Anaeasthesia and Analgesia In Childbirth

Question 1

What is the first stage of labour?

Answer 1

Contractions to cervical dilation of 10cm

• visceral pain from uterus (crampy)
• slow, unmyelinated C fibres
• T10 - L1
• paracervical ganglion and lumbar sympathetic chain

Question 2

What is the second stage of labour?

Answer 2

Uterine contractions to birth of baby

• pelvic and perineal distension causes pain
• somatic (sharp and localised) pain
• fast, myelinated A-delta fibres
• pudendal, ilioinguinal, genitofemoral
• Uterus (T10-L1) and sacral (L2-L4)

Question 3

Maternal effects of pain

Answer 3

Sympathetic stimulation

= hyperventilation (decreased CO2)
= increased CO, vasoconstriction and BP
- more oxygen consumption

Metabolic alkalosis from decreased CO2
Uterine vasoconstriction—> less O2 to baby

Question 4

Foetal effects of labour

Answer 4

Maternal hyperventilation causes decreased CO2 —> uterine vasoconstriction—> decreased foetal oxygen

Left shift Hb dissociation curve = increased maternal Hb affinity for oxygen —> decreased foetal oxygen

Question 5

4 categories of parturition analgesia

Answer 5

• non-pharmacological
• pharmacological
• neuraxial
• nerve blocks

Question 6

What types of non-pharmacological exist in parturition?

Answer 6

Birth partner

Hypnosis and breathing

Temperature and water

TENS (transcutaneous electrical nerve stimulation) —> pain gating

Question 7

What are pharmacological parturition analgesia?

Answer 7

• Entonox (gas and air)
• Opiates
  —> stimulates opiate receptors in substantia gelatinosa to hyperpolarise neurones (inhibit)
  = pethidine
  = morphine

Question 8

Epidural

Answer 8

Blocks pain sensation but not general sensation and motor

First stage of labour = T10-L1
Second stage of labour = L2-L4

Can be done anywhere along spinal cord
Catheter = can be topped up

Route

• Skin
• Subcutaneous tissue
• supraspinous lig.
• interspinous lig.
• ligamentum flavum
• epidural space

Question 9

Spinal

Answer 9

Blocks sensation and motor

Has to be done below the spinal conus (at L1)

Route

• skin
• subcutaneous tissue
• supraspinous lig.
• interspinous lig.
• ligamentum flavum
• epidural space
• dura
• CSF

Question 10

Contraindications for neuraxial?

Answer 10

• refusal
• altered anatomy (spina bifida + scoliosis)
• impaired coagulation
• infection