The analgesic efficacy of erector spinae plane block versus paravertebral block in thoracic surgeries: a meta-analysis

Background Acute postoperative pain after thoracic surgery might lead to chronic postsurgical pain (PSP), which lowers quality of life. The literature suggests thoracic paravertebral block (PVB) as a pain management approach. The ESPB (erector spinae plane block) is regarded to be an effective PVB alternative. The analgesic efficacy of the two analgesic therapies is controversial. The purpose of this study is to compare the analgesic efficacy of ESPB and PVB in preventing acute PSP. Methods We searched relevant articles in PubMed, Cochrane Library, Embase, Web of Science, and Google Scholar databases. The primary outcome was postoperative pain score, with secondary outcomes including analgesic consumption, the frequency of rescue analgesia, and postoperative nausea and vomiting. Results This meta-analysis included ten RCTs with a total of 670 patients. PVB significantly lowered the pain scores at movement at 12 h following surgery as compared to the ESPB. The PVB group used much less opioids within 24 h after surgery compared to the ESPB group. However, there were no significant differences between the groups in terms of postoperative rescue analgesia or in the incidence of postoperative nausea and vomiting (p > 0.05). Conclusion PVB produced superior analgesia than ESPB in patients who underwent thoracic surgeries. In addition, PVB demonstrated greater opioid sparing effect by consuming much less opioids. Systematic review registration This trial is registered on PROSPERO, number CRD42023412159.


Introduction
Acute postoperative pain after thoracic surgery reduces quality of life and raises the possibility of chronic postsurgical pain (PSP) (1,2).As a component of multimodal analgesia, regional anesthesia can efficiently manage pain, minimize the need for perioperative analgesic and anesthetic drugs, reduce postoperative nausea and vomiting, lower the risk of developing Fenta et al. 10.3389/fmed.2023.1208325Frontiers in Medicine 02 frontiersin.orgchronic pain, lower the incidence of postoperative respiratory complications, reduce the length of hospital stay, and increase patient satisfaction (3)(4)(5)(6)(7).Thoracic paravertebral block (PVB) (8,9), and erector spinae plane block (ESPB) (10-13) can be used for acute PSP management as a part of multimodal analgesia regimen for different types of procedures.Thoracic PVB is recommended by the enhanced recovery after surgery protocol as a trustworthy method for providing postoperative analgesia in thoracic procedures (14-16).However, it requires skilled hands due to its close proximity to the pleura, epidural space, and subarachnoid distance (6,17).
The innovative interfacial plane block known as ESPB was initially introduced by Forero et al. in 2016 (18) and offers extensive analgesia in thoracic surgery.It can be used as a substitute for PVB because it is less intrusive, simpler, and safer to apply plane blocks that are applied in the plane of the spine's erector muscles (1,19).In this procedure, a local anesthetic solution is injected deeply into the erector spinae muscle, with an anticipated paravertebral distribution in both cranial and caudal directions (3,20).
In thoracic PVB and ESPB, local anesthetics are injected into the costotransverse foramina, blocking the ventral and dorsal rami of the corresponding spinal nerves as well as sympathetic fibers, which causes sensory blockade over the anterolateral region of the thorax.The dermatomes covered by ESPB and PVB differ depending on the point of entrance, the amount, and the concentration of local anesthetics used (21, 22).
There is not a sufficient study comparing ESPB and TPVB.The few participants in the available studies contrasting ESPB with TPVB have yielded conflicting findings (12,23,24).Because ESPB is technically safe and simple, the hypothesis that it would be a better option to PVB is supported.Hence, we performed a meta-analysis to compare the analgesic effects of ESPB to the well-known thoracic PVB for patients who underwent thoracic surgery.

Materials and methods
The Preferred Reporting Items for Systematic and Meta-analysis (PRISMA) is used to report this study.This review protocol has been registered in international prospective register of systemic review with registration number CRD42023412159.

Search strategy
We searched relevant publications in the PubMed, Cochrane Library, Embase, Web of Science, and Google Scholar databases through April 2023.The search terms "Erector spinae plane block, " "Paravertebral block, " and "Thoracic surgery" were utilized.

Data extraction
Two authors looked through all of the article titles and abstracts to find publications that fulfilled the inclusion criteria.Studies with full paper copies were reviewed independently by two authors (Diriba Teshome and Simegnew Kibret), and choices on selection or rejection were made.A third reviewer settled any differences that might have arisen (Efrem Fenta).Names of authors, publication year, participant characteristics, sample size, block location, local anesthetic type and dose, operation type, duration of surgery, and study outcomes were retrieved from each included study (Table 1).The eligible publications were searched for raw data for continuous variables.If a variable's range and median were provided in the full texts, the mean and standard deviation were then calculated from the range and median (34).If data values were presented graphically, WebPlotDigitizer was used to extract the numerical data (35).The primary outcome was the postoperative pain score, while the secondary outcomes were the consumption of analgesics used, the frequency of rescue analgesia, and postoperative nausea and vomiting at 24 h after surgery.

Evaluation of the risk of bias assessment
Using the Cochrane risk of bias tool, the risk of bias was evaluated and rated as low, unclear, or high independently by two researchers (Efrem Fenta and Tadese Tamire).Random sequence generation (selection bias), allocation concealment (selection bias), blinding of participants and personnel (performance bias), blinding of outcome assessment (detection bias), incomplete outcome data (attrition bias), selective reporting (reporting bias), and other bias were all taken into consideration when rating the included articles.A third reviewer (Diriba Teshome) resolved the differences that arose between the researchers.Figure 1 provides an overview of the risk of bias assessment.

Statistical analysis
For this meta-analysis, Review Manager 5.4.1 (Cochrane Library, Oxford, UK) was utilized (Figure 1).A mean difference (MD) with a 95% confidence interval was reported for continuous data, including postoperative pain severity assessments and analgesic consumption at 24 h after surgery (CI).The relative risk (RR) at 95% CI was used to express the dichotomous data, such as the frequency of rescue analgesia and postoperative nausea and vomiting at 24 h after surgery.When the I 2 was below 50%, a fixed-effect model was used, and when    it was higher, a random-effect model was used.The funnel plot's symmetry demonstrated that there was no publication bias.

Postoperative rescue analgesia within 24 h after surgery
Five trials (9,25,28,29,31) assessed the postoperative rescue analgesia within 24 h after surgery, and the results of this study showed no significant difference between the PVB and ESPB groups (RR 0.87, 95% CI 0.63 to 1.20, p = 0.40; I 2 = 75%) (Figure 7).The symmetry of the funnel plot showed that there was no publication bias (Figure 8).

The incidence of postoperative nausea and vomiting
The incidence of postoperative nausea and vomiting was reported in six trials (25,27,29,(31)(32)(33).The pooled result of this meta-analysis found that, there was no significant differences in the incidence of postoperative nausea and vomiting (RR 1.05, 95% CI 0.71 to 1.56, p = 0.80; I 2 = 44%) between the PVB and ESPB groups (Figure 9).

Discussion
The analgesic effectiveness of PVB over ESPB in patients following thoracic surgery was demonstrated by this meta-analysis, which included 10 RCTs comprising a total of 670 patients.PVB and ESPB have progressively substituted thoracic epidural analgesia, due to a variety of drawbacks, such as dural puncture, epidural hematoma, the increased risk of hypotension, and urine retention (9,36).A systematic review and meta-analysis of 12 clinical trials involving a total of 541 patients revealed that thoracic PVB and thoracic epidural analgesia were comparable in terms of VAS scores at rest and during coughing at 4-8, 24-48 h postoperatively, but that the PVB group outperformed the epidural group significantly more effective at 48 at movement.Hypotension and urinary retention are more common in the group receiving epidural analgesia (37,38).However, due to how close the paravertebral space is to the pleura, doing ultrasonography guided PVB still has a higher risk of pneumothorax.This risk is intensified by the fact that it frequently takes several thoracic injections to deliver optimal analgesia (39).The ESPB, potentially safer and need less technical expertise, is required to be used (40).The ESPB, a new interfacial plane block, significantly reduces pain after thoracic surgery (41,42).It can be used as another PVB option with fewer complications because administering plane blocks in the plane of the erector spinae muscles is technically easy and safe (43).Using this method, a local anesthetic solution is deeply injected into the erector spinae muscle, with expected distributions to paravertebral space (44,45).We conducted this meta-analysis to see whether it would be an appropriate substitute for PVB by considering ESPB's ease of use and high success rate.
In this meta-analysis, we found that there were no statistically significant differences in pain scores at rest.The PVB significantly lowered the pain scores at movement at 12 h following surgery in contrast to the ESPB.For the other specified time points (1 h, 12 h, 24 h, and 48 h), there were no statistically significant differences in the reported pain severity scores during mobility.The findings of this meta-analysis also revealed that the PVB group used much less opioids within 24 h after surgery compared to the ESPB group.However, the results of this study showed no significant differences between the groups in terms of postoperative rescue analgesia within 24 h of surgery or in the frequency of postoperative nausea and vomiting.
Similar results were found in study by Xiong et  Forest plot of comparison: postoperative pain severity score at movement.Frontiers in Medicine 07 frontiersin.orgsignificantly decreased pain scores at 4-6 h, 8-12 h, and 24 h at movement, and significantly decreased opioid consumption at 24 h post-op.However, there were no significant differences between the two groups in terms of the frequency of postoperative nausea and vomiting.In contrast to our findings, the incidence of rescue analgesia was significantly lower in the PVB group compared to the ESPB group after thoracic surgery (46).In line with our findings, a retrospective study by Sertcakacilar et al. showed that PVB caused superior analgesia than ESPB when comparing the efficiency of ultrasound-guided erector spinae plane block versus paravertebral block for postoperative pain relief in single-port Forest plot of comparison: postoperative opioid consumption at 24 h (in morphine equivalents).
Funnel plot of comparison: postoperative opioid consumption within 24 h after surgery.
Forest plot of comparison: postoperative rescue analgesia within 24 h after surgery.There are some limitation of this meta-analysis.The primary limitation of this meta-analysis could be the limited sample sizes for the publications included (ten papers) that were taken into account.More studies comparing PVB with ESPB for thoracic surgeries are also needed.The study may also have significant limitations due to clinical and methodological heterogeneity, such as variations in the block's location, the dose and type of local anesthetics utilized during each procedure, and the types of thoracic surgeries performed.

Conclusion
PVB provides a superior postoperative analgesia compared to ESPB as a part of multimodal analgesic regimen for patients undergoing thoracic surgeries.Additionally, by using significantly less opioids, PVB showed superior opioid sparing.Further research contrasting PVB with ESPB for thoracic procedures might be beneficial.

FIGURE 1 Fenta
FIGURE 1Risk of bias summary for each included study.

FIGURE 3 Forest
FIGURE 3Forest plot of comparison: postoperative pain severity score at rest.

FIGURE 5
FIGURE 5 In this meta-analysis, patients (aged 18-81) who underwent thoracic surgery, randomized controlled trials, and studies comparing ESPB with PVB for postoperative analgesia were included in the study.

TABLE 1
Characteristics of included studies.
al., who found that PVB significantly decreased pain scores at 0-1 h, 4-6 h, and 4 h at rest,