Regional anaesthesia offers many advantages for the perioperative management of pain. From a classification perspective there exists two distinct approaches to peripheral nerve blockade; perineural injection of small volumes of local anaesthetic targeting a specific nerve or plexus and the injection of larger volumes of local anaesthetic into a fascial plane with the intention of using it as a conduit to spread local anaesthetic towards target nerves. The advent of increasingly high-resolution ultrasound imaging over the last 2 decades has made identification of fascial planes, and indeed individual nerves, much easier. This has led to an almost exponential increase in the number of novel fascial plane blocks all with purported advantages over one another. Shortly after the description of a new fascial plane block there is a flurry of attempts to find uses for it and efforts to demonstrate superiority over significantly more established techniques. While efforts to promote regional anaesthesia and its important benefits for patients are laudable, the limitations of the fascial plane blocks, especially when compared to tried and tested direct neural blockade, must be acknowledged.

One of the major drawbacks of fascial plane blocks is their lack of utility for surgical anaesthesia. The transversus abdominis plane (TAP) block will provide analgesia but not anaesthesia for caesarean section whereas the humble epidural will comfortably (pun intended) perform both roles. Likewise awake breast surgery under paravertebral block has been well described but could not be considered under interpectoral or serratus anterior plane block alone. Ultimately, while their analgesic effects are certainly notable, fascial plane blocks remain ineffective for surgery solely under regional anaesthesia and are therefore less versatile than their direct nerve block cousins.

With this limited scope of applications in mind, there are many important clinical instances where they have not been proven superior to direct neural blockade. A recent large meta-analysis comparing TAP blocks with epidural anaesthesia for abdominal surgery favoured the latter in terms of pain scores immediately post operatively and at 12 and 48 hours, and found no difference at 24hrs.¹ Indeed TAP blocks might not even be superior to local wound infiltrations placed at the end of surgery.² One possible explanation for the analgesia associated with fascial plane blocks is the systemic effects of the local anaesthetic being absorbed however this has not been fully investigated in the literature.

One might take the view that fascial plane blocks are safer than targeted nerve blocks. Whilst this is true of direct nerve injury they are by no means a benign intervention and serious complications can and do occur. A recent review article and consensus statement from a panel of Canadian experts described serious complications from almost every interfacial plane block including intramuscular and retroperitoneal haematomas, liver and bowel injuries, peritonitis and pneumothorax.³ They went on to suggest that TAP, rectus sheath, ilioinguinal/iliohypogastric and interpectoral blocks be considered as intermediate risk for bleeding complications whilst quadratus lumborum, being deeper and less compressible, should be considered high risk for bleeding complications. These blocks should therefore not be performed in patients who are coagulopathic or are receiving antiplatelet or anticoagulant medication. The paper also noted that, as of 2019, there was a paucity of safety data for most of the interfacial plane blocks due to many only having been recently described. Perhaps a contributing factor to these complications is that, compared to targeted nerve blocks, fascial plane blocks are far more likely to be performed in an anaesthetised patient, often immediately after surgery has finished (e.g. TAP blocks following an emergency laparotomy or caesarean section). This, accompanied by complacency can lead to significant delays in recognising complications, indeed the Canadian consensus statement noted that many of the reported complications were not immediately noticed and were only revealed at laparotomy or following radiological imaging.⁴

A benefit of improved ultrasound technology has been the ability to use smaller, and therefore safer, doses of local anaesthetic for reliable regional nerve block.^{5 6} Paradoxically, with ultrasound paving the way for the development of fascial plane blocks this has led to much higher (and often maximum) doses of local anaesthetic being used. This flies in the face of the conventional teaching of using the lowest dose of local anaesthetic possible to ensure success and indeed substantially increases the risk of local anaesthetic systemic toxicity (LAST). A recent paper by Macfarlane and colleagues noted the change in aetiology of cases of LAST over the last few decades with fascial plane blocks on the rise.⁷

While fascial plane blocks of the trunk have proliferated, it is important to note that they are not useful in many areas of the body where regional anaesthesia is commonly required, namely the upper and distal lower limb. It has been estimated that over a third of all peripheral nerve blocks are performed on the upper limb alone.⁸ As such, it is unsurprising that many anaesthetists rank upper limb and peripheral lower limb blocks as the most important for training and practice.^{9 10} It is important therefore that we do solely rely on knowledge of the ‘safer’ and ‘easier’ facial plane blocks and that anaesthesiologists at the end of their basic regional anaesthesia training must be able to perform an array of targeted blocks.

Conclusion In conclusion, whilst fascial plane blocks undoubtable have a role in perioperative analgesia they are by no means an adequate substitute for direct neural blockade.

References

1. Desai N, El-Boghdadly K, Albrecht E. Epidural vs. transversus abdominis plane block for abdominal surgery – a systematic review, meta-analysis and trial sequential analysis. Anaesthesia. Jan 2021;76(1):101-117. doi:10.1111/anae.15068

2. Yu N, Long X, Lujan-Hernandez JR, Succar J, Xin X, Wang X. Transversus abdominis-plane block versus local anesthetic wound infiltration in lower abdominal surgery: a systematic review and meta-analysis of randomized controlled trials. BMC Anesthesiol. 2014;14:121. doi:10.1186/1471-2253-14-121

3. Tsui BCH, Kirkham K, Kwofie MK, et al. Practice advisory on the bleeding risks for peripheral nerve and interfascial plane blockade: evidence review and expert consensus. Can J Anaesth. Nov 2019;66(11):1356-1384. doi:10.1007/s12630-019-01466-w

4. El-Boghdadly K, Wolmarans M, Stengel AD, et al. Standardizing nomenclature in regional anesthesia: an ASRA-ESRA Delphi consensus study of abdominal wall, paraspinal, and chest wall blocks. Reg Anesth Pain Med. Jul 2021;46(7):571-580. doi:10.1136/rapm-2020-102451

5. McNaught A, Shastri U, Carmichael N, et al. Ultrasound reduces the minimum effective local anaesthetic volume compared with peripheral nerve stimulation for interscalene block. Br J Anaesth. Jan 2011;106(1):124-30. doi:10.1093/bja/aeq306

6. Casati A, Baciarello M, Di Cianni S, et al. Effects of ultrasound guidance on the minimum effective anaesthetic volume required to block the femoral nerve. Br J Anaesth. Jun 2007;98(6):823-7. doi:10.1093/bja/aem100

7. Macfarlane AJR, Gitman M, Bornstein KJ, El-Boghdadly K, Weinberg G. Updates in our understanding of local anaesthetic systemic toxicity: a narrative review. Anaesthesia. Jan 2021;76(Suppl 1):27-39. doi:10.1111/anae.15282

8. Moody M, Spyridoulias A, Vats A. A snapshot survey of peripheral nerve block usage at a tertiary level centre in England. Regional Anesthesia and Pain Medicine. 2021;70:A105-A106.

9. Teixeira C, Artilheiro V, Silva R, Pereira M, Magalhães J. Peripheral Nerve Block Practice in Portugal: A National Survey. Cureus. Feb 2023;15(2):e35478. doi:10.7759/cureus.35478

10. Corvetto MA, Echevarria GC, Espinoza AM, Altermatt FR. Which types of peripheral nerve blocks should be included in residency training programs? BMC Anesthesiol. 2015;15:32. doi:10.1186/s12871-015-0001-4