The purpose of this study is to compare the effectiveness of three different intravenous (IV) patient-controlled analgesia (PCA) regimens-Fentanyl, Tramadol, and Ibuprofen-in managing postoperative pain and respiratory performance in patients undergoing Video-Assisted Thoracoscopic Surgery (VATS). While regional blocks like Erector Spinae Plane (ESP) block provide effective early analgesia, their effect typically diminishes after 8-12 hours, leading to potential 'rebound pain.' This study specifically investigates the period following the duration of the regional block's action. The primary goal is to evaluate which IV PCA protocol better controls pain (Visual Analog Scale scores) and supports better respiratory performance (measured by incentive spirometry) during the first 72 hours post-surgery

Thoracic surgery is associated with one of the highest incidences of both acute and chronic postoperative pain. Clinical evidence indicates that poorly controlled acute pain in the immediate postoperative period is a primary risk factor for the development of chronic neuropathic pain (post-thoracotomy pain syndrome). Furthermore, severe acute pain triggers a guarding reflex, leading to shallow breathing, impaired coughing, and ultimately compression atelectasis.

In alignment with the 2026 American Society of Anesthesiologists (ASA) guidelines, this study emphasizes a multimodal, opioid-sparing approach to optimize patient recovery. While regional techniques like the Erector Spinae Plane (ESP) block offer effective early analgesia, their effectiveness is typically limited to 8-12 hours. This study evaluates the effectiveness of three different IV Patient-Controlled Analgesia (PCA) regimens initiated specifically to bridge the analgesic gap after the regional block's effect diminishes.

Interventions:

All patients receive a standardized ultrasound-guided ESP block (20 ml 0.25% bupivacaine) at the end of surgery. PCA regimens (Fentanyl, Tramadol, or Ibuprofen) are initiated at the 6th postoperative hour (or earlier on patient demand). Postoperative static and dynamic pain scores (VAS), rescue analgesic requirements and respiratory performance (incentive spirometry volumes) are monitored for 72 hours.

The study hypothesizes that the Ibuprofen-based PCA will maintain comparable analgesia to opioid-based regimens while significantly improving respiratory performance by avoiding opioid-induced respiratory depression.

Study Design and Blinding:

This is a prospective, randomized, single-center trial. Patients are assigned to one of three intervention arms using a centralized randomization system with the sealed envelope method (1:1:1 ratio). The study follows a double-blind (participant and outcomes assessor) protocol. While the primary investigator manages the PCA devices, the patients and the researchers recording the visual analog scale (VAS) scores and incentive spirometry volumes are blinded to the group assignments.

Inclusion Criteria:

1. - Patients aged 18 to 80 years.
2. - ASA (American Society of Anesthesiologists) Physical Status Score of I-III.
3. - Body Mass Index (BMI) between 18 and 35 kg/m².
4. - Undergoing elective thoracic surgery via Video-Assisted Thoracoscopic Surgery (VATS).
5. - Voluntary participation confirmed by signing the written Informed Consent Form.

Exclusion Criteria:

1. - Age below 18 or above 80 years.
2. - Advanced organ failure (e.g., severe hepatic or renal impairment).
3. - ASA physical status > III.
4. - History of chronic pain treatment or long-term opioid use.
5. - BMI < 18 kg/m² or > 35 kg/m².
6. - Pregnancy or breastfeeding.
7. - Limited cooperation due to dementia or uncontrolled psychiatric disorders.
8. - Communication barriers (inability to communicate in the native language).
9. - History of substance or drug abuse.
10. - Known allergy or contraindication to the study drugs (Fentanyl, Tramadol, or Ibuprofen).
11. - Contraindication to regional block placement (e.g., infection at the injection site).

The individual participant data collected during the study are considered confidential institutional data according to the study protocol and informed consent forms approved by the local ethics committee. The data will only be available to authorized regulatory bodies and the investigation team to ensure participant privacy and data security.

While the primary investigator responsible for the administration and adjustment of the Patient-Controlled Analgesia (PCA) devices was aware of the group assignments, the patients were blinded to the specific drug they received. Furthermore, the researchers who recorded the Visual Analog Scale (VAS) scores and measured the incentive spirometry volumes at each visit were blinded to the treatment groups.