Comparison of Intercostal Nerve Block and Serratus Anterior Plane Block for Perioperative Pain Management and Impact on Chronic Pain in Thoracoscopic Surgery

Abstract

Objectives:

The intent of this study was to compare the analgesic efficacy of intercostal nerve block (ICNB) under direct thoracoscopic visualization and serratus anterior plane block (SAPB) with ultrasound guidance during thoracoscopic surgery’s perioperative period. Furthermore, it examined their impact on chronic pain and identifies potential risk factors associated with its development.

Materials and Methods:

In this prospective randomized controlled study, 74 thoracoscopic surgery patients were randomly assigned to ICNB or SAPB groups. Attending surgeons administered ICNB, while anesthesiologists performed SAPB, both using 20 mL of 0.5% ropivacaine. Primary outcomes included Visual Analog Scale (VAS) scores for resting and coughing pain at 6, 12, 24, and 48 hours postoperatively, perioperative opioid and NSAID consumption, and chronic pain incidence at 3 months postoperatively. Secondary outcomes aimed to identify independent risk factors for chronic pain.

Results:

The primary results reveal that the SAPB group exhibited significantly lower VAS scores than the ICNB group for postoperative coughing at 24 hours (P<0.001, 95% CI=0.5, 1) and for resting pain at 48 hours (P=0.001, 95% CI=0.2, 1). Conversely, the ICNB group demonstrated a reduced VAS score for resting pain at 6 hours compared with the SAPB group (P=0.014, 95% CI=−0.5, 0.5). SAPB group required significantly less intraoperative sulfentanil (P<0.001, 95% CI=2.5, 5), remifentanil (P=0.005, 95% CI=−0.4, −0.1), and flurbiprofen ester (P=0.003, 95% CI=0, 50) than ICNB group. Chronic pain incidence was similar (P=0.572, 95% CI=0.412, 1.279), with mild pain in both ICNB and SAPB groups. Secondary findings indicate that resting VAS score at 12 hours (OR=7.59, P=0.048, 95% CI=1.02, 56.46), chest tube duration (OR=3.35, P=0.029, 95% CI=1.13, 9.97), and surgical duration (OR=1.02, P=0.049, 95% CI=1.00, 1.03) were significant predictors of chronic pain occurrence.

Discussion:

ICNB and SAPB demonstrated comparable analgesic effects, with similar rates of chronic pain occurrence. Chronic pain independent risk factors included resting VAS score at 12 hours, chest tube duration, and surgical duration.

Video-assisted thoracoscopic surgery (VATS) is a minimally invasive, cost-effective, secure, and efficient approach for the treatment of lung tumors, offering fewer complications and faster recovery than thoracotomy.^1,2 Nevertheless, VATS patients frequently experience significant pain due to muscle and nerve trauma, chest tube irritation, inflammation, and ectopic neural activity, with up to 29% experiencing chronic pain 3 months postsurgery.^3,4 Inadequate pain management elevates complications and chronic pain risk.^5,6 Therefore, multimodal analgesic is crucial for VATS recovery.

Regional anesthesia is essential in multimodal analgesia, effectively alleviating postoperative pain, reducing opioids, and modulating inflammation.^7,8 Common techniques in thoracic surgery include thoracic epidural analgesia (TEA), thoracic paravertebral block (TPVB), erector spinae plane block, Pecs block, intercostal nerve block (ICNB), and serratus anterior plane block (SAPB).⁹ TEA is the gold standard for open chest procedures analgesia but has challenging and time-consuming placement and potential respiratory/circulatory depression.^10,11 TPVB offers comparable efficacy but risks of intrathecal injections, pneumothorax, bleeding, and hemodynamic fluctuations.^12,13 For minimally invasive VATS, prioritize approaches with minimal damage, fewer complications, enhanced safety, and simplified procedures.¹⁴

Both ICNB and SAPB offer simplicity, rapid execution, safety, and fewer complications, reducing opioids and enhancing postoperative recovery.^15,16 ICNB, typically administered by surgeons under direct thoracoscopic visualization before surgery concludes, provides unilateral, single-level analgesia but may require multipoint injections for optimal relief.¹⁷ ICNB provides effective pain relief within 6 hours postsurgery, declining afterward, and dissipating at 24 to 48 hours.^18,19 SAPB provides effective ipsilateral hemithorax analgesia with a single block, offering substantial relief for 12 to 14 hours postoperatively and significantly lowering pain scores within the initial 24 hours.^20,21 Neither ICNB nor SAPB affects sympathetic nervous system function, ensuring hemodynamic stability.²² Their puncture sites are distant from the pleura and central nervous system, minimizing associated complications.²³ Conducted under direct visualization or guided by ultrasound, both techniques minimize nerve injury and vascular puncture risks. In addition, they suit patients of varying positions, obesity, and coagulation profiles.²⁴ However, the comparative perioperative analgesic efficacy between traditional ICNB and the newer SAPB, their impacts on chronic pain, and associated risk factors remain unclear.

We hypothesize that utilizing ICNB and SAPB can effectively alleviate acute postoperative pain, thereby reducing the incidence of chronic pain. This study aimed to evaluate the efficacy and safety of ICNB versus SAPB in managing acute postoperative pain and to determine their long-term impact on the development of chronic pain. In addition, we attempted to identify risk factors associated with chronic pain and to develop a clinical predictive model to enhance pain management in VATS and promote personalized medicine approaches.

MATERIALS AND METHODS

Study Protocol and Patient Randomization

This prospective, randomized controlled study obtained approval from the Ethics Committee of the First Affiliated Hospital of China Medical University (2023-386), and it has been registered with the Chinese Clinical Trial Registry (Registration No: ChiCTR2300076230). Written informed consent was obtained from all participating patients.

The inclusion criteria were as follows: age between 16 and 80 years; patients scheduled for elective VATS; American Society of Anesthesiologists (ASA) physical status classification I-II. Exclusion criteria included: allergies to local anesthetics; severe obesity (body mass index >30 kg/m²); syncope, severe cardiopulmonary diseases, hepatic or renal disorders, chronic chest pain; opioid misuse or communication barriers; incomplete postoperative surveys regarding chronic pain. Patients were randomly assigned to either the ICNB group or the SAPB group using a computer-generated random number table. The randomization process was conducted in a blinded manner for both patients and researchers responsible for follow-up.

Nerve Blocks

In the ICNB group, attending surgeons performed a single-shot, multi-point ICNB after the completion of the VATS procedure. Under direct thoracoscopic visualization, a 22-G nerve block needle was carefully advanced into the intercostal bundle area, which is located below the intercostal muscles and above the parietal pleura. The needle was positioned at 3 specific sites: the surgical incision, the drainage tube insertion site, and one rib space above and below these points. Once the needle was correctly positioned, a total of 20 mL of 0.5% ropivacaine was evenly injected across the designated rib spaces. The injection was performed in a manner to ensure that the local anesthetic spread adequately while avoiding intravascular injection to minimize the risk of systemic toxicity. This multi-point approach was designed to provide comprehensive analgesia to the areas most affected by the surgical procedure and drainage placement.

In the SAPB group, after anesthesia induction and appropriate patient positioning, an anesthesiologist performed SAPB under ultrasound guidance. The ultrasound probe was placed parallel to the mid-axillary line at the level of T3-4 and moved bilaterally until the latissimus dorsi, serratus anterior muscle, intercostal muscles, ribs, and pleura were visualized. A 22-G nerve block needle was then advanced to the fascial plane between the latissimus dorsi and serratus anterior muscle (superficial SAPB) or between the serratus anterior and intercostal muscles (deep SAPB). After confirming the correct position with an injection of 1 mL of normal saline, 20 mL of 0.5% ropivacaine was slowly injected. Following injection, the injection site was gently massaged using gauze or the operator’s palm to ensure effective spreading of the local anesthetic along the fascial plane.

Perioperative Management

Upon entering the operating room, general anesthesia induction was initiated with intravenous administration of propofol (2.0 mg/kg), sufentanil (0.4 μg/kg), cisatracurium (10 mg), and dexamethasone (5 mg). Throat surface anesthesia was performed using 3 mL of 2% lidocaine, followed by endotracheal intubation with a double-lumen tube. Anesthesia maintenance involved propofol (4 to 5 mg/kg/h), sevoflurane (0.7% to 1.5%), and remifentanil (0.1 to 0.2 µg/kg/min), aiming to maintain the bispectral index between 40 and 60. Hypotension was treated with ephedrine or deoxyepinephrine, while bradycardia was managed using atropine to maintain invasive blood pressure and heart rate within ±20% of baseline values. Additional doses of sufentanil and cisatracurium were determined by the responsible anesthesiologist to achieve adequate analgesia and muscle relaxation. Thirty minutes before the conclusion of the surgery, flurbiprofen ester (50 mg or 100 mg) and tropisetron (5 mg) were administered intravenously. Patients requiring additional postoperative analgesic received dezocine intramuscular injections in the ward as needed.

Study Outcomes and Measurement Parameters

The primary outcomes of the study include Visual Analog Scale (VAS) scores at rest and during coughing at 6, 12, 24, and 48 hours postoperatively, perioperative consumption of opioids and NSAIDs, and the incidence of chronic pain at 3 months postoperatively. The secondary outcome focused on identifying independent risk factors for the development of chronic pain.

Postoperative pain levels were assessed utilizing a VAS ranging from 0 to 10 points. Patients received instructions on how to use the VAS ruler to rate their pain before the surgery. In addition, adverse reactions such as nausea, vomiting, and dizziness were monitored.

At 3 months postoperatively, patients were contacted for telephone follow-up, and the occurrence of chronic pain was investigated using the Brief Pain Inventory.⁴⁹ Brief Pain Inventory assessments encompassed pain intensity (evaluated using the Numeric Rating Scale, ranging from 0 for no pain to 10 for the most intense pain, with scores categorized as mild [1 to 3], moderate [4 to 6], and severe [≥7]). Moreover, the assessments included the examination of pain characteristics, such as stabbing pain and dull pain, the identification of pain location, and the evaluation of pain’s impact of pain on daily life functions (ranging from 0 for no impact to 10 for extremely impactful).

Sample Size

Based on preliminary experimental data, the projected average resting VAS score at 12 hours was 3.25 for the ICNB group and 2.75 for the SAPB group, with an SD of 0.707. To achieve a significance level of 0.05 and a test power of 80%, a minimum of 33 patients per group was calculated using a 1-way analysis of variance (ANOVA) power analysis. Assuming a dropout rate of 10%, at least 37 patients per group were required. Power calculations were conducted using PASS (NCSS LLC, Kaysville, UT).

Patient Characteristics

A total of 80 patients were initially enrolled in this study, but 6 patients were excluded: 2 patients underwent conversion to thoracotomy, 1 patient had a second open thoracotomy on the following day, and 3 patients were lost to follow-up. Eventually, 74 patients completed the study, with 37 patients in each group (Fig. 1). Baseline clinical and demographic characteristics of the 2 groups are presented in Table 1. There were no statistically significant differences between the 2 groups in terms of age, sex, body mass index, smoking and alcohol history, surgical history, underlying diseases, or ASA classification.

FIGURE 1.

Flow chart of the study. ICNB indicates intercostal nerve block; SAPB, serratus anterior plane block; VATS, video-assisted thoracoscopic surgery.

TABLE 1.

Baseline Clinical and Demographic Characteristics

	Group ICNB (n=37)	Group SAPB (n=37)	95% CI	P
Age, mean±SD (y)	58.27±10.38	59.62±9.98	−3.366, 6.068	0.570
Female, n (%)	22 (59.46)	23 (62.16)	0.542, 1.472	0.812
BMI, mean±SD (kg/m2)	25.77±2.99	25.99±3.21	−1.218, 1.655	0.762
Smoke, n (%)	16 (43.24)	16 (43.24)	0.625, 1.600	1.000
Drink, n (%)	8 (21.62)	7 (18.92)	0.653, 2.139	0.772
Surgical history, n (%)	22 (59.46)	20 (54.05)	0.772, 2.015	0.639
Hypertension, n (%)	14 (37.84)	12 (32.43)	0.78, 2.08	0.626
Diabetes, n (%)	8 (21.62)	8 (21.62)	0.569, 1.757	1.000
Coronary heart disease, n (%)	6 (16.22)	6 (16.22)	0.353, 2.832	1.000
ASA score, n (%)			0.464, 1.285	0.613
1	10 (27.03)	12 (32.43)
2	27 (72.97)	25 (67.57)

ASA indicates American Society of Anesthesiologists; BMI, body mass index; Group ICNB, group intercostal nerve block; Group SAPB, group serratus anterior plane block.

Statistical Analysis

Statistical analysis was conducted using the SPSS software package (IBM SPSS version 26.0, IBM Corp., Armonk, NY). Continuous variables were presented as mean±SD or median with interquartile range depending on the data distribution, while categorical variables were presented as proportions or percentages. Between-group comparisons of continuous variables were performed using independent sample t tests or Mann-Whitney U tests, while categorical variables were compared using χ² tests or Fisher exact probability test as appropriate. Mann-Whitney U tests were employed to evaluate between-group differences for ordinal variables. A significance level of P<0.05 was considered statistically significant.

Multivariate analysis was conducted using R software (version 3.4.1, R Foundation, Vienna, Austria), utilizing the “rms” package to establish a logistic regression model. Variables with P<0.1 from the comparison between the chronic pain group and the nonchronic pain group were included as independent variables, with the presence of chronic pain as the dependent variable. Stepwise regression, performed using the step function, was used to eliminate multicollinearity and identify the optimal combination of independent variables. These variables were then analyzed to identify independent risk factors for chronic pain and construct a predictive model. The model’s accuracy was evaluated using ROC curves, calibration curves, and decision curve analysis (DCA). The “DynNom” package was employed to visualize the model results as a nomogram.

RESULTS

Postoperative Pain Scores and Perioperative Analgesic Consumption

Postoperative pain scores demonstrated differences between the 2 groups at various time points: 6 hours at rest (ICNB group: 3 [3, 3] vs. SAPB group: 3 [3, 4], P=0.014, 95% CI=−0.5, 0.5), 48 hours at rest (ICNB group: 1 [0, 1] vs. SAPB group: 0 [0, 0.5], P=0.001, 95% CI=0.2, 1), and 24 hours on coughing (ICNB group: 3 [2.5, 3] vs. SAPB group: 2 [2, 2.5], P<0.001, 95% CI=0.5, 1) (Table 2). The SAPB group displayed lower pain scores at 24 hours of coughing and 48 hours at rest, while the ICNB group demonstrated lower pain scores at 6 hours of rest. No significant differences in pain scores were observed between the 2 groups at other time points (Fig. 2A, B). The SAPB group had lower intraoperative doses of sufentanil (25 [25, 27.5] vs. 30 [27.5, 30], P<0.001, 95% CI=2.5, 5), remifentanil (0.5 [0.3, 0.78] vs. 0.75 [0.6, 0.8], P=0.005, 95% CI=−0.4, −0.1), and flurbiprofen (50 [50] vs. 50 [50, 100], P=0.003, 95% CI=0, 50) compared with the ICNB group. However, there was no significant difference in the postoperative dose of dezocine between the 2 groups (Table 3). Neither of the groups experienced nausea or vomiting.

TABLE 2.

Postoperative Video-assisted Thoracoscopic Surgery Scores at Rest and on Coughing

	Group ICNB (n=37)	Group SAPB (n=37)	95% CI	P
Resting pain score at 6 h, median (Q1, Q3)	3 (3, 3)	3 (3, 4)	−0.5, 0.5	0.014*
Resting pain score at 12 h, median (Q1, Q3)	3 (2, 3)	3 (2.5, 3)	−0.5, 0.5	0.513
Resting pain score at 24 h, median (Q1, Q3)	2 (1, 2)	1 (1, 2)	−1, 1	0.094
Resting pain score at 48 h, median (Q1, Q3)	1 (0, 1)	0 (0, 0.5)	0.2, 1	0.001*
Coughing pain score at 6 h, median (Q1, Q3)	4 (3.5, 4)	4 (3.5, 4)	0, 0	1.000
Coughing pain score at 12 h, median (Q1, Q3)	3 (3, 3)	3 (2.5, 3.5)	−0.5, 0.5	0.152
Coughing pain score at 24 h, median (Q1, Q3)	3 (2.5, 3)	2 (2, 2.5)	0.5, 1	0.000*
Coughing pain score at 48 h, median (Q1, Q3)	2 (1, 2)	2 (1.5, 2)	−0.5, 0.5	0.212

Group ICNB indicates group intercostal nerve block; Group SAPB, group serratus anterior plane block.

^* P<0.05.

FIGURE 2.

(A) Visual Analogue Scale at rest. Data are expressed as median (horizontal bar), interquartile range (box), and maximum and minimum values (whiskers). *P<0.05 when ICNB compared with SAPB at 6 hours. **P<0.01 when ICNB compared with SAPB at 48 hours. (B) Visual Analogue Scale on coughing. Data are expressed as median (horizontal bar), interquartile range (box) and the maximum and minimum values (whiskers). **P<0.01 when ICNB compared with SAPB at 24 hours. (C) Receiver operating characteristic (ROC) curve of the diagnostic nomogram model (chronic pain model). AUC >0.75 indicates good discriminative ability. (D) Hosmer-Lemeshow test. P>0.05 indicates good calibration. (E) Decision curve analysis (DCA). The model curve was higher than the 2 reference lines indicating that the model has value and patients can benefit from it. (F) ROC curve after excluding the resting VAS score at 12 hours. (G) ROC curve after excluding the chest tube duration. (H) ROC curve after excluding surgical duration. The decrease in AUC value indicates that the model before exclusion is better. (I) Dynamic nomogram. The black line shows the risk of chronic pain with the shortest duration of chest tube insertion and surgery and the lowest resting VAS score at 12 hours. The blue line shows the risk of chronic pain with the longest chest tube insertion time, the shortest surgical duration, and the lowest resting VAS score at 12 hours. The red line shows the risk of chronic pain with the longest surgical duration, shortest chest tube insertion time, and lowest resting VAS score at 12 hours. The green line shows the risk of chronic pain with the highest resting VAS score at 12 hours, the shortest duration of chest tube insertion and surgery. The yellow line shows the risk of chronic pain with the longest duration of chest tube insertion and surgery, and the highest resting VAS score at 12 hours. AUC indicates area under the curve; ICNB, intercostal nerve block; SAPB, serratus anterior plane block; VATS, video-assisted thoracoscopic surgery.

TABLE 3.

Perioperative Analgesics Consumption

	Group ICNB (n=37)	Group SAPB (n=37)	95% CI	P
Sufentanil dose during surgery, median (Q1, Q3) (μg)	30 (27.5, 30)	25 (25, 27.5)	2.5, 5	0.000*
Remifentanil dose during surgery, median (Q1, Q3) (mg)	0.75 (0.6, 0.8)	0.5 (0.3, 0.78)	−0.4, −0.1	0.005*
Flurbiprofen Axetil dose during surgery, median (Q1, Q3) (mg)	50 (50, 100)	50 (50, 50)	0, 50	0.003*
Postoperative dezocine dose, median (Q1, Q3) (mg)	15 (2.5, 30)	10 (5, 35)	−10, 10	0.878

ICNB indicates group intercostal nerve block; SAPB, group serratus anterior plane block.

^* P<0.05.

Incidence of Chronic Pain

In the ICNB group, 7 patients reported experiencing chronic pain, while in the SAPB group, 9 patients reported experiencing chronic pain. The incidence of chronic pain was similar between the 2 groups (18.92% [7/37] vs. 24.32% [9/37], P=0.572, 95% CI=0.412, 1.279) (Table 3). Of the total patients with chronic pain (16 in total), the pain intensity was classified as mild, with an average pain score of 1 (1, 2). Among these patients, 11 individuals experienced pain at the surgical incision and chest tube insertion sites, while the remaining 5 patients had intrathoracic pain. Seven patients described the pain as sharp or stabbing, while the other 9 patients described it as dull or throbbing. Regarding the impact of chronic pain on patients (including daily activities, mood, ambulation ability, work, relationships with others, sleep, and interest in life, totaling 70 points), 11 patients reported no impact (0 points), while the remaining 5 affected patients scored 5.6±1.14 points.

Multivariate Analysis of Chronic Pain and Construction of a Clinical Prediction Model

Given the comparable incidence of chronic pain between the ICNB and SAPB groups, a combination of patients experiencing chronic pain from both groups was made for further analysis. The results revealed statistically significant differences in the prevalence of diabetes (ICNB group: 7 [43.75] vs. SAPB group: 9 [15.52], P=0.037, 95% CI=2.23, 8.02), duration of surgery (ICNB group: 91 [67.25, 133.5] vs. SAPB group: 69 [53, 103.5], P=0.049, 95% CI=1.2, 41.3), resting VAS score at 12 hours (ICNB group: 3 [3, 3] vs. SAPB group: 3 [2, 3], P=0.006, 95% CI=0, 1), coughing VAS score at 6 hours (ICNB group: 4 [4, 4] vs. SAPB group: 4 [3, 4], P=0.041, 95% CI=0, 1), and coughing VAS score at 48 hours ( ICNB group:2 [2, 2] vs. SAPB group: 2 [1, 2], P=0.016, 95% CI=0, 1).

Patients who developed chronic pain had longer surgery duration, higher resting VAS score at 12 hours, higher coughing VAS score at 6 hours, and higher coughing VAS score at 48 hours. Patients with a history of diabetes were more likely to develop chronic pain (Table 4). No statistically significant difference in other indicators (Supplemental Table 2, Supplemental Digital Content 1, http://links.lww.com/CJP/B161).

TABLE 4.

Data for Patients With and Without Chronic Pain

	Patients with chronic pain (n=16)	Patients without chronic pain (n=58)	95% CI	P
Diabetes, n (%)	7 (43.75)	9 (15.52)	2.23, 8.02	0.037*
Chest tube drainage, median (Q1, Q3) (d)	3 (2, 3)	3 (2, 3)	−1, 1	0.061
Operation duration, median (Q1, Q3) (min)	91 (67.25, 133.5)	69 (53, 103.5)	1.2, 41.3	0.049*
Sufentanil dose during surgery, median (Q1, Q3) (μg)	25 (25, 30)	30 (25, 30)	−3.5, 8.5	0.269
Remifentanil dose during surgery, median (Q1, Q3) (mg)	0.73 (0.46, 1.00)	0.6 (0.4, 0.8)	−0.1, 0.3	0.359
Flurbiprofen Axetil dose during surgery, median (Q1, Q3) (mg)	50 (50, 50)	50 (50, 100)	−50, 0	0.098
Postoperative dezocine dose,median (Q1, Q3) (mg)	22.5 (10, 37.5)	10 (0, 30)	−5, 20	0.070
Resting pain score at 6 h, median (Q1, Q3)	3 (3, 3.75)	3 (3, 3)	−0.25, 0.5	0.829
Resting pain score at 12 h, median (Q1, Q3)	3 (3, 3)	3 (2, 3)	0, 1	0.006*
Resting pain score at 24 h, median (Q1, Q3)	2 (1, 2)	1.5 (1, 2)	−0.5, 1	0.100
Resting pain score at 48 h, median (Q1, Q3)	1 (0, 1)	0 (0, 1)	−0.5, 1	0.171
Coughing pain score at 6 h, median (Q1, Q3)	4 (4, 4)	4 (3, 4)	0, 1	0.041*
Coughing pain score at 12 h, median (Q1, Q3)	3 (3, 3.75)	3 (3, 3)	−0.25, 0.5	0.560
Coughing pain score at 24 h, median (Q1, Q3)	3 (2, 3)	2 (2, 3)	−1, 1	0.575
Coughing pain score at 48 h, median (Q1, Q3)	2 (2, 2)	2 (1, 2)	0, 1	0.016*
Nerve blocks, n (%)			0.412, 1.279	0.572
ICNB	7 (43.75)	30 (51.72)
SAPB	9 (56.25)	28 (48.28)

ICNB indicates intercostal nerve block; SAPB, serratus anterior plane block.

^* P<0.05.

Based on the univariate analysis, we included variables with P<0.1 (diabetes, P=0.037; chest tube duration, P=0.061; surgery duration, P=0.049; intraoperative flurbiprofen usage, P=0.098; postoperative dezocine usage, P=0.070; intraoperative atropine dosage, P=0.057; resting VAS score at 12 h, P=0.006; coughing VAS score at 6 h, P=0.041; and coughing VAS score at 48 h, P=0.016) as independent variables, and the occurrence of chronic pain as the dependent variable, for inclusion in the logistic regression analysis for subsequent multivariate analysis. Stepwise regression using the step function was employed to eliminate multicollinearity and obtain the optimal combination of independent variables. The final variables included in the analysis were resting VAS score at 12 hours, chest tube duration, diabetes, surgery duration, and intraoperative flurbiprofen usage. The multivariate logistic regression analysis indicated that resting VAS score at 12 hours (OR=7.59, P=0.048, 95% CI=1.02, 56.46), chest tube duration (OR=3.35, P=0.029, 95% CI=1.13, 9.97), and surgery duration (OR=1.02, P=0.049, 95% CI=1.00, 1.03) significantly influenced the occurrence of chronic pain.

Based on these 3 variables, we constructed a clinical prediction model and validated the diagnostic model using discrimination (Fig. 2C, F, G, H), calibration (Fig. 2D), and DCA (Fig. 2E). The model was found to be reliable after verification, and a nomogram was constructed to visualize the predictive model (Fig. 2I). Notably, the graph demonstrates that a lower risk of developing chronic pain is associated with shorter chest tube and surgery durations, coupled with lower resting VAS score at 12 hours. Conversely, higher risks of chronic pain were observed with longer chest tube and surgery durations, alongside elevated resting VAS score at 12 hours. Furthermore, the resting VAS score at 12 hours exhibited the most pronounced impact on chronic pain occurrence, followed by chest tube duration, while surgery duration had the least impact. The nomogram facilitates personalized, precise, and digital risk prediction for chronic pain, providing valuable guidance for informed clinical decision-making. The information pertaining to the modeling process of the clinical prediction model has been relocated to the Supplemental Materials (Supplemental Digital Content 2, http://links.lww.com/CJP/B162) of the manuscript.

Surgical and Anesthetic Information

The types of thoracoscopic surgeries (including wedge resection, segmentectomy, and lobectomy), tumor staging, surgical duration, and PACU stay duration are summarized in Supplemental Table 3 (Supplemental Digital Content 3, http://links.lww.com/CJP/B163). No statistically significant differences were observed between the ICNB and SAPB groups. Both groups had an average chest tube duration of 3 days postoperatively, and most patients were hospitalized for 4 days after surgery. The nerve block duration in the SAPB group was shorter than that in the ICNB group (3.5 [3.00, 3.75] min vs. 4 [4, 4] min, P<0.001, 95% CI=[0.25, 1.00]) (Supplemental Table 3, Supplemental Digital Content 3, http://links.lww.com/CJP/B163). There were no statistically significant differences in the occurrences of intraoperative hypotension and bradycardia episodes, or in the usage of ephedrine, atropine, and deoxyepinephrine between the 2 groups.

DISCUSSION

ICNB and SAPB are effective and widely used for perioperative analgesia in thoracic surgery.^25–27 ICNB provides superior analgesia compared with systemic opioids, similar to TEA, and slightly less than PVB.¹⁹ SAPB offers better analgesia than systemic opioids and local infiltration anesthesia, with pain relief comparable to TEA and PVB.^28–31 Therefore, our study aimed to compare the effectiveness of ICNB and SAPB in postoperative pain management. Our findings revealed that both approaches exhibited similar acute postoperative pain control. ICNB provided better early pain relief, evidenced by lower resting VAS scores at 6 hours postoperatively. However, the clinical significance of pain scores at 6 hours, despite their statistical significance, remains limited. Conversely, SAPB demonstrated superior pain relief over an extended period with lower coughing VAS scores at 24 hours and resting VAS scores at 48 hours postoperatively. SAPB group had lower intraoperative consumption of sufentanil, remifentanil, and flurbiprofen than ICNB group, with no significant difference in postoperative analgesic consumption between the 2 groups. In line with our studies, Kim et al¹⁴ found that ICNB and SAPB provided similar analgesic effects, with lower NSAID use in SAPB. Lee et al³² reported no Numeric Rating Scale score differences within 24 hours postoperatively and similar fentanyl and ketorolac usage within 48 hours between ICNB and SAPB. Baldinelli et al³³ reported nonsignificant lower VAS scores and morphine use with SAPB versus ICNB. Zhao et al³⁴ found lower intraoperative sufentanil use and 24-hour coughing pain scores favoring SAPB. Collectively, ICNB and SAPB are effective alternatives to TEA and TPVB for analgesia.

Post-VATS pain results from incisions, muscle tearing, rib separation, pleura injury, and chest tube irritation.^35,36 Intercostal nerves innervate intercostal muscles and parietal pleura, and lateral cutaneous branches of it innervate the skin. The long thoracic nerve innervates the serratus anterior muscle.³⁷ Chest tubes irritate both parietal pleura and serratus anterior muscle. SAPB can block the long thoracic nerve and lateral cutaneous branches of intercostal nerves.³⁸ Therefore, ICNB and SAPB, blocking different VATS pain factors, may yield similar clinical outcomes.

In our study, the SAPB group required significantly fewer analgesics than the ICNB group, possibly due to the preemptive analgesic effect of preoperative SAPB, blocking nociceptive stimuli transmission during surgery and reducing intraoperative analgesic needs. In contrast, ICNB is administered late in surgery and does not directly affect intraoperative analgesia. ICNB group had significantly lower resting VAS scores at 6 hours postoperatively but significantly higher coughing VAS scores at 24 hours and higher resting VAS scores at 48 hours, with shorter analgesia duration than SAPB. These differences may be attributed to the superior short-term postoperative analgesic effect of ICNB, administered before surgery completion. However, ICNB administration involved repositioning patients to a supine position shortly after, and a shorter duration in the lateral decubitus position may have resulted in suboptimal local anesthetic dispersion, leading to slightly reduced analgesic effects and shorter duration. Conversely, the SAPB group maintained a lateral decubitus position throughout, facilitating optimal local anesthetic dispersion. Furthermore, SAPB had a shorter performing time than ICNB, as it involves a single fascial plane blockade in one intercostal space, while ICNB requires multiple point blockades, potentially prolonging the procedure and increasing the risk of secondary injuries.

The International Association for the Study of Pain (IASP) defines “chronic postoperative pain” as pain persisting for at least 3 months postoperatively.³⁹ Our study used a multimodal analgesic approach, including opioids, regional blocks, and NSAIDs, to effectively control acute pain after VATS surgery. At 3 months postsurgery, chronic pain incidence was 21.6%. Both ICNB and SAPB effectively managed acute postoperative pain, with no statistically significant difference in chronic pain incidence. Similar to Fletcher et al,⁴⁰ chronic pain patients had higher resting VAS scores at 12 hours, coughing VAS scores at 6 and 48 hours, indicating that elevated acute pain scores may predict chronic pain development. Patients with chronic pain also underwent longer surgical procedures. Our findings are in line with Chen et al⁴¹ and Clephas et al⁴² who reported an increased risk of chronic pain with prolonged surgical durations. Furthermore, consistent with Wang et al's⁴³ findings, our results indicated that patients with a history of diabetes were more susceptible to the development of chronic pain, highlighting diabetes as a significant risk factor. During multifactorial analysis, factors with P<0.1 were selected to avoid omitting essential factors. These factors included diabetes, chest tube duration, surgical duration, intraoperative flurbiprofen ester dosage, postoperative dezocine dosage, intraoperative atropine dosage, resting VAS score at 12 hours, coughing VAS score at 6 hours, and coughing VAS score at 48 hours. The model’s akaike information criterion was initially 70.11, by performing stepwise regression and removing multicollinearity among independent variables, it decreased to 64.72. Subsequently, multivariate logistic regression analysis on the remaining 5 variables showed that resting VAS score at 12 hours and surgical duration significantly influenced chronic pain occurrence consistent with univariate analysis. Multivariate analysis also revealed the critical importance of chest tube duration in the development of chronic pain. Discrepancies between the univariate and multifactorial analysis results might stem from collinearity among variables during univariate analysis, potentially leading to certain factors being mistakenly identified as influential. In addition, the true effects of certain factors might be obscured by the influence of other confounding variables. Conducting multifactorial analysis helps to unveil the independent impact of specific factors on the outcome event by mitigating the effects of other variables. Consistent with our findings, Mongardon et al⁴⁴ discovered an increased risk of chronic pain associated with longer chest tube duration after surgery, and Gupta et al⁴⁵ proposed that early removal of chest drainage tubes could prevent the onset of postoperative chronic pain.

Based on the results of the multifactorial analysis, we constructed a clinical prediction model utilizing chest tube duration, resting VAS score at 12 hours, and surgical duration. The validation of the model encompassed discrimination, calibration, and clinical DCA, demonstrating its effectiveness. By creating a nomogram to visualize the prediction model, we transformed the results into a simplified graphical format, enhancing readability and facilitating the assessment of patient’s conditions and the prediction of the risk of developing chronic pain. The nomogram clearly indicates that resting VAS score at 12 hours exerts the greatest significant influence over the incidence of chronic pain, followed by chest tube duration, with surgical duration exerting a relatively minor impact. This might be attributed to the fact that resting VAS score at 12 hours reflects postoperative acute pain control, with previous studies indicating a transition from acute to chronic pain postoperatively.⁴⁶ Insertion of a chest tube triggers stimulation of the pleura and serratus anterior muscle, substantially contributing to postoperative pain after thoracoscopic surgery. Refai et al⁴⁷ observed a 40% decrease in pain scores within the initial second after chest tube removal in patients undergoing lung resection, accompanied by a 13% increase in forced expiratory volume. In addition, as surgical duration increases, the extent of tissue trauma also escalates, and intraoperative tissue damage plays a decisive role in the development of chronic pain. Research has highlighted that acute surgical trauma can induce intense pain and hyperalgesia, which gradually resolves as the wound heals. In cases where wound healing is inadequate, chronic inflammatory responses may persist at the surgical injury site, culminating in the onset of chronic postsurgical pain.⁴⁸ Therefore, effective control of resting VAS score at 12 hours, chest tube duration, and surgical duration is crucial in preventing the occurrence of chronic pain. Using the prediction model we developed, it becomes possible to predict the risk of chronic pain based on specific clinical information, enabling personalized and precise perioperative pain management to reduce the occurrence of chronic pain and improve postoperative quality of life for patients.

Several limitations were identified in our study. Firstly, the evaluation of the sensory range and the rate of incomplete blockade for SAPB was hindered by the timing of its administration after the induction of general anesthesia. This restriction precluded the accurate assessment of its efficacy. Secondly, the study patient were recruited by different surgeons, introducing uncontrollable variations due to variations in surgical technique and approach. Lastly, during surgery, slight subcutaneous edema was observed when the surgeon incised the skin and subcutaneous tissues of patients in the SAPB group, suggesting the possibility of local anesthetic loss or diffusion.

In addition, in this randomized trial, patients were double-blinded, but anesthesiologists and surgeons were not, potentially introducing bias as their awareness of interventions could influence pain management and scores. To mitigate this, independent evaluators conducted pain assessments. Despite the intention-to-treat principle, we excluded 4 patients who underwent thoracotomy or additional surgeries due to procedural deviations and confounding variables. Three lost-to-follow-up cases resulted in missing data, but data imputation could introduce bias. Thus, excluding these cases maintains data integrity and reliability.

In conclusion, our prospective study reveals that both ICNB and SAPB have comparable effects on the control of acute postoperative pain, with similar rates of chronic pain incidence. Resting VAS score at 12 hours, chest tube duration, and surgical duration were identified as independent risk factors for the occurrence of chronic pain.

Supplementary Material

ajp-40-691-s001.docx ^{(18.3KB, docx)}

ajp-40-691-s002.docx ^{(17.1KB, docx)}

ajp-40-691-s003.docx ^{(17.2KB, docx)}