Invasive arterial blood pressure (IABP) monitoring is critical for perioperative and critically ill patients, yet traditional radial artery cannulation near the wrist joint is prone to catheter dysfunction (e.g., kinking, occlusion) due to positional changes, compromising accuracy and patient safety. This trial hypothesizes that modifying the cannulation site to 1.5-2.5 cm proximal to the radial styloid process may enhance catheter stability.

Methods and analysis:This is a prospective, parallel-group, randomized, controlled, analyst-blinded trial. A total of 486 participants (231 per group, adjusted for 5% dropout) will be enrolled. Eligible patients (18-75 years, ASA physical status I-III, requiring elective surgery with radial artery cannulation) will be randomized 1:1 to the modified group (1.5-2.5 cm proximal to the radial styloid process) or the conventional group (traditional site). The primary outcome is the incidence of arterial catheter dysfunction (defined by criteria such as blood sampling difficulty, position-dependent waveform, or improved waveform post-square wave test). Secondary outcomes include frequency of catheter dysfunction, damping abnormality rate, first-puncture success rate, number of arterial punctures,arterial cannulation time, complication incidence, and blood pressure measurement differences.

Sample size calculation:This trial utilized a superiority test for sample size calculation. In the 100-case preliminary experiment results, the incidence rate of abnormal arterial catheter function was 30% in the control group and 12% in the modified group. With a predefined superiority margin Δ of -6% (actual observed Δ of -18%), using a type I error rate (α) of 0.025 and statistical power (1-β) of 0.90, statistical calculations determined that 231 participants per group (totaling 462) would be required to detect this difference in a two-sided test. Considering a 5% dropout rate among study subjects, the final planned sample size was adjusted to 486 cases.

Inclusion criteria

1. Patients 18-75 years of age undergoing elective surgery who require radial artery cannulation;
2. Patients positioned in supine, lithotomy, or other face-up surgical postures;
3. American Society of Anesthesiologists (ASA) physical status classification: Grades I to III.

Exclusion criteria

1. Abnormal results from the modified Allen test;
2. Patients with a history of radial artery cannulation within the past 3 months, or with infection/trauma at or adjacent to the puncture site;
3. Coagulopathy or hypercoagulable state;
4. Patients undergoing anticoagulant therapy;
5. Comorbid vascular diseases (e.g., vasculitis);
6. Patients undergoing surgical procedures involving the same anatomic region;
7. Preoperative hemodynamic instability (including patients already on vasoactive medications, or with atrial fibrillation, atrial flutter, atrioventricular block of grade II or higher, multifocal ventricular premature beats, or ventricular premature beats with R-on-T phenomenon);
8. Patients lacking legal capacity to sign informed consent.

Deidentified participant data and statistical/analytic code will be available upon publication. Researchers who provide a methodologically sound proposal can request access by contacting Dr. Zhinan Zheng at zhengzhn5@mail.sysu.edu.cn. Data will be shared for specified purposes only and will require a signed data access agreement.

Data will be available beginning 12 months after publication of the primary results and will remain accessible for 5 years.

Access is granted to researchers with a valid research proposal, ethical approval from their institution, and a signed data use agreement (DUA). Requests are reviewed by the trial's data access committee. Data use is limited to non-commercial, scientific research purposes.