Modified Long-Axis In-Plane Ultrasound Versus Short-Axis Out-of-Plane Ultrasound For Radial Arterial Cannulation：A Prospective Randomized Controlled Trial

BACKGROUND Given a low first-pass success rate of the conventional SAX (short-axis) or LAX (long-axis) approach, ultrasound-guided radial artery cannulation in adults with radial artery diameter less than 2.2 mm may be still challenging. OBJECTIVE To assess the efficacy of modified long-axis in-plane(M-LAIP) versus short-axis out-of-plane (SAOP) or conventional palpation(C-P) approaches for ultrasound-guided radial artery cannulation. DESIGN A prospective, randomized and controlled trial. SETTING Operating room in a tertiary university hospital, from 1 July 2018 to 24 November 2018. PATIENTS A total of 201 patients (age 18 to 85 years, the diameter of the radial artery less 2.2 mm) were included. Patients with history of forearm surgery, ulnar artery occlusion, abnormal Allen test, etc, were excluded from this study. INTERVENTIONS All patients were randomized 1:1:1 to M-LAIP, SAOP or C-P. MAIN OUTCOME MEASURES The primary outcome was the cannulation success rate. Secondary outcomes included first location time and cannulation time, number of attempts. RESULTS The cannulation success rate was significantly higher in the M-LAIP group than in the SAOP group or C-P group (first success rate: 80.3% vs 53.8% or 33.8%; p =0.000; total success rate: 93.9% vs 78.5% or 50.8%; p =0.000). First location time (s) was significantly longer in the M-LAIP group compared with the SAOP group (31(28-35[12-44]) vs 15(14-17[10-21]); p =0.000) and the C-P group (31(28-35[12-44]) vs 12(8-13.5 [6-37]); p =0.000). However, the time of cannulation in the M-LAIP group (29(24-45[16-313])) was significantly shorter than that in the SAOP group (45(28.5-135.5[14-346]), p =0.002) and in the C-P group(138(27-308[12-363]), p =0.000). The number of attempts decreased in the M-LAIP group compared with SAOP or C-P group. CONCLUSION The M-LAIP procedure for ultrasound-guided radial artery cannulation can offer a higher success rate of the first-attempt and total cannulation, fewer attempts and less time of cannulation.