This document discusses subspecialty anesthesiology, focusing on pediatrics and obstetrics. It covers the key differences between adult and pediatric patients, including their psychology, anatomy, respiratory physiology, cardiovascular physiology, and more. It emphasizes that pediatric patients are not just small adults. It also discusses the unique considerations for obstetric anesthesia, noting that the pregnant patient and fetus must both be considered. Drugs are discussed in terms of their placental transfer and potential fetal effects.

1. DR ROWAN MOLNAR ANAESTHETICS
STUDY GUIDE PART VI
Part VI:
Sub-Specialty Anaesthesia

2. PART VI:
SUB-SPECIALTY ANAESTHESIA
INCLUDES:
1. Paediatrics
2. Obstetrics
3. Cardiothoracic
4. ENT/Head & neck
5. Neurosurgery

3. SUBSPECIALTY ANAESTHETICS A:
PAEDIATRIC
“They’re not just small adults”
. . . But . . .
“Nor are they all just big neonates, either”

4. CASE STUDY IV
Paediatric Hypospadias Repair

5. HISTORY
 4 year old boy (obviously!)
 Grade III hypospadias & chordee
 For EUA/repair
 Background: Mild asthma & ADHD

6. ISSUES
 Preop assessment & stabilisation
 Premedication
 Induction & IV insertion
 Prolonged surgery
 Postoperative analgesia
 Postoperative IV & IUDC

7. ADULT-PAEDIATRIC DIFFERENCES
 Psychosocial
 CNS
 Respiratory
Airway
Other
 Cardiovascular
 Renal/fluids
Gastrointestinal
Hepatic/metaboli
c
Endocrine
Haematological
Immunological
Musculoskeletal
Integument

8. THE PSYCHOSOCIAL DIMENSION
 There are (almost) always two patients – child and parent(s).
If you don’t keep the parents happy, or at least reassured, the
child won’t be either – no matter how good the anaesthetic.
 Children don’t understand that you are there to help – only
that you are a stranger.
 Children hate needles. Parents hate their children having
needles. Even without this, cannulation can be difficult.
Anything that ameliorates this is good: such as premedication,
EMLA to cannula sites & inhalational inductions.
 Parental presence at induction can be a good idea – as long
as the parent is going to cope. If in doubt, a generous premed
& a goodbye outside may be a better option.

9. ANATOMICAL DIFFERENCES 1
 Body proportions
Head larger
Limbs smaller
Increased surface
area to volume
ratio
 CNS differences
Brain & spinal cord
relatively larger

10. ANATOMICAL DIFFERENCES 2: AIRWAY
 Head larger
 Nares (relatively) larger
 Larynx higher
C3 in neonate -> C6 in
adult
 Epiglottis longer (&
softer)
 Cricoid ring narrowest
part of airway

11. PAEDIATRIC RESPIRATORY PHYSIOLOGY
 Chest wall mechanics & tracheobronchial tree
“floppier”.
 Tidal volume/dead space same as adults in
mls/kg
 Respiratory rate & minute volume higher
 FRC similar to adult in mls/kg, but vO2 higher, so
desaturate more quickly when apnoeic.
 Control of respiration immature till ~ 15/12 post
conceptual age – up till then vulnerable to
apnoeas – especially post GA &/or narcotics.

12. PAEDIATRIC CVS PHYSIOLOGY REFRESHER
 Fetal circulation/Postnatal transition
-predelivery: systemic & pulmonary circulations in parallel,
with oxygenation via placenta & high pressure/low flow on
(R) side.
-Transition at birth to systemic & pulmonary circulations in
series with fall in PVR & closure of shunts.
 Haemodynamics
Neonates & infants have fixed stroke volumes: CO dependant
on HR – i.e. bradycardia = hypotension & shock.
 Autonomic control
Different in neonates & children – response to hypoxia is
bradycardia (“Diving reflex”) rather than tachycardia.

13. BLOOD & BODY FLUIDS
 Blood volume 80-90 mls/kg (adult ~ 70)
 Birth Hb 180-200 g/L (adult 120-160)
Falls to ~ 110 @ 6/12 then rises.
 Fetal haemoglobin (HbF)
Different chains
Lower p50 (Hb-O2 curve shifted left)
75% of Hb at birth  minimal @ 6/12.
 Body water 75-80% in neonate (adult 65%)
 ECF compartment larger than ICF
(crossover @ ~ 4/12)

14. PAEDIATRIC THERMODYNAMICS
 Infants at higher risk of hypothermia
 Higher surface area to volume ratio
 Remember the four modes of heat loss:
1. Conduction
2. Convection
3. Radiation
4. Evaporation
All four occur more when the surface area to
volume ratio is higher

15. HEAT PRODUCTION & REGULATION
 Controlled in hypothalamus
 Balances heat loss & heat production
 Heat production
 Shivering – poorly developed in neonate/infant
 Metabolic thermogenesis (brown fat)
 Thermoneutral environment;
 Point of minimum O2 consumtion
 e.g. for unclothed term baby is ~ 33°C

16. SUBSPECIALTY ANAESTHETICS B:
OBSTETRICS
Remember, once again you have two patients – but this
time they are physically connected

17. CASE STUDY V
Caesarian Section

18. HISTORY
 38 yr old lady, P0G1
 Booked LSCS
 IVF pregnancy
 Moderate PIH/pre-ecclampsia
 History of back pain
 Wants to be awake for delivery
 Needle phobic

19. ISSUES
 Preop consultation
 Investigations
 Premedication
 Choice of anaesthetic technique
 Choice of IV fluids
 Backup anaesthetic plan
 Postoperative monitoring
 Analgesia plan

20. PRINCIPLES
 Pregnancy is a normal, but vulnerable condition.
 The prregnant patient is different
 Delivery is hazardous
 Operative intervention may be required
 Labour & delivery can be agonisingly painful
 Anaesthesia inevitably has (at least some) foetal
effects/implications.

21. DIFFERENCES IN PREGNANCY
 Psychosocial
 CNS
 Respiratory
Airway
Other
 Cardiovascular
 Renal/fluids
Gastrointestinal
Hepatic/metaboli
c
Endocrine
Haematological
Immunological
Musculoskeletal
Integument

22. DRUGS & THE PLACENTA
General rule: If it crosses the blood brain barrier,
it crosses the placenta!
Placental transfer:
Narcotics/Sedatives/GA agents - HIGH
Muscle relaxants -Essentially nil
Local anaesthetics – Significant (in freebase form) . .
. but peak maternal plasma levels usually post
delivery