PAEDIATRIC ANAESTHESIA

1. APPLIED ANATOMY AND
PHYSIOLOGY OF
PAEDIATRIC
ANAESTHESIA
Dr. KHAIRUNNISA BINTI AZMAN
Anaethesiology department TGH

2. What Makes Pediatric Anesthesia
Different?
Airway!! Airway!!! Airway!!!
• HYPOXIA is the most common cause of pediatric
perioperative cardiac arrest.
– INFANTS TURN BLUE FAST. UPPER AIRWAY OBSTRUCTION
during anesthesia (particularly at induction and
emergence) is a fairly common phenomenon.
• Complete and/or Partial LARYNGOSPASM is a fairly
common problem
• Infants and young children ARE NOT SMALL ADULTS.
"One size fits all" DOES NOT APPLY.

5. Difference between adult VS Paediatric airway
Tongue Larger in propotion to the oral cavity than in adult
Epiglottis Narrower, U-Shaped, flops posteriorly
Larynx High & anterior. Level of C3-C4. (C5-C6 in adult)
Cricoid More conically shaped in infants, narrowest at cricoid
ring whereas in adult it is at level of vocal cords
Trachea Deviated posteriorly & downwards
Become anatomically similar to adult between 8-10 yo
Head large head, short neck & prominent occiput
Sniffing position will not help bag mask ventilation or to
visualise the glottis  Head needs to be in neutral position
AIRWAY & RESPIRATORY SYSTEM

6. • Neonates preferentially breathe through their
nose
– Narrow nasal passage  easily blocked by
secretions & may be damaged by NG tube/ Nasal
ETT
– 50% Airway resistance is from nasal passages
• The airway is funnel shaped & narrowest at
level of cricoid cartilage
– The epithelium is loosely bound to underlying
tissue
– Trauma to the airway easily results in oedema
– 1mm of oedema can narrow a baby’s airway by
60%

7. • Narrowest at
cricoid rather
than vocal cords
• Tube may be
small enough to
pass through
cords but not
cricoid
• Larynx is funnel
shaped, so
secretions
accumulate in
retropharangeal
space

8. Ideal maneuvre is
combination of jaw thrust
& chin lift, keeping the
mouth open

9. • It is suggested that a leak present around the
ETT to prevent trauma resulting in subglottic
oedema & subsequent post-extubation stridor
• Neonates& infant have limited respiratory
reserve:
– Horizontal ribs prevent the “buckle-handle” action
seen in adult breathing and limit an increase in TV
– Ventilation is primarily diaphragmatic
– Bulky abdominal organ/ stomach filled with gases
from poor bag mask ventilation impinge chest
content & splint diaghragm  inadequate
ventilation

10. • The ribs are cartilaginous & perpendicular relative to the
vertebral column (Horizontal), reducing the movement of the rib
cage
• The infant chest wall is remarkably compliant & compliance
decrease with increasing age
• Subsequently the functional residual capacity (FRC) is
relatively low.
• FRC ↓ with apnoea & anaesthesia causing lung collapse

11. • The closing volume is larger than FRC until 6-8
yrs of age
– Increase tendency for airway closure at end of
expiration
– Thus, neonates & infant generally need IPPV during
anaesthesia & would benefit from a higher RR &
the use of PEEP (High RR to maintain FRC)
– CPAP during spontaneus ventilation improves
oxygenation & decreases the work of breathing
• Work of respiration may be 15% of O2
Consumption

13. • Muscle of ventilation are easily subject to
fatigue d/t low percentage of Type I muscle
fibres in diaphragm.
– The num ↑ to adult level over 1st year of life
• The alveoli are thick walled at birth:
– There is only 10% of the total number of alveoli
found in adults
– The alveoli clusters develop over the first 8 yrs of
life
• Apneas are common post-operatively in
premature infants
– Significant if last longer than 15 sec & are
associated with desaturation & bradycardia.

14. NEONATAL CARDIAC PHYSIOLOGY
• The transformation to neonatal circulation occurs with
the first few breaths, involes 2 major changes:
• A marked increase in systemic resistance
• A marked decrease in pulmonary resistance
• Remnats:Patent Foramen Ovale & Ductus Arteriosus

16. • The patent ductus contracts in the first few
days of life & will fibrose within 2-4 wks
• Closure of foramen ovale is pressure
dependant & closes in the 1st day of life but
may reopen within the next 5 years
• Neonatal pulmonary vasculature reacts to the
rise in PaO2 & pH & the fall in PaCO2 at birth
• However, alterations in pressure & in response
to hypoxia & acidosis, reversion to the
transitional circulation may occur in first few
weeks after birth.

17. CARDIOVASCULAR SYSTEM
• In neonates Myocardium less contractile causing
the ventricles to be less compliant & less able to
generate tension during contraction
– Limits the size of stroke volume
– Cardiac output therefore rate dependant
– Infant behaves as with fixed cardiac output state
• Cardiac output
– 300-400 ml/kg/min at birth
– 200 ml/kg/min within few months

18. • Vagal parasymphathetic tone is most dominant
which makes neonates & infants more prone to
bradycardias
• Bradycardia:
– Assc with reduced cardiac output
– If assc with hypoxia, should be treated with O2 &
Ventilation initially
– Cardiac compression will be required in neonate
with HR 60 or less OR 60-80bpm with adequate
ventilation
• sinus arrythmia is common in children, other
irregular rhythm are abnormal

21. • BP is low at birth (approx. 80/50) secondary to a
low SVR, d/t large propotion of vessels-rich tissue
in children
• BP increases within the 1st month to approx.
90/60
• Reach adult levels at approx. 16 y.o
• Neonates have a reactive pulmonary vasculature
– Reversion to transitional circulation may occur during
1st few weeks of life, precipitated by an increase in
PVR (Eg: acidosis, hypoxia, hypercapnia) & decrease in
SVR (eg: most anaesthetics)
CARDIOVASCULAR SYSTEM

22. Infant kidneys : Immature at birth, thus:
• ↓ GFR/ Renal blood flow
– Till 2yo, d/t high renal vascular resistance
• ↓ Concentrating capacity
– U/O 1-2mls/kg/hr
• ↓ Na reabsorption
– Tubular function is immature until 8 months, so
infants are unable to excrete a large sodium load
• ↓HCO3/H exchange
RENAL SYSTEM

23. • Dehydration:
– Poorly tolerated
– Premature infants have increased insensible losses
as they have large surface area relative to weight
– There is larger proportion of ECF in children (40%
BW as compared to 20% in adult)
• Conclusion:
– Newborn kidneys has limited capacity to
compensate for Volume EXCESS or Volume
DEPLETION

24. HEPATIC SYSTEM
• Liver fx is initially immature with decreased
function of hepatic enzymes
• Barbiturates & opiods for example have a
longer duration of action d/t slower
metabolism

25. GLUCOSE METABOLISM
• Hypoglycaemia is common in stressed neonate
glucose level should be monitored regularly
• Glycogen stores are located in the liver &
myocardium
• Neurological damage may result from
hypoglycaemia
– Prevention: IVI D10%
• Infants & older children maintain blood glucose
better
• Hyperglycaemia is usually iatrogenic

26. HAEMATOLOGY
• At birth, 70-90% of Hb molecules are HbF.
– Within 3 months, levels drop to around 5% & HbA predominates
– HB in newbown ~ 18-20g/dL , HCT ~ 0.6
– 3-6 Mo : 9-12 g/dl as the increase in circulating volume
increases more Rpidly the bone marrow function
• HbF combines more rapidly with 02 but release less readily
as there is less 2,3-DPG.
• O2 dissociation curve shifts to the right as the level of HbA
& 2,3-DPG rise.
• Vit K dependant clotting factor (II, VII, IX, X) & PLT fx are
deficient in first few months
• Transfusion recommended when 15% of the circulating
volume has been lost.

27. Temperature control
• Poorly developed shivering, sweating &
vasoconstriction mechanism d/t:
– Large surface area to weight ratio
– Minimal subcutaneous fat
• Heat loss during anaesthesia d/t:
– Conduction
– Convection & evaporation
• Optimal ambient temp to prevent heat loss:
– Premature infant: 34⁰C
– Neonates: 32⁰C
– Adults: 28⁰C

28. • The fetus floats in warm amniotic fluid that is
maintained at a temperature of approximately 98.6°F
with very little fluctuation.
• Birth exposes newborns to a cooler environment in
which they have to regulate their own body
temperature.
• Newborns have a higher ratio of surface area to
volume than adults.
- This means that their body has less volume
throughout which to produce heat, and more surface
area from which to lose heat.
- As a result, newborns produce heat more slowly and
lose it more quickly.

29. • Effect of low body temp:
– Causes respiratory depression
– Acidosis
– Decreaswd cardiac output
– Increases duration of action of drugs
– Decrease platelet function
– Increases risk of infection
Temperature control

30. CENTRAL NERVOUS SYSTEM
• BBB is poorly formed
– Drugs (barbiturates, opioids, antibiotics, bilirubin)
cross BBB easily cause prolong & variable duration
of action
• Cerebral vessels in preterm infant are thin
walled & fragile.
– Prone to IVH
– Risk increased with hypoxia, hypercarbia,
hypernatraemia, low HCT, Awake airway
manipulation, rapid bicarb administration, &
fluctuation in BP & CBF

31. Different Anatomy
Different Physiology
Different Pharmacology
Different psychology
↓↓↓↓↓
Different approach & preparation
CONCLUSIONS ???

32. Be aware of:
• Sudden changes in hemodynamics
• Unexpected responses
• Unknown congenital problem
Most of the complications that arise are
attributable to a lack of understanding of these
special considerations prior to induction of
anesthesia

33. THANK YOU

34. PRACTICALITIES FOR
ANAESTHETISING CHILDREN

35. PRE-OPERATIVE VISIT
• Evaluates:
– Medical conditions of the child
– The needs of planned surgical procedure
– Physiological makeup of patient & family
• Weight; all drugs must be calculated according to weight
• Investigations may occasionally be necessary:
– HB: Large expected blood loss, premature infant, systemic
disorder, congenital heart disease
– Electrolytes: Renal or metabolic disease, IV Fluid, dehydration
– CXR: Active respiratory disease, scoliosis, congenital heart
disease
• Discuss regarding post OP pain Mx
– If suppository medications to be used Explain & get consent

37. PRE-OPERATIVE FASTING
Solids 6 Hours
Formula milk 4-6 hours
Breast milk 3-4 hours
Clear fluids 2 hours
PREMEDICATIONS
Sedations Analgesics
Midazolam
Chloral hydrate
Ketamine
Clonidine
Paracetamol
Ibuprofen
Codeine phosphate
EMLA Cream

38. BASIC SET UP
TABLE &
WARMER
MACHINE/
CIRCUIT
MONITOR
SUCTION &
AIRWAY
EQUIPMENT
IV ACCESS DRUGS

41. Breathing Systems and Circuits
• The Pediatric Breathing Circuit is extendable
up to 60 inches, and comes with a 1L (default)
latex free reservoir bag.
• The Neonatal Breathing Circuit is a fixed length
circuit which commands very low compliance
loss volume.
• The neonatal circuit comes with a 0.5L
(default) reservoir bag. The Y connector is
designed to minimize anatomical dead space.

44. INTUBATION & INDUCTION

46. Greater alveolar
to FRC ratio
High cardiac
output to vessels
rich organ (eg:
Brain)
Reduced tissue
blood solubility
EFFECT OF FAST INDUCTION
INDUCTION:
1. IV Induction
2. Gas induction

52. FLUIDS MANAGEMENT
• Perioperative fluid management is divided
into three phases
– Maintenance, deficit and replacement of losses.
• Administration: Volumetric chambers/
Microdrip/Infusion Pump
• Warm fluid/blood/blood product
• Include dextrose in maintainance hydration
fluid if needed
– Risk of hypoglycaemia higher in premature babies

53. DAY 1 OL 50MLS/KG/HR D10%
DAY 2 OL 100MLS/KG/HR D10% ½ NS
> DAY 7 OL 150MLS/KG/HR D5-D10% ¼ NS

54. 3RD SPACE FLUID LOSS
Intra-abdominal surgery 6-10 mls/kh/hr
Intra-thoracic surgery 4-7 mls/kg/hr
Eye surgery
1-2 mls/kg/hr
Neurosurgery
Superficial surgery
Fluid deficits:
• Calculated and replaced based on duration of fasting, presence
of associated conditions like
• Fever,
• Vomiting,diahorrea, sweating
• Particular disease state or surgical problem likely to affect
fluid status (bowel obstruction, peritonitis etc).
INTRAOPERATIVE FLUID LOSS  3RD Space fluid loss & blood loss

55. ESTIMATED BLOOD VOLUME (EBV)
Premature Neonate 90-100mls/kg
Term neonate 80-90mls/kg
3mo – 1yr 75-80mls/kg
3-6 yrs 70-75mls/kg
>6 yrs 65-70 mls/kg
Allowable blood loss
ABL = WEIGHT x EBV X (H₀ - H₁)/Hₐ
H₀ = Starting Hematocrit
H₁ = Lowest acceptable hematocrit
Hₐ = average hematocrit
Intraoperative blood
loss replacement is
done with
Ringer’s lactate 3 ml
per 1ml of blood loss,
1 ml of colloid
solution for each ml
of blood loss and 0.5
ml of red cell
concentrates for each
ml of blood loss.

56. PAIN MANAGEMENT
• Regional:
– Caudal block
– Ilioinguinal block
• Local anaesthesia
• Post operative analgesia (Syp/Supp)

57. THANK YOU
AGAIN

58. REFERENCES:
• Dr. M.N.Chidananda Swamy, Dr. D. Mallikarjun. Applied aspect
of anatomy and physiology relevance to apaediatric
anaesthesia. Indian J Anaesth 2004
• Sue clark. The differences of anaesthetic care in paediatrics
compared to adult. The association of paediatric practice
2010
• F. Macfarlane. Paediatric anatomy & physiology and the basic
of paediatric anaesthesia. Anaethesia tutorial of the week
• Paediatric anaesthesia digital book
• Ahmad A.L. Paediatric anaethesia basic and beyond
presentation