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 Table of Contents  
Year : 2018  |  Volume : 35  |  Issue : 3  |  Page : 429-436

Ultrasound-guided serratus anterior plane block versus thoracic paravertebral block for postmastectomy analgesia

Department of Anesthesia, Faculty of Medicine, Benha University, Benha, Egypt

Date of Submission22-Jul-2018
Date of Acceptance26-Sep-2018
Date of Web Publication07-Jan-2019

Correspondence Address:
Samar R.M Amin
7 Ahmed Maher Street, Benha, Al-Qaluobia, 13621
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/bmfj.bmfj_162_18

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Background Women undergoing mastectomy surgery often experience severe postoperative pain and may develop into chronic pain.
Objective The current study compared the efficacy and safety of ultrasound-guided serratus anterior plane block (SAPB) with thoracic paravertebral block (TPVB) for controlling acute postmastectomy pain.
Patients and methods This prospective study was conducted on 60 female patients undergoing mastectomy surgery. Patients were randomized into two groups: the TPVB) group (n=30) included patients who received paravertebral block at T4 with 20 ml of bupivacaine 0.25% and adrenalin 5 µg/ml and the SAPB group (n=30) patients who received serratus intercostal plane block with 0.4 ml/kg bupivacaine 0.25% plus adrenalin 5 µg/ml. Both performed as single injection at the end of surgery. Postoperative visual analog scale pain scores, time to first analgesic requirement, total dose of rescue analgesic, hemodynamic parameters, and incidence of postoperative nausea and vomiting were all recorded.
Results Visual analog scale scores were significantly lower in the SAPB group compared with the TPVB group at 12th and 16th hour postoperatively. The total dose of rescue analgesic was significantly lower in SAPB compared with the TPVB. Time to the first analgesic dose was significantly longer in the SAPB compared with the TPVB. There was no significant difference between the study groups regarding the hemodynamic parameters and incidence of postoperative nausea and vomiting.
Conclusion Both SAPB and TPVB provide adequate analgesia for breast surgeries, but the current study found that SAPB superior to TPVB in terms of delayed requirement for the first rescue analgesia and 24 h reduced analgesic consumption, indicating that SAPB is a feasible and effective method for pain treatment after breast surgery.

Keywords: mastectomy, paravertebral block, postoperative analgesia, serratus anterior block

How to cite this article:
Amin SR, Abdelrahman EA, El Shahat Afify E, Elsayed EM. Ultrasound-guided serratus anterior plane block versus thoracic paravertebral block for postmastectomy analgesia. Benha Med J 2018;35:429-36

How to cite this URL:
Amin SR, Abdelrahman EA, El Shahat Afify E, Elsayed EM. Ultrasound-guided serratus anterior plane block versus thoracic paravertebral block for postmastectomy analgesia. Benha Med J [serial online] 2018 [cited 2020 Dec 5];35:429-36. Available from: http://www.bmfj.eg.net/text.asp?2018/35/3/429/249417

  Introduction Top

Mastectomy is a common surgical procedure, accounting for 31% of all breast surgery cases performed [1]. Postmastectomy pain managed by opioids alone often leads to side effects such as nausea and vomiting. Inadequate control of pain may later develop into chronic pain syndrome (paraesthesias, phantom breast pain, and intercostobrachial neuralgia) in 25–40% of the patients [2]. For these reasons, regional analgesic techniques have been advocated for effective pain management [3].

Several anesthetic techniques involving local wound infiltration [4], intercostal nerve block [5], thoracic paravertebral block (TPVB) [6],[7], and thoracic epidural analgesia [8] have been introduced in the management of acute postmastectomy pain, with the goal of decreasing the side effects associated with general anesthesia and opioid consumption. TPVB can be considered a well-established technique to provide analgesia for postmastectomy pain [9]. But TPVB demands more advanced technical skills and a longer learning curve.

Therefore, new interfascial plane blocks guided by ultrasound (US) such as pectoral nerve (PECS) block types 1 and 2 and serratus anterior plane block (SAPB) have been reported as alternatives, with the advantages of simplicity and ease of performance [10],[11],[12]. SAPB was initially described by Blanco to provide complete analgesia of the lateral part of the thorax through blockade of lateral cutaneous branches of the thoracic intercostal nerves [10]. The aim of this study was to evaluate the analgesic efficacy and safety of SAPB in comparison with TPVB for postmastectomy pain.

  Patients and methods Top

After the approval of the institutional ethics committee of Benha University Hospital, this prospective, single-blinded randomized study was conducted on 60 female patients between the age of 30 and 60 years, with cancer breast, American Society of Anesthesia (ASA) I and II, undergoing unilateral mastectomy operation. Refusal to participate, morbid obesity (BMI >40 kg/m2), renal insufficiency (creatinine >1.5 mg/dl), current chronic analgesic therapy (daily use >4 weeks), diabetes mellitus with polyneuritis, generalized or local infection, chronic pain in the anterolateral region of the chest or axilla, inability to communicate with the medical staff and ASA physical status III and IV were excluded.

The participants were allocated into two groups of 30 in each by a random sequence number generated by the computer kept in sealed envelopes. Group I had received US-guided TPVB and group II had received US-guided SAPB. Both blocks were given before recovery from general anesthesia.

Preanesthetic investigations were fulfilled in all patients, 1 h before the surgery. Intravenous access was established and all patients were premedicated with midazolam 0.02 mg/kg, and ranitidine 50 mg intravenously. In the operating room standard monitoring devices such as ECG, noninvasive blood pressure, and pulse oximetry were placed. A conventional balanced general anesthesia was administered. The induction protocol was standard for all patients and consisted of intravenous administration of propofol 2.5 mg/kg, cisatracurium besilate 0.15–0.2 mg/kg, and fentanyl 1–2 µg/kg. Anesthesia was maintained with oxygen 100%, isoflurane and supplements of cisatracurium. Volume-controlled ventilation (tidal volume: 8–10 ml/kg) was adjusted to maintain end-tidal carbon dioxide between 35 and 40 mmHg. At the end of the surgery and before recovery from general anesthesia, the regional block technique was performed.

Group I (TPVB): patients were placed on lateral decubitus position with the side that had been operated upward, and skin preparation and sterile draping applied. Target paravertebral space was located using US (GE Logiq P5) with a linear transducer (11 MHz). The paravertebral space between the third and fourth thoracic vertebrae was identified by counting down from the seventh cervical spine. In a paramedian view ∼3 cm lateral to the midline on the side of the surgery, both transverse processes were visualized, with the superior costotransverse ligament and the pleura visible in between ([Figure 1]). An 18 G, Tuohy-tip needle was inserted through the skin in-plane beneath the US transducer until it pierced the superior costotransverse ligament. If the ligament was not easily seen, the needle was advanced until it was directly above the pleura. Normal saline (2–3 ml) was injected to help identify the paravertebral space and observe the pleura being displaced anteriorly. A dose of 15–20 ml of 0.25% bupivacaine with 5 µg/ml epinephrine was slowly injected with gentle aspiration every 3 ml to rule out intravascular or intrathoracic needle tip placement.
Figure 1 Ultrasound visualization for the parasagittal approach to the paravertebral space (PVS). PVS is located superficial to the parietal pleura (PP) and deep into the costotransverse ligament (CTL). Transverse processes (TP) are also visualized.

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Group II (SAPB): patients were positioned supine with the upper limb abducted to 90°. Skin preparation and sterile draping were applied. The US (GE logiq P5) linear probe (11 MHz) was placed longitudinally in the midaxillary line at the level of the sixth intercostal space by counting ribs inferiorly and laterally below the clavicle. At the midaxillary line, the first plane to identify was the fatty subcutaneous tissues. The anterior serratus muscle, ribs, and external, internal, and intimate intercostal muscles were in the intermediate plane, and then the pleura and the lung were identified in the deep plane ([Figure 2]). From caudal to cranial and in-plane approach, an 18 G, Tuohy-tip needle was inserted until the tip was placed between the serratus anterior muscle (SAM) and the external intercostal muscle. To check for accurate positioning of the tip of the needle, hydrodissection was done by 2–3 ml of saline and this was followed by a local anesthetic (LA) injection of 0.4 ml/kg of bupivacaine 0.25% with 5 µg/ml epinephrine. The LA injection was visualized in real time.
Figure 2 Ultrasound view of the serratus anterior plane showing (lat) latissmus dorsi muscle, serratus anterior muscle (SAM), intercostal muscles (ICM), and parietal pleura (PP).

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Anesthesia was discontinued and neuromuscular blockade was reversed with neostigmine (0.05 mg/kg) IV and atropine IV (0.002 mg/kg). The patients were extubated and shifted to the postanesthesia care unit. Before induction of anesthesia the patients were learned how to use a 10 cm visual analog scale (VAS-0 with end-point labeled ‘no pain’ and 10 to ‘worst conceivable pain’) [13]. The degree of postoperative pain was assessed at postanaesthetic care unit (PACU), 4, 6, 8, 12, 16, 20, 24 h using the VAS score. Postoperative analgesia regimen was standard in all groups. When the VAS score was greater than 4, the patients were given morphine (5 mg IV).

The primary outcome measure included pain rescue analgesia consumption in the first 24 h (time of first rescue analgesic, total rescue analgesic requirement). Secondary outcome measures included assessment of the level of pain (on VAS scale scores). The incidence of nausea and any attack of postoperative vomiting was recorded which was controlled by ondansetron 4 mg. Blood pressure, heart rate, and respiratory rates were measured every 1 h for the first 6 h postoperatively. Finally the duration of hospital stay and any detected complications related to the blocks were recorded.

Statistical analysis

Data management and statistical analysis were done using SPSS (statistical program for social science version 25). Numerical data were summarized as means and standard deviations or medians and ranges. Categorical data were summarized as numbers and percentages. Comparisons between two groups were done using: independent t-test for normally distributed variables, Mann–Whitney U-test for non-normally distributed variables. Categorical variables were compared between two groups using χ2-test or Fisher’s exact test if appropriate. P values less than 0.05 were considered significant and less than 0.001 were considered highly significant.

  Results Top

Sixty patients were recruited in this study; the patients were divided into two groups of 30 each. As regards age, weight, height, and ASA status, the current study showed no significant statistical difference between both groups with a P value greater than 0.05 ([Table 1]).
Table 1 Demographic data of both groups

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As regards the primary outcome of this study, morphine consumption, which includes the time of first rescue analgesia and total dose of morphine consumption during 24 h postoperatively, the current study showed a longer duration of analgesia in group II (20±3 h) in comparison to group I (15±4 h). Statistical analysis showed that P value of 0.007 which is statistically highly significant. Also, the total dose of morphine consumption was lower in group II (5±2 mg/24 h) in comparison to group I (9±2 mg/24 h). Statistical analysis showed that P value of 0.01 which is statistically significant ([Table 2]).
Table 2 Pain rescue analgesia consumption in the first 24 h in both groups

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In general, the intensity of pain at rest and movement was low in both groups. As regards VAS during rest, there was reduction in the median VAS in group II compared with group I (2 vs. 3) at the 12th hour (P<0.001), which is statistically highly significant, and at the 16th hour (P=0.013) postoperatively, which is statistically significant. But, there were no significant differences between both groups at PACU, 4, 8, 20, and 24 h postoperatively ([Table 3]).
Table 3 Visual analog scale at rest in both groups during 24 h postoperatively

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As regards VAS during movement, there was reduction in the median VAS in group II compared with group I (2 vs. 3) at 12th (P<0.044), which is statistically significant, and at the 16th hour (P<0.002) postoperatively, which is statistically highly significant. But, there were no significant differences between both groups at PACU, 4, 8, 20, and 24 h postoperatively ([Table 4]).
Table 4 Visual analog scale at movement in both groups during 24 h postoperatively

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As regards patients having postoperative nausea and vomiting (PONV), the current study showed a lower incidence in both groups: three (10%) patients had nausea and two (6.7%) patients had vomiting in group I as compared with three (10%) patients having nausea and only one (3.3%) patient having vomiting in group II. These results are statistically nonsignificant with a P value of greater than 0.05 ([Figure 3]).
Figure 3 Comparison between both groups as regards postoperative nausea and vomiting.

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As regards the mean arterial blood pressure ([Figure 4]), heart rate ([Figure 5]), and respiratory rate ([Figure 6]), the current study showed no statistical differences between both groups on arrival to the PACU and every 1 h for the first 6 h postoperatively with a P value greater than 0.05. As regards the duration of hospital stay after surgery, the current study showed no statistical differences between both groups with a P value of 0.728 ([Table 5]). And there were no complications related to the blocks.
Figure 4 Comparison between both groups as regards mean arterial blood pressure (MAP).

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Figure 5 Comparison between both groups as regards heart rate.

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Figure 6 Comparison between both groups as regards respiratory rate.

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Table 5 Duration of hospital stay in both groups

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  Discussion Top

This randomized, controlled study compared TPVB with SAPB for analgesia after mastectomy with or without axillary dissection and found that SAPB had a longer duration of analgesia and lower morphine consumption 24 h after surgery. The postoperative vital data were comparable in both groups. The incidence of PONV was low in both groups, and there was no major complication.

US-guided TPVB is an excellent analgesic technique for breast surgery because not only does it decrease pain, but also decreases PONV and length of hospital stay. However, the learning curve of US‑guided TPVB is rather steep requiring a higher degree of skill. Furthermore, a number of complications have previously been reported with TPVB [14]. Blanco et al. [10] proposed SAPB as an alternative to TPVB for surgeries on the anterior and lateral thoracic wall including breast surgeries. SAPB is an easy block to learn and perform because the SAM is an easy sonographic landmark to identify for this block.

Our hypothesis of a longer duration of analgesia of SABP in comparison to TPVB is based on the mechanism of spread of LA in the two blocks. Hence, the breast is innervated by anterior and lateral cutaneous branches of the second to sixth thoracic intercostal nerves (T2–T6) and supraclavicular nerves [15]. The mechanism of action of SAPB is a blockade of the lateral cutaneous branches of the intercostal nerves (T2–T6) through LA diffusion across fascial planes and through muscle layers [16], while the TPVB blocks the spinal nerves directly, and the LA show unpredictable spread either laterally to block the intercostal nerves, or medially into the epidural space through the intervertebral foramina and also can spread longitudinally, cranially, or caudally in the paravertebral space [17]. Despite the academic debate on these distributions, there is no evidence about which way single injection may spread to provide a more consistent and ideal spread [18]. For mastectomy and axillary dissection, a block from at least T1–T6 will be required. A single level TPVB can block one to four dermatomes only. Therefore, single level injection would not be enough to produce sufficient analgesia [19]. This is supported by a study done at the National Cancer Institute at Cairo University in Egypt which compared SAPB with TPVB for mastectomy analgesia and reported that 84% of SAPB patients experienced none or very little postoperative pain and required no opioids during the first 24 h after surgery in comparison to 76% of TPVB patients [20].

Another study also reported that the time to first rescue analgesia postoperatively was significantly longer in the SAPB group 255.3±47.8 min as compared with the TPVB group 146.8±30.4 mins with a P value of less than 0.001. Postoperative total diclofenac consumption in the first 24 h was less in the SAPB group 138.8±44.0 mg compared with the TPVB group 210.0±39.2 mg with a P value of less than 0.001 [21].

Some researchers studied the effect of SAPB performed under direct vision on postoperative pain in breast surgery and found that 81% experiencing mild pain or no pain at all and all of these patients required no analgesia or only simple analgesia day 1 postoperatively compared with the control group [22]. Other researchers also studied the influence of the number of injections on the quality of TPVB. They found that the dermatomal block after a single thoracic paravertebral injection is unpredictable and varies widely, while increasing the number of paravertebral injections results in more reliable radiographic and sensory block distribution [23].

In contrast to the current study, a study published in the Indian journal of anesthesia found that the duration of analgesia (mean±SD) was significantly longer in the TPVB group compared with the SAPB group (346±57 vs. 245.6±58 min, P<0.001) and the postoperative 24 h morphine consumption (mean±SD) was significantly higher in the SAPB group (9.7±2.1 mg) compared with the TPVB group (6.5±1.5 mg) (P<0.001) when comparing both groups for modified radical mastectomy postoperative analgesia [24]. This difference in results may be explained by: first the previous study injected the LA superficial to the SAM, as it decreases the risk of pneumothorax and vascular trauma, compared with the deeper approach that the current study used. But with injection of LA deep into the SAM, sensory blockade spread up to the T2 dermatome as has been reported [25]. Also this avoids the possibility of transitory palsy of the LTN, leading to a winged scapula than can be mistaken with a surgical lesion of this nerve. Second, the volume of LA is also likely an important determinant of the extent and duration of analgesia for SAPB. Since SAPB is a fascial block, a larger volume is expected to promote LA spread [26]. The volume of LA used in the previous study was fixed (20 ml). However, in the current study, a higher volume of LA was injected in SAPB (0.4 ml/kg).However, the current study also has a number of limitations. We could not assess block onset time or sensory dermatomal level because both blocks were performed after induction of general anesthesia. We performed a single level injection, realizing that multiple injections or continuous techniques may provide more effective analgesia in TPVB. We hope that future studies will clear the remaining issues about the optimal injection approaches for SAPB (superficial or deep to SAM) and the duration of analgesia with and without adjuncts.

  Conclusion Top

The US-guided SAPB and TPVB provide good analgesia postmastectomy, but SAPB has a superior analgesic profile, with a longer duration of analgesia, with delayed requirement for the first rescue analgesia & 24 hours reduced analgesic consumption.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]

This article has been cited by
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Anesthesiology and Pain Medicine. 2020; 10(3)
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