Pain relief in labour
There are basically three main areas: non-medical, drugs and anaesthaesia.
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Non-drug
Transcutaneous electrical nerve stimulations (TENS) applies a mild electrical current to the skin via electrodes. Theoretically, it stops pain pathways working effectively but the evidence is pretty rubbish. Complementary therapies can also be used along with a water or birthing pool (not necessarily the same as a water birth). These are offered as they are cheap and can be helpful to some women, even if only psychologically.
Drugs
Nitrous oxide and oxygen (Entonox) affectionately and colloquially known as gas and air is as 50:50 mixture which is used during the first two stages of labour. It is under the mother's control and works quickly and lasts for a short period of time. Half of women achieve satisfactory relief. It is also very safe.
Pethidine is an opioid analgesic given intramusclarly which takes around 15 mins to work and lasts 2-3 hours. It's efficacy is debated. Remifentanil is patient-controlled analgesic which has been proven effective in small, intermittent boluses.
(It is important to note that with opiate analgesia, babies may develop respiratory distress after delivery which is treated with naloxone.)
Anaesthetic
Epidural
This involves blocking the central nerves using local anaesthetic, using a needle and catheter to adminster the medicine very close to the nerves which transmit pain. It is the most effective way to relieve pain during labour and provides complete relief in 95% of cases. There are however some disadvantages:
- Increase duration of 2nd stage
- Increased rate of instrumental delivery
- Dural tap in 1% - the needle penetrates the dura and goes into the CSF which causes a severe headache.
- Transient hypotension (20%)
- Higher number of abnormalities in fetal heart rate (possible relation to point above)
There is also the possibility of an ambulatory epidural. The dose is lower so the woman can still walk. Combined spinal-epidural is being introduced as it reduces the adverse effects of an normal epidural.
Local
When instrumental delivery or episiotomy/perineal tear repair is necessary but an epidural has not already been given, local analgesia is used
- Pudendal nerve block uses lignocaine (10ml, 0.5%) injected behind the ischial spines of the pelvis via vagina.
- Perineal nerve infiltration is acheived with lignocaine injection (20ml, 0.5-1%) around the posterior fourchette (the point where the labia minora meet).
