Ultrasound-guided serratus anterior plane block enhances postoperative analgesia and recovery in thoracoscopic surgery

Abstract

BACKGROUND

The serratus anterior muscle, located in the lateral aspect of the thorax, plays a crucial role in shoulder movement and stability. Thoracoscopic surgery, while minimally invasive, often results in significant postoperative pain, complicating patient recovery and potentially extending hospital stays. Traditional anesthesia methods may not adequately address this pain, leading to increased complications such as agitation due to inadequate pain management.

AIM

To evaluate the application value of ultrasound-guided serratus anterior plane block (SAPB) in patients undergoing thoracoscopic surgery, focusing on its effects on postoperative analgesia and rehabilitation.

METHODS

Eighty patients undergoing thoracoscopic surgery between August 2021 and December 2022 were randomly divided into two groups: An observation group receiving ultrasound-guided SAPB and a control group receiving standard care without SAPB. Both groups underwent general anesthesia and were monitored for blood pressure, heart rate (HR), oxygen saturation, and pulse. The primary outcomes measured included mean arterial pressure (MAP), HR, postoperative visual analogue scale (VAS) scores for pain, supplemental analgesic use, and incidence of agitation.

RESULTS

The observation group showed significantly lower cortisol and glucose concentrations at various time points post-operation compared to the control group, indicating reduced stress responses. Moreover, MAP and HR levels were lower in the observation group during and after surgery. VAS scores were significantly lower in the observation group at 1 h, 4 h, 6 h, and 12 h post-surgery, and the rates of analgesic supplementation and agitation were significantly reduced compared to the control group.

CONCLUSION

Ultrasound-guided SAPB significantly improves postoperative analgesia and reduces agitation in patients undergoing thoracoscopic surgery. This technique stabilizes perioperative vital signs, decreases the need for supplemental analgesics, and minimizes postoperative pain and stress responses, underscoring its high application value in enhancing patient recovery and rehabilitation post-thoracoscopy.

Key Words: Ultrasonic guidance, Serserus anterior plane block, Thoracoscopic surgery, Postoperative analgesia

Core Tip: This study evaluates the effectiveness of ultrasound-guided serratus anterior plane block (SAPB) in enhancing postoperative analgesia and facilitating rehabilitation in patients undergoing thoracoscopic surgery. The research highlights the SAPB's potential to significantly reduce postoperative pain, agitation, and supplemental analgesic use, thereby stabilizing perioperative vital signs and reducing stress responses. These findings suggest that SAPB could be a valuable addition to thoracoscopic surgery anesthesia protocols, offering benefits in patient comfort and recovery outcomes.

INTRODUCTION

The musculus serratus anterior (anterior serratus anterior), located in the lateral subcutaneous thorax, the upper part of which is covered by the pectoralis major and pectoralis minor, is a chest muscle that pulls the inner side of the shoulder blade forward. Two anterior serratus muscles in each group start from the ribs in the chest and extend to the shoulder blade around the side of the body. The postoperative pain of thoracic surgery is obvious. Although the incision of thoracoscopic surgery is small, the acute postoperative pain caused by thoracoscopic surgery still increases the postoperative complications and prolongs the hospital stay of patients[1]. Surgery is an effective means to treat thoracoscopy. Traditional thoracoscopic anesthesia mostly adopts static aspiration combined anesthesia, but it is easy to cause agitation due to postoperative pain, which affects the smooth operation[2]. Although anterior serserus plane block anesthesia can solve pain problems, it has disadvantages such as local anesthetic (LA) poisoning and influence on postoperative activities, which limits its clinical application[3]. In 2013, Patel et al[4] first proposed a novel regional blockade method for anterolateral thoracic wall analgesia, which involves the injection of LA into the superficial or deep plane of the serratus anterior muscle. This method, known as the serratus anterior plane block (SAPB), is technically straightforward to implement and can comprehensively cover the surgical area affected by video-assisted thoracic surgery, making it promising for thoracic wall analgesia. Datu and Prasetyadhi[5] observed patients undergoing thoracic surgery and found that those receiving continuous SAPB exhibited more stable hemodynamics compared to patients receiving continuous epidural blockade. They also noted that continuous SAPB offers advantages in reducing the use of postoperative opioid medications. Ultrasus-guided serratus plane block can better block the anterior thoracic sensory nerve innerve and has good anterior chest wall analgesic effect, which has been widely used in thoracoscopic surgery in recent years[6]. In this study, ultrasound guided serratus anterior block (SAP) was applied to 80 patients undergoing thoracoscopic surgery from August 2021 to December 2022 to evaluate its application value.

MATERIALS AND METHODS

General information

A total of 80 patients undergoing thoracoscopic surgery from August 2021 to December 2022 were selected and divided into observation group and control group with 40 patients in each group. In the observation group, there were 23 males and 17 females, aged 35-74 years. In the control group, there were 25 males and 15 females, aged 45 to 75 years. There was no significant difference in data between the two groups (P > 0.05), indicating comparability, as shown in Table 1. This study was in line with the principles of the Declaration of Helsinki, and the patients or their families were well aware of the content and scheme of the study and had signed informed consent.

Table 1 Comparison of general data between the two groups, mean ± SD, n = 40.

Group	Gender		ASA		Age (yr)	Body weight (kg)
	Male	Female	Ⅰ	Ⅱ
Observation group	22	18	14	26	56.75 ± 9.80	72.41 ± 10.20
Control group	20	20	16	24	59.58 ± 8.02	70.67 ± 9.40
t/χ2	0.200		0.213		-1.410	0.790
P value	0.654		0.644		0.162	0.432

ASA: American Society of Anesthesiologists.

Inclusion and exclusion criteria

Inclusion criteria: No history of respiratory tract infection in the past 1 wk; all preoperative examinations were normal; all were consistent with surgical indications; American Society of Anesthesiologists grade I-II; patients and their families were informed of the study and signed consent forms.

Exclusion criteria: Patients with hematological diseases; skin infection and ulceration at the puncture site; evidence of anesthesia contraindications; patients with abnormal coagulation function; liver and kidney insufficiency; people with mental illness.

Methods

Both groups were routinely prohibited from drinking and fasting before surgery, and venous channels were established after entry. Blood pressure, heart rate, oxygen saturation, pulse and so on were closely monitored. After induction of general anesthesia, a double-lumen tracheal catheter was inserted. The control group underwent surgery immediately after anesthesia induction. In the observation group, SAP block was guided by color Doppler ultrasound after the effect of anesthesia. A 7.5 MHz linear array probe was used to scan the chest wall at the level of the anterior axillary front between the 6^th and 7^th ribs. After obtaining the fascia image of the anterior serran muscle, the needle was inserted into the anterior serran muscle plane under the guidance of ultrasound, and 1-2 mL normal saline was injected after no blood was drawn. After its diffusion, 0.5% ropivacaine hydrochloride 30 mL was injected, and the operation was performed about 15 min later. After operation, sufentanil 100 μg was injected combined with analgesic pump.

Observation indicators

The total score was 10, 0 was no pain, and the higher the score was, the more severe the pain was. The supplemental rate of analgesics and the incidence of agitation were recorded in the two groups: (1) Postoperative eye opening time, awake time and incidence of agitation were recorded in the two groups; (2) venous blood was withdrawn from patients' right elbow before the surgery (T0), at the beginning of surgery (T1), immediately after pneumoperitoneum establishment (T2), 20 min after pneumoperitoneum establishment (T3), and 40 min after pneumoperitoneum establishment (T4), and was sent to the laboratory for testing plasma cortisol (Cor) and glucose (Glu) concentrations. Cor was detected by ELISA, the kit was selected from Shanghai Jining Industrial Co., LTD. Hexokinase assay was used to detect Glu. The kit was selected from Zhejiang Kuak Biotechnology Co., LTD; (3) systolic blood pressure (SBP) and diastolic blood pressure (DBP) of the two groups were recorded at T1-T4; (4) the total intraoperative use of propofol and sufentanil in the two groups was calculated; and (5) at 2, 8, 24, 48 h after surgery, the visual analogue scale (VAS)[7] was used to evaluate the pain situation of the two groups of patients, and the patients were instructed to select a scale matching their own pain from the scale of 0 to 10, with a total score of 10. The higher the score, the more severe the postoperative pain of the patients.

Statistical methods

SPSS20.0 software was used to process the data. The statistical data were expressed by n (%), χ² test. Measurement data were represented by independent T-test was performed between the two groups, and paired T-test was performed for perioperative indicators. VAS at 2, 8, 24 and 48 h after surgery was analyzed by repeated measure variance, and LSD-t test was used for pair comparison. The test level was α = 0.05.

RESULTS

Comparison of wake and agitation between the two groups

We initially compared the wakefulness and agitation between the observation and control groups (Table 2), to preliminarily explore the effects of ultrasound-guided SAPB on anesthesia and sedation. The statistical analysis revealed that the wakefulness time in the observation group was significantly longer than that in the control group (P = 0.001), with respective values of 22.89 ± 2.38 and 20.22 ± 2.00. Concurrently, the incidence of agitation in the observation group was significantly lower than that in the control group, with a P-value of 0.025. However, there was no significant difference in eye-opening time and awake time between the two groups (P > 0.05) (Table 2).

Table 2 Comparison of recovery agitation between the two groups (mean ± SD, min), n = 40.

Group	Eye opening time	Wakefulness time	Incidence of agitation
Observation group	15.52 ± 2.08	22.89 ± 2.38	4 (10.00)
Control group	15.63 ± 1.98	20.22 ± 2.00	12 (30.00)
t/χ2	-0.242	5.432	5.000
P value	0.809	0.001	0.025

Comparison of perioperative stress response between the two groups

Subsequently, we characterized the perioperative stress response of the two groups of patients by measuring Cor and Glu. At baseline (T0), there were no significant differences in the levels of Cor and Glu between the two groups (P < 0.05), providing a comparable foundation for subsequent analyses (Table 3). We then conducted both inter-group and intra-group comparisons of the test results. The intra-group comparison aimed to clarify the stress changes in response to the type of intervention within each group at different surgical periods. We observed that in both the control and observation groups, the levels of Cor and Glu at post-intervention phases T2, T3, and T4 were significantly higher than at baseline T0 (P < 0.05), as indicated in the content marked with 'a' in Table 3. The inter-group comparison was conducted to observe the differences in stress responses caused by different interventions. We found that at T2, T3, and T4, the levels of Cor and Glu in the observation group were significantly lower than those in the control group (P < 0.05), as indicated in the content marked with 'b' in Table 3.

Table 3 Comparison of perioperative stress response between the two groups (mean ± SD, nmol/L), n = 40.

Index	Group	T0	T2	T3	T4
Cor	Observation group	331.52 ± 42.21	382.02 ± 59.20a,b	369.21 ± 52.85a,b	349.86 ± 53.49a,b
	Control group	340.61 ± 36.22	649.04 ± 48.72a	582.21 ± 59.21a	539.02 ± 48.02a
Glu	Observation group	4.42 ± 0.52	5.84 ± 0.48a,b	6.42 ± 0.22a,b	5.22 ± 0.23a,b
	Control group	4.50 ± 0.62	7.62 ± 0.76a	7.12 ± 0.60a	5.62 ± 0.42a

^aP < 0.05 vs T0 in the same group.

^bP < 0.05 vs the control group at the same time.

Comparison of perioperative hemodynamic indexes between the two groups

In terms of hemodynamic assessment, we compared the levels of SBP and DBP between the two groups, conducting both intra-group and inter-group comparisons. The baseline SBP levels at T0 for the two groups were 93.33 ± 12.23 and 95.43 ± 12.62, respectively, and the baseline DBP levels were 51.33 ± 9.61 and 52.06 ± 10.23, respectively, with no significant differences observed (P > 0.05). At T2, T3, and T4, the SBP and DBP levels in the observation group were lower than those in the control group (P < 0.05). However, at T1, the values for both groups were similar to those at T0, showing no significant difference. Furthermore, in the intra-group comparison, inconsistent results were observed: In the observation group, both SBP and DBP at T1, T2, T3, and T4 were significantly lower than at baseline T0 (P < 0.05), while in the control group, SBP and DBP were significantly higher at T2, T3, and T4 compared to T0 (Table 4).

Table 4 Comparison of perioperative hemodynamic indexes between the two groups (mean ± SD, mmHg), n = 40.

Index	Group	T0	T1	T2	T3	T4
SBP	Observation group	93.33 ± 12.23	87.42 ± 9.21a	82.42 ± 8.54a,b	79.32 ± 12.34a,b	88.32 ± 9.32a,b
	Control group	95.43 ± 12.62	88.31 ± 11.02	110.68 ± 12.85a	108.60 ± 9.33a	102.23 ± 12.35a
DBP	Observation group	51.33 ± 9.61	48.33 ± 8.20a	42.29 ± 10.12a,b	43.33 ± 10.63a,b	46.55 ± 10.57a,b
	Control group	52.06 ± 10.23	49.33 ± 11.42	69.31 ± 9.34a	62.22 ± 9.20a	55.33 ± 10.25a

^aP < 0.05 vs T0 in the same group.

^bP < 0.05 vs the control group at the same time.

SBP: Systolic blood pressure; DBP: Diastolic blood pressure.

Comparison of dosage of sedative drugs and opioids between the two groups

In terms of the dosage of propofol and fentanyl, we found that the dosage of propofol in the experimental and control groups was 0.45 ± 0.26 and 1.19 ± 0.24, respectively, and the dosage of fentanyl was 0.68 ± 0.23 in the observation group and 1.33 ± 0.22 in the control group. The comparisons between the two groups were statistically significant (P < 0.01) (Table 5), clearly indicating that the dosages in the observation group were significantly lower than those in the control group.

Table 5 Comparison of dosage of sedative drugs and opioids between the two groups (mean ± SD), n = 40.

Group	Propofol (mg)	Fentanyl (μg)
Observation group	0.45 ± 0.26	0.68 ± 0.23
Control group	1.19 ± 0.24	1.33 ± 0.22
t	-13.227	-12.916
P value	< 0.001	< 0.001

Comparison of postoperative pain between the two groups

VAS score time, inter-group and interaction effects were statistically significant at different time points in the two groups (F_interaction =12.966, F_interaction =111.895, F time = 265.379, P < 0.001 for both). Two hours after surgery, VAS scores of the two groups were not different (P > 0.05). At the 8^th, 24^th and 48 h after surgery, the VAS score of the two groups was gradually decreased (P < 0.05), and the VAS score of the observation group was lower than that of the control group at the same time (P < 0.05) (Table 6).

Table 6 Comparison of postoperative pain between the two groups (mean ± SD, point), n = 40.

Group	2 h after operation	8 h after operation	24 h after operation	48 h after operation
Observation group	4.33 ± 1.26	2.46 ± 0.54a,b	2.13 ± 0.23a,b	1.45 ± 0.32a,b
Control group	4.39 ± 1.22	3.85 ± 0.41a	3.33 ± 0.22a	2.22 ± 0.33a
Finteraction, Pinteraction	12.966/< 0.001
Fintergroup, Pintergroup	111.895/< 0.001
Ftime, Ptime	265.379/< 0.001

^aP < 0.05 vs the same group 2 h after operation.

^bP < 0.05 vs a control group at the same time.

DISCUSSION

In thoracoscopic surgery, perioperative anesthesia management has a great impact on the operative effect and the prognosis of patients. Studies have shown that anterior serration plane block has rapid effect, mild impact on circulation and respiration and is easy to operate. The application of thoracoscopic surgery is conducive to improving patients' perioperative conditions and reducing the amount of general anesthetics. However, the traditional SAPB has a high failure rate, with risks such as punctured pleura and incomplete block[8,9]. However, ultrasound-guided SAPB can significantly improve the success rate and safety factor of puncture block, so the application rate of SAPB based on ultrasonic imaging has gradually increased in recent years[10]. Studies by some scholars have shown that anterior serratus plane block combined with laryngeal mask general anesthesia has the advantages of stable anesthesia hemodynamics, fast postoperative recovery, and less narcotic drug consumption for unilateral bullosa resection. Studies by some scholars have also shown that anterior serratus plane block can not only effectively maintain hemodynamic stability, but also reduce oxidative stress response, with fewer adverse reactions[11]. SAP blocks only superficial nerves in the anterior and lateral chest wall, and in contrast to paravertebral block, it does not cause sympathetic block and does not cause hypotension. Therefore, this study discussed the clinical application effect of ultrasus-guided anterior serrated muscle plane block in thoracoscopic anesthesia and postoperative analgesia.

In previous clinical thoracoscopic surgery, the extensive use of opioids was prone to adverse reactions such as excessive sedation, respiratory depression, nausea, and vomiting, which was not conducive to the prognosis of surgery[12]. Compared with traditional intravenous general anesthesia, nerve block combined intravenous anesthesia has a smaller amount of anesthetics, and has advantages such as quick recovery after surgery and ideal analgesic effect. Currently, the application of this anesthesia program in thoracoscopic surgery is gradually increasing[13-15]. SAPB is a new chest wall regional block method, whose principle is to inject LAs into the anterior serrate plane, and block the anterior branches of T6-L1 nerves after the anesthetics play their role, so that the muscles and skin innervated by sensory nerves cannot transmit pain signals to the brain, thus exerting the effect of chest wall nerve block and analgesic effect[16].

The occlusion plane involved in SAPB is basically the same as the plane required by thoracoscopic surgery, but in the actual process of puncture, the Petit triangle palpated may be obstructed, and the puncture needle does not have obvious sensation when entering the plane of serserus anterior muscle, plus the thin chest wall, which is prone to block failure, accidental injury and other situations[17]. In recent years, with the continuous development of clinical medical technology, SAPB is gradually applied in thoracoscopic surgery under the guidance of ultrasound. Compared with conventional blind puncture, SAPB can significantly improve the success rate of puncture, reduce the damage to patients, reduce the incidence of complications, and improve puncture safety[18,19].

Thoracoscopic surgery is more traumatic to patients, which may not only induce intraoperative bleeding, but also cause severe postoperative pain, further affecting the postoperative recovery of patients. Therefore, an effective anesthesia program to reduce postoperative pain is of great significance for the prognosis of patients. SAP block refers to the injection of local anesthesia drugs into the anterior sersaw muscle to block the nerve in order to achieve chest wall analgesia[20,21].

The results of this study showed that there was no difference in eye opening time and awake time between the two groups, and the incidence of agitation in the observation group was lower than that in the control group. Midline axillary approach block between the fifth and sixth ribs can effectively block the thoracodorsal nerve, the long thoracic nerve, and the lateral cutaneous branch of the intercostal nerve. Under ultrasonic guidance, the operation accuracy is improved and the effect of blocking weave is guaranteed. At the same time, the decreased incidence of agitation may also be related to the decreased stress level of patients in the perioperative period. Studies have found that SAP block can reduce the incidence of postoperative agitation and reduce the body's stress response, thus preventing excessive melatonin decline.

The operative time of patients undergoing thoracoscopic surgery should not be too long, and the use of drugs with fast metabolism and quick action is more in line with the requirements of surgery. But rapid metabolism can cause people to wake up early, and severe pain can make them afraid to breathe. The use of opioids in the observation group was significantly higher than that in the control group, because sedation and analgesia required a large number of opioids for analgesia, and significantly increased drug dosage may cause adverse reactions such as respiratory depression and severe vomiting, which was not conducive to the postoperative rehabilitation of patients. Some studies have found that SAP block can reduce the amount of analgesic drugs used by patients without affecting the anesthetic effect, and the results of this study are consistent with those of other studies[22,23]. In addition, acute stress response is caused by sympathetic excitation, and excessive release of catecholamines can lead to rapid increase of Cor and Glu in peripheral blood. Surgical stimulation and maintenance time of surgery can affect patients' stress response. The increase of stress response can lead to the high metabolism of the body, inducing arrhythmia, pulmonary hypertension and other adverse events[24-26]. The results of this study showed that the concentrations of Cor and Glu in the observation group were lower than those in the control group at moments T2, T3 and T4, and the hemodynamic indexes SBP and DBP were also significantly lower than those in the control group, indicating that SAP could reduce the perioperative stress response of patients and improve the safety of surgery.

CONCLUSION

In conclusion, ultrasus-guided anterior serrated muscle plane block anesthesia has high application value in thoracoscopic surgery, which can maintain the stability of perioperative vital signs, reduce the degree of postoperative pain, and reduce postoperative agitation, so it is worthy of application.