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Epidural analgesia in labour pain

Clinical bottom line:

Epidural analgesia is associated with pain relief during labour, and this is likely to be more effective than alternative treatments. However, it is likely that epidural blocks lengthen labour and result in increased rates of operative vaginal delivery. Epidural block maintained beyond the end of the first stage is associated with an NNT for assisted vaginal delivery is 9.6 (6.7 to 17) compared with control treatments. More information is needed to establish the effects of epidural blocks on longer-term effects in women and babies.

Although epidural analgesia is widely used during labour, questions have been raised about short- and long-term effects. Claims have been made that there may be an association between epidural block and increased chronic backache, maternal pyrexia, instrumental delivery, caesarean section for dystocia and adverse effects on the newborn.

Systematic review

Howell, C. J. Epidural versus non-epidural analgesia for pain relief in labour (Cochrane Review). In: The Cochrane Library. 1999(4). Oxford: Update Software.

Inclusion criteria were randomised or quasi-randomised, controlled trials of epidural versus non-epidural forms of pain relief during labour; primiparous or multiparous pregnancy; spontaneous or induced labour; women without obstetric complications such as pre-eclampsia or complex presentations including breech or twins; any type of epidural administration compared with any form of analgesia not involving regional blockade or compared with no analgesia.

Reviewers extracted information on outcomes of interest and calculated odds ratios, relative risks, proportional and absolute risk reductions using RevMan software (95% confidence intervals). Where relevant we have calculated the number-needed-to-treat with 95% confidence intervals.

Findings

Most trials used bupivacaine in varying concentrations. Controls were mainly intramuscular or intravenous injections of pethidine, with paracervical block (one trial), intravenous pethidine by patient controlled analgesia (PCA) in three, and intravenous butorphanol (one trial).

Quality of trials was variable, and no attempts had been made to collect evaluator-blind assessments.

Pain relief

Four of four trials reported benefit of epidural bupivacaine compared with control treatments: One trial of 111 women showed bupivacaine preload plus top-up was superior to pethidine, nitrous oxide/oxygen inhalation or prudental block given in second stage. However, epidural block did not always provide satisfactory pain relief. A second trial of 100 women showed that bupivacaine epidural (preload plus continuous infusion) (some also received 50 to 100 mg fentanyl) was better than 1 to 2 mg butorphanol (given every one to two hours). A third trial of 715 women showed similar epidural procedures were better than meperidine given as patient controlled intravenous analgesia. The fourth trial of 20 women showed a similar epidural procedure (given in stage one only) was better than fentanyl given as PCA during the first stage.

Painless labour: one of these trials provided dichotomous information suggesting that epidural of bupivacaine preload plus intermittent top up for stage one labour had a NNT of 2.6 (1.8 to 4.7) for painless stage one labour compared with a control of pethidine, nitrous oxide/oxygen inhalation or prudental block given in second stage. This benefit was not significantly different for stage two.

Other outcomes

For many of these outcomes there is insufficient data to draw strong conclusions.

Vomiting: two trials reported no differences (7/59 versus 6/61)

Maternal hypotension: one trial reported increased maternal hypotension (6/49 versus 1/51).

Progress of labour: four trials showed prolonged stage one and two with epidural based on weighted mean differences (approx. 1000 patients).

Oxytocin use: six trials showed increased need with epidural, based on the odds ratio (approximately 1000 patients).

Surgical amniotomy: one trial reported no difference (39/49 versus 46/51).

Motor blockade: one trial showed 29% of women with motor blockade with epidural (16/56 versus 0/54).

Foetal heart rate abnormality/meconium passage. Five trials showed no difference (92/518 versus 106/534).

Fever: one trial reported increased fever with epidural (58/243 versus 16/259).

Malposition: three trials suggested a predisposition to malposition of presenting part (23/154 versus 11/150).

Instrumental vaginal delivery: six trials of 1252 women showed that epidural block maintained beyond the end of the first stage is associated with increased assisted vaginal delivery. The NNT for assisted vaginal delivery is 9.6 (6.7 to 17) compared with standard control treatments. Based on a small number of women, there was no difference when a block was used for first stage only (18/67 versus 14/64).

Caesarean section: nine studies show no significant increase in overall rate (85/843 versus 65/831), and five trials show no increase for dystocia (38/553 versus 34/571). One trial combined rates of caesarean section and assisted deliveries for dystocia, and reported that the rate was increased in epidural group. No effect on foetal distress was seen (16/524 versus 10/539).

Foetus and neonate: no consistent picture emerged for effects on neonatal arterial pH or Apgar scores or neonatal jaundice. One trial reported preliminary evidence of increased rates of hypoglycaemia in neonates of mothers receiving epidural. This needs further confirmation.

Further reading

This review was originally published as:

Howell C, Chalmers I. A review of prospectively controlled comparisons of epidural forms of pain relief during labour. International Journal of Obstetric Anesthesia 1991; 2:1-17.

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