Ultrasound Guided Erector Spinae Block with Costotransverse Ligament Puncture is More Effective than Erector Spinae Block Alone; Eight Cases for Oncologic Breast Surgery; A Brief Technical Report

Objectives: Due to the complex breast innervation, postoperative analgesia after breast surgery is a challenge for the anesthesiologists. The erector spinae plane block (ESP) is a newly defined promising technique for this purpose. Since the description by Forero, ultrasound-guided erector spinae block (ESP) has performed for several surgeries for postoperative analgesia. Many regional methods pectoral nerve block (PECs), serratus plane block (SPB), were described in the literature for maintaining postoperative analgesia. Among all these regional anesthesia techniques, paravertebral block (PVB) is the most studied and found to be a valid regional technique for this purpose. Due to its anatomic proximity to the pleura and central neuraxial system, it’s also one of the most challenging techniques. Materials and Methods: Patients aged between 37 and 47 years, American Society of Anesthesiologists physical status I-II and scheduled for elective unilateral modified radical mastectomy (MRM) surgery without axillary lymph node dissection were enrolled to this case series. In this report, we describe a novel combination of ESP and simplified dle tip was directed to T4 superior costotransverse ligament, and the ligament was perforated at the top point where it attaches to the T4 transverse process. Results: The ESP block is used for a local anesthetic depot, as a safe and straightforward technique and costotransverse ligament puncture facilitates diffusion and ensures local anesthetic passage to the paravertebral area for thoracic postsurgical analgesia. Using lower doses, comparing this combination with all studies with ESP, it appears that there are a better Numeric Pain Rating Scale (NPRS) scores in the first postoperative hours. NPRS scores at the 12th and 24th hours appear to be similar to those performed in ESP without costotransverse ligament puncture. Conclusion: We submit the first description of a novel combination of ESP block and simplified paravertebral block (PVB) and its successful application in 8 cases of oncologic breast surgery.


Introduction
Many regional anesthesia techniques have been described for post-breast surgery analgesia [1]. Paravertebral block (PVB) is the most effective experienced technique, but it is compelling due to adjacent to pleura and central neuraxial system [2]. Erector spinae block (ESP), a comparatively safe and straightforward technique, has been used for postoperative analgesia in breast surgeries [3] [4] [5].
The ESP block is performed by depositing the local anesthetic (L.A.) in the fascial plane, more profound than the erector spinae muscle (ESM) at the tip of the transverse process of the vertebra. Therefore, LA is distributed in the craniocaudal fascial plane, one dermatome, a median of each 3.4 ml of injected volume [6]. Additionally, it diffuses anteriorly to the paravertebral and epidural spaces and laterally to the intercostal space at several levels [7]. Furthermore, the diffusion of L.A to the paravertebral space through the costotransverse foramina and the intertransverse complex (intertransverse and costotransverse ligaments: levators, rotators, and intercostal muscles) provides both visceral and somatic analgesia. This diffusion into the epidural space and the neural foramina has been reported in anatomical studies that examined 2 to 5 vertebral levels that were centered near the injection site. However, this diffusion was not observed consistently in all cadaver studies. We claimed that ESP blocks with cost transverse ligament puncture would ensure more effective pain control and fewer onset times of ESP blocks according to ESP blocks alone.
We present the first description of a novel combination of ESP block and simplified PVB, due to the mechanism of ESP block and its successful application in 8 cases of oncologic breast surgery. We discuss the onset times and numeric pain rating scales (NPRS) ranging from 0 (no pain) to 10 (worst imaginable pain), which is used for postoperative pain assessment.

ESP with Costotransverse Ligament Puncture Technique
Written informed consent was provided by all patients for inclusion in this report. Patients aged between 37 and 47 years, American Society of Anesthesiologists physical status I-II and scheduled for elective unilateral modified radical mastectomy surgery (ASA) without axillary lymph node dissection were enrolled in this report. The exclusion criteria were patients with coagulation disorder, chronic opioid use, hepatic or renal insufficiency, local infection at the injection site, spine or chest wall deformity, known allergy to local anesthetics. Blocks were performed 30 min before the induction of general anesthesia in the regional anesthesia block room. Patients were given 4 -5 lt/O 2 and underwent routine monitorization, including electrocardiogram, peripheral oxygen saturation, and non-invasive blood pressure. Intravenous access was secured, and sedation with midazolam 2 mg was administered.

Results
Demographical data, durations were similar, and types of surgeries were the same (Table 1). Since all of the blocks were performed at the T4 level, cases whose axillary dissection was planned from the beginning of surgery or turned Table 1. NPRS: Numeric Pain Rating Scale ranges from 0 (no pain) to 10 (worst pain imaginable); ASA 1 and 2: American Society of Anesthesiologists Scores; PONV: postoperative nausea and vomiting; MRM: modified radical mastectomy. Case  to axillary dissection according to the frozen result were excluded. No complications were observed in any case. The studies, comparing ESP block and PVB block before were examined, PVB was observed to be more effective [8]. In our new combination, NPRS scores were obtained close to PVB. Nausea and vomiting were not observed in any patient. Two of the patients had no postoperative Tramadol consumption. NPRS scores and postoperative total tramadol consumptions are better than ESP block alone according to the studies done before [9]. Comparing this combination with all studies performed only with ESP, it is seen that there are better NPRS scores in the first postoperative hours. The NPRS scores at the 12th and 24th hours seem to be similar to those performed in ESP without costotransverse ligament puncture.

Discussion
Although ESP blocks provide simpler and safer regional anesthesia techniques than traditional paravertebral blocks [10], the optimal injectate volume required for the successful single or multilevel paravertebral spread is unknown. A 20 ml volume of injectate in single ESP block seems to be inadequate in clinical practice, in cadaveric studies analyzing injectate spread patterns in ESP blocks also used 20 ml volume of dye correlatively [11] [12]. A recent cadaveric study [13] illustrated an exciting finding that there is no paravertebral spread in any 10 ml performed ESP blocks. Furthermore, this study demonstrated with an endoscopic evaluation that using a 30 ml dye solution, stained thoracic spinal nerves at the intervertebral foramina, and epidural spread was observed. Despite postmortem changes in the integrity of tissues that could affect the diffusion of the injectate, it seems paravertebral spread that occurs after ESP blocks is volume dependent. Chest movements during inspiration and expiration can steer the injectate solution to paravertebral or intercostal spaces.
Precisely at this point, this novel combination of ESP block and simplified PVB may be essential. First of all, interfascial blocks seem to be relatively safe from systemic toxicity associated with local anesthetics due to the low vascularity of fascial structures [14]. However, the potential for local anesthetic systemic toxicity was reported when performing ESP blocks with more than 40 ml of diluted local anesthetics [15]. This combination may be necessary for patients undergoing bilateral thoracal ESP to avoid toxicity, or it may be suitable for physiological conditions with local anesthetic susceptibility such as pregnancy, liver failure. Using this combination may lead to an adequate effect with lower doses and volumes.
We tried to describe this technique by combining ESP and facilitated PVB with this series of case reports. The sample size may be small but sufficient to explain how the technique is and how effective it is. This technical report demonstrated that the combination of ESP block and costotransverse ligament puncture is more effective with lower doses of local anesthetics. We also demonstrated that NPRS scores in the first postoperative hours. Therefore, costotransverse ligament acts as a barrier for ESP blocks clinically.
However, as the paravertebral space (PVS) is often small, even with the guidance of ultrasound, the risk for a pleural puncture, especially with a less skilled anesthesiologist, is still present. With this combination, due to the needle tip time to stay under the costotransverse ligament is very short and no negative aspiration is not required, it seems to be a practical method. Moreover, since no local anesthetic is given to the paravertebral area, no volume-related complications seen. None of the complications, such as nausea, vomiting, hypotension seen in the paravertebral block, observed with this combination.
The PVS is filled with fat and is traversed by the dorsal branches and ventral branches of spinal nerves, communicating branches, intercostal nerves and blood vessels, hemiazygos vein, thoracic duct and sympathetic trunk [16]. Placing a catheter or making injection in a small area with so many structures is highly associated with complications. In our technique, we are drilling through the costotransverse ligament at the top point where it attaches and drawback without going deep into the paravertebral area, and not keeping the needle tip for a short time protects all these structures and thus avoid complications.
In studies comparing PVB with ESP, the complication rate was higher in the PVB group [17]. The most important benefits of this new method are the absence of bilateral block, hypotension, intrathecal spread from PVB complications. The risk of pneumothorax is still constant but reduced.
Conventionally, the superior costotransverse ligament was assumed to be a compact ligament and that an effective PVB could only be achieved after direct penetration of the ligament. However, the PVB and intercostal nerves could be stained even if the dye was injected above the superior costotransverse ligament or intercostal muscle through the porous tissue around the superior costotransverse ligament [18]. Another study reported gaps between the medial and lateral portions of the superior costotransverse ligament [19]. Similar dye spreading patterns to the PVB were also reported in retrolaminar blocks, another alternative to paravertebral blocks, without pleural displacement or superior costotransverse ligament penetration [20].
Despite the fact that, the mechanism of the ESP remains unclear, local anesthetics injected beneath the erector spinae muscle (interfacial injection) can spread through the costotransverse foramen and peripheral porous tissues into the intercostal and thoracic paravertebral spaces [21] [22]. The costotransverse foramen is a bony gap between the neck of a rib and the TP of a vertebra. A cadaveric study reported that tracer dyes injected beneath the erector spinae muscle can spread into the deep structures of the external intercostal muscle and internal intercostal membrane through the costotransverse foramen [21]. We estimate that, this technique creates a tunnel between the paravertebral area and the ESP block, which acts as a local anesthetic depot. Reduced paresthesia onset times and better NPRS scores than ESP block during the first hours of the post-operative period supports this.
The ultrasound-guided retrolaminar block (RLB) is performed by ultrasound imaging in a paramedian sagittal plane by sequentially visualizing the pleura and ribs, transverse processes, and the corresponding laminae (from lateral to medial). The block needle is guided to contact the lamina, and the local anesthetic injectate is visualized under real-time imaging [23]. The actual distribution of the injectate with the ultrasound-guided retrolaminar block is not known and will be the subject of further studies. These studies will most likely rely on direct anatomic investigation, as clinical studies that rely on dermatomal mapping after paravertebral blockade are unable to distinguish among local anesthesia in the paravertebral, intercostal, or epidural spaces. Yang et al. demonstrated that the injectates of RLB and ESP reached the paravertebral space and infiltrated the superior costotransverse ligament in unembalmed cadavers [24]. The area stained with dye in ESP was more lateral, whereas the dye spread vertically along the posterior surface of the lamina in RLB. These findings indicated that RLB could involve the dorsal rami of the spinal nerve and may be more suitable for the analgesia of the thoracic back region than is ESP. A recent anatomical study of RLB using porcine cadavers suggested that the dye was distributed to the paravertebral space in a volume-dependent manner [25]. Conventionally, RLB is also performed with 20 mL or higher volumes.
The major advantage of this technique, if achieved correctly, is minimizing or even eliminating the risk of pneumothorax. Additionally, the risks of nerve root damage and inadvertent injection into a dural sleeve, an intervertebral foramen, or the epidural or intrathecal spaces should also be decreased. Furthermore, this technique requires less skill, as the exact identification of the costotransverse ligament, it is not compelling in experienced hands.

Limitations
In the application of this technique, the practitioner must master both methods (ESP and PVB) in the thoracic region. It may not always be possible to display costotransverse ligament in obese patients and low-resolution ultrasound devices. The practitioner must have advanced ultrasound techniques knowledge. Because PVB-induced pneumothorax, pleural puncture, hematoma, paravertebral muscle pain complications still exist.

Conclusion
To the best of our knowledge, according to the published data suggest using 20 mL, 25 mL, or higher volumes of local anesthetics of unilateral ESP block. The use of variable local anesthetics doses, often at the upper dose of limit, however, leaves question marks regarding the consistency and safety of the ESP block. Especially in bilateral blocks, since local anesthetics reach the toxic limit, blocking to another area goes beyond safety limits. For example, in patients undergoing mammoplasty and abdominoplasty, doing ESP block and Transversus abdominis plane (TAP) block simultaneously pushes the toxic dose limits.
Shorter block onset times also seem to be an advantage, thus reducing the

Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this paper.