Ultrasound-guided transversus thoracic muscle plane-pectoral nerve block for postoperative analgesia after modified radical mastectomy: a comparison with the thoracic paravertebral nerve block

This present study demonstrated that TTP-PECS can provide better postoperative analgesia than TPVB in patients undergoing MRM. Eighty female breast cancer patients enrolled in this study, and all received standard unilateral MRM with sentinel lymph node dissection (SLND) and axillary dissection (ALND). A transverse or longitudinal fusiform incision was done on the surgical site, the breast tissues including the lesion were removed, and it was freed in the superficial layer of the pectoralis major fascia. After the lesion was removed, the axillary lymph nodes should be cleaned (Xie et al., 2022) (Fig. 4A).

Fig. 4figure 4

A Modified radical mastectomy. B Innervation of the breast. C Innervation of the thoracic

From the anatomic point of view, the nerve supply to the breast is complex and innervated by a multiplicity of nerves. The anterolateral chest wall is innervated by the anterior cutaneous and lateral cutaneous branches of the T2–T6 nerves and long thoracic. Apart from the intercostal nerves, the lateral and the medial pectoral nerves also supply sensory and motor function to the skin and muscles of the chest wall. For procedures involving anterolateral, it is, therefore, necessary to block either the pertinent nerves at their origin or block their branches as they pierce their way into the subcutaneous tissue around the anterior axillary line or sternal border (Woodworth et al. 2017) (Fig. 4B, C).

Various regional anesthetic techniques have been used for pain management during breast surgery in recent years. TPVB has been widely studied for the prevention and treatment of acute pain and has been reported with varying degrees of success to provide analgesia after MRM (Simpson et al. 2014). However, TPVB have an inadequate block in the presence of axillary dissection, (Altıparmak et al. 2019). Patients undergoing TPVB frequently complain of postoperative pain in the axilla and upper limb due to sparing of the medial and lateral pectoral nerves (Mohamed et al., 2020). As we mentioned, MRM involves the removal of not only the breast but also the axillary lymph nodes. So, the main shortage of adequacy of TPVB is revealed during axillary dissection.

The pectoral nerve block (PECS I) aims to block targets medial and lateral pectoral nerves in the plane between the pectoralis major and pectoralis minor and block the lateral mammary area (Blanco 2011). It can provide analgesia related to surgical disruption of the pectoral muscles and related fascial structures. But PECS I block alone may lead to inadequate analgesia because of the highly innervated chest wall. Subsequently, Blanco et al. (2012) described a second version of the Pecs block called PECS II. The PECS II aims to block intercostal nerves 2 to 6, intercostobrachial, and the long thoracic nerves and produces a sensory loss in the axillary region in addition to the area affected by Pecs I block (Kelava et al. 2020). PECS II block incorporates analgesic blockade for axillary lymph node dissections, wide local excisions affecting the lateral breasts, and various breast reconstructive procedures (including breast expanders and subpectoral prosthesis insertion) (Maniker et al., 2020). However, intercostal nerve block has to be administered at multiple sites. Since PECS block can not provide adequate analgesia for procedures extending to the internal mammary area, Ueshima and Kitamura (2015) reported transversus thoracic muscle plane (TTP) block for analgesia of the inner breast region, and finally, TTP was added to suit the extent of surgery. Several studies (Zhang et al. 2018, You et al. 2019, Li et al., 2020) have confirmed this view. They found that TTP-PECS provided better analgesic efficacy for early postoperative analgesia than PECS II alone or PECS I combined with II in the patients undergoing MRM.

Based on these reports and the neural supply of the anterior chest wall and breast, we combined TTP with PECS together in this study and compare this TTP-PECS with the TPVB. We found that TTP-PECS shows consistent dermatomal spread in T2–T6 segments, even spread up to the T7 segment or more widely, as well as the axilla and upper limb areas. For TPVB, the sensory spread was usually observed at the level of injection (T3–T7), and less spread to T2 was observed, with very limited cephalad spread. TTP-PECS can complement the deficiency of TPVB. This suggested that both the two blocks can provide analgesia under the general anesthesia during the operation, but the blocking area of TTP-PECS was more suitable for the MRM.

However, we are more concerned with the postoperative analgesia, which is important for the early recovery and prognosis of patients. Firstly, we found that the duration of analgesia was significantly prolonged in patients receiving TTP-PECS as compared to the patients receiving TPVB. In the TTP-PECS group, the analgesia duration reached 12 h or more postoperatively.

Besides, in consideration of medical ethics, we did not want patients to suffer from moderate to severe pain after MRM. So, an intravenous PCIA pump with a background dose was used immediately after the operation in PACU, and flurbiprofen axetil was given as a remedial analgesia. VAS scores at rest of all the patients were lower than 3, and VAS scores during the activity of all the patients were lower than 5 suggesting none of the patients suffered severe pain in this clinical study. These results also imply our multi-mode pain managements for the participants were successful. There were no significant differences in VAS scores at rest and during activity between the two groups at 2 h, 6 h, and 24 h postoperatively, whereas at 12 h after the operation, the VAS scores at rest and during activity were both lower in the TTP-PECS group compared with the TPVB group. However, in practice, this absolute difference of 0.5 at rest and 0.75 with activity may not be clinically significant.

In addition, since the no difference in body weight between the two groups, the PCA press consumption (per bolus dosage multiply by the effective pressing times) could reflect the analgesic requirement. We observed marked advantages with the use of TTP-PECS. Total postoperative PCA fentanyl consumption, especially the PCA press consumption, and the rate of postoperative flurbiprofen axetil requirement were all decreased by the TTP-PECS compared with TPVB. These results suggested TTP-PECS to be more effective as a postoperative analgesic technique than TPVB which was consistent with several retrospective studies (Zhang et al. 2018, Li et al. 2021). Under real-time US guidance, with the deposition of local anesthetic drugs into the fascial planes, the TTP-PECS would be more accurate to provide higher analgesic efficacy for mastectomy and axillary clearance because of its complete paranesthesia of the hemithorax. Moreover, we also detected the NPY, PGE2, and β-endorphin in the patient blood and found that the serum levels of these pain-related mediators were also lower in the TTP-PECS group than those in the TPVB group at postoperative 12 h. These results indicate that TTP-PECS might be more effective in reducing hyperalgesia.

Also, we investigated the inflammatory response and found invasive MMR surgical procedures caused inflammatory response in varying degrees. However, the serum levels of these proinflammatory cytokines were all lower in the TTP-PECS group than those in the TPVB group at postoperative 12 h. Our finding is consistent with the previous report by Bagry et al. (2008). They reported a positive correlation between lower levels of inflammatory markers and pain in patients after knee surgery. Finally, we evaluated the early recovery of patients and found a remarkable improvement in life quality among patients treated with TTP-PECS. The improvement may be due to the fact that TTP-PECS relieved pain better.

Another important aspect is security. Actually, we discussed the security between these technical blocks in another study (Zhao et al. 2020). We found that TTP-PECS may reflect better mastering of the technique with time relative to the paravertebral technique. Also, TTP-PECS has a more stabled effect on perioperative hemodynamics. Furthermore, the incidence of complications such as spinal cord injury, epidural blockade, sympathectomy, and epidural hematoma was reduced in the TTP-PECS (Tighe and Karmakar, 2013). TTP-PECS is not restricted to the patients who are obese or use anticoagulants and also exhibited a satisfactory analgesic effect. It was also reported that most cases of TTP-PECS are performed under general anesthesia due to the advantage of easy positioning of the patient in the supine position. Comprehensive consideration of analgesic and security, TTP-PECS is an attractive alternative to TPVB for postoperative analgesia of MRM.

However, our study has several limitations. Firstly, a multicenter analysis was lacking. Secondly, we just comprehensively evaluated a series of short-term indicators; the postoperative pain outcomes and early recovery quality of patients were assessed only up to 24 h. Thirdly, on the basis of the available data from the current studies, we could not evaluate the efficacy in patients of different ages and for those with chronic pain. Clinical trials are needed to further explore and optimize this technique.

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