Efficacy of the erector spinae plane block in lumbar spinal surgery patients: a systematic review


 Background: Erector spinae palne block (ESPB) as a new trunk fascia block technique was proposed in 2016. Because of its clear analgesic effect and simple operation, it has aroused the interest of many nerve block experts. However, there are few clinical studies on ESPB for lumbar surgery, and its benefits are controversial. The goal of this review paper is to summarize the use of ESPB for lumbar spine surgery in order to better understand and promote this technique.Methods: Pubmed, EMBASE, Cochrane library, ClinicalTrial.gov databases were searched up to July 30, 2019. According to the inclusion and exclusion criteria established in advance, “lumbar spine surgery” and “ESPB” related MesH terms, free-text words were used. Data on pain scores, analgesic consumptions and adverse effects were reported. All processes follow PRISMA statement guidelines.Results: A total of 171 participants from 11 publications were identified, including two randomized controlled trials, one retrospective cohort study, four case report, four cases series. Block operation plane from T8 to L4. The main anesthetics used in block are bupivacaine, ropivacaine and lidocaine. There was evidence for reducing postoperative pain scores and analgesic consumptions.Conclusion: ESPB in lumbar spine surgery have the potential to relieve lumbar postoperative pain and reduce the use of analgesic drugs. Randomized controlled trials of high quality and large samples are needed to further clarify the benefits of ESPB in lumbar surgery patients.

postoperative pain, patients are unwilling to get out of bed at an early stage, which affects their recovery [1,2]. Patient-controlled analgesia or epidural injection analgesia is usually used in clinic. However, patient-controlled analgesia is prone to opioid-related side effects. Epidural injection is associated with infections, hematomas and other adverse events [3,4] Similarly, one study reported that ESPB relieved postoperative pain in patients with lumbosacral spine surgery, reduced the use of analgesic drugs, and promoted postoperative rehabilitation [11]. Furthermore, a recent study showed that the analgesic effect of ESPB may be better than that of epidural injection [12]. Reducing the use of analgesic drugs in perioperative period is beneficial to accelerate the recovery of patients and reduce the cost of hospitalization.
However, few clinical studies have focused on ESPB in lumbar surgery. What is more, there are differences in the mechanism and effect of block in different parts of erector spinal muscle [13]. Furthermore, some scholars question the practicability of ESPB in lumbar surgery. Tseng believes that postoperative analgesia in patients with lumbar spine surgery using thoracolumbar interfascial plane (TILP) block may better than ESPB [14]. Therefore, it is necessary to systematically summarize the use of ESPB in lumbar spine surgery so as to better understand and promote this technique and benefit patients undergoing lumbar surgery.
MeSH terms and free-text words were used, including "lumbar spine surgery", "decompression", "lumbar spinal stenosis", "spondylolisthesis", "ESP block", "erector spinae plane block". Search time up to July 30, 2019. References to relevant articles or reviews were screened to prevent missed inspection. Our retrieval method was developed together with experienced literature retrieval teachers. All the retrieval results were read independently by the two researchers (QY, ZTJ). According to the established inclusion and exclusion criteria, the title, abstract and full text were strictly evaluated, and the basic information included in the article was extracted. Disagreements would be resolved by discussing or consulting with another author. All processes followed PRISMA statement guidelines.

Data collection:
Type of publication, year of publication, journal name, authorship country of origin, type of block (single shot, continuous, intermittent bolus), anatomic location, patient age, multimodal analgesia use, opioid consumption, sensory and motor changes, reported single shot dosing, additives, opioid related and block related side effects and adverse events, VAS or NRS pain scores, patient satisfaction were collected.

Quality evaluation:
Risk of bias for RCTs (Randomized controlled trials) were assessed by two researchers using a modified Cochrane risk of bias assessment tool. RCTs were evaluated in terms of random sequence generation; allocation concealment; blinding of patients, clinicians, data collectors, outcome assessors, and data analysts; incomplete outcome data; and selective outcome reporting; other biases.
Each potential source of bias was graded as "low risk", "unclear risk" or "high risk".
Bias risk map and bias risk summary diagram were generated by RevMan 5.3 (The Cochrane Collaboration, 2014).

Search results:
A total of 171 participants from 11 publications were identified, including two randomized controlled trials, one retrospective cohort study, four case report, four cases series [11,[15][16][17][18][19][20][21][22][23]. The main reasons for the exclusion of the articles were nonlumbar surgery or unrelated to the purpose of the study. Figure 1 Included literature: Outcome indicators included morphine consumptions, pain scores, adverse reactions and patient satisfaction after lumbar spine surgery. The follow-up period was from 10 hours to 72 hours. Only one article reported that postoperative pain in the lumbar spine was relieved by ESPB and catheterization, and the other 10 articles were treated with bilateral single injection before operation. Block operation plane from T8 to L4. The main anesthetics used in block are bupivacaine, ropivacaine and lidocaine. What is more, almost all of the included studies showed that ESPB could effectively relieve lumbar postoperative pain and reduce the use of analgesic drugs. (Table 1) At the same time, a total of two RCTs were included, but the heterogeneity of outcome indicators could not be analyzed by meta-analysis. Both RCT found that ESPB significantly reduced lumbar postoperative pain scores and analgesic drug consumptions, and no operation-related adverse events occurred. However, the random blind method of the two studies did not do well. Furthermore, small RCTs may not be able to detect adverse effects of therapeutic procedures. ( It has been reported that pain is obvious at 4 hours after lumbar surgery and relieved after 72 hours. What is more, regional block anesthesia can help patients reduce pain and other discomfort [18,29]. Interestingly, Singh found that when 0.25% 20ml bupivacaine was injected on both sides of the T10 plane, the 6th hour NRS score was low, however the 8th hour NRS score was high after lumbar surgery, which suggested that the ESPB could last until 6 to 8 h after operation [30]. The duration of ESPB block was related to the type and dose of local anesthetics.
However, the safe doses of different local anesthetics were different. For example, the unilateral injection volume of ropivacaine was 20 to 40ml, the concentration was 0.25% to 0.5%, and the total safe dose was 150mg. It is recommended that each side of bilateral block should be given 0.375% ropivacaine 20ml in adults [15,31]. Therefore, the dose or concentration can be increased appropriately to prolong the analgesia time and help the patients to get through the most painful stage after operation.
The puncture plane was from T8 to L4, and the follow-up time was from 10 h to 72 h. However, in different studies, patients have different basic analgesia programs, and some researchers pay attention to the use of rescue painkillers, while some studies focus on the total amount of postoperative analgesia drugs [14,32]. Therefore, we should better proceed from the clinical practice, so that more anesthesiologists to master simple and practical cost-effective regional block technology. Because of its simple operation and low risk of infection, bleeding and spinal cord injury caused by puncture, ESPB should also be used as a basic operation technique for anesthesiologists. Although ESPB has been widely used in thoracic and abdominal surgery, the use of ESPB in lumbar surgery is still controversial [36]. Some researchers believe that TILP block is better than ESPB in patients undergoing lumbar surgery [13]. However, ESPB has the advantages of simple operation and less complications, and is more in line with the idea advocated by Turbitt and other experts to let general anesthesiologists master nerve block techniques and apply them. We believe that the clinical research quality of ESPB for lumbar surgery should be improved, and the mechanism of erector muscle block for postoperative analgesia and perioperative protection of lumbar spine should be further explored. At the same time, more general anesthesiologists are needed to master ESPB and apply it to patients undergoing lumbar surgery for the benefit of more patients.

Limitation
Although we have strictly formulated the scheme of literature retrieval and data extraction, there are few research reports that can be included. Only 2 RCT articles were included, howerver the outcome could not be analyzed. Furthermore, the sample size of the two articles is small, and the random, blind method and research quality need to be improved. We need more large sample size, high quality clinical trials to explore the benefits of ESPB for lumbar surgery patients.

Conclusions
ESPB is a good choice for postoperative analgesia in patients undergoing lumbar surgery. However, its safety and effectiveness need more evidence. In addition, the perioperative benefits of ESPB for patients undergoing lumbar surgery need to be further explored.

Ethics approval and consent to participate
Not applicable.

Consent to publication
Not applicable.

Availability of data and materials
The data used and/or analyzed during the current study are available from the public database GEO or the corresponding author on reasonable request.      PRISMA checklist.doc