Cardiothoracic surgeries are associated with significant pain. Optimal analgesia is a vital part of enhanced recovery after surgery strategies intended to improve patients’ perioperative experience and outcomes. Traditionally, analgesia in these types of surgeries has depended on large doses of I.V. opioids (Anesth Analg 2020;131:127-35). This is particularly pertinent given the current focus on removing needless perioperative opioid administration, and thereby decreasing the potential for opioid side effects.
As an alternative, there is a growing appreciation for the critical role that regional anesthesia can play in an overall multimodal anesthetic strategy (Anaesthesia 2020;75:e101-10). Among regional anesthesia strategies, techniques involving an injection of local anesthetic into fascial planes, rather than directly around discrete nerves, are growing more popular. The attraction of employing such regional blocks for cardiothoracic surgeries lies mainly in their relative reliability, ease of placement, and safety (Curr Opin Anaesthesiol 2020;33:692-7). The most performed and studied fascial plane blocks of the chest wall include the serratus anterior plane (SAP) block and pectoralis I and II (PECS I and II) blocks.
There are two types of SAP blocks: 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 (J Anaesthesiol Clin Pharmacol 2018;34:251-3). Both target the anterolateral branches of the thoracic intercostal nerves.
It remains uncertain if there is a clinically significant difference between injections superficial or deep to the serratus anterior muscle; there are currently no published clinical trials comparing both variants. SAP block has few reported complications in the cardiothoracic population. Although rare or unreported, potential complications may include infection, hematoma, and pneumothorax, hematoma, and local anesthetic systemic toxicity.
PECS I and II blocks
The term PECS block encompasses two separate techniques (Br J Anaesth 2018;120:846-53). The PECS I method blocks lateral and medial pectoral nerves by injecting the 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, providing more extensive coverage of the chest wall and the axilla.
PECS I and II blocks are considered safe procedures with predicted low complication rates. However, potential complications include infection, pneumothorax, thoracoacromial artery injury and hematoma, and local anesthetic systemic toxicity.
A systematic review of fascial plane blocks in cardiothoracic surgery
In a 2020 systematic review of mostly observational studies, Jack and colleagues analyzed the current state of evidence reporting the application of these fascial plane blocks in thoracic trauma, or in elective cardiac or thoracic surgical procedures to better define their clinical role and determine the quality of evidence that currently exists for these applications (Anaesthesia 2020;75:1372-85).
The researchers investigated relevant studies by searching multiple databases and trial registries from inception to June 2019. Eligible study types included: randomized controlled trials (RCTs); prospective non-randomized comparative studies; retrospective comparative and cohort studies; prospective observational cohort studies; and case series or reports. In total, the team identified 51 studies for inclusion of this review: nine RCTs, 13 cohort studies, 19 case series, and 10 case reports involving a total of 637 patients.
Seven of the RCTs studied SAPs, one studied PECS II block, and one compared both SAP block and PECS II block with a control group. Eight of the nine RCTs evaluated the SAP block in the setting of video-assisted thoracoscopic surgery (five studies) and thoracotomy (three studies). Five of these compared single-injection SAP blocks with systemic analgesia alone; one compared it with thoracic paravertebral blockade and with systemic analgesia alone; and one compared it with PECS II blocks and with intercostal nerve blocks.
The analysis indicated that single-injection SAP and the PECS blocks reduce pain scores and opioid consumption compared with systemic analgesia alone in cardiothoracic surgery, cardiac-related interventional procedures and chest trauma. They consistently improve early postoperative analgesia when added to systemic analgesia. The clinical duration of analgesia with single-injection techniques appears to be in the region of six to 12 hours, with greatest analgesic benefit in the first four to six hours. There were no reported complications, and the risk of hemodynamic instability appears to be low.
The team also noted that one of the major drawbacks of regional anesthesia in acute pain management is the limited duration of action. Block duration of effective analgesia is contingent on the type, volume, and concentration of injected local anesthetic.
The authors acknowledge the review had several limitations. For example, these are novel techniques with a limited number of RCTs, which included a little over 600 patients. The evidence supporting the use of SAP and PECS blocks in thoracic trauma is presently comprised of only small case series and reports. Additionally, many were available primarily as conference abstracts and consequently serve primarily as proof-of-concept. Moreover, meta-analysis was not undertaken due to the small number of comparative studies and the heterogeneity in surgical population, intervention technique, and comparators. Instead, studies were qualitatively summarized and stratified by type of surgery and comparator.
The team concluded that the results of this systematic review, though limited and still at an early stage, were encouraging and support the efficacy and safety of SAP and PECS blocks as an attractive alternative to thoracic epidural analgesia and paravertebral blockade due to their relative ease of performance and safety profile.
Areas that require further research include investigating the exact efficacy and safety of individual blocks or their combination for specific procedures, dosing regimens, and which technique offers the optimal benefit-to-risk ratio in specific surgical settings.