Alivio del dolor durante el parto

The pain that women experience during labour is affected by multiple physiological and psychosocial factors and its intensity can vary greatly. Most women in labour require pain relief¹. Most women do not require pain relief during early labour, but seek it once the active phase of first-stage labour begins.

Non-drug techniques can be learnt as part of antenatal care, including relaxation techniques. However, as pain increases with advancing labour, the woman should be aware that drugs are available and should not be made to feel that she has failed if she uses them.

Women who receive continuous support during labour are more likely to give birth unaided and are less likely to use analgesia, particularly if support is provided from early in labour.

Transcutaneous electrical nerve stimulation

Transcutaneous electrical nerve stimulation (TENS) applies controlled mild electrical stimulation to the skin by means of electrodes. Stimulating peripheral nerve endings in this way seems to inhibit the transmission of painful impulses at the dorsal horn of the spinal column, and/or activate some of the descending pain-inhibitory systems above the spine. TENS may also stimulate the body to produce natural endorphins.

• Randomised controlled trials provide no compelling evidence for TENS having any analgesic effect during labour².

• The National Institute for Health and Care Excellence (NICE) advises that it should NOT be offered to women in established labour³.

A Cochrane review looked at studies involving acupuncture, acupressure, aromatherapy, hypnosis, massage and relaxation techniques⁴⁵⁶⁷.

• The trials of acupuncture showed a decreased need for pain relief.

• Women taught self-hypnosis had decreased requirements for pharmacological analgesia, including epidural analgesia, and were more satisfied with their pain management in labour compared with controls.

• No differences were seen for women receiving aromatherapy⁸.

• Acupuncture and hypnosis may be beneficial for the management of pain during labour; however, the number of women studied has been small.

Few other complementary therapies have been subjected to proper scientific study.

Immersion in water during labour is claimed to increase maternal relaxation and reduce analgesic requirements. It is supported by the Royal College of Midwives (RCM) for healthy women with uncomplicated pregnancies⁹. Concerns have been raised, however, that there may be greater harm to women and/or their babies - eg, a perceived risk associated with neonatal inhalation of water and maternal/neonatal infection.

• A Cochrane review found that water immersion during the first stage of labour reduces the use of analgesia and reported maternal pain, without adverse effects on labour duration, operative delivery or neonatal outcome¹⁰.

This is a 50:50 mixture inhaled during painful contractions during the first and second stages of labour. It is often used as a supplement to pethidine.

• The main advantages are that it is under the patient's control, it takes effect within seconds and wears off quickly with no side-effects.

• Inhaled analgesia appears to be effective in reducing pain intensity and in giving pain relief in labour¹¹.

Parenteral opioids provide some relief from pain in labour but are associated with adverse effects - eg, maternal nausea, vomiting and drowsiness¹². Pethidine is widely used. It is effective within 15 minutes and lasts for 2-3 hours. There has been wide debate over the efficacy of pethidine.

Remifentanil

This is given as patient-controlled analgesia (PCA). A double-blind, randomised, controlled clinical trial showed that an intermittent, incremental regime with repeated small-dose PCA boluses of remifentanil, provided effective and reliable analgesia during labour and delivery¹³. Studies have shown that epidural analgesia is superior to remifentanil in terms of pain intensity score but that there is no difference in satisfaction with pain relief between both treatments¹⁴.

Epidural analgesia is a central nerve block technique achieved by injection of a local anaesthetic close to the nerves that transmit pain. It is widely used as a form of pain relief in labour.

Advantages

It is the most effective way of relieving pain in labour - providing complete relief in 95% of cases. It also has the benefit of avoiding need for greater analgesia/general anaesthetic if forceps, vacuum extraction or caesarean section are required. It is not associated with increase in symptoms related to perineal trauma and pelvic floor muscle weakness¹⁵.

Disadvantages

• Dizziness or shivering may occur.

• It increases the length of the second stage³.

• There is an increased rate of operative vaginal delivery¹⁶. Many delivery units discontinue epidural to reduce operative delivery rate. However, there is insufficient evidence to support this practice¹⁷. There is evidence that it increases the rate of inadequate pain relief in the second stage of labour.

• Transient hypotension occurs in 20% women.

• Increased numbers of non-reassuring fetal heart tracing on setting up and topping up the epidural - this may be linked to the previous point. This necessitates greater levels of monitoring of mother and child.

• Dural tap occurs in 1% of women and this causes severe headache in 50%.

Epidurals are not available in the community and may steer the woman towards a more interventionalist environment than she wants.

This is a low-dose epidural that relieves pain, but allows women to walk about during labour¹⁸. Staying mobile in the first stage of labour for women with epidural analgesia has not been shown to produce any benefit to delivery outcomes or satisfaction with analgesia, but there are no obvious harms either¹⁹.

The combined spinal-epidural (CSE) technique has been introduced in an attempt to reduce the adverse effects noted with epidural.

• It has been shown to provide a faster onset of effective pain relief from the time of injection, and to increase the incidence of maternal satisfaction²¹.

• However, CSE women experience more itch.

• There is no difference between CSE and epidural techniques in the incidence of forceps delivery, caesarean section rates or admission of babies to the neonatal unit²².

This is used for women who have not had an epidural but require forceps or vacuum extraction delivery. It is also used for repair of episiotomy or perineal tear. Pudendal and paracervical block are the most commonly performed local anaesthetic nerve blocks²³.

Pudendal nerve block

• This uses 10 ml of 0.5% lidocaine injected behind each ischial spine of the pelvis via the vagina.

• Use 10 ml for perineal infiltration.

Perineal nerve infiltration

• Inject, in a fan-like pattern, 20 ml of 0.5-1.0% lidocaine from the posterior fourchette at the midline in three lines.

• Test before the procedure.