This multicenter, prospective randomized controlled trial investigates the effect of dilute epinephrine irrigation versus tourniquet use on visual field clarity (VFC) during ankle arthroscopy. Patients are randomized into an epinephrine group (normal saline with 1 mL of 1:1000 epinephrine per 3 L bag; tourniquet placed but not inflated unless needed) or a standard tourniquet group. The primary outcome is arthroscopic visual field clarity assessed using a 4-point Likert-style numeric rating scale. Secondary outcomes include postoperative pain intensity at 2 and 24 hours (VAS), and the incidence of hypotension, bradycardia, and cardiovascular adverse events.

Study Objective and Design

This study aims to evaluate the effect of dilute epinephrine irrigation versus tourniquet use on visual field clarity (VFC) during ankle arthroscopic surgery, while also assessing the incidence of hypotension/bradycardia events and potential cardiovascular adverse effects.

This is a multicenter, prospective, randomized controlled trial comparing the intraoperative arthroscopic field clarity between patients receiving epinephrine-containing irrigation and those undergoing surgery with a tourniquet.

Participants are randomized into two groups:

Epinephrine Group: Irrigation fluid consists of normal saline mixed with 1 mL of 1:1000 epinephrine per 3-liter bag. A tourniquet is placed but not inflated; it may be inflated as a rescue measure if necessary.

Tourniquet Group: Standard tourniquet application as routinely practiced.

3.2.4 Primary Efficacy Outcome

Visual field clarity (VFC) under ankle arthroscopy, assessed using a Likert-style 4-point numeric rating scale (NRS).

3.2.5 Secondary Efficacy Outcomes

Pain intensity scores at 2 and 24 hours postoperatively, measured using the Visual Analog Scale (VAS).

Inclusion Criteria:

• Able to understand the procedures and methods of the clinical trial
• voluntarily provide written informed consent
• Aged from 15 to 65 years old , regardless of sex
• Diagnosed with a condition requiring ankle surgery
• Be scheduled to undergo unilateral ankle arthroscopy

Exclusion Criteria:

• Patients who decline to participate in the study
• Known history of heart disease (e.g., coronary artery disease, cardiac conduction abnormalities), diabetes, or asthma
• Poorly controlled hypertension
• Age under 15 years or above 65 years old
• Intellectual disability
• Pregnant or breastfeeding women
• Known allergy to sulfites

Contraindications to ISBPB (including planned injection site infection, pre-existing neurological deficits, allergy to local anesthetics, severe chronic obstructive pulmonary disease, or contralateral phrenic nerve dysfunction)

This study was conducted using a double-blind design. After concealed randomization, only the principal investigator had access to group assignments, while participants, observers, and surgeons were blinded and identified solely by subject numbers.

Upon enrollment and signing of informed consent, participants were informed that they would be randomly assigned to either the epinephrine group or the tourniquet group. Observers received only the corresponding subject numbers from the principal investigator and were responsible for data collection and recording without knowledge of group allocation.

For surgeons, both groups had an inflatable tourniquet placed at the standard position prior to surgery. After verification by all three parties (participant, investigator, and surgical team), the surgeon left the room for 15 minutes. Group-specific interventions (inflating the tourniquet or not) were implemented after surgical draping was completed. Surgeons were then called in to perform th