1. Dr . S. Parthasarathy
MD. DA. DNB., Dip.diab. MD(acu) , DCA,
Dip. Software-statistics.
PhD (physio)
Mahatma Gandhi medical college
and research institute ,
puducherry – India
Practical paediatric anaesthesia
3. Definitions
Neonates – a baby within 44 weeks of age
from the date of conception
Infants – a child of up to 12 months of age
Child – 1 to 12 years
Adolescent – 13 to 16 years
4. Physiology, Pharmacology
and practical considerations
• oxygen consumption in infants may
exceed 6ml/kg/min, twice that of adults
• physiological adaptations in paediatric cardiac
and respiratory systems to meet this increased
demand.
5. physiology
• The cardiac index
• (defined as the cardiac output related to the
body surface area)
• is increased by 30-60 percent in neonates and
infants to help meet the increased oxygen
consumption.
• Neonates have a higher haemoglobin
concentration (17 g/dl) and blood volume
6. Cardiovascular system
• Neonatal myocardium is stiff and increase in
cardiac output is rate dependent
• Stroke volume ?? So tachycardia is important
• BUT
• The sympathetic nervous system is not well
developed predisposing the neonatal heart to
bradycardia.
• Sinus arrhythmia is common in children and
all other irregular rhythms are abnormal
8. Respiratory- airway
• The head is relatively large with a prominent
occiput
• The neck is short.
• The tongue is large.
• The airway is prone to obstruction because of
these differences
10. Infant airway
• Infants and neonates breathe mainly through
their nasal airway, although their nostrils are
small and easily obstructed.
• The larynx is higher in the neck (more
cephalad), being at the level of C3 in a
premature infant and C4 in a child compared
to C5-6 in the adult.
11. Infant airway
• The epiglottis is large, floppy and U shaped.
The trachea is short (approximately 4-9cm)
directed downward and posterior and the
right main bronchus is less angled than the
left.
• Right main stem intubations are therefore
more likely.
12. Infant airway
• The glottic opening (laryngeal opening) is
more anterior and the narrowest part of the
airway is at the cricoid ring. (In the adult
airway the narrowest point is the vocal cords).
• At cricoid level, epithelium is loosely bound to
the underlying areolar tissue. Trauma to the
airway easily results in oedema.
16. Respiratory system
• Ribs and cartilages are more pliable
• Chest wall collapse more with increased negative
intrathoracic pressure
• Control of respiration poor
• Prolonged apnoea common after anaesthesia
• (caffeine 10 mg/kg)
• Hypoxia inhibits rather than stimulates breathing
17. Resp. system
• Respiration is mainly diaphragmatic (type 1 fibres
20%) Minute ventilation is more rate dependent
• The closing volume is larger than the FRC until 6-8
years of age
• RR = 24 – age/2
Spontaneous ventilation
• TV = 6-8 ml/kg; IPPV TV = 7-10ml/kg
18. Length and type
• length (Age / 2) + 12
• 1-2-3-----7,8,9 formula
• Size of the ETT
• (Age /3) + 3.5 or (Age /4) + 4.5
• Below 8 years – uncuffed – allow leak at 30
cm water pressure
19. LMA sizes
• 1 LMA up to 5 kg;
• 1.5 LMA 5-10 kg;
• 2 LMA 10-20 kg;
• LMA 2.5 20 – 30 kg;
• LMA 3 for over 30 kg
20. Renal System
• Renal blood flow and glomerular filtration are
low in the first 2 years of life due to high renal
vascular resistance..
• GFR 45 ml/min to adult values of 125 ml/min
• Tubular function is immature until 8months,
• so infants are unable to excrete a large sodium
load.
• Dehydration poorly tolerated
• Urine output 1-2 ml/kg/hr
21. Renal
• a faster turnover of extracellular fluid
• Renal function – almost normal in adult
levels -- age of 2 years
• 4-2-1 formula of IV fluids acceptable
• Options
• RL
• 1/2 NS
• 1/5th NS
22. Hepatic System
• Liver function is initially immature
• Cytochrome P450 enzymes (phase I reactions)
are fully developed, whereas others are
approximately 50% of adult values.
• Phase II reactions, usually impaired in neonates
• Barbiturates, opioids – prolonged action
• Age of 1 year - ok
23. Temperature regulation
• Neonates and infants have a large surface area
to volume ratio and therefore a greater area
for heat loss, especially from the head
• increased metabolic rate but insufficient body
fat for insulation and heat is lost more rapidly
• They don’t shiver
• Take all precautions to maintain temperature
24. Central Nervous System
• Neonates can appreciate pain
• The blood brain barrier is poorly formed
• The cerebral vessels in the preterm infant are
thin walled, fragile
• Cerebral autoregulation is present
25. Psychology
• Less than 6 months – separation ok
• Children up to 4 years of age are upset by the
separation
• Parental anxiety
• fear narcosis and pain
26. Pharmacologic principles
• Excess body water
• Suxa . Antibiotics
• Fat and muscle content ↓ ↓
• Fat soluble drugs – Vd less- thio more
dose
• a drug that redistributes into muscle
may have a longer clinical effect (e.g.,
fentanyl,)
28. Anaesthetic agents
• smaller lung functional residual capacity per
unit body weight and a greater tissue blood
flow, especially to the vessel rich group (brain,
heart, liver and kidney)
• Induction and recovery faster
• MAC of inhalational agents are greatest in the
young and decrease with age
30. Halothane ok
• Halothane has undoubtedly been wrongly
incriminated in many patients for hepatic
injury when a more detailed investigation
would have cleared the anaesthetic from any
blame.
31. Other agents
• Enflurane – pungent smell not much use
Epileptiform activity
• Isoflurane – pungent smell but maintenance
ok
• Desflurane - pungent smell- excellent rapid
recovery
32. Sevoflurane
• Smooth and Rapid induction and recovery
• Non pungent
• Turn the vaporizer to 8%
• No coughing , spasm
• No use of adding N2O
• Ideal in patients with airway obstruction
33. Intravenous agents – more doses
• Thio 5-6 mg/kg
• Propofol induction and maintanance – Ok
• Pain on injection
• Anticholinergic + benzodiazipines + ketamine
acceptable but hallucinations may occur in
the recovery period
34. Muscle relaxants
• Neonates and infants require more
suxamethonium for skeletal muscle paralysis,
• 2 mg/kg for infants
• Neonates and infants are more sensitive than
adults to non-depolarising muscle relaxants.
• Initial doses are similar in both age groups
• because the increased extracellular fluid volume
and volume of distribution in younger patients
36. • Clonidine , midazolam – ok
• 0.1-0.15 mg/kg IM
• 0.5-0.75 mg/kg orally
• Midazolam – effect ??
• The dose of neostigmine per kg required for
antagonism of non-depolarising muscle relaxants is
similar in children to adults
37. Regional anaesthesia
• Spinal cord ends at L2 L3
• Lower projection of dural sac
• Delayed myelinization of nerve fibers
• Cartilaginous structure of bones and vertebrae
• Delayed development of curvatures of the spine
• Tuffier's line, L 5 and lower
• Increased fluidity of epidural fat and Loose
attachment of sheaths
