Minimising acute post-operative pain following caesarean birth is a priority for anaesthetists. Optimising recovery is imperative given the unique impact on the wellbeing of both mother and baby. Regional anaesthesia techniques are a key component of multimodal strategies and enhanced recovery protocols. There is interest in the role of using such techniques as adjuncts to central neuraxial anaesthesia/analgesia.
Transversus abdominis plane block (TAP)
The TAP block provides somatic analgesia of the anterior abdominal wall and parietal peritoneum by targeting the T6 to L1 spinal nerves running between internal oblique and transversus abdominis muscles. It has been a popular choice following caesarean delivery and the most studied truncal block in this group of patients.
There are a variety of approaches, however, data suggest that posterior blockade may offer better and prolonged analgesia compared to a lateral injection site.¹ TAP blocks confer no additional benefit over long-acting intrathecal opioids, but provide superior analgesia after caesarean delivery where the latter are not used.² They may therefore be more appropriately placed as a rescue technique rather than a standard intervention for all patients. Liposomal bupivacaine may extend the duration of TAP block analgesia in patients receiving intrathecal morphine, though there is a paucity of data and the available literature remains limited.
Mitigating the risk of local anaesthetic systemic toxicity is an important consideration when performing bilateral volume-dependent blocks in well-vascularised fascial planes. This is particularly relevant in the obstetric cohort of patients where altered physiology may enhance sensitivity to local anaesthetic. Current evidence is in favour of using lower doses (bupivacaine equivalents of £ 50mg for each side) as the effects are comparable to higher dose regimens.³
Quadratus lumborum blocks (QLBs)
The quadratus lumborum group of ultrasound-guided blocks have been highlighted as a potential analgesic technique for caesarean delivery. There are three main variations (anterior, lateral and posterior) each defined by their location relative to the quadratus lumborum muscle. Unlike the TAP block, QLBs may provide both visceral and somatic analgesia with their main mechanism of action postulated as thoracic paravertebral spread.
In recent years a systemic review and network meta-analysis showed no significant differences in analgesic outcomes between QLBs and TAP blocks.4 Like TAP blocks, in the absence of intrathecal morphine, QLBs offer a significant reduction in post-operative systemic opioid use and superior analgesic profile when compared to no block or placebo. Importantly, there is no perceived benefit of QLBs when combined with intrathecal opioids.5
The expertise required and proximity to vital organs and blood vessels may explain why QLBs have not achieved the widespread popularity and familiarity of TAP blocks. Furthermore, there are ongoing studies and debate about the optimal approach.
Others
Recently there has been some interest in several other abdominal wall blocks for caesarean delivery. Techniques described have included erector spinae plane (ESP), rectus sheath (RS), ilioinguinal (II) and iliohypogastric (IH)blocks.
The ESP block has attracted significant attention due to its versatility. Like the RS block, it is one of seven ‘Plan A’ blocks proposed by Regional Anaesthesia UK. However, both have been used with varying success in the caesarean delivery setting. Similarly, there is conflicting data regarding the efficacy of II-IH blocks.
The heterogeneity and limited studies supporting the use of these techniques in caesarean delivery cannot therefore inform current practice guidance. Further research is required to evaluate the efficacy of these blocks alongside and in the absence of neuraxial opioids.
Summary
Regional techniques play a crucial role in multimodal analgesia for managing acute post-operative pain following caesarean delivery. Current literature supports that abdominal wall blocks confer the most benefit when neuraxial opioids are precluded (i.e. caesarean delivery under general anaesthesia). More studies are needed to establish the role of ESP, RS and II-IH blocks.
Dr. Manpreet Bahra is an ST6 Anaesthetic trainee at North Central London School, RA-UK trainee board member, ESRA residents and trainees, representative.
