Before the emergence of novel myofascial plane blocks, regional thoracic anesthesia and analgesia was limited to thoracic epidural, paravertebral (PVB), and intercostal nerve blocks. The most commonly performed and studied fascial plane blocks of the chest wall include the pectoralis I and II (PECS I and II), serratus anterior plane (SAP), and erector spinae plane (ESP) blocks. Recently, studies examining the less commonly performed transversus thoracis plane (TTP) block have been described. Fascial plane blocks are performed with the injection of local anesthetic between two myofascial layers, most commonly with ultrasound guidance. This interfascial plane technique allows nerves to be blocked without having to be directly imaged. Indications and techniques for these fascial plane blocks will be reviewed, highlighting the latest research involving their use.
PECTORALIS I AND II BLOCKS
Indications and recent research
The PECS I and II blocks are most commonly used for analgesia involving operations of the chest wall. Several studies have validated their efficacy in breast surgery including modified radical mastectomy [1▪], breast augmentation [2▪▪], and partial or simple mastectomy with lymph node dissection [3▪].
Zhao et al. performed a meta-analysis of eight randomized control trials (RCTs) and two cohort studies involving 993 patients to determine the analgesic efficacy of PECS blocks after radical mastectomy. A PECS I or II block and general anesthesia experimental group was compared with a control group having exclusively general anesthesia (some including placebo injections in PECS block regions). This analysis found the PECS II group reduced intraoperative and postoperative opioid use, incidence of postoperative nausea and vomiting (PONV), need for postoperative rescue analgesia, and pain scores within 0–6 h after surgery [1▪]. A prospective randomized study by Omer et al. found that the combined use of PECS I and II blocks provide superior postoperative analgesia compared with general anesthesia alone, resulting in lower Visual Analog Scale (VAS) pain scores, and decreased postoperative patient-controlled fentanyl consumption in patients undergoing breast augmentation. Both PACU and hospital length of stay was significantly shorter in the block group (10.1 ± 1.9 versus 15.2 ± 1.6 min; P < 0.001) and (24.4 ± 1.2 versus 27.0 ± 3.1 h; P < 0.001), respectively [2▪▪]. Versyck et al. conducted a meta-analysis of 13 RCTs that included 815 patients comparing analgesic efficacy of the PECS II block versus systemic analgesia alone, and in contrast to a thoracic PVB, for breast cancer surgery. They demonstrated that PECS II blocks offer better analgesic efficacy versus systemic analgesia alone, when comparable with thoracic PVBs [3▪].
In another analysis, Kaushal et al. performed a comparison study constituted of 108 children with congenital heart disease requiring surgery through an open thoracotomy. They demonstrated that deep SAP and PECS II blocks are equally efficacious in postthoracotomy pain management compared with intercostal nerve blocks based on postoperative Modified Objective Pain Scores (MOPS). This study also demonstrated the benefits of longer duration of analgesia and ease of performance [4▪▪].
The PECS I block targets the medial and lateral pectoral nerves and is performed by injecting local anesthetic within the fascial plane between the pectoralis major and minor muscles. The PECS II block, which includes performing a PECS I block, involves an additional injection deep to the PECS I plane within the fascia between the pectoralis minor and serratus muscles. This injection targets the lateral cutaneous branches of intercostal nerves, the long thoracic, and thoracodorsal nerves .
The patient is positioned supine with the ipsilateral arm to the blocked side either kept aside or abducted and their head turned contralaterally. The PECS I plane is found by placing a straight linear array transducer in the midclavicular parasagittal plane and identifying the pectoralis major and minor muscles, axillary vessels, and pleura. The second and third ribs can be identified by sliding the ultrasound probe inferiorly. Rotating the inferior end of the probe towards the axilla helps bring the view more parallel to the deltopectoral groove. The needle is then inserted, in-plane or out-of-plane, so the tip lies within the interpectoral fascia between the pectoralis major and minor muscles using an injection of 1–2 ml of isotonic saline for confirmation. Local anesthetic is injected once the correct plane is identified.
For the PECS II block, the patient positioning and ultrasound probe orientation are similar to the PECS I block. However, the needle is advanced through the interpectoral fascia and pectoralis minor muscle to lie within the fascial plane between the pectoralis minor and the serratus anterior muscles. When a PECS II block is performed, the two injections can be performed in either order, superficial-to-deep, or deep-to-superficial. Some practitioners advocate performing the deep injection first as a superficial injection can create a less clear ultrasound image of the deep plane by displacing the tissue layers and inadvertently introducing small air bubbles.
SERRATUS ANTERIOR PLANE BLOCK
Indications and recent research
Much of the research in the use of SAP blocks, also referred to as PECS III, have been in thoracic surgery.
Semyonov et al. performed a prospective, randomized, double-blinded single-center study of 104 patients who underwent elective thoracoscopy. Patients were randomized to receive either a superficial or deep SAP block in addition to standard pain control consisting of parenteral opioids, NSAIDs and acetaminophen, versus a standard pain control group alone. They found that patients who received either block reported significantly lower VAS pain scores requiring significantly less morphine and tramadol rescue during the first 8 h after surgery. Total morphine dosages required were 5.48 ± 4.29 mg in the block group and 10.14 ± 5.26 mg in the control group (P < 0.0001). Total tramadol dosages required were 220.21 ± 25.2 mg in the block group and 307.01 ± 23.1 mg in the control group (P < 0.02). Coincidentally, the incidence of PONV was also lower among the block group, presumably related to less opiate use for rescue analgesia [6▪].
Further research has been conducted to compare SAP blocks with other regional techniques, such as PVB and ESP blocks, to manage pain after thoracic surgery. Wang et al. demonstrated that the addition of a single-injection superficial SAP or single-level thoracic PVB at the T5 or T6 level, in patients undergoing uniportal video-assisted thoracoscopic surgery (VATS), had a reduction in both postoperative opioid consumption and pain scores . In a small randomized study of 60 patients undergoing VATS, Gaballah et al. demonstrated that an ESP block provided superior analgesia and longer time to first required analgesic than a superficial SAP block [8▪]. There have also been case reports of SAP blocks being used to manage postoperative pain after open thoracotomy for lung transplantation .
The SAP block is performed by injecting local anesthetic within the superficial fascial plane created by the latissimus dorsi, teres major, and serratus anterior muscles, or within the deep fascial plane created by the serratus anterior and intercostal muscles between the fourth and fifth ribs. The long thoracic, thoracodorsal, and intercostobrachialis nerves, along with the lateral cutaneous branches of the intercostal nerves (T3--T9), are primarily targeted with this block.
The patient is positioned either supine, with the ipsilateral arm to the block side abducted, or in the lateral decubitus position with the operative side up and arm flexed forward. A straight linear array transducer is placed in the parasagittal plane below the clavicle and the fourth rib is identified by inferior translation of the probe. The probe is then moved laterally, tilting the inferior end into the midaxillary to posterior axillary line in order to identify the latissimus and serratus anterior muscles. The needle is inserted, in-plane or out-of-plane, so the tip lies within either the fascial plane superficial or deep to the serratus anterior muscle, using an injection of 1–2 ml of normal saline for confirmation. Local anesthetic is then injected.
ERECTOR SPINAE PLANE BLOCK
Indications and recent research
The ESP block has been described to provide analgesia for rib fractures as well as back and chest wall surgeries.
A small prospective RCT of 60 patients by Abu Elyazed et al.[10▪] demonstrated that the use of ultrasound-guided bilateral ESP blocks resulted in lower postoperative VAS pain scores and decreased consumption of both intraoperative fentanyl and postoperative rescue analgesia for patients undergoing open epigastric hernia repair compared with a control group receiving bilateral sham blocks.
The use of ESP blocks for pain management after cardiac surgery is increasing. In a prospective, randomized, controlled, single-blinded study, Krishna et al. demonstrated that patients undergoing elective coronary artery bypass grafting, valve replacement, or atrial septal defect closure, who received an ESP block, had superior analgesia for a longer duration [based on Numeric Rating Scale (NRS) pain scores], and decreased opioid rescue compared with an intravenous paracetamol with tramadol regimen control [11▪▪]. Macaire et al.[12▪▪] reported that the use of a fast-track recovery protocol including a continuous bilateral ESP block was associated with a significant decrease in intraoperative and postoperative opioid consumption, optimized rapid patient mobilization, and early chest tube removal after open cardiac surgery.
In a comparison study between PECS and ESP blocks for patients undergoing radical mastectomy, Altiparmak et al.[13▪] demonstrated that the use of a PECS II block reduced postoperative pain scores and tramadol consumption more effectively than an ESP block.
A retrospective cohort study by Adhikary et al.[14▪] demonstrated that continuous ESP blocks were associated with improved inspiratory capacity and analgesic outcomes (based on incentive spirometry volume, maximum NRS static pain scores and 12 h opioid consumption) following rib fractures, without any hemodynamic instability.
The ESP block is performed by depositing local anesthetic within the fascial plane located in the posterior chest wall between the anterior surface of the erector spinae muscles and the posterior surface of the transverse processes of the thoracic vertebrae. The dorsal rami of the spinal nerves are primarily targeted, however, there is some evidence that local anesthetic reaches the ventral rami via the paravertebral and epidural spaces [15,16].
The patient is positioned in either the lateral, sitting, or prone position. A straight linear or curvilinear array ultrasound transducer can be used. The target vertebral level is identified by either counting down from the C7 spinous process or scanning down from the first rib using ultrasound. The transducer is placed in the parasagittal plane about 2–3 cm lateral to the spinous process of the desired vertebral level. Transverse processes are identified by their ‘squared-off’ profile as opposed to the ‘rounded’ appearance of the ribs laterally and the presence of a visible pleural line deep to them. The fascial plane between the anterior surface of the erector spinae muscles and the posterior surface of the transverse processes is identified. The needle is inserted, in-plane, cephalad-to-caudad, with a shallow trajectory to contact the edge of the targeted transverse processes then passing into the fascial plane. Needle tip location is confirmed by injecting 1–2 ml of normal saline. Local anesthetic is then injected.
Transverse, lateral, and out-of-plane techniques have also been recommended to help identify the correct fascial plane and avoid inadvertent intramuscular injection [17,18].
TRANSVERSUS THORACIS PLANE BLOCK
Indications and recent research
The TTP block is a newer myofascial plane block of the anterior chest wall. This block has been shown to be useful in providing analgesia for procedures and injuries involving the medial chest and sternum including sternotomy, sternal or anteromedial rib fractures, medial coverage for breast surgery, and pacemaker/ICD placement [19–22].
Most recently, Fujii et al. conducted a pilot study of 19 patients undergoing elective cardiac surgery with sternotomy. Patients were randomized to receive either a TTP block or standard care as control on admission to the ICU after surgery. Patients in the block group, performed under ultrasound guidance, received 20 ml of either 0.3 or 0.5% ropivacaine bilaterally. Mean (SD) NRS pain scores, at rest, 12 h postoperatively, were 3.3 (3.2) in the block group versus 5.6 (3.2) in the control group. The authors concluded, based on preliminary data that using a TTP block for pain management after sternotomy was well tolerated and resulted in better pain management and patient satisfaction than standard care [23▪].
The TTP block anesthetizes the anterior cutaneous branches of the second to sixth intercostal nerves and the sympathetic plexus around the internal thoracic artery. The nerves lie within the fascial plane between the internal intercostal and transversus thoracis muscles.
Patient position is dictated by comfort, usually either supine or in a semi-inclined position. A straight linear array ultrasound probe is placed on the chest in the parasagittal plane. Using the midclavicular line as a guide, the third or fourth rib space, ribs, pleura, pectoralis major, and intercostal muscles are identified. This can be accomplished by scanning in a lateral-to-medial fashion. The transversus thoracis muscle should be visualized lying deep to the intercostal muscle and superficial to the pleura. Of note, the internal thoracic artery also runs in this plane and can be identified in cross-section. The needle is inserted, in-plane, with a shallow trajectory until the tip is confirmed to be within the facial plane between the internal intercostal and transversus thoracis muscles. The type, concentration, and volume of local anesthetic used for this block has not been well described and requires further study [24,25].
A parasternal intercostal (PSI) nerve block, or technically identical pectointercostal fascial block (PIFB), performed superficially to the TTP within the fascial plane between the pectoralis major and intercostal muscles has also been described. This block is perceived by some practitioners to allow for better ultrasound imaging and lower risk of both pleural and arterial punctures [26,27].
RETROLAMINAR AND RHOMBOID INTERCOSTAL AND SUB-SERRATUS BLOCKS
The retrolaminar block (RLB) is similar in many ways to an ESP block. One key difference is that the RLB is performed more medial (1 cm lateral to the SP) and posterior to the lamina while still anterior to the erector spinae muscles of the desired vertebral body level. The injectate within the retrolaminar space has been shown to diffuse into the paravertebral and epidural spaces as well as the intervertebral foramina, resulting in blockade of the ventral and dorsal spinal rami in addition to the lateral cutaneous and small branches of the thoracic intercostal nerves [28▪,29]. Continuous RLBs have been used for analgesia after mastectomy and rib fractures [30–33].
The rhomboid intercostal and sub-serratus (RISS) block is a novel ultrasound-guided block that has been shown to provide analgesia of T2–T11 dermatomes . It is a two-injection technique within both the rhomboid intercostal and sub-serratus spaces that results in blockade of the ventral and dorsal spinal rami of the thoracic intercostal nerves . The RISS myofascial tissue plane extends deep to the erector spinae muscles medially and deep to the serratus anterior muscle laterally. The RISS block has specifically been described being used for rib fractures and postlung transplantation thoracotomy pain [35,36].
Thoracic myofascial plane nerve blocks provide effective analgesia for a variety of surgical procedures. These techniques offer the anesthesiologist additional options for managing postsurgical pain. The relative ease of performance and safety profile make fascial plane blocks appealing. Further research is needed to better characterize their effectiveness in specific settings, dosing regimens, and continuous catheter applications.
We would like to acknowledge Dr Patrick McQuillan for his expertise in editing this manuscript.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING
Papers of particular interest, published within the annual period of review, have been highlighted as:
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