A randomised controlled trial of radial artery cannulation guided by Doppler vs. palpation vs. ultrasound.

We randomly allocated 749 participants to radial artery cannulation by anaesthetic trainees, guided by Doppler (244), palpation (256) or ultrasound (249). Ultrasound increased the rate of cannulation at the first attempt by 14% (95% CI 5-22%), from 39% with Doppler or palpation, p = 0.002 for both. There were no differences in the rates of cannulation 5 min after the procedure started: 147/244 (60%) with Doppler; 160/256 (63%) with palpation; and 171/249 (69%) with ultrasound, p = 0.13.