This prospective observational study aims to investigate whether preoperative central sensitization and sleep quality are associated with acute postoperative pain levels in patients undergoing breast cancer surgery.

The study includes 41 female patients scheduled for unilateral breast cancer surgery. Before surgery, participants are evaluated using two self-report questionnaires: the Central Sensitization Inventory (CSI) and the Pittsburgh Sleep Quality Index (PSQI). Based on their scores, participants are categorized into groups according to central sensitization level and sleep quality.

After surgery, all participants receive a standardized multimodal analgesia protocol. Pain severity is measured using the Numeric Rating Scale (NRS) at five time points within the first 24 hours: 30 minutes, 2, 6, 12, and 24 hours postoperatively. Additional assessments include sedation level (Ramsay Sedation Scale), nausea and vomiting (Verbal Descriptive Scale), and presence of delirium (Nursing Delirium Screening Scale - NuDESC).

The primary question this study seeks to answer is whether higher levels of central sensitization and/or poor sleep quality prior to surgery are predictive of greater acute postoperative pain.

This prospective observational cohort study is designed to evaluate the association between preoperative central sensitization levels, sleep quality, and acute postoperative pain intensity in female patients undergoing breast cancer surgery. The study is being conducted at Istanbul University-Cerrahpaşa, Cerrahpaşa Medical Faculty, Department of Anesthesiology and Reanimation, in collaboration with the Department of General Surgery, from March 2025 to June 2025, following ethics committee approval and prospective registration.

A total of 41 female patients, aged between 18 and 80 years, undergoing unilateral breast surgery with sentinel lymph node biopsy (SLNB)-including simple mastectomy, breast-conserving surgery, or mastectomy with immediate reconstruction-are included. All participants provide written informed consent before enrollment.

Preoperative assessments are performed one day prior to surgery. Central sensitization is measured using the Central Sensitization Inventory (CSI), a 25-item self-report questionnaire assessing symptoms commonly associated with central sensitization. A CSI-A score ≥40 is considered indicative of high central sensitization. Sleep quality is evaluated with the Pittsburgh Sleep Quality Index (PSQI), a validated instrument assessing sleep characteristics over the past month; PSQI scores ≥5 are accepted as reflecting poor sleep quality.

All patients receive standardized general anesthesia and multimodal analgesia including:

Induction: Fentanyl 2 mcg/kg (lean body weight), propofol 2 mg/kg (lean body weight), rocuronium 0.6 mg/kg (actual body weight).

Maintenance: Sevoflurane and additional opioid supplementation as needed. Intraoperative analgesia: Morphine 0.05 mg/kg (lean body weight). Postoperative analgesia: Scheduled paracetamol and NSAIDs; opioids as rescue medication if required.

Pain severity is measured using the Numeric Rating Scale (NRS) at five postoperative time points: 30 minutes, 2, 6, 12, and 24 hours. Additional assessments include:

Sedation level: Ramsay Sedation Scale (RSS) Nausea and vomiting: Verbal Descriptive Scale (VDS) Delirium screening: Nursing Delirium Screening Scale (NuDESC) Participants are categorized into groups according to their CSI and PSQI scores. Postoperative pain scores and secondary outcomes are compared across these groups using non-parametric statistical methods (e.g., Mann-Whitney U test for independent samples). Correlation analyses (Spearman's rank) are performed to assess relationships between CSI, PSQI, and postoperative pain scores.

The primary objective is to determine whether high central sensitization and/or poor sleep quality are predictive of increased acute postoperative pain. Secondary objectives include evaluating the relationship between preoperative risk factors and sedation, nausea/vomiting, and delirium outcomes.

A power analysis was conducted based on expected effect sizes from previous literature, targeting a minimum of 31 participants for 80% statistical power with an alpha of 0.05. A 20% dropout margin was included, resulting in a final sample size of 41 participants.

All data are collected using standardized case report forms. Data entry is conducted by trained personnel and monitored for consistency and completeness. Ethical approval was obtained from the institutional review board prior to participant recruitment. The study does not receive external funding.

InclusionCriteria:

• Female patients aged between 18 and 80 years
• Scheduled to undergo one of the following unilateral breast cancer surgeries with sentinel lymph node biopsy (SLNB):
• Simple mastectomy
• Breast-conserving surgery (BCS)
• Simple mastectomy with immediate breast reconstruction
• ASA Physical Status Classification I-III
• Able to understand the study procedure and provide informed consent
• Fluent in Turkish and capable of completing self-report questionnaires
• Preoperative completion of the following assessments:
• Central Sensitization Inventory (CSI)
• Pittsburgh Sleep Quality Index (PSQI)

ExclusionCriteria:

• Pregnant or lactating women
• Allergy or contraindication to any component of the analgesic regimen (e.g., paracetamol, dexketoprofen, tramadol, fentanyl, or morphine)
• Planned or performed intraoperative regional nerve block (e.g., paravertebral or PECS block)
• Use of sedative-hypnotic drugs, opioids, or gabapentinoids within the last 7 days
• History of prior breast or axillary surgery
• Conversion to emergency surgery or development of major intraoperative complications
• Admission to the intensive care unit (ICU) postoperatively
• Patient refusal to participate in postoperative assessments
• Evidence of metastatic disease

The study population consists of female patients aged 18 to 80 years who were admitted for elective breast cancer surgery at the Department of Anesthesiology and Reanimation, Istanbul University-Cerrahpaşa, Cerrahpaşa Medical Faculty Hospital. Participants were selected consecutively among those scheduled for unilateral simple mastectomy, breast-conserving surgery, or mastectomy combined with immediate breast reconstruction. All surgeries were performed under general anesthesia. Preoperative evaluations and postoperative follow-up (within 24 hours) were conducted in a tertiary-care academic hospital setting. Patients were evaluated using standardized self-report questionnaires.