Transcutaneous Electrical Acupoint Stimulation to Prevent Ipsilateral Shoulder Pain After Video-Assisted Thoracoscopic Surgery: A Multicenter Randomized Controlled Trial Protocol

Abstract

Background

Ipsilateral shoulder pain (ISP) after video-assisted thoracoscopic (VATS) surgery is common, distinct from incisional pain, and frequently overlooked in clinical practice. Transcutaneous electrical acupoint stimulation (TEAS) is a non-invasive, safe non-pharmacological analgesic modality. This trial protocol aims to evaluate the potential preventive effect of TEAS on ISP after VATS surgery.

Patients and Methods

We will conduct a multicenter, single-blind randomized trial of 216 patients undergoing unilateral VATS surgery. Patients will be randomized 1:1 to receive either TEAS or sham stimulation. The TEAS group will receive two 30-minute sessions at acupoints Hegu (LI4), Neiguan (PC6), Jianliao (SJ14), and Jianyu (LI15) on the evening before surgery and before anesthesia induction on the day of surgery. The sham stimulation group will receive sensory-matched sham stimulation. The primary outcome is the incidence of ISP during shoulder movement at 24 hours postoperatively. Pain intensity will be assessed using the verbal rating scale (VRS), and ISP is defined as a VRS score ≥ 1. Secondary outcomes are cumulative opioid consumption within 24 hours postoperatively and postoperative nausea and vomiting at 24 hours. Other outcomes include shoulder pain during movement and at rest at 48 and 72 hours, opioid consumption at other time intervals, postoperative quality of recovery assessed with the 15-item Quality of Recovery scale (QoR-15), time to first flatus, and nausea and vomiting at different time points.

Discussion

We hypothesize that TEAS reduces ISP incidence, opioid consumption, and improves postoperative recovery after VATS surgery. The findings of this trial will provide further evidence-based support for the prevention and management of perioperative ISP after VATS surgery, as well as a reference for the clinical application of non-pharmacological analgesic strategies.

Trial Registration

ClinicalTrials.gov, NCT07494591.

Introduction

Ipsilateral shoulder pain (ISP) after VATS surgery is common, distinct from incisional pain, and frequently overlooked clinically. Its reported incidence ranges from 21% to 97%.¹ ISP typically begins within the first postoperative hour as dull, movement-exacerbated pain and persists 3–4 days.² Intraoperative pleural, diaphragmatic, or phrenic nerve injury and patient positioning contribute to ISP.^3,4 In a small subset of patients, ISP may progress to chronic pain.²

ISP represents referred pain from diaphragmatic and mediastinal pleural irritation transmitted via the phrenic nerve (C3–C5).^5,6 Because phrenic and supraclavicular nerves (C3–C4) converge at the cervical spinal cord, diaphragmatic irritation manifests as ipsilateral shoulder pain. This explains why thoracic epidural analgesia fails to relieve ISP: it controls somatic incisional pain but not visceral-referred pain. Conversely, phrenic nerve block reduces ISP without affecting incisional pain. Intraoperative shoulder positioning and musculoskeletal strain contribute an additional somatic component, distinguishing ISP from incisional and chest wall pain.^7,8

Phrenic nerve block reduces ISP but impairs diaphragmatic function and increases postoperative respiratory depression risk.^9,10 Modifying arm position is simple but lacks proven efficacy.³

TEAS reduces postoperative pain and opioid consumption across surgical settings. In patients undergoing VATS, TEAS combined with general anesthesia reduced VAS scores at 6, 24, and 48 hours postoperatively and sufentanil consumption.¹¹ Meta-analysis confirms reduced VAS scores after minimally invasive surgery.¹² TEAS also improves recovery quality and reduces anesthesia-related adverse effects in ambulatory surger.¹³

Acupoint stimulation is a well-established non-pharmacological analgesic technique.¹⁴ TEAS, a non-invasive derivative of acupuncture, offers safety, simplicity, and high patient acceptability.^15,16 TEAS reduces postoperative pain via endogenous analgesic pathways and suppressed nociceptive transmission.^17,18 In shoulder pain (periarthritis, cervical spondylosis), meridian-based TEAS relieves periscapular pain and improves range of motion, with efficacy demonstrated in randomized trials.^19–23

According to meridian theory, ISP represents qi stagnation with meridian obstruction. Surgical trauma impairs meridian flow, resulting in obstructive pain.^11,24 We selected four acupoints based on their anatomical location and known analgesic effects: Hegu (LI4)—effective for head, face, and trunk pain;²⁵ Neiguan (PC6)—indicated for chest discomfort;²⁶ Jianliao (SJ14) and Jianyu (LI15)—both located in the shoulder region and effective for shoulder pain.²⁷ These acupoints target local meridians and visceral functions relevant to ISP pathophysiology, supporting their use in TEAS intervention.

TEAS targets multiple pathways underlying ISP. First, 2/100 Hz stimulation activates endogenous opioids—low-frequency promotes β-endorphin and enkephalin (μ and δ receptors), high-frequency triggers dynorphin (κ receptors)—suppressing spinal nociceptive transmission.^28,29 Second, TEAS enhances descending pain inhibition by increasing spinal serotonin and norepinephrine, thereby suppressing dorsal horn excitability. This is particularly relevant to ISP: phrenic-nerve referred pain involves cervical visceral–somatic convergence, which descending inhibition can modulate.^30,31 Third, TEAS reduces proinflammatory cytokines (IL-6, TNF-α) that sensitize the phrenic nerve and diaphragmatic pleura.^32,33 These mechanisms enable TEAS to reduce both peripheral sensitization and central pain amplification in ISP.

This trial protocol aims to evaluate whether preoperative TEAS can reduce the incidence of early postoperative ISP in patients undergoing video-assisted thoracoscopic lung surgery, and to explore its potential opioid-sparing effect.

Methods

Study Design

We designed a multicenter, randomized controlled trial to evaluate TEAS efficacy in preventing ipsilateral shoulder pain after unilateral VATS surgery. Shanghai Pulmonary Hospital is the coordinating center. Ethical approval was obtained from the Shanghai Pulmonary Hospital Medical Ethics Committee on June 19, 2025 (approval #L25-604). The trial was registered with ClinicalTrials.gov (NCT07494591) on March 27, 2026. Participating centers include Fudan University Shanghai Cancer Center and Shanghai East Hospital. All participants will provide written informed consent prior to study enrollment. The study will be conducted in compliance with the Declaration of Helsinki. The preparation and reporting of this study protocol comply with the Standards for Reporting Interventions in Clinical Trials of Acupuncture (STRICTA) and the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) statement.

Patient and Public Involvement (PPI)

In accordance with the SPIRIT 2025 statement, patient and public involvement was incorporated into the design of this trial. Three former patients who had undergone video-assisted thoracoscopic lung surgery were consulted during protocol development. Their feedback informed the selection of the primary outcome (shoulder pain during movement, which they identified as the most distressing postoperative symptom), corresponding to the period of maximum shoulder discomfort), and the wording of the participant information sheet. No patients or public representatives were involved in data collection, analysis, or interpretation. The results of this trial will be disseminated to participants via a plain-language summary upon study completion.

Patients

Eligible patients for this study are those scheduled to undergo unilateral VATS surgery, aged 18 years or older regardless of sex, with an American Society of Anesthesiologists (ASA) physical status classification of grade I to III, and without severe cardiopulmonary insufficiency or other major systemic diseases; patients will be excluded if they have pre-existing shoulder pain or dysfunction prior to surgery, severe mental illness or cognitive impairment, are planned for bilateral VATS surgery, or present with any other condition deemed inappropriate by the investigators, with the corresponding reasons for exclusion documented. The study flow diagram is shown in Figure 1.

Figure 1.

Study flow diagram. Eligible patients undergoing unilateral video-assisted thoracoscopic lung surgery will be screened and randomized 1:1 to receive either active TEAS or sham TEAS. Two 30-minute sessions will be administered: one on the evening before surgery (Day −1) and one before anesthesia induction (Day 0). Postoperative outcome assessments, including ISP incidence, VRS pain scores, opioid consumption, and quality of recovery, will be performed at 24, 48, and 72 hours after surgery.

Randomization and Blinding

An independent statistician generated a computerized randomization sequence using stratified block randomization by study site. Allocations were placed in sequentially numbered, opaque, sealed envelopes kept by non-study assessors to ensure allocation concealment.

Independent operators will administer interventions on the evening before surgery and before anesthesia induction on the day of surgery. Both groups will receive identical treatment procedures: standardized acupoint electrode placement, skin preparation, device appearance. The sham group will receive an identical stimulation to that of the TEAS group for the first 30 seconds to produce tingling sensation indistinguishable from that of the TEAS group, then the device will continue operation (lights and interface active) without active current output. In both groups, the device screen will be concealed from participants to prevent unblinding based on sensory feedback or operational cues.

Participants, outcome assessors, and statisticians will remain blinded to group allocation throughout the study. All outcome assessments will be performed by researchers trained to blinding standards and blinded to group assignment. Emergency unblinding will only be performed if a participant experiences an adverse event, and knowledge of group allocation is necessary to guide appropriate clinical management. Because the intervention and control groups required different stimulation parameters, the personnel administering the intervention could not remain blinded to group assignment. However, this setting does not affect the integrity of blinding for the core study procedures, and can minimize performance bias to the greatest extent.

At 24 hours postoperatively, before unblinding, participants will be asked to guess their group allocation (“Do you believe you received active TEAS or sham TEAS?”) with response options: active, sham, or uncertain. The outcome assessor will also be asked to guess group allocation at the same time point. The proportion of correct guesses will be reported as a measure of blinding success.

Anesthesia Management

After entering the operating room, patients will receive routine monitoring (blood pressure, electrocardiography, pulse oximetry) and general anesthesia with double-lumen endotracheal intubation. Induction will consist of propofol 1.5–2 mg/kg, sufentanil 0.5 μg/kg, and dezocine 5 mg intravenously, followed by rocuronium 0.6–1 mg/kg. Maintenance anesthesia will be achieved with propofol 4–8 mg/kg/h and remifentanil 0.05–0.1 μg/kg/min, supplemented with rocuronium as needed. Lung-protective ventilation will be applied with tidal volumes of 4–6 mL/kg and recruitment maneuvers. Ondansetron 4 mg and acetaminophen 500 mg will be administered 15–30 minutes before anticipated surgical completion. Multimodal postoperative analgesia includes patient-controlled intravenous analgesia with sufentanil (2 μg/h basal infusion, 1 μg bolus, 10-minute lockout), oral acetaminophen 500 mg every 8 hours, and rescue analgesia with compound paracetamol-dihydrocodeine tablets.

Standardized Postoperative Multimodal Analgesia

Patient-controlled intravenous analgesia (PCIA) with sufentanil will be initiated at the end of surgery, with the following parameters: background infusion rate of 2 μg/h, bolus dose of 1 μg, and lockout interval of 10 minutes. The PCIA pump will be continued for 48 hours postoperatively and may be discontinued when the patient’s verbal rating scale (VRS) pain score at rest is ≤3 for at least 4 consecutive hours without rescue analgesic requirement. Oral non-opioid analgesia will be administered routinely for 72 hours postoperatively, consisting of acetaminophen 500 mg every 8 hours, with a total 24-hour dose not exceeding 4 g. If the VRS pain score remains ≥4 at rest or during movement despite the above regimen, flurbiprofen axetil will be administered intravenously at 50 mg per dose, with a minimum interval of 12 hours between doses and a maximum of 2 doses per day. Non-opioid analgesics will not be converted to morphine milligram equivalents (MME) and will be recorded separately.

Interventions

Transcutaneous electrical acupoint stimulation (TEAS) will be delivered using a Han’s acupoint nerve stimulator (HANS-200A, Nanjing Jisheng Medical Appliance Co., Ltd, Nanjing, China). Self-adhesive electrodes (5 * 5 cm) will be placed with the acupoint at the center of each electrode pad. Channel 1 will connect the distal acupoints Hegu (LI4) and Neiguan (PC6), and Channel 2 will connect the shoulder acupoints Jianliao (SJ14) and Jianyu (LI15), all on the side ipsilateral to surgery.

Rationale for 2/100 Hz dense-disperse stimulation. The 2/100 Hz dense-disperse frequency was selected based on established neurophysiological evidence. Low-frequency (2 Hz) stimulation promotes the release of β-endorphin and enkephalin, acting on μ and δ opioid receptors, whereas high-frequency (100 Hz) stimulation triggers dynorphin release via κ receptors. The alternating dense-disperse pattern engages all three endogenous opioid systems simultaneously, providing a broader analgesic effect than either frequency alone. This parameter has been validated in prior perioperative TEAS studies and is the standard setting for the HANS device.

Active TEAS group. Patients will receive active stimulation at 2/100 Hz dense-disperse wave, with current intensity titrated upward from 2 mA to the highest level the patient can tolerate. Two 30-minute sessions will be administered: one on the evening of the day before surgery and the other before anesthesia induction on the day of surgery.

Sham TEAS group. Patients will undergo an identical procedure with inactive stimulation output: active stimulation will be delivered for the first 30 seconds to match sensory perception, while the device maintains active indicator lights and interface operation; no active current will be delivered thereafter. Sham stimulation will also be administered in two 30-minute sessions, at the same time points and the same ipsilateral acupoints (LI4, PC6, SJ14, LI15) as the active group.

The purpose of the 30-second initial active stimulation is to produce an initial cutaneous sensation identical to that of the active group, thereby reducing the likelihood that participants can distinguish group allocation based on the presence or absence of initial sensation. This design has been applied in prior TEAS randomized controlled trials and is superior to non-stimulation controls because it preserves the sensory experience of electrode placement and initial stimulation. Although no sham design is perfectly inert, the brief 30-second stimulation is expected to have a negligible physiological effect compared with 30 minutes of continuous active stimulation, and is unlikely to exert a clinically meaningful impact on the incidence of ipsilateral shoulder pain at 24 hours postoperatively.

Acupoint localization and operator training. Acupoint localization will follow the World Health Organization standard acupuncture point location criteria. All operators will complete a standardized training program covering acupoint localization practice, device operation, and deqi assessment, to ensure cross-center consistency.

Deqi assessment and treatment completion criteria. At the onset of stimulation, the operator will adjust the current and assess deqi using a standardized four-item scale (tingling, numbness, heaviness, warmth); a patient reporting ≥2 of these sensations will be defined as deqi-positive. A TEAS session will be considered complete if the patient receives the full 30-minute stimulation with the device operating continuously and no premature discontinuation due to intolerance or adverse events.

Supplemental Table 2 provides a detailed intervention description based on the STRICTA guidelines, covering the complete protocols for both active and sham TEAS.

Outcomes

Primary Outcome

The primary outcome is the incidence of ISP during shoulder movement at 24 hours postoperatively. Participants will be positioned sitting or standing with the elbow extended and will perform full circumduction of the shoulder joint. Pain intensity will be assessed using the verbal rating scale (VRS; 0–10, where 10 indicates the most severe pain). ISP is defined as a VRS score ≥ 1. The minimum clinically important difference is defined as a 50% relative reduction in pain incidence in the intervention group compared with the control group.

As no established minimum clinically important difference (MCID) currently exists for ISP incidence, the 50% relative reduction was specified as the effect size assumption for sample size calculation, based on the effect observed in our pilot study (35% in control vs 18% in TEAS, a 50% relative reduction).

We selected the VRS threshold of at least 1 to capture any report of shoulder discomfort, consistent with prior ISP studies that used “any shoulder pain” as the incidence endpoint. This definition increases sensitivity and therefore maximises the ability to detect any preventive effect of TEAS.

Secondary Outcomes

The secondary outcomes are cumulative opioid consumption within 24 hours postoperatively and postoperative nausea and vomiting (PONV) within 24 hours. Total opioid consumption will be recorded and converted to intravenous morphine milligram equivalents; the conversion list is shown in Supplemental Table 1.³⁴ A difference of ≥10 mg will be considered clinically significant.³⁵ The incidence of PONV will be defined as the number of participants experiencing nausea and/or vomiting within 24 hours postoperatively.

Other Outcomes

Secondary outcomes will include the incidence of shoulder pain during movement and at rest at 48 and 72 hours postoperatively, cumulative opioid consumption from 25 to 48 hours postoperatively, and postoperative quality of recovery assessed by the Quality of Recovery-15 scale at 24, 48, and 72 hours postoperatively. The Quality of Recovery-15 (QoR-15) is a 15-item patient-centered instrument with total scores ranging from 0 to 150, where higher scores indicate better recovery quality. We will also record time to first flatus and the incidence of nausea and vomiting from 25 to 48 hours and 49 to 72 hours postoperatively. An exploratory analysis will examine the association between shoulder pain at 24 hours postoperatively and postoperative quality of recovery.

Data Collection

This study protocol adheres to the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) guidelines. Demographic information, American Society of Anesthesiologists physical status classification, and comorbidities will be recorded preoperatively. Surgical procedure, operative duration, and anesthesia duration will be documented intraoperatively. Blinded outcome assessors will record pain intensity, cumulative opioid consumption, quality of recovery, and time to first flatus during the postoperative follow-up period. Postoperative adverse events, including nausea and vomiting and surgery-related complications, will be documented throughout the study period. An independent data monitoring committee will be established, comprising a statistician, an anesthesiologist, a clinical research administrator, an anesthesia nurse, and a thoracic surgeon (Table 1).

Table 1.

Participant Timeline: Schedule of Enrollment, interventions, and Assessments

Timepoint	Trial Period
	Enrollment		Post-Randomization
	−7 to −1d	−1d	Before Anesthesia Induction	1~6h After Surgery	7~12h	12~24h	25~48h	49~72h
Enrollment:
Inclusion criteria	X
Exclusion criteria	X
Informed consent	X
Baseline data	X
Randomization		X
Allocation		X
Intervention/Comparator:
TEAS Group		X	X
Sham Group		X	X
Assessments:
ISP				X	X	X	X	X
VRS				X	X	X	X	X
Cumulative Opioid Consumption				X	X	X	X
Quality of Recovery						X	X	X

Sample Size

Based on retrospective data from leading centre that met the eligibility criteria for this project (preliminary control group: 34 patients, 12 events; TEAS group: 34 patients, 6 events), the incidence of ipsilateral shoulder pain at 24 hours after surgery was 35% in the control group and 18% in the TEAS group. We performed the sample size calculation in PASS 15 using the Tests for Two Proportions module, with a two-sided significance level of α=0.05, a statistical power of 0.8, and a 1:1 allocation ratio between groups. Accounting for a 5% dropout rate, the calculation indicated that 108 participants were required per group, for a total of 216 participants.

Statistical Analysis Methods

Analysis populations. Four populations will be defined: the intention-to-treat (ITT) population includes all randomized patients and is used for the primary analysis; the per-protocol (PP) population includes ITT patients who receive at least one intervention session, complete the primary outcome assessment, and have no major protocol deviations, and is used as a sensitivity analysis; the modified ITT (mITT) population includes all randomized patients who receive at least one intervention and have a primary outcome assessment; the safety population includes all patients who receive at least one intervention and is used for safety analyses.

Normality of continuous variables will be assessed with the Kolmogorov–Smirnov test. Non-normally distributed variables will be presented as median (interquartile range) and categorical variables as number (percentage). Baseline balance will be evaluated using the absolute standardised difference (ASD), with an ASD ≥ 0.27 (calculated as: ) was defined as clinically meaningful imbalance.

Primary outcome. The incidence of ISP at 24 hours will be compared between groups using a log-Poisson regression model with robust standard errors, adjusted for study center; results will be reported as risk ratio (RR) with 95% confidence interval (CI). Chi-square or Fisher’s exact test will serve as supplementary analysis. Prespecified sensitivity analyses will repeat the primary comparison in the PP population and using VRS ≥3 as the ISP threshold. For missing data, complete case analysis will be used if missingness is ≤5%; multiple imputation under the missing-at-random assumption will be applied if >5%.

Secondary outcomes. Longitudinal VRS pain scores will be analyzed using a linear mixed model (LMM) with group, time, and group×time interaction as fixed effects and patient as a random effect, adjusted for center, reported as mean difference (MD) with 95% CI. Cumulative opioid consumption will be compared using independent samples t-test or Mann–Whitney U-test, with MD or Hodges–Lehmann estimator and 95% CI. Categorical outcomes (PONV, adverse events, pulmonary complications) will be compared using chi-square or Fisher’s exact test, reported as RR with 95% CI.

Center effects. Study center will be included as a fixed-effect covariate in the primary model. A generalized linear mixed model with center as a random effect will be used as an additional sensitivity analysis.

All tests will be two-sided with α=0.05. Bonferroni or Benjamini–Hochberg correction will control type I error for multiple comparisons. Analyses will be performed using R (version 4.5.1 or later).

Discussion

Ipsilateral shoulder pain (ISP) after video-assisted thoracoscopic surgery (VATS) is a common yet frequently overlooked postoperative complication. It not only causes patient discomfort but may also impede early mobilization and enhanced recovery. The frequent oversight of ISP is partly attributed to its anatomical separation from the surgical incision, leading both patients and clinicians to misattribute it to temporary positioning-related soreness rather than a distinct complication.³⁶ The lack of a standardized assessment protocol further contributes to underestimation of its incidence.³⁷ Notably, regional analgesic strategies optimized for incisional pain—including thoracic epidural blockade—are largely ineffective against ISP,⁵ reflecting the distinct neuroanatomical pathway of this pain entity.

Current prophylactic strategies for ISP remain suboptimal. Intraoperative phrenic nerve block has shown preventive efficacy in several studies,^1,9 but its invasive nature carries inherent risks. Interscalene approaches may cause respiratory depression,³⁸ while supraclavicular approaches, though diaphragm-sparing,⁷ are associated with bleeding, pneumothorax, and patient discomfort. Pharmacological prophylaxis with paracetamol alone has proven insufficient, with ISP incidence remaining as high as 61.9% at 24 hours postoperatively.³⁹ Positioning modifications have also failed to demonstrate a significant reduction in ISP incidence.³ These limitations underscore the need for a non-invasive, safe, and repeatable prophylactic strategy.

TEAS represents a promising non-invasive candidate, and we hypothesize that it may reduce ISP incidence through several complementary mechanisms. As a modern extension of acupuncture, TEAS delivers controlled electrical currents to acupoints, engaging neurophysiological pathways consistent with those of manual acupuncture.^40,41 Acupoint stimulation may inhibit ascending nociceptive transmission at the spinal dorsal horn via gate-control mechanisms while simultaneously activating descending pain inhibitory pathways.^42,43 The 2/100 Hz dense-disperse protocol used in this trial is designed to engage multiple endogenous opioid systems—low-frequency stimulation promoting β-endorphin and enkephalin release, and high-frequency stimulation triggering dynorphin release—thereby providing a broader analgesic effect than a single frequency. Additionally, TEAS has been associated with reduced perioperative inflammatory cytokine levels, which may attenuate phrenic nerve and diaphragmatic sensitization. In the VATS setting, prior randomized studies have reported associations between perioperative TEAS and reduced postoperative pain scores and opioid consumption, although these studies did not specifically target ISP as a primary endpoint. Whether these mechanisms translate into a clinically meaningful reduction in ISP incidence remains the central hypothesis to be tested in this trial.

The potential influence of perioperative medications on ISP incidence warrants careful consideration. Opioids, the mainstay of postoperative analgesia, exert their primary effect on somatic nociception and may have limited efficacy against the phrenic-nerve-mediated referred pain that characterizes ISP; moreover, opioid-induced hyperalgesia could theoretically amplify pain perception. Non-steroidal anti-inflammatory drugs (NSAIDs) may reduce inflammatory sensitization of the diaphragm and pleura, but their specific effect on ISP has not been rigorously established. Paracetamol, as noted, has shown inadequate efficacy against ISP.³⁹ Local anesthetic techniques targeting the phrenic nerve are the most effective prophylaxis but are invasive. To minimize confounding by these variables, our trial standardizes the perioperative analgesic regimen across both groups, including uniform PCIA parameters, regular acetaminophen, and a defined rescue analgesia protocol. Any between-group difference in ISP incidence can therefore be more confidently attributed to the TEAS intervention rather than variability in concomitant analgesic use.

The selection of ISP incidence during shoulder movement at 24 hours postoperatively as the primary outcome is grounded in both clinical and methodological considerations. Twenty-four hours corresponds to the peak incidence of acute ISP after thoracic surgery, making it the most sensitive time point for detecting a preventive effect. Assessing pain during active shoulder movement, rather than at rest, captures the functional impact of ISP and aligns with the clinical scenario in which shoulder pain is most disabling. The VRS ≥1 threshold defines “any shoulder pain”, consistent with prior ISP studies that have used this endpoint to maximize sensitivity. We acknowledge that this threshold may capture very mild discomfort; accordingly, the incidence of clinically more meaningful pain (VRS ≥3) will be reported as a secondary analysis to contextualize the primary finding.

This study has several limitations that should be acknowledged. First, although participants, outcome assessors, and statisticians remain blinded, the intervention administrators cannot be blinded, which may introduce performance bias; we have mitigated this through standardized operating procedures and unified training. Second, the sham TEAS design—30 seconds of active stimulation followed by inactive current—carries a residual risk of unblinding once the initial sensation fades, particularly because the primary outcome is subjective pain; a postoperative blinding integrity assessment has been added to evaluate this risk. Third, ISP is assessed subjectively via VRS, which may be influenced by patient expectation and psychological factors; however, the use of a validated scale and blinded assessors helps standardize this measurement. Fourth, as a multicenter trial, center-level heterogeneity in surgical technique, anesthesia practice, and baseline ISP incidence may affect the results; we address this through stratified randomization and covariate adjustment for study center in the primary analysis. Fifth, the 72-hour follow-up period is designed to evaluate acute postoperative ISP only; this trial is not powered to assess chronic pain or long-term pain chronification, and no such claims will be made. Finally, this study does not include a cost-effectiveness analysis, which would be needed to inform health policy decisions regarding routine implementation.

In summary, this trial protocol is designed to rigorously test whether preoperative TEAS can reduce the incidence of early postoperative ISP after VATS. If confirmed, TEAS would offer a non-invasive, safe, and easily implementable prophylactic option that may reduce reliance on invasive nerve blocks. The findings will also help define the boundary of TEAS efficacy in this specific clinical context and guide future optimization of stimulation parameters and acupoint selection.

Conclusion and Prospects

This multicenter randomized controlled trial protocol is designed to evaluate whether preoperative TEAS reduces the incidence of early postoperative ISP in patients undergoing unilateral video-assisted thoracoscopic lung surgery. Given the non-invasive nature of TEAS and the high prevalence of ISP after VATS, a positive result would offer a safe and easily implementable prophylactic option for clinical consideration. However, this study does not directly compare TEAS with invasive nerve blocks, does not assess long-term pain chronification, and does not prespecify subgroup analyses in elderly or high-risk respiratory patients; accordingly, no claims regarding these aspects will be made. The findings will help define the efficacy boundary of TEAS for ISP prevention and inform future research on non-pharmacological analgesic strategies in thoracic surgery.

Funding Statement

This study was supported by the Shanghai Medical Innovation & Development Foundation (SMIDF2024-128-13). Shanghai Association of Integrated Traditional Chinese and Western Medicine Young Physicians in Anesthesiology and Pain Medicine Special Scientific Research Fund (2025-MT-04). Project of Key Supported Disciplines by Shanghai Municipal Health Commission (2023ZDFC0204), Shanghai Leading Talent Program of Eastern Talent Plan, Research-Oriented Physician Talent Program of Shanghai Pulmonary Hospital (LYRC202404).

Data Sharing Statement

No new data has been generated during the study.

Ethical Approval

Shanghai Pulmonary Hospital serves as the lead center, and the study received approval from the IRB on June 19, 2025 (approval #L25-604). Fudan University Shanghai Cancer Center and Shanghai East Hospital joined as participating centers, each obtaining approval from its respective IRB.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

All authors have declared that they have no potential conflicts of interest.