Continuous erector spinae block as an anesthetic technique in breast surgery: What is the current evidence?

Adequate perioperative pain management is essential after mastectomy. Poorly controlled acute pain may lead delayed recovery, increased morbidity, prolonged length of hospital stay, increased opioid requirement and its related adverse effects, and may also increase the risk of chronic mastectomy pain.[1] Perioperative pain increases the stress response and suppresses the immune system and may promote cancer progression.[2] Traditionally, opioids are the most commonly used drugs for perioperative pain management. However, opioids also suppress the immune system by interfering with natural killer (NK) cell activity and may promote cancer recurrence.[13] Opioids are also associated with postoperative nausea and vomiting (PONV), pruritus, constipation, and respiratory depression. Regional anesthesia (RA) has been proposed to reduce the cancer recurrence and metastases by attenuating the stress response to surgery, reduce pain, and minimize the perioperative opioid requirement.[1] Local anesthetics (LA) seem to have a protective effect against tumor growth and metastases through direct cytotoxicity, inducing apoptosis, inhibition of cancer cell proliferation, migration, invasion, and gene modulation by methylation.[4] RA also offers host of other advantages, such as superior analgesia, reduced volatile agents and opioid requirement, reduced general anesthesia in high risk indicated cases, early mobilization, and decreased incidence of PONV. A retrospective study of 129 patients showed that patients who received paravertebral (PVB) with general anesthesia had four times greater recurrence-free survival as compared with those who received intravenous patient-controlled analgesia.[5] The breast and surrounding tissues derive its innervation from several distinct nerves. The anterior cutaneous branches of the T2 to T5 intercostal nerves (with variable contribution from T1 and T6) innervates the medial part of breast and lateral cutaneous branches of the T2 to T5 intercostal nerves (with variable contribution from T1, T6, and T7) innervates the lateral aspect of breast. The axillary tail of the breast, the axilla, and medial upper arm is supplied by the Intercostobrachial nerve. A RA technique that blocks all these nerves may provide effective analgesia and even anesthesia for breast surgeries. Introduction of ultrasound (USG) has lead to a paradigm shift toward RA. The anesthesiologists’ armamentarium is continuously being expanded with the addition of newer fascial plane blocks for breast surgery, such as pectoralis blocks, serratus anterior plane block, and erector spinae plane block (ESPB). Gradually, PVB or thoracic epidural block is losing popularity to simpler, safer, and cost-effective myofascial blocks. ESPB is a recently introduced myofascial plane block by Forrero et al. in 2016 for chronic postthoracic neuropathic pain poorly responsive to oral pharmacotherapy.[6] The exact mechanism by which ESPB provides analgesia is still unclear. One mechanism that is widely accepted is the diffusion of LA into PVB space, which blocks both the dorsal and ventral rami of spinal nerves and rami communicants that transmit sympathetic fibers to provide anesthesia and analgesia.[7] However, a recent cadaveric study by Ivanusic et al. demonstrated extensive craniocaudal and mediolateral dye spread superficial and deep to erector spinae muscle, but there was lack of spread of the dye anteriorly to PVB space.[7] Adhikary et al. used magnetic resonance imaging to compare ESPB and retrolaminar block in cadavers.[8] They noted the spread of dye to intercostal spaces, neuroforaminal areas, and epidural space in ESPB. Chin et al. have proposed differential block theory which may help to reconcile the disputing results between the clinical effects and cadaveric study.[9] According to this theory, fascial plane blocks, where LA is deposited away from the target nerves; the volume or mass of LA is small so that detection by conventional means is difficult. Also, the sensory and motor block is not discernible nevertheless analgesia is produced. There are many case reports and series that have documented the efficacy of ESPB for analgesia following breast surgery.[1011] Recently, Ohgoshi et al. also reported two cases in which continuous ESPB provided effective analgesia without any use of additional opioids for breast reconstruction using tissue expanders.[12] However, the literature on use of ESPB as a sole anesthetic technique in breast surgery is limited. In this issue, authors have reported the use of continuous ESPB with sedation as an anesthetic technique in a high-risk patient with ostium secundum atrial septal defect and pulmonary hypertension scheduled for modified radical mastectomy. It provided anesthesia from T3 to T8 dermatomes with no requirement for rescue analgesics for 24 h. About 20 mL of 0.5% bupivacaine and 10 mL of 2% lignocaine were administered initially and 10 mL of 0.5% bupivacaine every eighth hourly for 24 h in the postoperative period.[13] The simplicity to perform, multiple dermatomal spread, good analgesia, comparative safety to PVB block as it aims toward bony structures rather than PVB space near pleura have evoked vivid interest in ESPB for providing postoperative analgesia. The drawback is that it can be performed only with ultrasound guidance and not as a blind or landmark technique. The other limitations are that it may not be feasible to put the block in patients with injury/infection at the site of needle insertion; the effect of the block may be variable due to interindividual variability in skill and variation in LA spread. Also, it only gives unilateral thoracic analgesia and we may need to give bilateral blocks for incisions that cross midline. Another lacuna is lack of randomized trials as most of the reported literature is in the form of case reports and small case series. ESPB can be a promising technique to provide effective perioperative anesthesia in various breast surgeries and may be good option in high-risk cases. Further randomized trials are required to validate the benefits and complications of ESPB as a sole anesthetic technique.

Abstract licence: CC BY-NC-SA

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