A modified arterial needle with an extended flashback chamber improves first-attempt success in radial artery cannulation: a randomized controlled trial

Abstract Background: Palpation-guided radial artery cannulation has a first-attempt success rate of only 48–55%, while ultrasound guidance is often unavailable in low-resource settings. We developed a modified arterial needle with an extended flashback chamber (0.5–0.8 mL vs. standard 0.1–0.2 mL) that enables a retained-stylet technique. This study tests whether this simple, low-cost modification improves success and efficiency without additional equipment. Methods: In this single-center, prospective randomized controlled trial (n = 198, ChiCTR2500095957), elective surgery patients requiring radial artery cannulation were assigned 1:1 to a modified needle or standard needle. The primary outcome was first-attempt success rate. Secondary outcomes included procedural time, needle consumption, and operator-rated ease. Results: The modified needle significantly improved first-attempt success (70.7% vs. 52.5%, P = 0.009) and shortened procedural time [55.0 (52.0–87.0) s vs. 59.0 (54.0–107.5) s, P = 0.004]. Needle use became more consistent (IQR 1.0–1.0 vs. 1.0–2.0), and operator-rated ease was higher [10 (8–10) vs. 10 (5–10), P = 0.022]. In patients with BMI ≥ 25 kg/m², first-attempt success rose from 39.4% to 66.7% (P = 0.030). Overall cannulation success rates were similar (89.9% vs. 88.9%, P = 0.817),but the modified needle reduced procedural variability. Conclusion: A simple extension of the flashback chamber—costing <$0.50 per procedure—turns a blind palpation technique into a visually guided, more reliable maneuver. It achieves first-attempt success rates comparable to ultrasound (70.7% vs. 68–75%) without capital investment, offering an ideal bridge solution for resource-limited settings. Trial Registration Chinese Clinical Trial Registry, ChiCTR2500095957. Registered on January 15, 2025. Retrospectively registered (the first participant was enrolled prior to registration).