the basics of peds anesthesia [autosaved]
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125 slides about the updated topic in pediatric anesthesia,and laparoscopy in pediatricsTRANSCRIPT
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