Effects of Interscalene Block on Visual Clarity in Arthroscopic Surgery

Our study will be conducted prospectively, and no additional medication or interventional procedure will be administered to the patients. A total of 80 patients, 40 from the general anesthesia group and 40 from the interscalene block anesthesia group, who meet the inclusion criteria, will be included in the study. In both groups, systolic arterial blood pressure (SAB), diastolic arterial blood pressure (DAB), mean arterial blood pressure (MAP), and heart rate (HR) values will be recorded every 5 minutes throughout the operation after the surgical procedure begins. At the end of the operation, visual clarity will be assessed by the same surgeon (M.O) using a Numeric Rating Scale (0 = very poor, 10 = excellent). To detect a 2-point (20%) difference in the NRS score for visual clarity, a total of 37 patients are required with 80% power and a significance level of 0.05. This calculation assumes that such an effect is clinically significant and that the standard deviation is 2.21. Assuming a 10% dropout rate, we calculated that a total of 80 patients would be needed for two groups, with 40 patients per group.

Descriptive statistics, including mean, standard deviation, median, minimum, maximum, frequency, and percentage, will be used to summarize the data. The Kolmogorov-Smirnov test will be employed to assess the distribution of variables. For the comparison of quantitative data, the Independent Samples t-test and Mann-Whitney U test will be utilized. For the comparison of qualitative data, the Chi-Square test will be used. A p-value less than 0.05 will be considered statistically significant.

The cut-off values of quantitative parameters will be determined using ROC analysis.

Inclusion criteria

• Patients able to provide informed consent.
• Patients able to reliably report their symptoms to the research team.
• ASA physical status classification of 1-3.
• Scheduled to undergo arthroscopic rotator cuff repair surgery in the lateral decubitus position.

Exclusion criteria

• Contraindications to anesthesia.
• Patients under 18 years old.
• Cognitive impairment or communication barriers.
• BMI > 40.
• Weight less than 50 kg or more than 100 kg.
• Psychiatric disorders.
• Chronic opioid therapy for pain.
• Severe liver, heart, or kidney failure.
• Hypertension (possibly severe, depending on the study context).
• Use of opioids for any reason.
• Revision shoulder surgery.
• Diaphragmatic paralysis on the opposite side of the planned intervention.
• Concurrent anticoagulation therapy or coagulopathy.
• Skin deformities or infections in the block area.
• Progressive neurological deficits affecting peripheral nerves.
• Allergy to amide-structured local anesthetics.
• ASA physical classification score ≥4.
• Suspected or confirmed pregnancy.
• Breastfeeding mothers.
• Patients who do not consent to participate in the study.