Indications Difficulty in localizing the radial artery by palpation Contraindications Absolute contraindications None Relative contraindications There are some relative contraindications for radial artery cannulation, but once an appropriate site is identified, there are no contraindications to use of ultrasonography other than Untrained or inexperienced ultrasound operator Complications None There are a number of complications of radial artery cannulation, but these are unrelated to use of ultrasonography.