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分娩中の女性の疼痛管理:システマティック・レビューの概要

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Abstract

Background

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 relief. Pain management strategies include non‐pharmacological interventions (that aim to help women cope with pain in labour) and pharmacological interventions (that aim to relieve the pain of labour).

Objectives

To summarise the evidence from Cochrane systematic reviews on the efficacy and safety of non‐pharmacological and pharmacological interventions to manage pain in labour. We considered findings from non‐Cochrane systematic reviews if there was no relevant Cochrane review.

Methods

We searched the Cochrane Database of Systematic Reviews (The Cochrane Library 2011, Issue 5), The Cochrane Database of Abstracts of Reviews of Effects (The Cochrane Library 2011, Issue 2 of 4), MEDLINE (1966 to 31 May 2011) and EMBASE (1974 to 31 May 2011) to identify all relevant systematic reviews of randomised controlled trials of pain management in labour. Each of the contributing Cochrane reviews (six new, nine updated) followed a generic protocol with 13 common primary efficacy and safety outcomes. Each Cochrane review included comparisons with placebo, standard care or with a different intervention according to a predefined hierarchy of interventions. Two review authors extracted data and assessed methodological quality, and data were checked by a third author. This overview is a narrative summary of the results obtained from individual reviews.

Main results

We identified 15 Cochrane reviews (255 included trials) and three non‐Cochrane reviews (55 included trials) for inclusion within this overview. For all interventions, with available data, results are presented as comparisons of: 1. Intervention versus placebo or standard care; 2. Different forms of the same intervention (e.g. one opioid versus another opioid); 3. One type of intervention versus a different type of intervention (e.g. TENS versus opioid). Not all reviews included results for all comparisons. Most reviews compared the intervention with placebo or standard care, but with the exception of opioids and epidural analgesia, there were few direct comparisons between different forms of the same intervention, and even fewer comparisons between different interventions. Based on these three comparisons, we have categorised interventions into: " What works" ,“What may work”, and “Insufficient evidence to make a judgement”.

WHAT WORKS

Evidence suggests that epidural, combined spinal epidural (CSE) and inhaled analgesia effectively manage pain in labour, but may give rise to adverse effects. Epidural, and inhaled analgesia effectively relieve pain when compared with placebo or a different type of intervention (epidural versus opioids). Combined‐spinal epidurals relieve pain more quickly than traditional or low dose epidurals. Women receiving inhaled analgesia were more likely to experience vomiting, nausea and dizziness.

When compared with placebo or opioids, women receiving epidural analgesia had more instrumental vaginal births and caesarean sections for fetal distress, although there was no difference in the rates of caesarean section overall. Women receiving epidural analgesia were more likely to experience hypotension, motor blockade, fever or urinary retention. Less urinary retention was observed in women receiving CSE than in women receiving traditional epidurals. More women receiving CSE than low‐dose epidural experienced pruritus.  

WHAT MAY WORK

There is some evidence to suggest that immersion in water, relaxation, acupuncture, massage and local anaesthetic nerve blocks or non‐opioid drugs may improve management of labour pain, with few adverse effects.  Evidence was mainly limited to single trials. These interventions relieved pain and improved satisfaction with pain relief (immersion, relaxation, acupuncture, local anaesthetic nerve blocks, non‐opioids) and childbirth experience (immersion, relaxation, non‐opioids) when compared with placebo or standard care. Relaxation was associated with fewer assisted vaginal births and acupuncture was associated with fewer assisted vaginal births and caesarean sections.

INSUFFICIENT EVIDENCE

There is insufficient evidence to make judgements on whether or not hypnosis, biofeedback, sterile water injection, aromatherapy, TENS, or parenteral opioids are more effective than placebo or other interventions for pain management in labour. In comparison with other opioids more women receiving pethidine experienced adverse effects including drowsiness and nausea. 

Authors' conclusions

Most methods of non‐pharmacological pain management are non‐invasive and appear to be safe for mother and baby, however, their efficacy is unclear, due to limited high quality evidence. In many reviews, only one or two trials provided outcome data for analysis and the overall methodological quality of the trials was low. High quality trials are needed.

There is more evidence to support the efficacy of pharmacological methods, but these have more adverse effects. Thus, epidural analgesia provides effective pain relief but at the cost of increased instrumental vaginal birth.

It remains important to tailor methods used to each woman’s wishes, needs and circumstances, such as anticipated duration of labour, the infant's condition, and any augmentation or induction of labour.

A major challenge in compiling this overview, and the individual systematic reviews on which it is based, has been the variation in use of different process and outcome measures in different trials, particularly assessment of pain and its relief, and effects on the neonate after birth. This made it difficult to pool results from otherwise similar studies, and to derive conclusions from the totality of evidence. Other important outcomes have simply not been assessed in trials; thus, despite concerns for 30 years or more about the effects of maternal opioid administration during labour on subsequent neonatal behaviour and its influence on breastfeeding, only two out of 57 trials of opioids reported breastfeeding as an outcome. We therefore strongly recommend that the outcome measures, agreed through wide consultation for this project, are used in all future trials of methods of pain management.

分娩中の女性の疼痛管理:概要

分娩中における女性の疼痛の感じ方は、大きく異なる。ほとんど疼痛を感じない女性もいれば、非常に苦痛と感じる女性もいる。分娩中の女性の体勢、可動性、恐怖や不安、または逆に自信は、疼痛の感じ方に影響すると考えられる。薬剤を用いた介入や薬剤以外の介入がいくつかあり、本レビューでは、分娩中の疼痛を低減させるために行った異なる介入のシステマティック・レビューを18件評価した。そのうち、15件がコクラン・レビューである。

薬剤以外の介入に関するエビデンスの大半は、わずか1〜2試験に基づいていたため、その所見の信頼性は低い。しかし、水浴、リラクゼーション、鍼やマッサージは疼痛を緩和させ、疼痛緩和による満足度も良好であった。水浴およびリラクゼーションは、出産に伴う満足度も良好であった。リラクゼーションおよび鍼によって、鉗子の使用頻度が減少し、鍼によって、帝王切開の数が減少した。催眠術、バイオフィードバック、生理食塩水注入、アロマセラピー、TENSが分娩中の疼痛緩和に有効かどうかを判断するには、エビデンスが不十分である。

全般的に、薬剤を用いた介入の試験の方が多かった。亜鉛化窒素(エントノックス®)吸入は疼痛を緩和させたが、だるさや悪心を感じたり、気分が悪くなったりする女性もいた。非オピオイド系薬剤(鎮静剤など)は疼痛を緩和させ、プラセボや治療なしと比較して疼痛緩和に伴う満足度は高くなる場合もあったが、疼痛緩和に伴う満足度はオピオイドよりも低かった。硬膜外麻酔は疼痛を緩和させるが、鉗子を必要とする出産の数、低血圧、運動ブロック(足の動きを阻害する)、発熱および尿貯留のリスクを増加させる。脊髄硬膜外麻酔の併用は、疼痛緩和を促進させるが、硬膜外麻酔のみの場合よりも、そう痒を伴うことが多い。ただし、尿閉が問題となる可能性は低かった。局所麻酔剤による神経ブロックは満足度の高いものであるが、目眩、発汗、ひりひり感などの副作用や乳児の心拍数低下を引き起こす。出産前のオピオイド投与(ペチジンや関連薬の注入)は、硬膜外麻酔よりも有効性が低いが、出産中の疼痛緩和のためのその他の介入よりも有効性が高いかどうかを判断するエビデンスは不十分である。

全般的に、出産中に最も役立つと女性が感じる疼痛管理法であれば、女性が自由に選択するべきである。薬剤以外の疼痛管理法を選択した女性は、必要に応じて、薬剤を用いた介入に自由に移行するべきである。女性は妊娠中、疼痛管理のさまざまな方法について、自分自身と胎児への有益性と考えられる有害作用を知らされるべきである。疼痛強度などのアウトカムの評価方法について、試験ごとにかなりばらつきがみられ、また、いくつかの重要なアウトカムはほとんどまたはまったく検討されていなかった(例えば、分娩中のコントロール状態、授乳、母親と乳児の意思疎通、費用、乳児のアウトカム)。分娩中の疼痛管理に対する薬剤以外の介入について、さらなる研究が必要である。