Labour analgesia

Question 1

nerve supply to perineum

Answer 1

S1-2-3 (posterior femoral cutaneous)

Question 2

Pudendal nerve: nerve roots?

Answer 2

S2,3,4.

Question 3

Mons/Anterior labia majora innervation

Answer 3

Iliohypogastric (L1), ilioinguinal (L1), genitofemoral (L2)

Question 4

Pain pathways involved in first stage of labour

Answer 4

• C fibres
• Sympathetic fibres within uterine, cervical, hypogastric nerve plexuses into the main sympathetic chain.
• T10-L1 posterior nerve roots to synapse in dorsal horn of spinal cord.
• Spinothalamic tract to brain
• Hypothalamic and limbic systems
• Referred to T10-12 dermatomes felt in lower abdomen, sacrum and back.

Question 5

Pain pathways involved in second stage of labour?

Answer 5

Somatic pain (2nd stage of labour)
-	A delta fibres

• S2-S4
  o Pudendal nerves and perineal branches of posterior cutaneous nerve of the thigh
• L1-L2
  o Cutaneous branches of ilioinguinal and genitofemoral nerves
• Dorsal horn cells
• Spinothalamic tract to brain
• Hypothalamic and limbic systems
• Sharp in character and localised in vagina, rectum and perineum

Question 6

Cochrane review of systematic review on labour pain management classifies analgesia as ‘effective’, ‘may be effective’, and ‘insufficient evidence’. Given 2 examples of each.

Answer 6

Effective: epidural, spinal epidural, 1:1 support

May be effective: music, birthing ball, water immersion, NO, relaxation/massage, acupuncture, non-opioids, sterile water, remifentanil PCA

Insufficient evidence: TENS, biofeedback, hypnosis, aromatherapy, oral/parenteral opioids.

Question 7

Adverse obstetric outcomes associated with regional anaesthesia

Answer 7

assisted vaginal delivery

prolonged second stage of labour

Question 8

List possible complications of epidural anaesthesia.

Answer 8

failure to work (10%)
pruiritis and shivering
significant hypotension (1/50)
severe headache 1%
temporary nerve damage 1/1000
permanent nerve damage 1/13,000
infection/meningitis or epidural blood clot <1/50,000
paraplegia/death 1/140,000

Question 9

Care and observations recommended for regional analgesia?

Answer 9

IV access prior
do not administer routine preloading and maintenance fluid
Check BP every 5 min for 15 minutes during establishment or after further boluses
anaesthetic review after 30 min if woman not pain free
hourly sensory block check
continuous EFM for 30 min during establishment or after boluses of 10mL or more

Question 10

Antidote for severe local anaesthetic toxicity with cardiovascular collapse

Answer 10

Intralipid 20%.
Bolus 1.5mL/kg IV over 1 min. Q5min interval. Max 3 bolus
infusion 30ml/kg/hr.
Cumulative max dose 12ml/kg

Question 11

Drug used for seizures secondary to local anaesthetic toxicity?

Answer 11

benzodiazepines. Can also consider propofol use

Question 12

Treatment of hypotension with local anaesthetic toxicity?

Answer 12

Intravenous normal saline. Inotropes if required. Avoid vasopressin.

Question 13

Treatment for ventricular dysrhythmia in local anaesthetic toxicity?

Answer 13

sodium bicarbonate 1-2mmol/kg up to 100mmol. IV 1-2min until perfusing rhythm obtained. Can also use amiodarone. Avoid CCB/B-blockers.

Question 14

Treatment for methaemoglobinaemia in local anaesthetic toxicity?

Answer 14

methylene blue IV 1-2mL/kg. IV Q5min.

Question 15

Maximum dose lignocaine?

Answer 15

4-5mg/kg.

Question 16

ECG changes local anaesthetic toxicity?

Answer 16

Prolonged PR and QRS