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Alternative neural blocks for labour analgesia 

Alternative neural blocks for labour analgesia
Alternative neural blocks for labour analgesia

Outi Palomäki

and Petri Volmanen

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date: 01 December 2020

Although neuraxial analgesia is available to the majority of parturients in developed countries, alternative neural blocks for labour analgesia are needed for medical, individual, and institutional reasons. Paracervical and pudendal blocks are usually administered transvaginally by an obstetrician. An injection of 0.25% bupivacaine using a superficial technique into the lateral fornixes gives rapid pain relief and has been found to have no negative effect on either fetal oxygenation, or maternal and neonatal outcomes. Low rates of post-analgesic bradycardia and high rates of spontaneous vaginal delivery have been described in low-risk populations. The analgesic effect of a paracervical block is moderate and is limited to the first stage of labour. A pudendal block, administered transvaginally, can be used for pain relief in the late first stage, the second stage, in cases of vacuum extraction, or for episiotomy repair. In clinical use, 1% lidocaine gives rapid pain relief but the success rate is variable. The complications of pudendal block are rare and localized. The sympathetic and paravertebral blocks are currently mainly of historic interest. However, they may benefit parturients in exceptional conditions if the anaesthesiologist is experienced in the techniques. Lumbar sympathetic block provides fast pain relief during the first stage of labour when a combination of 0.5% bupivacaine with fentanyl and epinephrine is employed. With the currently available data, no conclusion on the analgesic effects of thoracic paravertebral block can be drawn when it is used for labour pain relief. Potential maternal risks limit the use of these methods in modern obstetrics.

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