Pectoral nerves (PECS) block is a block that can be used for multiple lateral cutaneous anterior branches of intercostal nerves (Th2-6) present in the internal mammary region, and is reported to be effective for acute postoperative analgesia after breast cancer surgery    . In addition, a local anesthetic for primary cancer surgery must have some advantages, such as reduced incidence of recurrence and metastasis  .
A PECS block is generally performed by administrating the first injection between the pectoralis major and pectoralis minor at the third rib and second injection between the pectoralis minor and serratus muscles at the fourth rib   . However, the first injection normally does not provide analgesic efficacy because the nerve that is blocked by the first injection is a motor nerve, such as the lateral pectoralis muscle nerve and internal pectoralis muscle nerve. However, as reported, motor nerve block can prevent muscle contraction, while the PECS block may be effective for motor recovery of the upper limb after breast cancer surgery   . In this study, we retrospectively investigated the effect of the PECS block on motor function during the postoperative period.
2. Materials and Methods
2.1. Patients and Design
This retrospective study was approved by the Showa University Hospital Institutional Review Board (approval number 1952). In addition, the study was registered at the University Hospital Medical Information Network (UMIN ID number 000020016). From April to September 2015, we selected patients who had undergone modified radical mastectomy. The patients were divided into two groups: a general anesthesia group (G group) and general anesthesia and PECS block group (P group). The number of difficulties related to motor function of the upper limbs (flexion, extension, abduction, adduction, external rotation, and internal rotation) were counted at postoperative day 5 (D5) and postoperative month 6 (M6) by performing telephonic interviews. We also assessed the type of the difficulty related to motor function of the upper limbs at postoperative day 5 and postoperative month 6 in the G group. The exclusion criterion was the inability to communicate with some patients about bilateral breast cancer surgeries and secondary surgery.
2.2. Ultrasound-Guided PECS block
We used a 12 L-RS linear probe of the LOGIQ e Premium system (GE Healthcare Japan, Tokyo, Japan) for an ultrasound-guided PECS block. Before the block, the precordium was firmly cleaned with chlorhexidine. The blocks were then performed using a 20-gauge Tuohy needle. A PECS block was administered by injecting 10 mL of 0.15% levobupivacaine between the pectoralis major and pectoralis minor at the third rib (first injection) and 25 mL of 0.15% levobupivacaine above the serratus anterior muscle (second injection).
2.3. Statistical Analysis
The age of the patients, body mass index (BMI), operation time, anesthesia time, and fentanyl amount used were analyzed using the nonparametric Mann-Whitney’s U-test and were expressed as an average (standard deviation). The number of difficulties related to motor function of the upper limbs was determined by χ2 test with JMP® 11 (SAS Institute Inc., Cary, NC, USA). The level of significance for both tests was set at P < 0.05.
213 patients were included during the study period. Of these patients, 93 patients received only general anesthesia (G group). The other 85 patients received PECS block with general anesthesia (P group). 35 patients (G group: 30 patients, P group: 5 patients) were excluded from the study because of not connecting phone (Figure 1).
Patient demographics are presented in Table 1. The amount of fentanyl administered to the P group during the surgery was lower than that administered to the G group (P = 0.0011). The number of difficulties related to motor functioning of the upper limbs in the P group (2) was lower than that in the G group (15) at D5 (P = 0.042). The number of difficulties related to motor function of the upper limb in the P group (0) was lower than that in the G group (10) at M6 (P = 0.043; Table 2). The upper limb motor functions that were affected in the G group were mainly flexion and internal rotation (Table 3).
The results of this study revealed that administration of a PECS block aided in the early recovery of motor function of the upper limbs during the postoperative stage of breast cancer. A PECS block can provide not only relief from acute pain during the perioperative period but also aids in the early recovery of motor function of the upper limbs. In addition, since the upper limb motor functions that were affected were mainly flexion and internal rotation in the G group, which involved the pectoralis major muscle, we speculate that the first injection, which can block the pectoral nerve-dominated pectoralis major muscle, was ef-
Figure 1. Flowchart of this study.
Table 1. Patients demographics data: age, body mass index, ASA classification, operation time, anesthesia time, intraoperative fentanyl consumption.
Average (Standard Deviation).
Table 2. The number of the difficulty of motor function of the upper limbs at postoperative day 5 and postoperative month 6 by performing telephone interviews. G group: only general anesthesia, P group: general anesthesia and PECS block.
Table 3. The type of the difficulty of motor function of the upper limbs at postoperative day 5 and postoperative month 6 by performing telephone interviews on G group.
fective for the recovery of upper limb motor functions  . In other words, the muscle contraction prevention by first injection may promote the recovery of upper limb motor functions.
There were some limitations to this study. Firstly, this study was a retrospective study. Therefore, we performed the telephone survey. He should need not only the telephone survey but a medical examination. Also, the nerves that dominate the pectoralis major muscle involve not only the pectoral nerves but also the anterior branches of the spinal nerves. We need to investigate which anterior branches affect the pectoralis major muscle.
In the future, we need to conduct a prospective study with a longer study duration than a postoperative month 6.
The results of this study indicate that the PECS block (especially, first injection) can prevent contraction of the pectoralis major and pectoralis minor muscles. Therefore, we recommend that clinicians should administer the first injection for breast cancer surgery.
Assistance with the letter: none.
Financial support and sponsorship: none.
Conflict of interest: none.
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