Comparison of Rhomboid Intercostal Block, Erector Spinae Plane Block, and Serratus Plane Block on Analgesia for Video-Assisted Thoracic Surgery: A Prospective, Randomized, Controlled Trial.

Background: Thoracic surgery is one of the most painful surgical steps. An important tool for managing postoperative pain is effective postoperative analgesia. This research aimed at comparing the analgesic roles of three new fascial block techniques in the postoperative period after video-helped thoracoscopic operation (VATS).
Methods: We randomly allocated ninety patients into three teams experiencing ultrasound-directed serratus plane block, erector spinae plane block, and the rhomboid intercostal block, respectively. 0.4% ropivacaine of 20 mL was received by all groups. Outcomes. At 0-12 hours, sufentanil consumption was significantly lower in the RIB (35.2 ± 3.3 mg) and ESP (35.4 ± 2.8 mg) groups than that in the SAB (43.3 ± 2.7 mg) group (P < 0.001), and no obvious diversity in sufentanil consumption was shown between the RIB and ESP groups (P=0.813). At 12-24 hours, sufentanil consumption was greatly lower in the RIB and ESP groups than that in the SAB group (P < 0.001), and no great diversity in sufentanil consumption was found between the RIB and ESP groups (P=0.589). No great diversity in sufentanil consumption was shown between the RIB (50.4 ± 1.4 mg), ESP (50.4 ± 1.5 mg), and SAB (51.0 ± 1.7 mg) groups at 24-48 hours (P=0.192). At 6, 12, 18, and 24 hours, the postoperative dynamic NRS scores were significantly lower in the RIB and ESP groups than in the SAB group ((P < 0.05) for all contrasts). Nevertheless, no great diversity was observed in postoperative pain marks at 0.5, 1, 3, 6, 12, 18, 24, 36, and 48 hours after the surgery across the three groups. No statistical diversity was found in the postoperative NRS mark between groups RIB and ESP within 48 hours after surgery in case of active patients ((P < 0.05) for all contrasts). At 24 hours after surgery, a significant difference in IL-1β and IL-6 inflammatory factor concentrations was found between RIB and ESP compared with SAB block ((P < 0.05) for all contrasts). However, no great diversities were observed in IL-1β, and IL-6 inflammatory factor concentrations between RIB, ESP, and SAB at 24 hours preoperatively and at 48 hours postoperatively ((P < 0.05) for all comparisons).
Conclusion: The dosage of sufentanil can be effectively reduced by ultrasound-directed rhomboid intercostal block and erector spinae plane block within 24 hours after VATS surgery, and pain can be relieved effectively within 24 hours by comparing with serratus plane block.

1. Introduction

Pain is severe after video-assisted thoracoscopic surgery (VATS) [1-3], and regional nerve block techniques are playing an increasingly important role in multimodal analgesia, which not only provides good postoperative analgesia but also reduces the use of opioids and the associated side effects [4-6]. Currently, several regional nerve blocks are used for analgesia after thoracic surgery, such as serratus plane block (SAB), erector spinae plane block (ESP), and rhomboid intercostal block (RIB). However, their analgesic effects vary in strength, and the question of which technique is safer and more effective is still controversial [7-10]. Further clinical studies are needed to answer this.

RIB is a novel regional nerve block technology used for analgesia after thoracic surgery, first reported by Elsharkawy et al. in 2016 [11]. Several research studies have shown that ultrasound-guided RIB applied to VATS is not only safe and analgesic but also far from the surgical incision site [12-14].

ESP is a regional nerve block technology for analgesia after thoracic surgery observed by Forero et al. in 2016 [15], and several research studies have noted its superior quality of patient recovery, lower morbidity, and better analgesic effect [16, 17].

Similarly, as a novel analgesic technology put forward by Blanco et al. [18], SAB shows good results for postoperative analgesia in VATS patients [19, 20]. Finnerty et al. [16] found higher-quality recovery, lower morbidity, and excellent analgesic effect at 24 hours after minimally invasive thoracic surgery with ESP compared to SAB. However, the use of RIB, ESP, and SAB blocks for analgesia after VATS has been reported less frequently in relation to the comparative analgesic roles of these three blocks after surgery. In the present study, the analgesic roles of these three nerve blocks were compared after VATS.

Considering the relatively small amount of the scientific literature, this research primarily aimed at comparing the strength of the analgesic effect by the comparison of the use of RIB, ESP, and SAB in postoperative sufentanil use in VATS. Our secondary goal was to compare the Numerical Rating Scale (NRS), time to first postoperative analgesic demand, patient content, etc.

2. Materials and Approaches

2.1. Patient Recruitment and Research Design

A potential, single-center, randomized, and regulated clinical research on October 1, 2020. The principles below summed up in the Claim of Helsinki were followed, and the ethical approval number was obtained from the Medical Ethics Committee. We invited all screened patients meeting the eligibility standards to participate in the trial, and enrolled patients offered informed consent in writing.

We required patients to provide agreement upon arrival at the operating room or in the hospital the night before the operation. Inclusion criteria were ASA grades one through three, ages eighteen to eighty, patients experiencing common anesthesia for unilateral VATS, and no contraindication for peripheral area anesthetic block. Exclusion criteria included contraindication for local anesthesia, preexisting infection at the block place, preexisting chronic pain or recognized dysfunction, and history of opioid abuse that would stop patients from precisely taking part in the postoperative quality of recovery and analgesia evaluation.

2.1.1. Anesthesia Application

All patients were supervised for vital signs in the operating room with normative electrocardiography (ECG), peripheral oxygen saturation, noninvasive blood pressure, and thermometer. After placing a 20-gauge intravenous line, all patients went through a 15 mL kg−1 h−1 isotonic saline infusion intravenously. Anesthetic administration observed a normative agreement. Induction of anesthesia began with preoxygenation for three to five minutes and an intravenous (IV) injection of sufentanil (0.5 μg/kg), midazolam (0.05 mg/kg), propofol (2 mg/kg), and rocuronium bromide (0.6 mg/kg). Ventilation was completed with a single-lumen endotracheal catheter. An end-tidal level of carbon dioxide at 35–40 mm Hg was kept by setting ventilation with positive pressure.

To maintain anesthesia, the surgical team employed a 2% sevoflurane with 50% oxygen, remifentanil (0.1–1 μg/kg/min), and propofol (50–150 μg/kg/min). Besides, rocuronium bromide injection (0.6 mg/kg) was managed on basis of the surgical protocol. The blood pressure within 20% of the base value was maintained by adjusting the doses of anesthetics. The intravenous injection of an extra amount of remifentanil (0.1–1.0 μg/kg/min) was conducted as required. If the blood pressure declined by >20% from the baseline value, 250 mL of 0.9% physiological saline solution and ephedrine (0.1 mg/kg) were administered. If the heart rate declined by >20% of the base value, atropine (0.01 mg/kg) was provided. After the VATS step, neostigmine (0.05 mg/kg) and atropine (0.02 mg/kg) were employed to change the role of cisatracurium. After smooth extubation, patients were transferred to the postoperative recovery room.

2.2. Surgical Procedures

Among patients with one trochlear port, a single incision of 3.0–4.0 cm was conducted in the fourth or fifth intercostal space of the anterior axillary line, and a trochal port was inserted into the chest wall. Next, the operation was conducted via the trochal port. The insertion of a thoracic drainage tube was made by closing the incision before the skin of the fourth or fifth intercostal segments.

2.3. Patient Grouping and Randomization

After the endotracheal intubation, the patients were fallen into SAB, ESP, and RIB. Patient grouping was on basis of a computer-based randomization table brought by a scholar who did not take part in the research. A random identification number (ID) was assigned to each patient, and the individual IDs were sealed in opaque envelopes. The nerve block technique was performed by another anesthesiologist who was completely unaware of the patient's ID. All patients were blinded to the group allocations. The patient ID was adopted by a blinded anesthesiologist (AIU) while gathering information postoperatively in the surgical ward. The surgeons, attending anesthetist, outcome assessor, and data analysts were not informed of the group assignments.

2.4. Application of Block Intervention

In the SAB group, an anesthetist suffering from interfascial blocks conducted the ultrasound (US)-directed technology with a linear probe (6–12 MHz), a US equipment (LOGIQ e US system, Deutschland GmbH and Co. KG, Solingen, Germany), and a 21G × 80 mm echogenic needle. As the patient lies supine and the arm abducts at 90°, the positioning of the US probe was made in a sagittal plane at the midaxillary line. The identification of the fascial plane between the serratus anterior muscle and external intercostal muscles was performed between the fourth and fifth ribs in the midaxillary area [18]. If the needle arrived at the interfascial plane between the serratus anterior muscle and external intercostal muscles, 20 mL of 0.4% ropivacaine was administered.

In the ESP group, patients were put in the lateral decubitus place. There was a US probe in longitudinal orientation during the T4 spinous process and then was put three centimeters laterally from the midline to the side taking part in the operation. The identification of US labels, T4 transverse process, and the overlying trapezius, rhomboideus, and erector spinae muscles was performed. In aseptic situations, the insertion of a 21G × 80 mm block needle was conducted in-plane at an angle of 30–40° in the cranial-to-caudal direction until the tip touched the T4 transverse process. After confirming the correct needle-tip position by the hydrodissection with 2–3 mL of isotonic saline solution, the injection of 20 mL of 0.4% ropivacaine was made into the interfascial plane between the rhomboideus major and erector spinae muscle. US guidance [15] was employed to visualize the expansion of local anesthetic in a fascial longitudinal pattern deep to the erector spinae muscle.

In the third group (RIB), the positioning of patients was made in the lateral decubitus place with the related breast lying superiorly. The scapula was moved laterally by abducting the psilateral arm across the chest. A high-frequency (6–12 MHz) linear US probe was put medial to the medial boundary of the scapula in an oblique sagittal plane. The identification of US labels, trapezius muscle, rhomboid muscle, intercostal muscles, pleura, and lung was conducted. In aseptic situations, the insertion of a 21 G × 80 mm needle was made in the plane angle of the US probe at the level of T5 to T6 processes. The injection of 20 mL of 0.4% ropivacaine was made into the interfascial plane between the rhomboid major and intercostal muscles [11]. Ultrasonography was employed to visualize the expansion of local anesthetic solution under the rhomboid muscle. Next, the patient was put in the supine position. The same anesthesiologist (BA) who had undergone with SAB and ESP conducted all block steps and RIB blocks in more than thirty cases before this study.

From each patient, 2 mL of venous blood was collected in the RIB, ESP, and SAB groups (24 hours before the operation, 24 hours after the operation, and 48 hours after the operation, respectively), and blood samples were collected in EDTA vacuum tubes and centrifuged using a 6 k microcentrifuge (Allsheng, China, Hangzhou). The plasma was isolated and kept at −80°C until measurement. Plasma levels of IL-1β and IL-6 were analyzed by standard enzyme-linked immunosorbent assay (ELISA) approaches using commercial ELISA kits (Human IL-1β ELISA kit and Human IL-6 ELISA kit, Fcmacs, Hangzhou, China) and according to the instructions.

2.5. Analgesia Protocol, Evaluation of Pain, and Sensorial Block

In the PACU, all patients experienced patient-regulated intravenous analgesia (PCIA): 150 μg sufentanil with 150 mL in total, loading dose of 2 mL, background dose of 2 mL, and locking duration of fifteen minutes. Another blinded anesthesiologist (AIU) conducted pain assessments after a half hour postoperatively with the 11-point Numerical Rating Scale (NRS) ranging from 0 (meaning “no pain”) to10 (meaning “worst pain imaginable”). Patients were prescribed parecoxib sodium for an IV injection of 40 mg as required for postoperative pain in the surgical ward until the NRS pain mark was ≤3 according to hospital policy. The patients were sent to the surgical ward after a half hour. In the surgical ward, patients were evaluated again after 0.5, 1, 3, 6, 12, 18, 24, 36, and 48 hours. In case of the postoperative NRs greater than 3 points, the pain was assessed after thirty minutes. In the case of the NRS greater than 3 points, a parecoxib sodium injection of 40 mg was administered intravenously. Serum was collected from all patients before surgery and 24 and 48 hours after surgery to measure IL-1 and IL-6 concentrations.

2.6. Result Methods

The initial result methods were to compare the roles of US-RIB, ESP, and SAB on postoperative sufentanil consumption of patients, and to record the postoperative pain marks of the patients receiving unilateral VATS. The secondary result methods were the dose of remifentanil and propofol, time to first postoperative analgesic demand, and the content mark of patients (1–10, where 10 was the highest). Except for these methods, postoperative nausea and vomiting (PONV, which were rated on a 4-point verbal scale: none = no nausea, mild = nausea but no vomiting, moderate vomiting = one attack, severe vomiting > one attack) and block-associated complications including pneumothorax, bleeding, allergy, and local anesthetic toxicity were recorded.

2.7. Sample Size

PASS 15 was employed to measure the sample size of the research on basis of pilot research with ten patients in every group. The mean sufentanil consumption at 48 hours was 112.0 ± 3.8 μg in group SAB, 109.4 ± 2.7 μg in group ESP, and 108.8 ± 1.9 μg in group RIB. In case of an α error = 0.01 (two-tailed) with a power of 0.90, at least nine participants were required per group and ten in total. In terms of the dropout rate and profits for patients (on basis of initial research), the sample size was increased, and thirty patients were included finally in each group.

2.8. Statistical Analysis

We performed statistical explorations with SPSS v25.0 (IBM, Armonk, NY, USA). The Shapiro–Wilk test was adopted to assess the shapes of the distributions of the variables, to decide in case of normal or skewed observation. If the test outcomes suggested normal allocation of information, the information with mean ± standard deviation (SD) was reported. We detailed the constant data which yielded the nonparametric dispersion with median and IQR, and it was explored that data with the Mann–Whitney U-test to discover the group-wise diversities. The diversities of outcome coefficients (age, BMI, step duration, duration of anesthesia, dose of remifentanil and propofol, NRS mark, NRS dynamic mark, time to first postoperative analgesic demands, overall sufentanil consumption (μg) at 48 hours, satisfaction score, IL-1β, and IL-6) were compared with one-way ANOVA among groups SAB, ESP, and RIB.

Post hoc exploration and the Student–Newman–Keuls q-test were adopted to pairwise compare one-way ANOVA. We compared the differences among males/females, ASAI/II/III, operation step, and surgical incision (left chest/right chest) with the chi-square test. Kruskal–Wallis test was adopted to analyze operation procedure and PONV scores, and The assessment of PONV was made with a 5-point numerical scale (0 = no symptom, 1 = scarcely, 2 = usually, 3 = most of the time, 4 = all the time). P values < 0.05 were obvious for the test result shown.

3. Results

There were 107 patients chosen to meet the inclusion criteria in this research. Seventeen patients were excluded, of which ten patients failed to satisfy the inclusion criteria, two patients rejected participation in this research, and two patients underwent a bilateral operation. Ninety patients were fallen into the research groups equally. One patient in the SAB group was excluded because the operative method was changed. Two patients in the ESP group were excluded because the operative method was changed and because of PCA failure. One patient in the RIB group was excluded because of PCA failure. Ultimately, we analyzed the data of ninety patients. Figure 1 shows the consort diagram. Table 1 illustrates the demographic features of the three groups of patients.

Figure 1

Consort diagram for the study. SAB: serratus plane block; ESP: erector spinae plane block; RIB: rhomboid intercostal block.

Table 1

Descriptive variable characteristics of patients in three groups ( ± SD).

Sample size (n)	SAB	ESP	RIB	P value
	29	28	29
Age (years)	61.7 ± 6.8	55.6 ± 12.9	59.1 ± 10.1	0.088∗
Gender (male/female)	7/22	11/17	9/20	0.468#
BMI (kg/m2)	23.4 ± 3.5	23.8 ± 4.0	24.0 ± 3.1	0.825∗
Procedure duration (min)	104.0 ± 28.8	109.9 ± 37.2	99.7 ± 28.4	0.479∗
Duration of anesthesia (min)	123.5 ± 30.7	128.9 ± 38.5	120.0 ± 31.3	0.608∗
ASA class I/II/III	0/27/2	0/27/1	0/28/1	0.780#
Surgical incision (left/right)	10/19	13/15	10/19	0.058#
Operation procedure				0.988∗∗
Wedge resection	2 (6.9%)	4 (14.3%)	4 (13.8%)	—
Bullectomy	1 (3.5%)	1 (3.6%)	1 (3.5%)	—
Lobectomy	26 (89.6%)	23 (82.1%)	24 (82.7%)	—

P value is obtained with one-way analysis of variance. #P value is obtained with Pearson's χ2 test. P value is obtained with Kruskal–Wallis test.

At 0–12 hours, sufentanil consumption was significantly lower in the RIB (35.2 ± 3.3 μg) and ESP (35.4 ± 2.8 μg) groups than that in the SAB (43.3 ± 2.7 μg) group (P < 0.001) (Table 2), and no obvious diversity in sufentanil consumption was shown between the RIB and ESP groups (P=0.813). At 12–24 hours, sufentanil consumption was greatly smaller in the RIB and ESP groups than that in the SAB group (P < 0.001) (Table 2), and no great diversity in sufentanil consumption was found between the RIB and ESP groups (P=0.589). No great diversity in sufentanil consumption was shown between the RIB (50.4 ± 1.4 μg), ESP (50.4 ± 1.5 μg), and SAB (51.0 ± 1.7 μg) groups at 24–48 hours (P=0.192) (Table 2).

Table 2

Postoperative sufentanil consumption in three groups ( ± SD).

Sample size (n)	SAB	ESP	RIB	P value
	29	28	29
Postoperative opioid consumption of sufentanil (μg)
0–12 h	43.3 ± 2.7	35.4 ± 2.8	35.2 ± 3.3	<0.001∗
12–24 h	35.3 ± 2.6	31.8 ± 1.4	31.5 ± 1.4	<0.001∗
24–48 h	51.0 ± 1.7	50.4 ± 1.5	50.4 ± 1.4	0.192∗

P value is obtained with one-way analysis of variance.

At 6, 12, 18, and 24 hours, the postoperative dynamic NRS scores were significantly lower in the RIB and ESP groups than in the SAB group (P < 0.05 for all contrasts) (Figure 2(b)). Nevertheless, no great diversity was observed in postoperative pain marks at 0.5, 1, 3, 6, 12, 18, 24, 36, and 48 hours after the surgery across the three groups (Figure 2(a)). No statistical diversity was found in the postoperative NRS mark between groups RIB and ESP within 48 hours after surgery in case of active patients (P < 0.05 for all contrasts) (Figures 2(a) and 2(b)).

Figure 2

NRS score at different times after surgery in the three groups. (a) NRS score when patients were at rest. (b) NRS score when patients were active. SAB: serratus plane block; ESP: erector spinae plane block; RIB: rhomboid intercostal block. P < 0.05 compared with the SAB group.

The time-to-first postoperative analgesic demand and the satisfaction scores in groups RIB and ESP were greatly shorter than those in group SAB (P < 0.05 for all contrasts) (Figures 3(a) and 3(b)), No great diversity was observed in the time-to-first postoperative analgesic demand (P=0.449), and satisfaction marks (P=0.597) between the RIB and ESP groups. At 24 hours after surgery, a significant difference in IL-1β, and IL-6 inflammatory factor concentrations was found between RIB and ESP compared with SAB block (P < 0.05 for all contrasts) (Figures 4(a) and 4(b)). However, no great diversities were observed in IL-1β and IL-6 inflammatory factor concentrations between RIB, ESP, and SAB at 24 hours preoperatively and at 48 hours postoperatively (P < 0.05 for all comparisons) (Figures 4(a) and 4(b)).

Figure 3

(a) Time to first postoperative analgesic request. (b) Satisfaction score in the three groups 24 h after surgery. SAB: serratus plane block; ESP: erector spinae plane block; RIB: rhomboid intercostal block. P < 0.05 compared with the SAB group.

Figure 4

(a) Three groups of IL-1β before operation, 24 hours after operation and 48 hours after operation. (b) Three groups of IL-6 before operation, 24 hours after operation and 48 hours after operation. AB: serratus plane block; ESP: erector spinae plane block; RIB: rhomboid intercostal block. P < 0.05 compared with the SAB group.

No great diversity was shown in the dosage of agreement (P=0.952 for all contrasts), remifentanil (P=0.079 for all contrasts), PONV marks (P=0.990 for all contrasts), and PACU duration (P=0.732 for all contrasts) across the three groups (Table 3). No great diversity was observed in all patients with a postoperative complication (P=0.867 for all contrasts) among the RIB, ESP, and SAB groups (Table 4).

Table 3

Intraoperative anesthetic dosage, postoperative analgesic, and recovery of three groups ( ± SD).

Sample size (n)	SAB	ESP	RIB	P value
	29	28	29
Remifentanil (μg)	389.7 ± 68.9	360.3 ± 80.4	353.4 ± 91.7	0.079∗
Propofol (mg)	351.4 ± 76.8	346.4 ± 87.9	344.8 ± 84.4	0.952∗
PACU duration (min)	44.1 ± 2.2	43.8 ± 2.6	43.5 ± 2.7	0.73∗
PONV scores, n (%)				0.990∗∗
0	15	14	17
1	8	10	7
2	5	3	4
3	1	1	1
4	0	0	0

P value is obtained with one-way analysis of variance. #P value is obtained with Pearson's χ2 test. ∗∗PONV scores were analyzed using Kruskal–Wallis test, and PONV was assessed using a five-point numerical scale (0 = no symptom, 1 = scarcely, 2 = usually, 3 = most of the time, 4 = all the time).

Table 4

Postoperative complications in three groups ( ± SD).

Sample size (n)	SAB	ESP	RIB	P value
	29	28	29
Total number of patients with a postoperative complication	3	2	2	0.867#
Postoperative pneumonia	2	1	1
Surgical site infection	0	0	0
Recurrent pneumothorax/air leak requiring further intervention	0	0	0
Arrhythmia	0	0	0
Bleeding requiring transfusion	1	1	1
Unplanned ICU admission	0	0	0
Acute kidney injury	0	0	0

# P value is obtained with Pearson's χ2 test.

4. Discussion

It was found that patients receiving RIB and ESP blocks had lower sufentanil consumption and dynamic NRS marks in the first 24 hours postoperatively by comparing with SAB blocks, and no significant differences in sufentanil consumption and NRS scores in the 24–48 hour period compared to all three blocks. RIB and ESP blocks had a longer time-to-first postoperative analgesic demand and higher patient content by comparing with SAB blocks. Nevertheless, no great diversity was displayed in PACU duration, incidence of PONV, and all patients with postoperative complications for RIB, ESP, and SAB blocks.

RIB and ESP blocks had less sufentanil consumption and lower NRS marks at 24 hours by comparing with SAB blocks, whereas no significant diversity was observed in sufentanil consumption and NRS marks at 24–48 hours. We determined anatomically that the RIB block resulted in an almost complete sensory block of the hemothorax, such as T2–T9 dermatomes [11]. ESP blocks the dorsal and ventral branches of the thoracic spinal nerve, causing some degree of sympathetic blockade and thus providing better analgesia [15], whereas SAB targets the superficial nerves confined to the anterolateral wall, providing a hemithoracic analgesic approach without blocking the posterior main branch [18].

Finnerty et al. found that ESP had a higher-quality recovery, lower morbidity, and better analgesia at 24 hours after minimally invasive thoracic surgery compared to SAB [16]. Ekinci et al. noted that ultrasound-guided ESP may provide better pain control than SAB after VATS [21]. Elsabeeny et al. showed that ESP had significantly lower VAS scores in the postanesthesia care unit at 24 hours rest and that the SAB group had significantly higher cough VAS scores at 8 hours and 24 hours [22].

The findings of our study were similar to those of the two studies above. However, there is no clinical report on the analgesic effect of RIB versus SAB block or RIB and ESP block in VATS. This experiment compared the analgesic roles of RIB, ESP, and SAB block with each other in VATS at the same time, which provides a clinical reference value for the selection of more effective nerve block modality to finish postoperative analgesia in VATS patients, which can both decrease the pain of patients and the amount of analgesic drugs used for postoperative treatment. It has a facilitating effect on the recovery of postoperative patients.

We also found that RIB and ESP blocks resulted in a longer time-to-first postoperative analgesic demand and higher patient content compared to SAB blocks. The possible reason is that the analgesic role of the RIB and ESP blocks was stronger and longer. The RIB and ESP blocks in this trial required less sufentanil consumption and yielded lower NRS pain scores, resulting in higher patient satisfaction. Complications associated with this trial, such as postoperative pneumonia and pulmonary atelectasis, occurred less frequently. Two cases of postoperative pneumonia happened in the SAB block group, one case of postoperative pneumonia in the ESP block group, and one case of postoperative pneumonia in the RIB block group; however, all four patients were cured of pneumonia after postoperative treatment.

The expression levels of inflammatory factors including IL-1β and IL-6 were abnormal under the stimulation of factors such as lung injury after one-lung ventilation, surgical pain, and excessive intraoperative stress response [23]. In this experiment, one-lung ventilation in thoracic surgery and other factors predisposed the lung to ischemia-reperfusion injury and consequently to oxidative stress, lung injury, and release of inflammatory factors [24, 25]. Effective regional nerve block induced less oxidative stress during the postoperative period [26]. Some studies have explored the relationship between nerve block and inflammatory factors and found that nerve block blocking pain stimulation inhibited the increase of inflammatory factors in plasma [27, 28].

In our study, 24 hours after surgery, IL-1β and IL-6 inflammatory factor concentrations were lower in the RIB and ESP groups than those in the SAB group, but no significant diversities were observed at 24 hours before surgery and at 48 hours after surgery. That indicates that the influence of anesthesia, surgery, and other related factors easily lead to the release of inflammatory factors by the organism. Twenty-four hours after surgery, the ESP and RIB groups showed lower IL-1β and IL-6 than the SAB group, which may be because ESP and RIB blocked afferent pain stimulation to the injured site, enhanced intravenous analgesia and inhibited postoperative inflammation more effectively [29].

Our research has some limitations. First, the patient nerve block after general anesthesia was given, so the range of anesthesia cannot be evaluated very well. Second, the depth of anesthesia during maintaining general anesthesia was not monitored, which may have influenced the anesthetic dosage or impacted the patient's intraoperative knowledge. Moreover, intraoperative awareness was prevented with sevoflurane, and any intraoperative knowledge during the postoperative return visits was reported by none of the patients.

5. Conclusion

The dosage of sufentanil can be effectively reduced by ultrasound-directed rhomboid intercostal block and erector spinae plane block within 24 hours after VATS surgery, and pain can be relieved effectively within 24 hours by comparing with serratus plane block.