Mohamed AF Galal (MD)1, Moustafa Kamel Riad (MD)2, Alaa Mohamed Ahmed Ahmed (MsC)3, Mohamed Osman Awad Taeimah (MD)
ORCID
Recibido: 2026-01-05
Aceptado: 2026-07-10
©2026 El(los) Autor(es) – Esta publicación es Órgano oficial de la Sociedad de Anestesiología de Chile
Revista Chilena de Anestesia Vol. 22 Núm. 5 | https://doi.org/10.25237/revchilanestv55n5-21
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Eficacia analgésica del bloqueo del nervio pectoral II en comparación con el bloqueo del plano superficial del serrato anterior en la mastectomía radical modificada
Abstract
Introduction: Thoracic interfascial plane blocks represent a safe and safe regional anesthetic techniques commonly utilized in breast surgery. These blocks have demonstrated efficacy in managing acute postoperative pain following mastectomy. Nevertheless, randomized controlled trials directly comparing different interfascial plane block techniques remain limited. Objective: This study aimed to assess the analgesic efficacy of ultrasound-guided modified pectoral nerve (PECS II) block in comparison with the superficial serratus anterior plane block (SSAPB) for postoperative pain management in patients undergoing modified radical mastectomy (MRM). Materials and Methods: A total of 70 female patients scheduled for MRM under general anesthesia were enrolled in this randomized study. They were equally allocated into two groups of 35 patients each. Group I received an ultrasound-guided SSAPB using 30 mL of 0.25% bupivacaine, while Group II received an ultrasound-guided PECS II block with an equivalent total volume and concentration of bupivacaine. All blocks were administered prior to skin incision. Primary outcomes was total pethidine consumption within the first 24 postoperative hours. Results: The current study showed statistically significant difference between the 2 groups. Time of first rescue analgesia was significantly longer in PECS II group (7.4 ± 1.3 h) when compared to SSAPB (5.2 ± 1.6 h). Additionally, median pethidine rescue dose was significantly lower in PECS II group (30.0 ± 11.2 mg versus 57.7 ± 18.8 mg in SSAPB). Conclusion: This study suggests that PECS II block might provide superior postoperative analgesia compared with the SSAPB in patients undergoing MRM under general anesthesia. block.
Resumen
Introduction: Thoracic interfascial plane blocks represent a safe and safe regional anesthetic techniques commonly utilized in breast surgery. These blocks have demonstrated efficacy in managing acute postoperative pain following mastectomy. Nevertheless, randomized controlled trials directly comparing different interfascial plane block techniques remain limited. Objective: This study aimed to assess the analgesic efficacy of ultrasound-guided modified pectoral nerve (PECS II) block in comparison with the superficial serratus anterior plane block (SSAPB) for postoperative pain management in patients undergoing modified radical mastectomy (MRM). Materials and Methods: A total of 70 female patients scheduled for MRM under general anesthesia were enrolled in this randomized study. They were equally allocated into two groups of 35 patients each. Group I received an ultrasound-guided SSAPB using 30 mL of 0.25% bupivacaine, while Group II received an ultrasound-guided PECS II block with an equivalent total volume and concentration of bupivacaine. All blocks were administered prior to skin incision. Primary outcomes was total pethidine consumption within the first 24 postoperative hours. Results: The current study showed statistically significant difference between the 2 groups. Time of first rescue analgesia was significantly longer in PECS II group (7.4 ± 1.3 h) when compared to SSAPB (5.2 ± 1.6 h). Additionally, median pethidine rescue dose was significantly lower in PECS II group (30.0 ± 11.2 mg versus 57.7 ± 18.8 mg in SSAPB). Conclusion: This study suggests that PECS II block might provide superior postoperative analgesia compared with the SSAPB in patients undergoing MRM under general anesthesia. block.
Introduction
In modified radical mastectomy (MRM) surgery, effective pain control in the immediate postoperative period contributes to enhanced patient comfort, improved mobility, earlier ambulation, and accelerated recovery[1]. Several regional anesthesia techniques like thoracic epidural, paravertebral blocks and thoracic interfascial plane blocks have been used in breast cancer surgeries[2]. In thoracic interfascial plane blocks, needle insertion and local anesthetic (LA) injection targets a compartment between two distinct anatomical layers, thereby interrupting afferent nociceptive transmission[3]. Due to their minimally invasive nature, these techniques are considered safer alternatives to central neuraxial blocks[4]. Several thoracic interfascial plane blocks, including serratus anterior plane block (SAPB) and PECS I (interpectoral) and II (interpectoral and subpectoral) blocks, have been studied recently[5].
Anatomically, the intercostal, brachial plexus, and superficial cervical plexus nerves innervate the breast and underlying chest wall. Therefore, to achieve complete postoperative analgesia for breast cancer surgery, it is necessary to block dermatomes from C5 to T6[4]. Given the complexity of the innervation, it is unlikely that a single regional anesthetic technique can guarantee complete level of peri-operative analgesia[6]. PECS II block is an easy and reliable superficial nerve block. It is characterized by a two-plane injection technique, whereby LA is deposited between two separate fascial planes. It attempts to block the axilla, which is essential for axillary clearing, and the thoracic intercostal nerves, which are required for extensive breast excisions[7].
Comparably, serratus anterior plane block (SAPB), which can be applied superficially or deeply to serratus anterior muscle, is a safe and efficient method[8]. SAPB offers some technical advantages, including the avoiding of multiple needle insertion sites and the need for repeated changes in needle direction required during PECS II block. In addition, SAPB provides more selective blockade of the thoracic nerves when compared with PECS blocks[9]. Both of PECS II block and SAPB, block the lateral branches of the upper intercostal nerves. The present study hypothesizes that PECS II block has a higher analgesic efficacy than SAPB.
Although, the pectoserratus plane block (subpectoral component of “PECS II”) provides sensory coverage over the lateral aspect of the breast and axilla similar to SAPB, but the pectoral component of PECS II (interpectoral plane block) provides additional blockade of the pectoral nerves. These nerves are linked to myofascial pain brought on by pectoral muscle disruption, which frequently happens during MRM. Because of this additional property of pain relief in PECS II, we hypothesize that PECS II block yields a higher quality of pain control than SAPB in surgical procedures involving disruption of the pectoral muscles, such as MRM.
In this study, superficial serratus anterior plane block (SSAPB) approach was selected. As it was reported that SSAPB was more effective regarding anesthesia diffusion and duration of LA effect than deep SAPB (dSAPB).6 Given the limited number of detailed randomized studies directly comparing these two regional techniques, their analgesic efficacy was evaluated by comparing the total amount of postoperative rescue analgesics used over the first day.
Methodology
Ethical approval for this study (FMASU MS 576/ 2021) was provided by the Ethics committee of Ain Shams University Hospital, Abbasia, Cairo, Egypt on 28/9/2021. The study was registered with Pan African Clinical Trial Registry (PACTR) with Registration Number PACTR202510755407070 in accordance with WHO and ICMJE standards. After the approval of the hospital’s ethical committee, 70 female participants scheduled for elective unilateral MRM surgery were recruited. Written informed consent was obtained from all participants.
Study population
Age 20-75 years and American Society of Anesthesiologists physical status (ASA-PS) I-II. The exclusion criteria were those who declined to participate in the study, had a LA allergy, had a locally advanced breast malignancies with skin ulcers or chest wall infiltration or had surgery lasting longer than 3 h. Randomization and allocation concealment was performed using computer-generated random numbers put into opaque sealed envelopes which were pulled by a nurse who was unaware of the groups’ allocation. Additionally, all the staff involved in data collection (in addition to patients) were blinded to the group assignment. Patients were randomly allocated into one of two groups (35 patients each).
1. SSAPB group underwent US-guided superficial serratus anterior plane block (30 ml was deposited. between latismuss dorsi and serratus anterior (SA) muscle).
2. PECS II block group underwent US-guided pectoral nerve block (10 ml was deposited. between PMm and Pmm and 20 ml was deposited between Pmm muscle and SA muscle). This dosing regimen was in accordance to previous existing literature[10],[11],[12].
Perioperative management
Standard monitoring equipment was used in the operation room to record baseline measurements of heart rate (HR) and mean arterial pressure (MAP). General anesthesia was induced with intravenous fentanyl (1 µg/kg) and propofol (2 mg/kg). Endotracheal intubation was facilitated by the administration of intravenous cisatracurium (0.15 mg/kg). Mechanical ventilation was adjusted to maintain an end-tidal carbon dioxide level of approximately 35 mmHg. Prior to surgical incision, patients received intravenous paracetamol (1 g in 100 mL) and ketorolac 30 mg. Anesthesia was maintained by isoflurane 1.5-2% vapor concentration in 50% oxygen/air mixture. Supplemental fentanyl boluses (0.5 µg/kg IV) were administered if MAP and/or HR increased by 20% or more relative to baseline values. Following general anesthesia induction and securing of the endotracheal tube while the patient was in the supine position the authors performed either of ultrasound guided PECS II block or SSAPB according to each patient’s group allocation.
Technique was performed as described Blanco and their colleagues[7],[8]. Then the authors waited 20 minutes as recommended in previous literature before the surgeon can start surgical incision.2 Neostigmine (0.05 mg/kg) and atropine (0.02 mg/kg) were used to reverse the muscle relaxant at the end of the surgery. After fully awake extubation, all patients were transferred to the post-anesthesia care unit (PACU). During the first 24 postoperative hours, intravenous pethidine 25 mg was administered as rescue analgesia if patients reported pain with a visual analogue scale (VAS) score of 3 or higher, with repeat dosing permitted after 15 minutes if pain persisted. Postoperative analgesia was supplemented with intravenous paracetamol (1 g in 100 mL) every 8 hours and ketorolac 30 mg every 12 hours.
During the first 24 postoperative hours, intravenous pethidine 25 mg was administered as rescue analgesia if patients reported pain with a visual analogue scale (VAS) score of 3 or higher, with repeat dosing permitted after 15 minutes if pain persisted. Postoperative analgesia was supplemented with intravenous paracetamol (1 g in 100 mL) every 8 hours and ketorolac 30 mg every 12 hours.
Outcomes
The primary outcome measure was the total amount of pethidine consumed within the first 24 hours following surgery. The number of patients who needed extra intraoperative fentanyl boluses, the time it took for the initial rescue analgesia, and the visual analog scale (VAS) scores at 1, 4, 8, 12, 16, 20, and 24 hours after surgery were the secondary outcomes. LA toxicity, hemodynamic instability, respiratory depression, pares-
thesia, pneumothorax, and hematoma were among the complications that were recorded.
PECS II block
In 2012, Blanco7 first described PECS blocks as high-volume thoracic interfascial blocks. The PECS I block is designed to anesthetize the medial and lateral pectoral nerves, whereas the PECS II block extends the area of coverage to include the long thoracic nerve in addition to the pectoral, intercostobrachial, and the third to sixth intercostal nerves[11]. The use of ultrasound guidance makes the PECS block procedure relatively simple to perform.
The principal anatomical landmarks identified using ultrasound include: PMm, Pmm, SA muscle, and the cross-section of the ribs[13]. The PECS II block has a wide range of clinical applications, particularly in breast surgery, and may also be utilized for analgesia in traumatic chest injuries, pacemaker implantation, and chest tube placement[7]. A high-frequency linear US probe is positioned just below lateral third of the clavicle. The US probe is placed infero-laterally until the PMm, Pmm and SA muscles were visible through one plane at the level of the 3rd and 4th ribs. The block needle is advanced in plain view until it visualizes the interfascial line between PMm and Pmm muscles.
The PMm being more superficial and the Pmm muscle being deeper and smaller. Between these muscles, the thoracoacromial artery is located. It is very important to locate as both pectoral nerves are nearby. 10 mL of LA is injected next to the pulsating artery[3]. This is PECS I block (also called: interpectoral plane block). The needle is then advanced till its tip reaches the interfascial plane between the SA and Pmm, and the patient will receive another 20 ml of LA.
This is PECS II block (also called: modified PECS block)[10]. It must be noted that the PECS I block is included in the PECS II block by default, and thus, the term “PECS I + PECS II” must be avoided. Alternatively, it can be called “interpectoral plane + pectoserratus plane blocks” or (interpectoral plane + subpectoral plane block)[14]. PECS block offers several advantage; better T2-dermatomal spread (unlike paravertebral block), more liberal anticoagulant use, and dense motor and sensory nerve-blockade (unlike wound infiltration). PECS blocks are not associated with sympathetic blockade or other complications, such as hypotension, pneumothorax, or spinal cord trauma[15]. Complications are rare with the use of ultrasound. But intravascular injection into the pectoral branch of the thoracoacromial artery and puncture of the axillary fascia has been reported. These potential adverse events can be readily minimized through proper ultrasound training, and looking for the right pattern of spread of LA[7].
SSAPB
The serratus anterior plane block (SAPB) was first described by Blanco[8]. It primarily impacts the lateral cutaneous branches of the intercostal nerves, as well as the long thoracic, intercostobrachial, and thoracodorsal nerves. The LA here is injected more dorsally. As a result, SAPB block can precisely anesthetize more intercostal nerves[11]. It has been used to provide analgesia for a variety of procedures, such as breast surgery, thoracoscopy, rib fracture, and shoulder surgery[16].
Depending on the injection level, SAPB can be classified as SSAPB, dSAPB, or modified serratus anterior plane block. 1SSAPB refers to the injection of a LA at the level of the fifth rib on the midaxillary line, between the latissimus dorsi and SA muscles[17]; 2Deep serratus anterior block (also called serratointercostal fascial block) describes the injection of LA between the external intercostal muscle and the serratus anterior muscle at the same rib level and SSAPB anatomical line. As the serratus anterior muscle is innervated by the long thoracic nerve, which courses along its superficial surface, SSAPB may partially or completely block this nerve in addition to the lateral cutaneous branches of the intercostal nerves. In contrast, dSAPB does not affect the long thoracic nerve, thereby allowing postoperative assessment of its function[14]; 3Modified serratus anterior block involves injection of LA between the latissimus dorsi and serratus anterior at the level of the sixth rib on the posterior axillary line. This modification in injection site is particularly advantageous in procedures involving latissimus dorsi flaps, as it facilitates blockade of the thoracic and thoracodorsal nerves[17].
The serratus anterior plane block (SAPB) technique offers several advantages. First, it eliminates the need for multiple needle insertion points and changes in needle orientation required in PECS II block. Second, it provides more selective targeting of the thoracic nerves compared with PECS II block. Third, axillary analgesia is improved over PECS II block by injecting the anesthetic drug just above the lateral cutaneous nerve’s outflow through the midaxillary line[8],[9],[18]. However, adverse effects have been reported during mastectomy procedures. In particular, SSAPB has been associated with disruption of the axillary fascia, which may interfere with surgical dissection and operative performance[19].
Sample size
Kaur et al.[19], reported an effect size of 0.73-0.78 comparing pain score of shoulder and static pain between the two studied groups. A sample size of at least 31 cases per group (al least 62 cases in the two groups) achieves 0.8 power to detect an effect size of 0.73 using independent two samples t-test with level of confidence of 0.
05. A 10% increase in the sample size to compensate for the loss of follow-up and so the final sample size would be 35 per group.
Statistical analysis
All data will be recorded, analyzed and statistically compared between both groups to identify any significant differences between them. Recorded data were analyzed using the statistical package for social sciences, version 23.0 (SPSS Inc., Chicago, Illinois, USA). The quantitative data were presented as mean ± standard deviation and range. The p-value was considered significant as the following: P-value < 0.05 was considered significant, P-value < 0.001 was considered as highly significant, P-value > 0.05 was considered insignificant.
Results
Seventy patients were recruited as per inclusion and exclusion criteria during the study period. All patients completed the study and were included in the final analysis. There was no statistically significant difference noted in the demographic data in both groups.
A statistically significant difference was found in the requirement for opioid analgesic medications between the two study groups as follows. Intraoperatively, the number of patients who received fentanyl incremental dose was higher in SSAPB (42.9%) versus PECS II block (20%). Postoperatively, the number of patients who needed rescue analgesic dose was higher in SSAPB (37.1%%) versus PECS II block (14.3%). Additionally, SSAPB group patients had higher postoperative VAS score when compared to PECS II group patients, from the 30th minute till the 12th postoperative hour from PACU arrival. There was no significant difference in VAS scores between the 2 groups at 16 h, 20 h and 24 h after surgery.
The mean time to the first request of analgesic given was lower in SSAPB (5.2 ± 1.6 h) when compared to PECS II group patients (7.4 ± 1.3 h) (Table 1). The mean dose of postoperative pethidine during the 1st 24 hours was higher in SSAPB (57.7 ± 18.8 mg) when compared to PECS II group patients (30.0 ± 11.2 mg) (Table 2). Finally, no recorded side effects.
Table 1. Time to 1st rescue analgesia (hours) in cases required rescue analgesia among the studied groups
| Measures | SSAPB | PECS II | Ap-value |
|---|---|---|---|
| Mean±SD | 5.2 ± 1.6 | 7.4 ± 1.3 | 0.013* |
independent t-test, SD: Standard deviation.
PECS II: Modified pectoral nerves, SSAPB: superficial serratus anterior plane block.
Table 2. Total pethidine dose (mg) in cases required rescue analgesia among the studied groups
| Measures | SSAPB | PECS II | Ap-value |
|---|---|---|---|
| Mean±SD | 57.7 ± 18.8 | 30.0 ± 11.2 | 0.007* |
independent t-test, SD: Standard deviation.
PECS II: Modified pectoral nerves, SSAPB: superficial serratus anterior plane block.
Discussion
Among patients undergoing breast cancer surgery, the incidence of severe pain in the immediate postoperative period has been reported to be approximately 60%. The use of preventive analgesia within a multimodal analgesic strategy aims to suppress sustained nociceptive neuronal activity, thereby reducing the risk of chronic pain development as well as associated morbidity and mortality[19]. To date, clinical trials have reported significant perioperative analgesic benefits associated with either of PECS II block[1],[18],[20],[21],[22],[23] or with SSAPB[12],[24] in MRM when compared to control group. However, owing to the limited number of randomized studies directly comparing PECS II block and SSAPB, the present work sought to evaluate and compare their efficacy with respect to the duration and quality of analgesia. The present study demonstrated that the PECS II block may provide superior postoperative analgesia compared with SSAPB, as reflected by a longer time to first rescue analgesia and reduced postoperative analgesic requirements during the first 24 hours after surgery. These findings are supported by the work of Kubodera and colleagues[25], who, in a retrospective observational study, suggested that PECS II block may be more effective than SSAPB for postoperative pain control. In their analysis, 55% of patients in the PECS II group reported no pain two months following surgery, compared with only 19% of patients in the serratus anterior plane block group. Furthermore, patients who received PECS II block exhibited lower median numerical rating scale (NRS) pain scores during the first 24 postoperative hours. Although not statistically significant, but postoperative analgesic consumption during the same period was also lower in the PECS II group. In agreement with the findings of the present study, Fujii and colleagues[26] reported that the PECS II block was more effective than SSAPB in reducing the incidence of chronic post-mastectomy pain at six months (10% versus 33%). Additionally, PECS II block was associated with lower median morphine consumption during the first 24 postoperative hours compared with SSAPB (4 mg versus 6 mg). In contrast to our results, Amir and colleagues[9] compared the postoperative analgesic efficacy of SSAPB and PECS II block in patients undergoing MRM and concluded that SSAPB provided superior analgesic quality and longer duration. In their study, patients receiving SSAPB required their first rescue analgesic dose significantly later, at a mean of 1,280 minutes postoperatively, compared with 826 minutes in the PECS II group. Moreover, total analgesic consumption over the first 24 postoperative hours was substantially lower in the SSAPB group than in the PECS II group. The discrepancy between their findings and ours may be attributed to the smaller volume of LA administered into the pectoserratus plane during the PECS II block. This anatomical plane is intended to anesthetize the long thoracic nerve, as well as the pectoral, intercostobrachial, and third through sixth intercostal nerves[11]. Although no studies have established a fixed-dose regimen for PECS II block, it is plausible that relatively larger volumes of LA are necessary to achieve optimal clinical efficacy. Notably, most studies evaluating PECS II block have employed volumes of approximately 10 mL in the interpectoral plane and 20 mL in the pectoserratus or subpectoral plane[27].
Conclusion
The current study showed that ultrasound-guided PECS II block provided superior postoperative analgesia when compared with the superficial serratus anterior plane block. This was evidenced by a longer time to first rescue analgesia and a lower total postoperative opioid requirement. Further studies with larger sample sizes, inclusion of control groups, and the addition of parasternal intercostal plane block supplementation are warranted to validate and expand upon these results.
Availability of data and material: The datasets used and/
or analyzed during the current study are available from the corresponding author on reasonable request.
Acknowledgments: We have no affiliations with or involvement in any organization.
Authors contribution: On behalf of all the contributors I will act and correspond with the journal from this point onward at all stages of refereeing and publication, also post-publication. All authors have contributed intellectually to the manuscript and the manuscript has been read and approved by all the authors. All authors contributed to the study conception and design. All authors read and approved the final manuscript. The contents have not been published else where and the paper is not being submitted elsewhere. We adhere to bioethical principles (see http://www. icmje.org/).
Ethics approval and consent to participate: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Ethical approval for this study ((FMASU MS 576/ 2021)) was provided by the Ethics committee of Ain Shams University hospital, Abbasia, Cairo, Egypt on 28/9/2021
Table 1. Time to 1st rescue analgesia (hours) in cases required rescue analgesia among the studied groups
| Measures | SSAPB | PECS II | Ap-value |
|---|---|---|---|
| Mean±SD | 5.2 ± 1.6 | 7.4 ± 1.3 | 0.013* |
independent t-test, SD: Standard deviation.
PECS II: Modified pectoral nerves, SSAPB: superficial serratus anterior plane block.
Table 2. Total pethidine dose (mg) in cases required rescue analgesia among the studied groups
| Measures | SSAPB | PECS II | Ap-value |
|---|---|---|---|
| Mean±SD | 57.7 ± 18.8 | 30.0 ± 11.2 | 0.007* |
independent t-test, SD: Standard deviation.
PECS II: Modified pectoral nerves, SSAPB: superficial serratus anterior plane block.
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