Invasive arterial blood pressure monitoring allows continuous assessment of blood pressure and repeated arterial blood sampling during general anesthesia. The conventional radial artery at the wrist is commonly used for arterial catheterization. However, wrist flexion or extension, arm fixation, surgical drapes, and external pressure may compress or bend the catheter and result in damping or loss of the arterial pressure waveform.
During robot-assisted urologic surgery, both arms are commonly tucked alongside the body. After surgical positioning and robot docking, direct access to the arterial catheter may be limited. A distal radial arterial catheter placed near the anatomical snuffbox or on the dorsal aspect of the hand is located distal to the wrist joint and may therefore be less affected by wrist position and forearm compression.
This is a single-center, prospective, randomized, open-label, superiority study. Seventy adult participants undergoing robot-assisted urologic surgery under general anesthesia and requiring invasive arterial pressure monitoring will be randomly assigned in a 1:1 ratio to conventional radial arterial catheterization or distal radial arterial catheterization. Randomization will be performed using a computer-generated block randomization sequence after written informed consent and confirmation of eligibility.
Both procedures will be performed under ultrasound guidance using standard sterile technique and a standard 20-gauge or 22-gauge over-the-needle arterial catheter. In the conventional radial artery group, the catheter will be inserted at the wrist, approximately 1 to 2 cm proximal to the radial styloid. In the distal radial artery group, the catheter will be inserted into a suitable segment of the distal radial artery in the anatomical snuffbox or dorsal hand. Up to three skin puncture attempts will be permitted. If catheter insertion is unsuccessful or further attempts are considered inappropriate, rescue arterial catheterization will be performed according to standard clinical practice.
Routine prophylactic wrist-extension splints will not be applied in either group. Additional fixation, repositioning, catheter replacement, or other corrective measures may be performed at any time if required for reliable blood pressure monitoring or participant safety. The observation period will begin after both arms have been tucked and will continue until robot undocking or release of the arm-tucked position.
The primary objective is to compare the occurrence of clinically significant arterial catheter dysfunction requiring troubleshooting or rescue intervention during the observation period. Such dysfunction may include persistent damping or loss of the arterial waveform, clinically relevant disagreement between invasive and noninvasive blood pressure measurements, inability to aspirate blood, suspected catheter kinking or compression, or the need for interventions such as flushing, line assessment, dressing adjustment, hand or wrist repositioning, arm untucking, splint application, catheter replacement, or alternative arterial access.
Secondary assessments will include overall and first-attempt insertion success, insertion time, number and duration of waveform damping or loss episodes, difficulty with arterial blood aspiration, need for rescue catheterization, and the procedural burden of maintaining reliable arterial pressure monitoring. Safety assessments will include bleeding, hematoma, vasospasm, infection, pain or sensory symptoms, signs of hand ischemia, suspected radial artery occlusion, catheter replacement, and other unexpected adverse events. Clinically necessary treatment will not be delayed or restricted by study procedures.
