Pediatric anesthesia The Basics and Beyond

Ahmad Abou Leila MD

Dr.Roland Kaddoum

Presentation facts and objectives

125 slides(72+53)

REVIEW the Peds anesthesia basics

Updated Basics

Some of the SVI mission in Egypt

Infants are not small adults

Different Anatomy Different Physiology

Different Pharmacology Different psychology

Better understanding of peds

anesthesia principles

Different Approach and preparation

The different Physiology

Limited blood volume 80ml/kg(full term)

Limited stroke volume

CO=SV x HR

CO=SV x HR

High Heart Rate to maintain CO

The parasympathetic system is mature in newborns Dominant

Vagotonic

50% of apparently healthy babies

24 hours EKG recording

Have shown rhythm changes resembles complete 2:1 Block

Anything causes bradycardia Hypoxia,hypothermia,laryncoscopy Affect the CO

Pediatric Fundamentals – Heart and Circulation

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

HIGH HR……..Risk of fatigue

compensation

LOW afterload

Lowest acceptable SBP=70 + (age x2)

CO can be assessed clinically by stethoscope

Heart sounds become softer and muffled in low CO states

Contractile element is 30% (60%in adults)

Starling law is at maximum Cannot tolerate volume overload

Thin wall atria and ventricle Risk of tamponade during central line

insertion

Born T wave upright in all chest leads

In few hours T wave isoelectric or inverted in left chest

In 7 days T wave inverted in the Right chest leads (V1-V4)

Failure of T wave inversion in V1-V4 is the earliest sign of RV hypertrophy

Respiratory System

Almost all cardiac arrest due to respiratory problem

Limited AP expansion Limited Lateral expansion

Ventilation depend on the Diaphragm

Diaphragm in neonates and infants<2y

easy fatigue (lacks the Type I muscle fibers )

Any restriction of the Diaphragm movement Results in respiratory difficulties

stomach inflation due to forceful inflation will hinder ventilation

High Risk of barotrauma on MV -PCV

Small lung volume relative to their body size

Small FRC

High RR to maintain the FRC

High RR on MV

Under general anesthesia, FRC declines by

10-25% in healthy adults 35-45% in 6 to 18 year-olds

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

Higher O2 Consumption 6ml-7ml/kg

Adults (3-4ml/kg) rapid desaturation

Aspiration Risk

Children < 3 years at greater risk of aspiration

Higher incidence of

GERD

Short esophagus

Limited stomach

compliance

Baby trust

Excessive air swallowing

during crying

No muscle relaxants

Inadequate anesthesia

4 hours

6 hours

8 hours

Encourage water intake within two hours

Less dehydration (better induction

hemodynamic profile)

Less agitation and crying

Promotes motility Decrease gastric volume

Neonatal period the HB is HBF

HBF has high affinity to O2 ……P50 is ………

HBF decline with age HBA peaks at 9 month

O2 dissociation curve shifts to the right by acidosis(more delivery) O2 dissociation curve shifts to the left by alkalosis (less delivery)

MV in neonates avoid the hyperventilation induced alkalosis

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

Maximal allowable blood loss MABL: EBV x (Hcti-Hctf)/averaage Hct

Neonates have immature WBCs function ..risk of infection is high

Vitamin k dependent factors(II,VII,IX,X) 20-60% of adult values

Infants of mother who have received anticoagulation may develop severe bleeding like

Vitamin K deficiency

Babies on MV showed significant thrombocytopenia

Large surface area relative to body weight(2-2.5x BW)

Thin skin and subcutaneous fat( less insulation)

Neonates no shivering

Immature thermoregulation center

Forced air warming systems always available Fluid warmer Room temperature

immature function at birth:

GFR (‘til 2 years old)

concentrating capacity

Na reabsorption

HCO3 /H exchange

free H2O clearance

urinary loss of K+, Cl-

Infant kidneys

What it means:

Newborn kidney has limited

capacity to compensate for

volume excess or

volume depletion

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

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

Rules 1

Always Use volumetric Chambers or Microdrip

(infusion pumps may continue to infuse through dislodged catheters with out alarm)

Rule 2

Warm up all infused fluid

Crystalloids safe up to 54 C

Blood safe up to 42 C..risk of hemolysis)

Rule 3 Include dextrose in the maintenance hydration

fluid (Dextrose 1% or Dextrose 2.5%) Risk of Hypoglycemia is higher in

Premature Sick babies(malnutrition,cardiac)

Regional anesthesia Glucose infusion

hypoglycemia Apnea

Cyanosis Respiratory distress

Limpness Sweating Seizures

Rule 4

Replace Deficits,losses, and bleeding by isotonic fluid (not glucose containing

fluid) Risks of Hyperglycemia

Rule 5 Monitor intravascular volume closely by

BP

UOP

SVV

Heart sounds

Warm extremities

Capillary refill

Rule 6

Montior electrolytes closely Risk of Hyponatremia..Na losers

Risk of hyperkalemia .. blood transfusion

>1-2ml/kg/min

Different anatomy

Short distance between tongue and the glottis

Tongue easily obstruct the airway

Proximity of tongue to glottis visualization more difficult

more angulation between the oral axis and the laryngeal axis

Straight blade preferred more effectively in tongue lift

Epiglottis axis acute angle with airway axis..more difficult to lift

Stiff Omega shape ,touch the soft palate(easy airway

obstruction)

Large occiput (flexed head) Till one year

Shoulder Roll (deflex the head + stabilize the head)

Extreme extension will cause obstruction

Head parallel to the ceiling

The narrowest area is…………………………….

MRI of sub vocal cords area MRI at level of cricoid cartilage (not

ring)

Bronchoscopy of glottis area and sub glottis Bronchoscopy of cricoid cartilage

Abide to the rules of ideal tube selection

for cuffed tube Age(yrs)/4 +3.5

Tube Size Age(yrs)/4 +4(un cuffed)

Don’t push the tube through tight glottis opening Prepare smaller tube size

Subvocal cords area is the narrowest

un-Cuffed

Cuffed

Radiologic evidence Airway is oval not circular

Clinical evidence No difference in incidence of post intubation croup

No complications in cuffed tube

Cuffed tubes can be used in kids< 8 years

Neonates have reduced incidence of subglottic stenosis

Immature cartilage High water content in cartilage

Less susceptible for ischemic injuries

Short Neck

Short trachea

Risk of endobronchial Intubation

Airway management

Age (yrs) + 10

Depth of insertion Age/2 + 12

Depth of insertion

One study used CXR to confirm the correct placement of tube

The foot length was accurate as weight based formulas

Tube size X 3

Other uses of Tube size

Tube size 2 X Tube size=size of NG tube 3 X Tube size =Depth of tube insertion 4 X Tube size =size of chest tube

Intubation using Left molar approach

1. Left-molar Approach Improves the Laryngeal View in Patients with Difficult LaryngoscopyAnesthesiology. 2000 Jan;92(1):70-4 Full Text

2. Comparative Study Of Molar Approaches Of Laryngoscopy Using

Macintosh Versus Flexitip BladeThe Internet Journal of Anesthesiology 2007 : Volume 12

Number 1

3. The use of the left-molar approach for direct laryngoscopy combined with a gum-elastic bougieEuropean Journal of Emergency Medicine December 2010

;17(6):355-356

Another anatomical difference

Spinal cord ends at L3 In adults it ends at……..

Be cautious in neuroaxial anesthesia Lumbar puncture

Epidural or caudal block LOR with saline LOR with air not recommended

Pharmacological difference

Altered protein binding High Volume of Distribution

Small proportion of fat and muscles Immature Kidney and liver functions

More free fraction of medication Greater effect

Drugs high protein bound Barbiturates Bupivacaine

Alfentanil Lidocaine

Water soluble Drugs will distribute more Higher loading dose to achieve desired serum

levels Muscle relaxants

Antibiotics

Drugs that redistribute to fat Have larger initial peak levels (Opioids)

Less muscle mass (more sensitive to muscle relaxants)

Delayed metabolism and excretion

Inhalation agents

MAC

HIGHER MAC

Highest MAC in infants 6 months and 1 year

Fast induction

Greater Alveolar ventilation to FRC

ratio

Reduced tissue blood solubility

High cardiac out put to vessel rich

organs(brain)

Fast inhalation induction

97

SEVOFLURANE HALOTHANE

ISOFLURANE DESFLURANE

When to intubate?

Pediatric psychology

Pediatric Perioperative anxiety

40%-60% of infants experience perioperative anxiety

Highest incidence 1-5 years

Consequences

Bad dreams, wake up crying or walking

Disobeying parents

New onset enuresis

Crying leads to aerophagia and then stomach inflation Higher risk of aspiration and inefficient ventilation

Parental presence induction anesthesia(PPIA)

To date the experimental evidence doesn’t support the routine use of PPIA

Pharmacologic intervention superior to other intervention

Parent are less anxious

Midazolam is most commonly used(85%)

0.5mg/kg PO is the best dose(less side effects , and rapid onset)

Impulsive children shows paradoxical response to Midazolam

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 5 years: Separation anxiety major Selected parental presence

Midazolam 0.5 mg/kg orally 10 min before separation

>6 years: Child becomes primary focus. Explain exactly what will happen; what you will do Then do it that way. (Be trustworthy!)

Less insufflation pressure 6mmHg for infants 12mmHg for children

Abdomen insufflation causes vagal stimulation

Abdomen insufflation with Cold CO2 Increase the risk of hypothermia

Abdomen insufflation Trend position Higher risk of endobronchial intubation

Higher risk of Hypovolemia Longer time for bleeding control

Indication for Cuffed ET tube Higher risk of aspiration Accurate CO2 sampling

Infants < 5 kg Peri-umbilical area shouldn’t be used for port access Risk of umbilical artery injury

This lecture is posted on www.anesthesia-resident.blogspot.com

Thank you all And have a nice day