SAP block is one of the newest thoracic regional anesthetic techniques. This procedure is an alternative to TEB, PVB, intercostal blocks, and intrapleural blocks that are commonly used as postoperative analgesia of the thoracic region . Anatomically, SAP block was performed in the superficial plane which was considered safer than other regional anesthetic techniques . SAP block is indicated in conditions that require pain management in the thoracic region, such as rib fractures, rib contusions, thoracoscopic surgery, thoracotomy, breast surgery, and post-mastectomy pain syndrome .
SAP block exerts its analgesic effects on the lateral thoracic region  This effect is achieved by nerve blockade in the axillary fossa which includes the intercostobrachial nerve, the cutaneous intercostal nerve (T3-T9), the thoracic longus nerve, and the thoracodorsal nerve located in the compartment between the serratus anterior muscle and latissimus dorsi muscle, and between the posterior and mid-axillary lines . The main anatomical landmarks in the SAP block are the latissimus dorsi muscle and serratus anterior muscle. The thoracodorsal arteries run in the fascia plane between these two muscles . Using USG, the anterior serratus muscle appears as a thick hypoechoic appearance below the latissimus dorsi muscle and above the rib cage . To date, there are still no definitive criteria for optimal volume and concentration for local anesthetic in SAP blocks . In this study, SAP block was performed using roughly 0.4 ml/kg of long-acting local anesthetic.
Blanco et al. studied the effectivity of SAP blocks with USG in 4 volunteers . The authors found 2 types of space for injection, which were superficial and deep. The distribution of dermatomes in superficial SAP block tends to be wider than deep SAP than SAP, which is T3-T9 . Bhoi et al. found that pain levels were lower in the superficial SAP block group than in the deep SAP block group. This finding may be due to the effect of long thoracic nerve and thoracodorsal nerve blockade in superficial SAP blocks . Both patients in this case underwent superficial SAP block. Patient 2 underwent surgery with a particularly high incision, reaching T2 level. The incision might trigger the pain that required rescue analgesia since the intraoperative pain stimulus has exceeded the dermatomal level of the SAP block, which was T3.
SAP blocks are relatively easy procedure with a high success rate and minimal complications when performed by a trained anesthetist. SAP blocks usually only require one injection, whereas most of other regional blocks require repeated injections . The analgesia effect produced by the SAP block may last up to 12 h postoperatively . Semyonov et al. found that patients who underwent SAP block had significantly lower pain levels after thoracic surgery, compared to patients in the standard pain control group . The total dose of morphine and tramadol needed to relieve pain during the first few postoperative hours is significantly lower in patients that underwent SAP block. The incidence of side effects such as nausea and vomiting is significantly lower as well . Chen et al. demonstrated that SAP blocks provided superior analgesic effect, where pain scores and opioid consumption were significantly lower in the postoperative period . Either of our patients did not require intraoperative opioid use, except when given as rescue analgesia in patient 2. Intravenous tramadol 100 mg/8 h was given as postoperative analgesics in both patients, and not exceeding 24 h. The duration of the analgesia effect of the SAP block is consistent with literature, where both patients have a minimum NRS and only begin to increase 12 h after the surgery or 14 h after the block was performed. The duration of this effect was also influenced by other analgesics. In both patients, there were no side effects up to 24 h postoperatively. This finding was expected since opioid administration was minimized. The results of these two cases suggested the need of clinical investigations focusing on opioid consumption and postoperative unpleasant symptoms and recovery.
In conclusion, SAP block can be used as one of the modalities in managing the pain of patients undergoing MRM surgery. This procedure was effective in reducing the need for both intraoperative and postoperative opioids usage.