Comparison of short-axis out-of-plane vs. long-axis in-plane ultrasound-guided radial artery cannulation: a randomized controlled trial

Background and Importance: Radial artery cannulation is a critical procedure in anesthesia and critical care, facilitating continuous hemodynamic monitoring and arterial blood sampling. Ultrasound guidance has significantly improved success rates compared to traditional palpation techniques. However, the optimal ultrasound-guided approach – short-axis out-of-plane (SAOOP) versus long-axis in-plane (LAIP) – remains debated. This study compares these techniques to determine which offers better first-attempt success rates, shorter cannulation times, and fewer complications. Methods: This was a single-blinded, randomized controlled trial conducted at a tertiary care center. A total of 80 adult patients requiring radial artery cannulation were randomly assigned to either the SAOOP or LAIP technique. The primary outcome was the first-attempt success rate. Secondary outcomes included ultrasound-guided localization time, cannulation time, number of attempts, and incidence of complications. Data were analyzed using SPSS, with statistical significance set at P < 0.05. Results: The first attempt success rate was 92.5% in the SAOOP group and 80% in the LAIP group, although the difference was not statistically significant ( P = 0.105). The SAOOP technique resulted in significantly shorter localization (2.33 ± 0.90 vs. 4.50 ± 2.37 s; P < 0.001) and cannulation times (30.28 ± 8.90 vs. 45.18 ± 11.70 s; P < 0.001). Hematoma formation was slightly higher in the SAOOP group but was not statistically significant ( P = 0.077). Conclusion: Both techniques were effective for radial artery cannulation. SAOOP demonstrated shorter cannulation times and a higher first-pass success rate, making it a viable option, although operator expertise and patient factors must be considered.