Dynamic needle tip positioning may improve first-attempt success rate in short-axis radial artery cannulation: A systematic review and meta-analysis of randomized trials.

BackgroundUltrasound-guided radial artery cannulation is routinely performed; however, the optimal imaging approach remains debated. The short-axis out-of-plane approach facilitates vessel centering; however, it limits continuous needle-tip visualization, whereas the long-axis in-plane approach enables tip visualization but can be technically demanding. Dynamic needle tip positioning is a modified short-axis out-of-plane strategy designed to improve needle-tip tracking.MethodsWe conducted searches across PubMed, Embase, the Cochrane Library, Scopus, and Web of Science databases from inception through 1 January 2026. Randomized controlled trials involving adults that have compared the short-axis out-of-plane (dynamic needle tip positioning or traditional non-dynamic needle tip positioning) and long-axis in-plane approaches were included. The primary outcome was first-attempt success. Secondary outcomes included total success; time to cannulation; and hematoma, posterior wall puncture, and vasospasm incidences. Random-effects models were used, with prespecified subgroup analysis stratified by dynamic needle tip positioning. The protocol was registered in the International Prospective Register of Systematic Reviews (CRD420251276500). Small-study effects were assessed using Egger's regression for outcomes reported in ≥10 studies.ResultsThirteen trials (1482 participants) were included. Overall, first-attempt success rates did not differ between the short-axis out-of-plane and long-axis in-plane (relative risk = 0.99, 95% confidence interval: 0.85-1.15) approaches. Subgroup analysis showed higher first-attempt success rates with the dynamic needle tip positioning short-axis out-of-plane approach than with the long-axis in-plane approach (relative risk = 1.22, 95% confidence interval: 1.13-1.32), whereas the non-dynamic needle tip positioning short-axis out-of-plane approach demonstrated no advantage (relative risk = 0.88, 95% confidence interval: 0.72-1.09). Total success rates were similar (relative risk = 0.99, 95% confidence interval: 0.95-1.02), and time to cannulation did not differ (mean difference (short-axis out-of-plane-long-axis in-plane)) = -3.52 s, 95% confidence interval: -11.09 to 4.05). Hematoma incidence was comparable (relative risk = 1.79, 95% confidence interval: 0.89-3.58). Overall, posterior wall puncture incidence did not differ; however, the non-dynamic needle tip positioning short-axis out-of-plane approach increased the posterior wall puncture risk compared with the long-axis in-plane approach (relative risk = 3.29, 95% confidence interval: 1.33-8.11). Vasospasm incidence was similar overall using both approaches (relative risk = 0.74, 95% confidence interval: 0.38-1.43), with a lower incidence reported in the dynamic needle tip positioning trials (relative risk = 0.27, 95% confidence interval: 0.09-0.80).ConclusionsThe short-axis out-of-plane and long-axis in-plane approaches showed comparable overall efficacy. The dynamic needle tip positioning-based short-axis out-of-plane approach may improve first-attempt success rates and reduce the incidence of vasospasm without an apparent increase in posterior wall puncture risk, whereas the traditional short-axis out-of-plane approach may involve a higher posterior wall puncture risk. These findings suggest that needle-tip tracking is as important as the imaging plane itself; however, larger pragmatic trials are needed to confirm this finding.