Anesthetic Consideration in Pediatric and Obstetrics

1. Special Perioperative
Considerations : Paediatric Patient

2. Physiological Differences
Pediatric vs Adult Patients and It’s Effect
RESPIRATORY CONSIDERATIONS
• Tidal Volume : 7ml/kg, Dead Space: 2.2ml/kg
• FRC: 30ml/kg
• Greater Minute Ventilation (VA ) in neonate (100-
150ml/kg/min) vs Adult (60-70ml/kg/min)
• VA : FRC Ratio 5:1 vs 2:1 in adult
• Oxygen Consumption : 2x adult (6ml/kg)
• Alveolar ventilation : 2x adult

3. • Closing Capacity = Residual Volume + Closing
Volume (CV)
• In healthy young adults CV= 10% of Vital
Capacity but in infants and orderly it may
exceed FRC – Airway closure occurs at normal
tidal volumes.
• FRC decreases under anesthesia -> more
atelectasis. PEEP and CPAP important

4. Hematological Considerations
CATEGORY BLOOD VOLUME
PRE TERM 100-120 ml/kg
NEONATE 90 ml/kg
INFANT 85 ml/kg
CHILD 80 ml/kg
• Adult : 70 ml/kg
• Shock manifests at about 25% blood loss

5. GASTROINTESTINAL CONSIDERATIONS
• Liver is immature. Enzyme systems not fully
matured – some drugs metabolized more
slowly.
• Carbohydrate reserves are low in neonates-
vulnerable to hypoglycemia.
• The ability to coordinate swallowing with
respiration does not fully mature until the
infant is 4-5 months of age – high incidence of
gastro esophageal reflux in newborns is very
common

6. RENAL CONSIDERATIONS
• Renal function is immature. Renal blood flow
is reduced due to high renal vascular
resistance.
• Neonates cannot excrete a large solvent or Na
load. Thus, reduced dosages or prolonged
frequency intervals may apply.

7. NEUROLOGICAL CONSIDERATIONS
• The BBB is more permeable in neonates –
barbiturates, opioids, antibiotics all cross
more readily
• The brain contain higher proportion of fat –
may allow volatile agents to reach
concentration more rapidly.

8. Thermoregulation
• Poorly developed temperature regulatory
mechanism
• High body surface area ratio with minimal SC fat
and poor insulation – vulnerable to hypothermia
- Hypothermia: assoc. with delayed awakening,
cardiac irritability, resp depression, altered drug
responses.
- Premature infant even more susceptible d/t
very thin skin & limited fat stores.
• Measures : warm mattress, warming the OR, hot
air blankets, warm anesthetic gases.

9. Pre-op Assessment of Pediatric Patient
1) Medical History and Anesthetic
History
2) Physical Examination
3) Investigation AND Risk assesment

10. 1. Medical History and Anesthetic History
• Any previous problems with anesthetics (inc
family history)
• Allergies
• Previous medical problems (Incl congenital
anomalies)
• Recent respiratory illness
• Current medications
• Recent Immunizations
• Loose teeth?
• Fasting times

11. 2. Physical Examination
• Children MUST be weighed – all drug doses
relate to body weight.
• BP monitoring during preoperative period :
detect any decreased cardiovascular reserve
or exaggerated hypotensive responses.
• Temperature Monitoring : To detect
hypothermia or malignant hyperthermia.

12. 3. Pre-op Investigations
• Hemoglobin : Large expected blood loss,
premature infants, systemic disease, CHD.
- Preop Hb <10g/dl is abnormal and needs to
be investigated.
• Electrolytes: Renal/metabolic disease, IV fluids,
dehydration
• Urinalysis: Renal disease or UTI
• Cardiac Evaluation: Arrhythmias, conduction
defects. EEG, ECHO.
• Pulmonary Function Test : Lung impairment
• Chest X-Ray : Active respiratory disease, scoliosis,
CHD

13. Pre-Medication of Paediatric Patient
• Routine sedative is unnecessary – Parents is the
best premedication
• Some children will require pre-op sedation :
- Excessively upset child
- Childen with previous unpleasant experiences
- Children with developmental delay
• Infants have not yet developed strangers
anxiety– low risk, Pre school kids – most at risk

14. Pre-medications :
• Oral Midazolam (0.5mg/kg)
• Temazepam (10-30mg)
• Ketamine (2mg/kg)
• Clonidine (4ug/kg)
• Children undergoing cardiac surgery – heavily
premedicated.
- Morphine
- PethCo (Pethidine, Promathazine &
Chlormazine)

16. Post-op Care for Paediatric Patient
• PostOperative Nausea & Vomitting(PONV)
- Morphine increases risk of PONV by 30%
- Mgmt: Combination antiemetic + 5HT3
antagonists with dexamethasone 0/1mg/kg
• PostOp Pain Relief
- Paracetamol & NSAIDS: minor cases/day surgery
- Caudal Analgelsia
- Morphine Infusions

18. Anesthetic Considerations
in Obstetric Patients

19. CVS – Plasma Volume
• An increase in plasma volume (50%), RBC
volume (20%) and total blood volume (35%).
• Most of the rise take place before 32 – 34
weeks gestation; after that there is relatively
little change.
• The increase is related to the size of fetus and
can be associated with multiple pregnancy.

20. • The changes in plasma volume result in
haemodilution with subsequent decrease in
RBC volume, haematocrit, haemoglobin and
serum protein levels.
• Physiological anaemia of pregnancy.

21. CVS – Cardiac Ouput
• Cardiac output increases during pregnancy (
40 – 50 %).
• The increase begins at 8th week of gestation
and reaches a maximum of 30 – 50% above
normal near term.
• During early labour, CO increases further due
to catecholamine secretion in response to pain.

22. CVS – Aortocaval Compression
• During pregnancy, increase in CO is sustained by
increasing HR as SV reduces towards term.
• In supine position late in pregnancy, uterine contraction
and maternal hypotension (due to aortocaval
compression) markedly enhance the obstruction effects
on the aorta and its branches.
• The vascular region exposed to uterine compression is
the most protruding part of vertebral column at L4-L5.
• The force of the contracting myometrium and the
uterine gravitation may exert a pressure 2 – 3 times
greater than the same force distributed over the large
surface area of the amniotic cavity.

24. CVS –Peripheral Vascular Resistance
• A decreased in peripheral vascular resistance
results in a small decrease in SBP and in mid-
pregnancy a more marked decrease in DBP.
• Central venous pressure (CVP) remain normal
during pregnancy but is elevated 4 – 5 cm of
H20 with each contraction due to transient
blood volume increases.
• Maternal bearing down and oxytocin infusion
also increase CVP.

25. CVS – Anaesthethic Considerations
• Blood loss at vaginal delivery ranges from 250 –
500 ml, with caesarean section it ranges from 500
– 1000 ml.
• At delivery, autotransfusion of as much as 500 ml
of blood into maternal circulation from uterus and
placenta into maternal circulation minimizes the
impact of maternal haemorrhage.
• Must constantly reasess the parameters of O2
availability; Hb, SPO2, CO etc when deciding if
transfussion is necessary.

26. • Vasomotor block from induction of spinal or epidural
anaesthesia or other procedures may deprive patient of
compensatory vasoconstriction.
• Patient with severe aortocaval syndrome are particularly
vulnerable to this. Anaesthetist should ascertain the degree
of the block by measuring BP first with the patient on her
left side and then again after she ahs been supine for 5 – 15
minutes.
• Avoid techniques that produce vasomotor block, if not
possible, prevention measures such infusion of fluids prior
to block and lateral displacement of uterus or left lateral tilt
after induction must be taken to avoid severe arterial
hypotension.

27. • During pregnancy, the peridural venous plexus
is distended. This leads to:
1. Increased epidural space pressure, with less
reliability on the ‘hanging drop’ technique.
2. Decreased epidural capacity, results in use of smaller
volumes of local anaesthetics.
3. Increased risk of intravascular placement of the
epidural needle and catheter, with greater potential
for local anaesthetic toxicity.
• The dosage for spinal anaesthetics must also be
reduced.

28. Respiratory System
1. Airway
2. Lung volumes
3. Ventilatory mechanics
Airway – Capillary Engorgement
• Throughout the respiratory tract. So nasopharynx,
larynx, trachea and bronchi become swollen and
reddened.
• These changes stimulate inflammation often causing
changes in the voice and make breathing through the
nose difficult for the women at term.

29. Respiratory System
Lung volumes:
• The growing uterus causes the diaphragm to rest 4
cm higher, but it does not impair its excursions.
• The abdominal muscles have much less tone and
are less active in pregnancy.
• Total Lung Capacity (TLC) is reduced due to the
rise in diaphragm, but is compensated by the
increased anterior-posterior and transverse
diameters of the rib cage.

31. RSP – Ventilatory Mechanics
• Significant ventilatory changes are not seen until
the 5th or 6th month of pregnancy.
• After that, there is a progressive decrease of both
the Expiratory Reserve Volume (ERV) and
Residual Volume (RV).
• At term, the sum of these two volumes, the
Functional Residual Capacity (FRC) is decreased
by 17%.
• However, there is a concomitant increase in
Inspiratory Capacity (IC) with the result that the
Vital Capacity (VC) and TLC remain unaltered.

33. • Minute Ventilation (VE) is increased by 50% at term.
• Tidal volume increased (40%) more than respiratory
rate (15%) and this decreases the dead space
component of ventilation. So, alveolar ventilation
reaches a level 70% above that in non-pregnant state.
• During labour and delivery, pain acts as a potent
ventilatory stimulus. O2 consumption increases by 10 –
20% during pregnancy and is further elevated as much
as 100% over normal during labour.
• This occurs in response to demand by the growing
fetus, placenta and uterus and to increase cardiac and
respiratory work, particularly during labour.

34. • Hyperventilation during pregnancy, mainly
due to increase in tidal volume, is attributed to
the action of progesterone as has been shown
in a study.

35. RSP – Anaesthetic Consideration
• Increased alveolar ventilation augments the
transfer of gases between mother and fetus.
• Because of these changes, patient is much more
susceptible to rapid changes in respiratory blood
gas levels during respiratory complications than
the non-pregnant woman.
• Consequently, hypoxia, hypercarbia and
respiratory acidosis as a result of hypoventilation,
breath-holding or respiratory obstruction develop
more readily.

36. RSP – Anaesthetic Consideration
• During an endotracheal intubation, even by a skilled
anesthetist, the oxygen tension may fall precipitously after
only a brief period of apnea.
• Conversely, moderate to severe hyperventilation can
quickly lead to severe respiratory alkalosis with arterial
carbon dioxide tensions as low as 10-15 mmHg and pH as
high as 7.7.
• Inhalational anesthesia is rapidly induced because
hyperventilation, particularly during labor, delivers more
anesthetic to the alveoli.
• At the same time, a smaller than usual functional residual
capacity results in less dilution of incoming gases, allowing
higher alveolar concentrations to be reached more quickly.

37. Gastrointestinal System
• Prolonged gastric emptying is noted from at
least the 34th week of pregnancy and is most
likely hormonal in origin (progesterone).
• Anxiety and excitement have a severe
depressant effect on gastric motility and this
effect is mediated by the splanchnic nerves.
Pain and emotional disturbances which
accompany labour also depress gastric motility
and delay gastric emptying.

38. • During pregnancy there is an increase in
intragastric pressure. In pregnant women without
heartburn, the gastroesophageal sphincter
responded to this increase in pressure by an
increase in maximum sphincteric pressure. In the
group of pregnant women with heartburn, there
was no significant increase in sphincter pressure,
and the stomach-to-sphincter pressure gradient
was decreased. Under these circumstances, the
sphincter does not maintain competence of the
gastroesophageal junction and the symptoms of
reflux occur.

39. GIT – Anaesthetic Consideration
• With regard to general anesthesia, pregnant women
from 32 weeks gestation onward must be considered as
having "full stomachs” and when general anesthesia is
employed, have a rapid intravenous induction followed
by cricoid pressure and tracheal intubation.
• The patient should be extubated awake when reflexes
are intact.
• Whenever feasible and appropriate, the use of regional
anesthesia should be employed. The use of prophylactic
antacids at the present time is a controversial issue due
to the untoward effects of aspiration of antacid
materials themselves.

40. Plasma Cholinesterase
• Plasma cholinesterase activity declines during
pregnancy and in the immediate postpartum period.
• Anesthetic considerations: Since plasma cholinesterase
is responsible for the hydrolysis of succinylcholine, a
low degree of enzymatic activity may result in an
undesirably long duration of paralysis following
succinylcholine administration.
• It is strongly recommended that whenever
succinylcholine is being administered to a patient, that
the neuromuscular status be monitored by a peripheral
nerve stimulator.

41. Maternal Physiological Changes
Value Non-pregnant Pregnant
Haematocrit 0.37 – 0.47 0.32 – 0.41
Haemoglobin (g/dL) 11.5 – 16.0 11.0 – 15.0
WCC ( /L) 4.0 – 11.0 X 109 5.0 – 16.0 X 109
Platelets ( /L) 150 – 400 X 109 134 – 400 X 109
ESR (mm/hr) (age in years + 10) 2 44 – 114
Fibrinogen (g/L) 2 – 4 4 – 6
Albumin (g/L) 35 – 50 28 – 40
Urea (mmol/L) 2.5 – 6.7 1.6 – 6.0
Creatinine (mmol/L) < 110 38 – 90
pCO2 (mm/Hg) 34 – 46 27 – 32
pO2 (mm/Hg) > 80.6 > 80.6
HCO3 (mmol/L) 24 – 28 18 – 23

42. Pain of childbirth
Nociceptive pathways
involved
Uterine pain:
T10 – L1 during labor
(sensory fibres ending in
dorsal horns)
Vaginal pain:
S2-S4 for delivery
(pudendal nerve)

44. Analgesia for labor and delivery
• Non-medication
• Inhalational
• Parenteral
• Regional

45. Analgesia- Non medication options
• Breathing exercises
• Autohypnosis
• Acupuncture
• White Noise/ Music
• Massage/ walking
• TENS  transcutaneous electrical nerve
stimulation
• Water bath

46. Inhalation Medications
• Nitronox/Entonox: 50:50 mixture of oxygen and
nitrous oxide
Advantages: on demand delivery, relatively safe
Disadvantages: variable efficacy, nausea, drowsiness,
neonatal depression

47. Parenteral Medications
• Narcotics: meperidine/pethidine/demerol, fentanyl
Advantages: relatively good analgesia, beneficial when
regional analgesia is contraindicated
Disadvantages: nausea, vomiting, sedation, neonatal
depression, short duration of action

48. Regional Analgesia
• Epidural, spinal, combined spinal-epidural
Advantages: provide most effective pain relief,
reduces maternal sympathetic stimulation and
hyperventilation, less drug transfer to fetus,
improved uterine blood flow, decrease in birth
trauma e.g. use of forceps, minimal neonatal
depression
Disadvantages: invasive technique, side effects
(hypotension, headache, itching, nausea,
urinary retention, limited mobility), nerve
damage, infection, association with prolonged
labour

49. Regional Analgesia
Indications
• Maternal request
• Expectation of operative delivery
• Maternal disease
• Specific CVS disease
(regurgitation valvular lesion)
• Severe resp disease (CF)
• Specific neurological disease
(intracranial AV malformations)
• Obstetric disease (pre-eclampsia)
• Morbid obesity
Contraindications
• Maternal refusal
• Allergy
• Local infection
• Uncorrected hypovolaemia
• Coagulopathy (platelet
>80x109 /L and INR < 1.4 are
safe for neuraxial
procedure; still need clinical
judgment for each cases)

50. Combined Spinal Epidural Analgesia
(CSE)
• Low dose subarachnoid LA and/or opioid together
with subsequent top-ups of weak epidural LA.
• Rapid onset with minimal motor block and
effective analgesia.
• Epidural alone produce similar degree of
analgesia and motor block, but take 10 – 15 min
longer to establish.

51. Epidural Anesthesia
• Potential Complications:
– Hypotension
– Headache (approx 1:100)
– Transient backache ~24hrs
– Urinary retention
– Unintentional spinal injection
– Intravascular injection of local anesthetic
– Neurological damage
– Infection

52. CSE
• Potential Complications:
– Hypotension
– Headache (rare ~1:100)
– Backache (temporary ~24hrs)
– Nausea/vomiting (secondary to BP, narcotics)
– Neurological damage (very rare)
– Anaphylaxis (very rare)

53. Pre medication of C-sect patient
• Use antacid and prokinetic agent – elevate gastric pH & reduce the
intragastric volume
• A suggested regime is :
 Elective surgery :
-150mg ranitidine orally 2hr & 12hr before surgery
-10mg metoclopramide orally 2hr before surgery
-30ml 0.3M sodium citrate immediately before surgery
 Emergency surgery (if prophylaxis has not been given) :
-50mg ranitidine by slow IV injection immediately before surgery.
-10mg metoclopramide IV injection immediately before surgery
-30ml 0.3M sodium citrate orally immediately before surgery

54. Modalities of anaesthesia for C-sect
A.Regional
I. Epidural
II. Spinal
III.Combined spinal epidural
B. General

55. Regional - EPIDURAL
Advantages Disadvantages
Easy to top up labour epidural Slow onset
Stable BP Large doses of LA
Intraoperative top up possible Poorer quality of block than spinal anaesthesia
Epidural can be used for post op analgesia

56. Indications
• Already have epidural analgesia established
for labor
• Specific maternal disease. Eg : cardiac disease

57. Technique
• History, examination, explanation and consent
• Antacid prophylaxis has been given
• 16G/larger IV access. Start 10-15ml/kg crystalloid co load
• Epidural catheter at L2/3 or L3/4 vertebral interspace
• Top up the epidural incrementally with local anaesthetic &
opiod
-8-10 ml boluses of 2% lidocaine with 1:200000 every 2-
3minutes, max 20ml or
-8-10ml o.5% bupivacaine/levobupivacaine every 4-5 min,
max 2ml/kg in any 4hr period
• 100μg fentanyl or 2.5mg diamorphine improves the quality
of the analgegesia

58. Cont
• S4-T4 block. Check sacral dermatomes, as epidural
sacral dermatome doesn’t spread caudally. Document
level of block & adequacy of perioperative analgesia
• Patient in supine position with left lateral tilt or wedge.
Give facemask if SpO2 <96% on air.
• If hypotension
- Fluid
- 50-100μg phenylepinephrine IV bolus or 6mg
ephedrine IV
- Increasing left uterine displacement

59. • 9IU (3, 3, 3 )oxytocin IV bolus at delivery. If
tachycardia
must be avoided then an IV ( ?? IU ) oxytocin in
500ml crystalloid over 4hr.
• NSAID given at the end of procedure -
(CI -100mg diclofenac PR)

60. Regional - SPINAL
• Commonly used for elective C-sect
• Rapid in onset and dense block
• With intrathecal opiod- long acting post
operative analgesia

61. Advantages Disadvantages
Quick onset Single shot
Good quality analgesia Limited duration
Easy to perform Inadequate analgesia is difficulty to correct
Rapid changes in BP and cardiac output

62. Technique
• History/examination/explanation and consent.
• Ensure that antacid prophylaxis has been given.
• Establish 16G or larger IV access. Start 10–15ml/kg
crystalloid co-load.
• Perform spinal anaesthetic at L3/4 interspace using a
25G or smaller pencil-point needle. With the orifice
pointing cephalad, inject the anaesthetic solution, e.g.
2.5ml 0.5% hyperbaric bupivacaine with 300µg
diamorphine or 15µg fentanyl. Intrathecal diamorphine
improves postoperative analgesia, while intrathecal
fentanyl has little postoperative analgesic benefit.

63. Cont
• During the insertion of a spinal anaesthetic, some anaesthetists
place patients in a sitting position, while others lie patients on their
side. The sitting position usually makes the midline easier to find
(important in obese patients), and may be associated with a faster
onset, although the height of block is less predictable. A lateral
position is associated with a slower onset of block, particularly if a
full lateral position is maintained until the block has fully
developed. This position also avoids aortocaval compression. With
both positions, when hyperbaric local anaesthetic solutions are
used, it is important that the cervical spine is kept elevated (pillow)
to prevent local anaesthetic spreading to the cervical dermatomes.
• Hypotension is more common with spinal anaesthesia than epidural
anaesthesia. Patients may benefit from a continuous infusion of
pressor agent initiated at the time of insertion of spinal block.
• Continue as for epidural anaesthesia for Caesarean section

64. Regional - CSE
Advantages Disadvantages
Quick onset Rapid change in BP & cardiac output
Good quality analgesia More difficult with higher failure rate of spinal
injection
Intraoperative top up possible Untested epidural catheter
Epidural can be used for postop analgesia

65. Indications
• Prolonged surgery.
• Using the epidural catheter for postoperative
analgesia.
• Limiting the speed of onset of a block. A small
initial intrathecal dose of local anaesthetic can
be supplemented through the epidural catheter
as required.

66. Technique
• History/examination/explanation and
consent.
• Ensure that antacid prophylaxis has been
given.
• Establish 16G or larger IV access. Give 10–
15ml/kg crystalloid co-load.
I. Needle through needle technique
II. Two needle technique

67. General Anaesthesia
 Indications for general anaesthesia include:
• Maternal request.
• Urgent surgery. (In experienced hands and with a team
that is familiar with rapid regional anaesthesia, a spinal or
epidural top-up can be performed as rapidly as a general
anaesthetic.)
• Regional anaesthesia contraindicated (e.g.
coagulopathy, maternal hypovolaemia).
• Failed regional anaesthesia.
• Additional surgery planned at the same time as
Caesarean section

68. Technique
• History and examination. In particular assess the maternal
airway— mouth opening, Mallampati score, thyromental
distance, neck mobility
• Antacid prophylaxis
• Start appropriate monitoring
• Position supine with left lateral tilt or wedge.
• Preoxygenate for 3–5min or, in an emergency, with 4–8 vital
capacity breaths with a high flow through the circuit. Ensure a
seal with the facemask. At term, women have a reduced FRC
and a higher respiratory rate and oxygen consumption. This
reduces the time required for denitrogenation, but also
reduces the time from apnoea to arterial oxygen desaturation.

69. • Perform rapid sequence induction with an adequate dose of
induction agent (e.g. 5–7mg/kg thiopental). A 7.0mm endotracheal
tube is adequate.
• Propofol has also been used for Caesarean section without any
major reported complications, although at present thiopental probably
is still the most commonly used agent in the UK.
• Ventilate with 50% oxygen in nitrous oxide. If severe fetal distress is
suspected then 75% oxygen or higher may be appropriate. Maintain
ETCO 2 at 4.0–4.5kPa (30–34 mmHg).
• Use ‘overpressure’ of inhalational agent to rapidly increase the end
tidal concentration of anaesthetic agent to at least 0.75 of MAC (e.g.
2% isoflurane for 5min, then reduce to 1.5% for a further 5min).

70. • At delivery:
 Give 9IU (3, 3, 3) oxytocin IV bolus. If tachycardia must be
avoided then an IV infusion of ( ?? IU )syntocinon in 500ml
crystalloid, infused over 4hr, is effective.
 Administer opioid (e.g. 0.1 – 0.2mg/kg morphine).
 Ventilate with 35% inspired oxygen concentration in nitrous
oxide. Inhalational agent can be reduced to 0.75 MAC to
reduce uterine relaxation.
 At end of procedure give an NSAID (e.g. 100mg diclofenac
PR). Bilateral ilioinguinal nerve blocks for postoperative
analgesia.
 Extubate awake in the head-down left lateral position.
 Give additional IV analgesia as required.

71. Effect of general analgesia on the fetus
• Anaesthetic agents cross the placenta –
Thiopental can be detected in the fetus
• Opiods may cause fetal depression
• Neonatal respiratory depression – reversed
with ??

72. Post op analgesia for C-sect patient
a) Opioids
• IV patient-controlled or oral can be used. May be
transferred to the neonate through breast milk, but
with negligible effect
• Intrathecal/epidural opioid :
-Bolus at the beginning, Fentanyl last longer than LA & no
post-op analgesia. Epidural fentanyl, ( ? Mg/kg) up to
2hourly for 2-3 doses.
-Intrathecal diamorphine (0.1-0.2 mg/kg) can be expected
to provide 6–18hr of analgesia. More than 40% of women
will require no other postoperative opioid.

73. -Epidural diamorphine (2.5mg in 10ml saline)
provides 6–10hr of analgesia after a single dose.
-Intrathecal preservative-free morphine (0.1-0.2
mg/kg) provides long- lasting analgesia (12–18hr).
Doses above 150µg are associated with increased
side effects without improved analgesia.
b) NSAIDs
-effective postoperative analgesics, reducing opioid
requirement

74. SPECIAL PERIOPERATIVE
CONSIDERATIONS : PAEDIATRIC
PATIENT

75. Anatomical Differences between
Paediatric and Adult Patients
 RESPIRATORY SYSTEM
• Terminal bronchiole opens into single alveolus. The alveoli
are thick and only 10% of adult (growth cont until 6-8yr).
• Cartilagenous ribs are horizontally aligned ; ‘bucket handle’
of adult thorax isn’t possible. Intercostal muscles are poorly
developed- fatigue easily. Diaphragm is more horizontal-
reduce mechanical advantage.
• Ventilation is essentially diaphragmatic and rate
dependent. Abdominal distension may cause splinting
diaphragm- respiratory failure.
• Closing volume is within tidal breathing. Decrease FRC-
increase pulmonary shunt & lung collapse. CPAP improves
oxygenation & reduce effort.

76. Cont
• Narrow airways- increased resistance(up to
8y/o). Nasal resistance accentuate children
with nasal congestion.
• Apnea : common post-op problem in preterm
neonate. (Episode >15s, induce cyanosis,
bradycardia). Use CPAP.
• High metabolic rate & alveolar minute volume
– volatile agents has rapid induction &
emergence than with adult.

77. Cardiovascular System
• PVR falls in response to rise PaO2 & fall in PaCO2.
closure of foramen ovale & ductus arteriosus- lead to
pulmonary HPT & right to left shunt.
• Small ventricle- reduced contractile mass & poor
ventricular compliance. CO is higher than adult
(200ml/kg/min).
• Heart rates up to 200bpm is tolerated. Bradycardia
should be treated with oxygen. Heart rate <60bpm
(neonate, infant) require external cardiac compression.
• Autonomic & baroreceptor is fully functional at term,
mediated parasympathetic tone predominates.

78. Gastrointestinal System
• Liver is immature. Enzyme matured by 12wk.
Some drugs are metabolized slowly by different
enzyme pathways from adults.
Eg : barbiturates & opioids have a longer duration in
the neonate.
• Glucuronyl transferase system was poorly
developed- rise in unconjugated bilirubin.
Eg : sulphonamides, diazepam, vit K- displace
bilirubin from plasma protein.
• Carbohydrate reserves are low – vulnerable to
hypoglycaemia.

79. Renal System
• Nephron formation is complete at term but
renal function is immature.
• Renal blood flow & glomerular filtration are
low in first 2 years of life d/t high renal
vascular resistance.
• Tubular function is immature until 8 months.
• Neonates cant excrete large solvent or sodium
load – reduced drug dosages or prolonged
frequency intervals.

80. Haematology
• At birth, 70-90% Hb are HbF. Within 3 months
HbA predominates.
• HbF combines more readily with oxygen but
released readily.
• O2/Hb dissociation curve shifts to the right – HbA
& 2,3-DPG rise.
• Factor II, VII, IX, X & platelet function are deficient
in the first few months.
• Transfusion is recommended when 15% of
circulating blood volume has been lost.

81. CNS
• Neurons are complete at term, but brain cells are reduced.
Dendritic proliferation, myelination & synaptic connections
developed in the 3rd trimester & first 2 years of life.
• BBB are permeable in neonates – barbiturates, opioids,
antibiotics and bilirubin all cross readily.
• Neonates can appreciate pain & associated with increase
heart rate, BP and neuro-endocrine response.
• Cerebral autoregulation is function from birth.
• Cerebral vessels are thin walled,fragile – prone to
intraventricular haemorrhages. Risk is increased with
hypoxia, hypercarbia, hypernatraemia, low haematocrit.

82. REFERENCES
• Oxford Handbook of Anesthesia 3rd Edition
2012
• Royal Children Hospital’s Guideline of Pediatric
Anesthesia

83. THANK YOU!