

Induction

  • First

  • Warm the OR, especially for young infantsComplete the pre-anesthesia checklist.

  • Two main categories of pediatric anesthetic induction:Parent(s) present - usually best

    • Without parents - role of premedication important

  • General methods of induction:

  • inhalational

  • intravenous (IV)

  • intramuscular (IM)

  • rectal

  • oral

  • http://metrohealthanesthesia.com/edu/ped/induction1.htm


    Pediatric anesthesia

    Induction

    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


    Pediatric anesthesia

    Induction

    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


    Pediatric anesthesia

    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


    Pediatric anesthesia

    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)


    Pediatric anesthesia

    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


    Pediatric anesthesia

    LMA and LMA-Fiberoptic Technic Sizes

    http://metrohealthanesthesia.com/edu/ped/lmatable.htm


    Pediatric anesthesia

    For more cool stuff about

    Pediatric Anesthesia

    check out the lessons and quizzes at

    http://metrohealthanesthesia.com/edu/ped/peds1.htm


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