Clinical review

Relief of pain

Inger Findley,  Geoffrey Chamberlain. 

Labour is usually painful. Exceptionally, a very few women may not feel pain; others can control their response so as to reduce pain. Most women think that pain is going to be a major part of giving birth. Professionals can help to reduce women's fears by giving precise, accurate, and relevant information beforehand and explaining what pain relief will be available at the place where the woman will be in labour. If a women has plans about the sort of pain relief she wants, these should be discussed in advance with the woman and her partner.

The National Birthday Trust has performed nationwide surveys since the second world war, and the table shows the proportions of women going through labour using various methods of analgesia. Chloroform and trilene are no longer used; pethidine achieved a popularity that is now waning; nitrous oxide is a mainstay; and epidural and spinal methods are increasing in use.

View larger version (29K): [in this window] [in a new window]   Equipment for self administration of nitrous oxide and oxygen (Entonox) with a mouth piece (top) and a face mask (bottom)

The trust's 1990 report, Pain Relief in Labour, is based on the experiences of over 10 000 women who delivered in the United Kingdom during one week. It is the best source of national statistics on both pharmacological and non-pharmacological analgesics. Much of this article is based on the report; some practices may have changed in the years since the surveyfor example, the increased use of epidural and spinal anaesthesia for caesarean section.

	Pharmacological methods

Top Pharmacological methods Non-pharmacological methods Coping with pain

Nitrous oxide
Premixed nitrous oxide and oxygen is now provided as Entonox. It is a 50:50 mixture and is available at virtually all places of delivery.

View larger version (15K): [in this window] [in a new window]   Percentage of women using nitrous oxide by distribution of numbers of labour units in Britain

Pethidine
This analgesic and antispasmodic drug is usually given intramuscularly (50-150 mg). It is decreasing in popularity as nausea, drowsiness, and lack of control are important adverse effects.

View larger version (16K): [in this window] [in a new window]   Percentage of women using pethidine by distribution of numbers of labour units in Britain

Morphia and diamorphine
Opiates are still used for pain relief in labour in about 5% of women in Britain, usually if epidural analgesia is not available; some 85% of women experience good pain relief with them, but they have depressive effects on neonatal respiration. In addition, morphine is frequently used after a caesarean section, via patient controlled pumps.

Epidural analgesia
Epidural analgesia provides the most effective pain relief. An indwelling plastic catheter is introduced into the epidural space through a needle with a curved tip. After the initial dose, analgesia can be extended with intermittent top ups by midwives or increasingly by the patient herself. Epidural analgesia can be given by continuous infusion via a syringe pump. It is used by about a fifth of women in England and Wales.

View larger version (48K): [in this window] [in a new window]   Siting of an epidural block

View larger version (16K): [in this window] [in a new window]   Percentage of women wishing to use epidural at next delivery

View larger version (38K): [in this window] [in a new window]   Percentage of units in United Kingdom reporting 24 hour epidural cover for labour, 1994

Spinal anaesthesia
Spinal anaesthesia is increasingly used for operative procedures: caesarean section, instrumental delivery, and manual removal of the placenta. The local anaesthetic is injected into the cerebrospinal fluid through a very fine (25G) atraumatic needle. The onset of action is rapid, and the effect lasts for about two hours. Headache after a spinal injection is rare nowadays.

View larger version (36K): [in this window] [in a new window]   Siting of spinal anaesthetic with specially pointed atraumatic needle

View larger version (40K): [in this window] [in a new window]   Differentiation of regional blocks (usually done by anaesthetist) and field blocks (commonly performed by obstetrician)

Nerve blocks
A pudendal nerve block with lignocaine plus an infiltration of the perineum with local anaesthetic gives good pain relief for low cavity, forceps, or vacuum extraction, but it would be unkind to use Keilland's forceps, which should be reserved for use with an epidural or spinal block. Local nerve block is an easy technique, which is performed by the obstetrician at the time of delivery, and has few complications. Repair of an episiotomy is readily done under this type of analgesia.

View larger version (14K): [in this window] [in a new window]   Pudendal block technique. The injection is into the pudendal nerve in the region of the ischial spine each side. The nerve usually leaves and re-enters the pelvis around this spine, but because this is not constant, anaesthesia should be located around the spine

General anaesthesia
In Britain general anaesthesia is still used for some caesarean sections, about 30% of elective procedures, and 40% of emergency procedures. It is also used for manual removal of the placenta, especially when major blood loss is anticipated.

	Non-pharmacological methods

Top Pharmacological methods Non-pharmacological methods Coping with pain

Anything that helps a woman's pain is acceptable if it does no harm. Increasing numbers of women use non-drug centred methods, possibly to maintain control, a matter of great importance to some. The least formal of these methods is the removal of anxietythrough educating the woman and a trusted companion who will be present at the birth.

Relaxation and massage
Relaxation and massage are usually taught in antenatal classes. Some 90% of women find relaxation and massage to be good for pain relief. Its effectiveness depends very much on the compliance of the woman, the stage of labour at which it is used, and the availability of the partner to help.

View larger version (17K): [in this window] [in a new window]   Percentage of women using relaxation methods by distribution of numbers of labour units in Britain

TENS
Transcutaneous electrical nerve stimulation (TENS) is a popular method of distraction therapy. Low grade stimulatory electrical waves act on the posterior roots of the nerves supplying the uterus. TENS may postpone the need for pharmacological analgesia.

View larger version (20K): [in this window] [in a new window]   Transcutaneous electrical nerve stimulation equipment

Warm water baths
Although the professionals may be divided about underwater births, women in labour like to use warm water baths in the first and early second stages of labour. The heat is analgesic and the buoyancy of water is relaxing. Warm water baths seem to be a good method of pain relief, although few reliable trials have been performed.

	Coping with pain

Top Pharmacological methods Non-pharmacological methods Coping with pain

In the National Birthday Trust's survey, mothers, partners, and midwives all assessed relaxation and massage as giving good or very good pain relief in almost 90% of cases. They agreed that Entonox and epidural were good in about 90% and 97% of cases respectively, but pethidine was useful in only 58% of cases.

Many women find it unhelpful to be confined to bed during labour or to have to use unwanted positions. Women usually find the presence of a companion and an individual midwife helpful in the relief of pain.

Women are often dissatisfied when they have to use a formal method of analgesia which they had initially not wished to use. This is a difficult area, which should be discussed well before labour. Women should not feel guilty about changing their mind about pain relief.

View larger version (25K): [in this window] [in a new window]   Percentage of women using various methods of pain relief and whether they found them helpful

	Acknowledgments

All the graphs are adapted with permission from Pain Relief in Labour, the report by the National Birthday Trust.

	Footnotes

Inger Findley is a consultant obstetric anaesthetist at St George's Hospital, London.

The ABC of Labour Care is edited by Geoffrey Chamberlain, emeritus professor of obstetrics and gynaecology at the Singleton Hospital, Swansea. It will be published as a book in the summer.