The Pectoral (PECS) Regional Block: A Scoping Review

Among the various surgical procedures, breast surgeries rank as a frequently conducted procedure. Interfacial blocks such as the Pectoral (PECS) block became possible with the currently available knowledge on innervations and ultrasound. Interfacial blocks target the deep fascial planes, which are potential spaces for injecting local anesthetics. The Pectoral I (PECS I) consists of the injection of local anesthetics in the plane between the pectoralis major and minor muscles. The PECS II block, a modified version of the block, is achieved by adding another, deeper injection in the plane between the pectoralis minor and the serratus anterior muscle. We conducted a scoping review using Arkesy and O’Malley's framework, as described by Levac. We identified our research question as the uses of the PECS regional block technique with the choice of local anesthetics, including adjuncts, and its effectiveness in intraoperative and postoperative analgesia in the first 24 hours and incidence of postoperative nausea and vomiting. Subsequently, we identified the relevant studies that met our inclusion criteria and charted the data. Lastly, we summarized and reported the results. The PECS block was used in various breast surgeries, among which radical mastectomies with/without lymph node dissection were the most common. It was found that the PECS block reduced intraoperative opioid consumption in 60% and 24-hour postoperative opioid consumption in 93.3% of the included papers. Various local anesthetics were used such as ropivacaine, bupivacaine, and levobupivacaine. Ultrasound-guided interfacial plane blocks, such as the PECS block, are a recent development in regional anesthesia that offers analgesia for patients undergoing breast surgeries. The authors conclude that PECS block can provide a decrease in intraoperative and postoperative opioid consumption, a decrease in the incidence of nausea and vomiting, and can lead to overall patient satisfaction in terms of lower pain scores compared to systemic analgesia.


Introduction And Background
Breast surgery is one of the most common types of surgery worldwide [1].These surgeries are accompanied by significant pain and have a high incidence of chronic pain postoperatively, even following minor procedures [2].Poor management of perioperative pain can lead to chronic pain, psychological trauma, reduced quality of life, as well as delayed functional recovery, and post-anesthesia care unit discharge [3,4].Regional blocks have been implemented in the perioperative setting to provide superior pain control.Additionally, regional blocks have the potential benefits of decreasing the incidence of chronic pain and reducing opioid consumption and postoperative pulmonary complications.With lower opioid consumption, a lower rate of adverse effects (nausea, vomiting, respiratory complications, hyperalgesia, and immunosuppression) can be achieved [5].The Pectoral I (PECS I) block was first described by Blanco in 2011.In this technique, local anesthetics are injected in the plane between the major and minor pectoralis muscles to achieve a block of the medial and lateral pectoral nerves.As these nerves mostly innervate the pectoralis muscles, the PECS I block is theoretically suited for surgery involving these muscles.In 2012, the same author proposed a modified version of the block called the PECS II block.It is achieved by adding another, deeper injection in the plane between the pectoralis minor and the serratus anterior muscle.This technique is believed to contribute to more extensive anesthesia of the chest wall by also blocking the long thoracic nerve and the lateral branches of the intercostal nerves from T3 to T6 [6].We conducted a scoping review to compare the type of block performed for each type of breast surgery, the local anesthetic used, intraoperative opioid use, postoperative pain, postoperative opioid consumption, and postoperative nausea and vomiting.

Review Methodology
This study was conducted using Arkesy and O'Malley's framework for scoping reviews, as described by Levac, consisting of five stages described below [7,8].

Stage 1: Identifying the Research Question
To capture a wide range of publications, we identified broad research questions to identify current practices and their advantages.Identifying the questions was a continual process between the authors which resulted in the following questions: (1) What are the uses of the PECS block regional technique?(2) Is the PECS block regional technique effective for intraoperative and postoperative analgesia in the first 24 hours?(3) What type of local anesthetic and adjuvants were used?

Stage 2: Identifying Relevant Studies
The following search terms were used: PECS block, regional anesthesia, breast surgery, and pectoralis nerve block.Two independent authors searched five databases (MEDLINE, EMBASE, EBSCO, Scopus, and Web of Science) on September 3, 2022.We limited our search to articles published since 2010 to provide an overview of past and current PECS block techniques.Publications were collected using a shared bibliography, and duplicate articles were removed.

Stage 3: Selecting Studies for Inclusion
A total of 22 articles were identified during the first search, and 15 articles were included in our scoping review.The inclusion criteria were original investigations, articles published in English, original data presented in the study, and a description of the use of PECS regional block for patients undergoing breast surgery.
We included studies that involved adult patients undergoing breast surgery with PECS regional block as the primary modality of anesthesia or as part of the postoperative analgesia plan.Studies published in English between 2010 and September 2022 were included in the review.All original articles were included (case reports, case series, clinical trials, and systematic reviews).Studies were excluded if not in the English language and/or if described as an ongoing research protocol.

Stage 4: Charting the Data
For every study, we extracted author names, year of publication, study title, article type, the aim of the study, methodology used, outcomes that were assessed, population, results, anesthesia technique, block technique, drugs that were used, inclusion and exclusion criteria, number of participants, and conclusion.
The appropriate study data was condensed in a tabulated form; two authors performed this step independently for all articles, and a final table was compiled after a discussion between the authors.

Stage 5: Summarizing and Reporting the Results
Adhering to the scoping review methodology, we adopted an approach to summarize and report the data by our four research questions in a thematic analysis.We provided a narrative synthesis of the findings to help guide future research (Figure 1).

Results
We included 15 studies.The median number of patients included in the studies was 517.5 patients [3-6,9-19] (Table 1).2023     What Are the Uses of the PECS Block Regional Technique?

Discussion
This scoping review explores the current evidence of using the PECS regional block technique over the past years for chest wall surgeries.Facial plane blocks may have a role in improving intraoperative and postoperative pain relief and opioid consumption, quality of recovery, and patient satisfaction.The type, concentration, and volume of local anesthetic that can provide the optimum effect is yet to be determined for the PECS regional block.

Type of Surgery and Intraoperative Opioid Consumption
The reviewed patients underwent various breast surgeries, including unilateral modified mastectomy with or without sentinel lymph node dissection, breast augmentation, and breast-conserving surgery with lymph node dissection.Intraoperative opioid consumption was the only outcome in common among all the included articles in this review.Most studies showed a decrease in opioid use intraoperatively in the intervention groups [3,5,[10][11][12][15][16][17][18][19].Conversely, some randomized controlled trials showed no statistically significant difference in opioid consumption [4,6,14].One study used sufentanil for every case [9].
This data shows that using the PECS block regional technique in breast surgeries is feasible and may effectively reduce intraoperative pain.The discrepancy in the studies that showed no statistically significant difference in intraoperative opioid consumption could be attributed to either a failed block (by location, type, concentration, or volume of the injectate), a low study power, or both.

Immediate Postoperative Pain and Opioid Consumption
Most studies showed a statistically significant decrease in postoperative opioid consumption and patientreported pain scores [3,5,[9][10][11][12][13][14][15][16][17][18][19].One study showed no difference in postoperative opioid consumption [4], and another showed an increased opioid consumption [6].The authors of this article suspect that part of the discrepancy in Maxim Roy's trial is due to the unusual method of administering local anesthetic with the block on one side and a sham block (0.9% NaCl) on the other side making each patient their own control group, on top of the low number of patients included in their study (N = 19).
The available data suggest that the PECS regional block technique for breast surgery can be an effective modality in decreasing postoperative opioid consumption and patient-reported pain scores.This would lead to increased patient satisfaction and comfort while decreasing the risk of high-dose-opioid side effects such as postoperative nausea and vomiting and respiratory depression.Reproduced with permission from NYSORA.com [21].

Conclusions
Facial plane blocks may offer an innovative approach to the classical way of regional blocks.We target only the essential nerves to relieve intraoperative and postoperative pain and reduce opioid consumption.The persistent debate on their effectiveness can partly be explained by patients' and providers' observed high expectations and the underestimation of the needed provider skills in performing this seemingly easy but elusive block technique.The authors conclude that PECS block can provide a decrease in intraoperative and postoperative opioid consumption, a decrease in the incidence of nausea and vomiting, and can lead to overall patient satisfaction in terms of lower pain scores compared to systemic analgesia.The local anesthetic type, concentration, and volume vary widely between the studies, which paves the way for further research.

FIGURE 1 :
FIGURE 1: A thematic analysis of represented data.