4. Discussion
This is the first randomized, double-blind clinical trial to compare the analgesic effects of SAB, ESP, and RIB block after MRM. We demonstrated that the patients who received RIB block and SPB block before operation had lower tramadol dosage and dynamic NRS score within 24 hours after operation, indicating that RIB block and SPB block had better analgesic effect than SAB. At the same time, RIB block and SPB block had longer first pain time and less times of complaining pain after single injection than SAB block. However, there was no difference in intraoperative anesthetic consumption, incidence of adverse reactions and patient satisfaction among SAB block, SPB block and RIB block. In addition, we found that SAB block, SPB block and RIB block were less effective in relieving axillary pain.
Blanco et al reported for the first time that SAB block has a blocking effect on the intercostal nerve of T2~T9 and can provide chest wall and axillary regional anesthesia [9]. Previous studies have reported the effects of SAB blockers and placebos on opioid consumption in patients with breast cancer after modified radical mastectomy [13, 14]. Recently, Yao et al. [14]reported that pre-operative administration of SAB with ropivacaine improved the quality of recovery, postoperative analgesia, and patient satisfaction following breast cancer surgery, However, Fu jii et al.[15] found that compared to SAB block, the PECS-2 block reduced chronic pain six months after MRM. Their findings were similar to our results. In this study, we found that in patients receiving the SAB block for MRM compared with the ESP and RIB block, the dosage of tramadol was higher, the postoperative analgesic effect was worse, and the nerve block time was shorter.
ESP block is a kind of new plane block, which provides analgesia for thoracic and abdominal segmental innervation according to the level of spinal cord injection[8]. After horizontal injection of T4 transverse process, the local anesthetic spread to multiple segments of the cranial tail.The local anesthetic diffused forward through the costal transverse foramen and into the paraspinal space of the thoracic vertebrae. The US-ESP block could block the ventral and dorsal branches of the spinal nerve, as well as the communicating branches of the spinal nerve [16]. Gürkan et al.[17] reported that ESP block has a good analgesic effect after modified radical mastectomy for unilateral breast cancer. Recently, Finnerty et al.[12] found that compared with SAP, ESP had higher recovery quality, and better analgesic effects within 24 hours after minimally invasive thoracotomy. Their findings are similar to those of the present study, which found for the first time that during MRM, the application of ESP block resulted in lower tramadol consumption, lower postoperative pain score, longer duration to first pain, fewer complaints of pain, and higher postoperative patient satisfaction than those achieved using SAB block.
RIB block is a novel interfascial plane block technique described by Elsharkawy et al [18]. Following the injection of local anesthetic into the interfascial plane between the rhomboid major and intercostal muscles, the block provides analgesia between the T2 and T9 dermatomes [18]. In addition, RIB has the advantage of being an easily applicable technique and the injection site is distant from the surgical area. Recently, Altıparmak et al[3]. reported that RIB block promoted enhanced recovery and decreased opioid consumption need after mastectomy. Tulgar et al. [19] applied RIB block to an 82-year-old woman who required MRM, and 40 mL local anesthetic (LA) (20 mL bupivacaine, 0.25 mL 2% lidocaine, and 20 mL saline) were injected to the rhomboid muscle and the fifth costal fascia. Ultrasonography demonstrated the spread of LA between the second and seventh ribs, under the rhomboid muscle. The total anesthesia time was 75 min. In this study, we also found that RIB block can provide good postoperative analgesia for patients undergoing MRM. In addition, we found for the first time that ESP block and RIB block resulted in better postoperative analgesic effect than the SAB block for MRM. Both the RIB and ESP blocks had similar analgesic effects after MRM.
Our study also has some limitations. First of all, we give the patient nerve block after general anesthesia, so we can’t evaluate the scope of anesthesia very well. Secondly, patients who undergo nerve block may also have back injection pain, which is likely to let patients know what kind of nerve block they are performing, which makes it impossible for the experiment to be a double-blind trial. However, there were only four such patients; thus, it was unlikely to have affected the results of the study. Third, we did not monitor the depth of anesthesia during the maintenance of general anesthesia, which may have affected the anesthetic dosage or influenced the patient’s intraoperative knowledge. Nonetheless, in this experiment, we used sevoflurane to prevent intraoperative awareness and none of patients reported any intraoperative knowledge during the postoperative return visits.