1. Obstetric Anaesthesia

2. Physiological changes in pregnancy
Mechanical
Hormonal
Increased metabolic demands
Fetoplacental circulation

4. Respiratory changes FRC decreased 20%
Ventilation increased (progesterone)
At term minute ventilation increased 50%
O2 consumption increases 40 – 60% and 100% in labour
Blood gas: compensated resp alkalosis
O2 dissociation curve shifted to right

5. Consequences Greater risk of hypoxaemia Decreased O2 stores
Increased O2 demand

6. CVS Changes Blood volume increases 30 – 40% CO increased 43%
SVR decreased 21%
During labour CO increases a further 43% (Pain)
Aortocaval compression
Delivery – autotransfusion < 500ml

7. Blood Constituents Plasma protein concentration decreases
Decreased A/G ratio
COP decreases 13%
Pulmonary oedema
Hypercoagulable state

8. Consequences
Airway difficulties
Oedema
Worse Malampatti Score

9. GIT Function Increased gastric acid Delayed gastric emptying
Decreased lower oesophageal sphincter tone
Increased risk of G-O reflux
Increased aspiration risk
Prophylactic measures mandatory

10. Placenta Not autoregulated
Hypotension can lead to severe uteroplacental insufficiency and fetal distress

11. GA vs Regional for C/S?

12. Regional Anaesthesia is SAFER
But………
Mortality with both

13. National Committee on Confidential Enquiries into Maternal Death of SA 1999 – 2001
25 deaths under Spinal

14. Advantages of Regional
Improved safety
Risk of Intubation averted
Hypoxia
Aspiration
Bonding between mother & baby

15. Regional Techniques Spinal Anaesthesia Epidural Anaesthesia
Combined Spinal - Epidural

16. Regional anaesthesia SPINAL Fast onset Small dose Good quality block
Single shot
EPIDURAL
Slow onset
Large dose
Missed segments
Top-ups possible
Post op analgesia

17. Contraindications to Regional
Patient refusal
Operator inexperience
Absent resuscitation equipment
However……
The above applies to any procedure!!

18. Contraindications to Regional Specific
Hypovolaemia
Coagulation abnormalities
Thrombocytopaenia (<75 x 109/L)
Local sepsis
CVS co-morbidity – MS, AS
Raised intracranial pressure
Allergy

19. Spinal Anaesthesia History / examination / explanation / consent
Antacid prophylaxis
IV access and crystalloid at the time of block
ml Kg-1 (co-loading)
Spinal at L 3/4: 25 G pencil point needle
2 ml 0,5% Bupivacaine (10 mg), plus 10 g Fentanyl (0,2 ml)
T4 block in most cases
Position supine with 150 L lateral wedge/tilt i.e. L side down
GREATER SPLANCHNIC NERVE SYMPATHETIC NERVE AFFERENTS (PAIN) EXITS AT T5

20. Spinal (continued) Facemask oxygen Rx hypotension At delivery
Ephedrine / Phenylephrine
Increase L uterine displacement
Fluid
At delivery
Oxytocin 2,5 iu over 30 seconds
Oxytocin infusion 10 iu in 1000 ml

21. Inadequate block Pre – Sx Intra-operatively Inhaled nitrous oxide
Alfentanil 250 μg or Fentanyl 50 μg
BZD small dose (Midazolam mg)
NB Amnesia and respiratory depression LA
Convert to GA

22. Complications of Spinal
Hypotension
Sympathetic block
Bradycardia
Aorto-caval compression
Occult haemorrhage
High motor blockade
Failed block
Headache

23. Spinals and
Epidurals

24. Spinal Anaesthesia

25. Spinal Needles
Quincke
Whitacre

26. Epidural Anaesthesia
Tuohy needle

27. Epidural Set

28. General Anaesthesia for C/S
Two patients with differing requirements

29. Indications for GA Maternal request Urgent surgery
Regional anaesthesia contraindicated
Failed regional anaesthesia

30. Technique History / examination Antacid prophylaxis Monitoring
L lateral tilt
Preoxygenate
Rapid Sequence Induction / Intubation (RSI or “Crash Induction”) with Thiopentone / Suxamethonium

31. Rapid Sequence induction

33. Technique Pre delivery At delivery At end of case
Nitrous oxide / oxygen 50%
Volatile agent (Halothane or Iso)
At delivery
Oxytocin 2.5 iu
Ergometrine 0,1 mg incrementally to 0,5 mg (PGF2 must never be given IV) if required
Opiate: Morphine or Fentanyl
Nitrous oxide 65%
At end of case
Extubate awake on side if feasible

34. Malampatti Score

35. Suspected difficult intubation
Senior anaesthetist
Optimise position of head
Different blades
Full range of ETTs
Manipulate larynx
Gum elastic bougie
Well functioning suction

36. Failed Intubation Drill
Need to continue?
Mother’s life at risk
Regional not feasible – coagulation etc
Severe fetal distress – prolapsed cord
If not - wake patient up
Spinal or epidural

37. Mother comes first!!

38. Severe pre-eclampsia
Arterial BP > 160 mm “Hg” systolic or >110 mm “Hg” diastolic
Proteinuria >3+
Oliguria
Cerebral signs
Pulmonary oedema
Impaired liver function or hepatic rupture
Thrombocytopenia
HELLP Syndrome (Haemolysis, Elevated Liver enzymes, Low Platelets)

39. Pre-eclampsia

40. Severe pre-eclampsia Management Fluid & vasodilator therapy
Seizure prophylaxis
Expeditious delivery
<120 ml per hour
Spinal: < 10 ml / kg
Emphasis on vasopressors

41. Severe pre-eclampsia
Spinal anaesthesia method of choice if no contraindications even if NRFHT
Platelet count > 75 x 109 l-1
Fetal bradycardia is an indication for GA
Use normal doses for spinal anaesthesia
Similar doses of vasopressors
<120 ml per hour
Spinal: < 10 ml / kg
Emphasis on vasopressors

42. Major anaesthetic problems
Airway management
Pre O2, range of ETTs, bougie, LMA
Intubation response
MgSO4, Alfentanil
Neuromuscular blockade
MgSO4 prolongs NDMRs

43. Eclampsia
GA favoured
Postoperative ventilation, depending on presence of cerebral oedema

44. References
Prevention & Rx of CVS instability during spinal anaesthesia for C/S Dyer et al. SAMJ 94;3:
Oxford Handbook of Anaesthesia Allman & Wilson