Dear Editor,

We thank Prof. Raghuraman M. Sethuraman for his kind comments on our recently published article “Research Progress on Serratus Anterior Plane Block in Breast Surgery: A Narrative Review” [1]. Below are our detailed replies to each of the comments.

We refer to the paper published by Kumar et al. [2] in Anesthesiology in 2021; in Table 1 titled “Potential clinical indications for serratus anterior plane block (SAPB)”, breast augmentation was supported by a randomized controlled trial without indicating the literature source. In Table 1 in our review, we created a secondary citation from this authoritative journal, marked by the same superscript. After receiving Prof. Raghuraman M. Samuraman's letter, we conducted a series of searches with keywords including serrated anterior block, serrated anterior plane block, SAP block, SAPB, and breast augmentation. In addition, we manually searched for references in the relevant literature and found a randomized controlled study of SAPB combined with thoracic nerve block for breast augmentation surgery [3]. We believe that SAPB can provide some auxiliary pain relief for breast augmentation surgery. In the following paragraphs, we will elaborate on the mechanism of pain generation after breast augmentation surgery, as well as the anatomical basis of SAPB and its role in postoperative pain relief.

Pain after breast augmentation involves the medial and lateral thoracic, intercostal, long thoracic, and dorsal thoracic nerves. There are three sources of pain after breast augmentation. First, surgical incision can cause pain due to skin injury; the skin incision may be periareolar, inframammary, or transaxillary. Nerves involved in pain related to skin incision are the anterior and lateral branches of the intercostal nerves from T2 to T4, from T5 to T6, or the long thoracic nerves. Second, during breast augmentation surgery, the intercostal nerves may be stretched or damaged, leading to postoperative chest wall pain. Third, when the prosthesis is placed on the deep surface of the pectoralis major muscle in surgery, it is necessary to separate and dissect this muscle to create space for the prosthesis. This can lead to pectoralis major muscle and fascia damage, which is a significant source of pain after breast augmentation [4].

Familiarity with breast innervation, the scope of surgical invasion, and the anatomical basis of local nerve block techniques can help choose an appropriate nerve block technique to better alleviate pain during breast augmentation surgery. PECS1 and PECS2 have been reported to relieve pectoralis major muscle spasm by blocking the medial thoracic and lateral thoracic nerves, so as to relieve pain after breast augmentation surgery. In our latest literature search, we found one study reporting the effectiveness of intercostal nerve block in reducing postoperative pain after breast augmentation with implants [5]. There is limited literature on intercostal nerve block for breast augmentation and its effectiveness requires further research. SAPB can block the external branches of the T2–T9 intercostal, long thoracic, and dorsal thoracic nerves. Due to the inability to block the medial and lateral thoracic nerves, it is often used in conjunction with thoracic nerve block to better alleviate postoperative pain in breast augmentation surgery. A randomized controlled study using a chest anterior wall combination for multimodal analgesia (PECS2 + SAPB) in breast augmentation surgery has confirmed its effectiveness [3]. The management of pain after breast augmentation surgery is a direction that anesthesiologists need to continue to pay attention to, and there is still no consensus on the optimal plan.

Furthermore, PECS II is indeed a technical term that is easily overlooked and misunderstood. The expression in the article was not detailed or precise enough. The PECS II block, which includes performance of a PECS I block, involves an additional injection deep into the PECS I plane within the fascia between the pectoralis minor and serratus muscles. This injection targets the lateral cutaneous branches of the intercostal nerves, and the long thoracic nerves [6].

Finally, we deeply thank Prof. Raghuraman M. Sethuraman again for his contribution to this discussion. We believe that his comments have added further insights into this topic.

Sincerely,

Xianhui Kang