Since Erector Spinae Plane Block (ESP) was first described by Forero et al.¹ in 2016, more than 103 prospective, retrospective, animal and paediatric RCTs have been published.² There is great interest in ESP block that is seen on plethora of indications and different publications ranging from acute to chronic pain and surgery on upper limb through the trunk and spine to lower limb.^{3 - 6} Several meta-analyses have shown that ESP block can provide sufficient analgesic effects and reduce postoperative opioid consumption; however, the results are not convincing enough due to the small number of cases included and significant heterogeneity among studies.^7,8

There are blocks in the past that have been used in variety of indications like 3-in-1 block, transversus abdominis plane (TAP) block or ganglion sphenopalatine block (GSPB) before they have been put to the test in RCTs. Only a handful of complications associated with ESP have been published and same applies on negative results, therefore we can expect publication bias. On the other hand, there are randomized controlled trials (RCTs) documenting ESP block efficacy.⁹

We know that statistical significance is not the same as clinical significance, or it is? For example, an RCT from China analyzed efficacy of ESP block in relation to perioperative pain control and short-term outcomes in lumbar laminoplasty.¹⁰ Postoperative sufentanil consumption was 75.375±9.349 in control group and 65.067±13.421 in ESP group in 48 hours postoperatively (p = 0.000). Is it clinically important if we have mean difference of 10 mcg of sufentanil in 48 hours? I would say no, it is not.

There is another thing about ESP that jumps out when analyzing data. Consistency of analgesia is low. The number of PCA Attempts after laminoplasty has a much wider range in the ESP group than in the control group (10). Also, a retrospective study from USA concluded that there was no difference in VAS score, but statistically significantly lower Morphine equivalent dose by 15 mg in 24 hours and faster discharge with 5-hour difference with high heterogeneity in ESP group.⁷

This field block brought new light to the world of spine surgery anaesthesia. These patients often fear postoperative pain, which can be a source of considerable preoperative distress. In spine surgery, postoperative pain can often be severe, especially in first 24 hours after surgery.¹¹ It is difficult to achieve pain control if a one-dimensional approach is used. There have been many studies that combined different modalities, like epidural catheters, spinal and epidural morphine, or local infiltration, in pain treatment after spine surgery.¹² There are often contraindications, severe pain that prevents positioning or technical difficulties to site catheter, that won’t interfere with surgical field. Spine surgery is perhaps the only field where, when performing the ESP block, the relatively greater distance of the needle tip from nervous structures, which might be compromised by acute or chronic process that brought patient to the OR, is beneficial when compared to the gold standard techniques. But again, the benefits of ESP block in spine surgery according to data seems to be marginal.⁷ In modern era of perioperative medicine, ultrasound is ubiquitous, therefore performance of plane blocks like ESP block and other novel techniques are relatively easy and safe. These new blocks are common in clinical practice despite of limited proof of effectiveness ^{6, 13}; therefore ESP block is not recommended for spine surgery by PROSPECT because of limited evidence.²⁰

Besides, the mechanism of ESPB is still indeterminate. In the cadaveric study, no spreading of the dye into the paravertebral space was observed to involve the origin of the ventral and dorsal branches of the thoracic vertebral nerves¹⁴ indicating the extent of blockage was not as wide as that observed in the initial clinical finding.¹ Besides, ESP block was performed in six male volunteers, and the authors found that cutaneous sensory loss varied greatly between individuals¹⁵ and didn’t reach anterior thorax which suggests that only posterior rami of spinal nerves are involved in ESP block. Direct evidence is presently lacking and analgesia of ESP block is unpredictable and variable, that result from myriad factors at play.¹³

Meta-analysis of available RCTs by Oh on ESP block used in lumbar surgery brought the conclusion that higher-quality evidence is needed¹⁶ while meta-analysis of RCTs where single shot ESP block was used in various surgeries concluded that: ESP block reduced the accumulated opioid consumption during the first 24 h after surgery, but with considerable heterogeneity. This plane block also reduced time to first analgesia after surgery by 5 hours, but again with considerable heterogeneity.² Another meta-analysis from Kyeong et al. showed that ESP block provided effective analgesia after lumbar spine surgery. However, the low-grade quality of evidence compromised the findings, therefore further high-quality of evidence is required.²⁰

Many times, choice of ESP block over other techniques is influenced by contraindications to gold standard, lower complication risk, fewer medication side effect, missing personal with expertise to deliver gold standard RA technique. Many RCTs concluded that patients may benefit from ESP block when compared to systemic analgesia only.¹⁵ Only research in the future will show if there is more than statistical significance that makes ESP block attractive in clinical practice.

References

1. Forero M, Adhikary SD, Lopez H, et al. The Erector Spinae Plane Block: A Novel Analgesic Technique in Thoracic Neuropathic Pain Regional Anesthesia & Pain Medicine 2016;41:621–627.

2. Cui Y, Wang Y, Yang J, et al. The effect of single-shot erector spinae plane block (ESPB) on opioid consumption for various surgeries: a meta-analysis of randomized controlled trials. J Pain Res. 2022; 15:683–699 https://doi.org/10.2147/JPR.S346809

3. Ueshima H, Inagaki M, Toyone T, et al. Efficacy of the erector spinae plane block for lumbar spinal surgery: a retrospective study. Asian Spine J 2019 Apr;13(2):254–257. doi: 10.31616/asj.2018.0114. Epub 2018 Nov 15. PMID: 30424594; PMCID: PMC6454283.

4. Tsui BCH, Mohler D, Caruso TJ, et al. Cervical erector spinae plane block catheter using a thoracic approach: an alternative to brachial plexus blockade for forequarter amputation. Can J Anaesth 2019 Jan;66(1):119–120. doi: 10.1007/s12630-018-1170-7. Epub 2018 Jun 4. PMID: 29868941.

5. Josh Luftig PA, Mantuani D, Herring AA, et al. The authors reply to the optimal dose and volume of local anesthetic for erector spinae plane blockade for posterior rib fractures. Am J Emerg Med 2018 Jun;36(6):1103–1104. doi: 10.1016/j.ajem.2018.03.051. Epub 2018 Mar 21. PMID: 29622391.

6. Tulgar S, Kose HC, Selvi O, et al. Comparison of ultrasound-guided lumbar erector spinae plane block and transmuscular quadratus lumborum block for postoperative analgesia in hip and proximal femur surgery: a prospective randomized feasibility study. Anesth Essays Res 2018 Oct-Dec;12(4):825–831. doi: 10.4103/aer.AER_142_18. PMID: 30662115; PMCID: PMC6319070.

7. Soffin EM, Okano I, Oezel L, et al. Impact of ultrasound-guided erector spinae plane block on outcomes after lumbar spinal fusion: a retrospective propensity score matched study of 242 patients. Reg Anesth Pain Med 2022;47(2):79–86. doi: 10.1136/rapm-2021-103199. Epub 2021 Nov 17. PMID: 34795027.

8. Ma J, Bi Y, Zhang Y, et al. Erector spinae plane block for postoperative analgesia in spine surgery: a systematic review and meta-analysis. Eur Spine J 2021; 30:3137–3149.

9. Leong RW, Tan ESJ, Wong SN, et al. Efficacy of erector spinae plane block for analgesia in breast surgery: a systematic review and meta-analysis. Anaesthesia 2021; 76:404–413.

10. Jin Y, Zhao S, Cai J, et al. Erector spinae plane block for perioperative pain control and short-term outcomes in lumbar laminoplasty: a randomized clinical trial. J Pain Res 2021; 14:2717–2727. Published 2021 Sep 3. doi:10.2147/JPR.S321514

11. Nielsen RV, Fomsgaard JS, Dahl JB, et al. Insufficient pain management after spine surgery. Dan Med J 2014;61: A4835

12. Benyahia NM, Verster A, Saldien V, et al. Regional anaesthesia and postoperative analgesia techniques for spine surgery - a review. Rom J Anaesth Intensive Care 2015 Apr;22(1):25–33. PMID: 28913452; PMCID: PMC5505328.

13. Chin KJ, Lirk P, Hollmann MW, et al. Mechanisms of action of fascial plane blocks: a narrative review. Regional Anesthesia & Pain Medicine 2021;46:618–628.

14. Ivanusic J, Konishi Y, Barrington MJ. A cadaveric study ınvestigating the mechanism of action of erector spinae blockade. Reg Anesth Pain Med 2018; 43:567–571.

15. Zhang, J., He, Y., Wang, S., et al. The erector spinae plane block causes only cutaneous sensory loss on ipsilateral posterior thorax: a prospective observational volunteer study. BMC Anesthesiology 2020, 20(1). doi:10.1186/s12871-020-01002-0

16. Oh SK, Lim BG, Won YJ, et al. Analgesic efficacy of erector spinae plane block in lumbar spine surgery: A systematic review and meta-analysis. J Clin Anesth 2022 Jun; 78:110647. doi: 10.1016/j.jclinane.2022.110647. Epub 2022 Jan 11. PMID: 35030493.

17. Byrne K, Smith C. Human volunteer study examining the sensory changes of the thorax after an erector spinae plane block. Reg Anesth Pain Med 2020; 45:761–762

18. Huang J, Liu JC. Ultrasound-guided erector spinae plane block for postoperative analgesia: a meta-analysis of randomized controlled trials. BMC Anesthesiol 2020;20(1):83. Published 2020 Apr 14. doi:10.1186/s12871-020-00999-8

19. Seok Kyeong Oh, Byung Gun Lim, Young Ju Won, et al. Analgesic efficacy of erector spinae plane block in lumbar spine surgery: A systematic review and meta-analysis. Journal of Clinical Anesthesia 2022; 78:110647, ISSN 0952–8180, https://doi.org/10.1016/j.jclinane.2022.110647.

20. Waelkens, Piet, Alsabbagh, Emissia, Sauter, Axel, et al on behalf of the PROSPECT Working group∗∗ of the European Society of Regional Anaesthesia and Pain therapy (ESRA) Pain management after complex spine surgery, European Journal of Anaesthesiology 2021; 38 (9): 985–994, doi: 10.1097/EJA.0000000000001448