Analgesia in labour

Question 1

What causes pain in the first stage of labour?

Answer 1

Uterine contractions + dilatation of the cervix:
-VISCERAL pain (colicky, poorly localised)
-Pain in UTERUS carried via T10-L1 roots
-Pressure on PELVIC STRUCTURES causes pain with afferent nerves via L2-S1 roots

Question 2

What causes pain in the second stage of labour?

Answer 2

-Continued pain from first stage (dilation and pressure on pelvic structures + pelvic floor)
As well as:
-SOMATIC pain (sharp, well localised)
-PUDENDAL nerves
-S2,3,4 roots

Question 3

What factors contribute to increased pain in labour?

Answer 3

-Malposition of the baby (occipito-posterior)
-Large baby
-Pelvic anatomy
-Strength of contraction
-Complications eg uterine rupture, trauma
-Previous complications / primigravida (tissues dilate more freely if delivered before)
-Anxiety, fear, social / cultural factors

Question 4

What are some non-pharmacological methods of analgesia in labour?

Answer 4

-Antenatal information and preparation
-Positioning
-Birthing partner support
-Hypnosis
-Massage
-Acupuncture
-Breathing techniques
-Hydrotherapy
-Aromatherapy
-Placebo injections
-TENS

Question 5

What is an example of an inhalation pharmacological analgesia and what are its effects?

Answer 5

-ENTONOX (50% NO2, 50% O2)
-Often provides significant but incomplete analgesia
-Quick onset and offset
-Must start at the beginning of a contraction
-SEs include dizziness, nausea and amnesia

Question 6

What are some opioid analgesics and what are their effects?

Answer 6

NB opioids CROSS THE PLACENTA
-Examples = codeine, pethidine, morphine, fentanyl
-Given IV or IM
-Provides incomplete analgesia
-SEs include sedation, N+V, respiratory depression

Question 7

What regional analgesics are used in labour?

Answer 7

-Lumbar epidural
-Spinal
-Combined spinal + epidural
-Para-cervical infiltration and caudal (rare)

Question 8

When are combined spinal + epidurals (CSEs) used?

Answer 8

-In advanced labour
-Presence of perineal pain
-Re-siting an epidural

Question 9

What are some immediate and delayed complications from regional anaesthetics?

Answer 9

IMMEDIATE
-Failure
-Hypotension (acts on sympathetic nervous system)
-LA toxicity
-Total spinal
DELAYED
-Post-dural puncture headache (PDPH)
-Haematoma in vertebral canal (–> weakness, caudaa equina)

Question 10

What are some contraindications for regional anaesthetics?

Answer 10

ABSOLUTE
-Anticoagulants and bleeding disorders
-Infection
-Anaphylaxis
RELATIVE
-Spinal surgery or deformities
-Massive haemorrhage

Question 11

What are some common misconceptions about epidurals?

Answer 11

1. They prolong labour
   -Partially true but not significant (contractions not as strong so mum might not push as much)
2. They increase risk of C-section
   -False but they do increase the risk of instrumental delivery
3. They cause chronic back pain
   -False but may have leg pain if nerve damage occurs as a complication

Question 12

What are the effects of labour on the CV, respiratory and GI systems (and placenta)?

Answer 12

CV - increased:
-Catecholamines
-Contractility and SVR
-BP
-O2 consumption
RESP:
-Hyperventilation –> maternal hypocapnia –> respiratory alkalosis
-Oxyhaemoglobin dissociation curve shifted
-Decreased O2 offloading to foetus
GI:
-Elevated progesterone
-Smooth muscle relaxation
-Slowed peristalsis
-Delayed gastric emptying
PLACENTA
-Reduced O2 delivery due to above factors