Does Longitudinal or Transverse Orientation of The Ultrasound Probe Improve Cannulation Success In Minimally Invasive Venous Surgery: A Multicentre Randomised Controlled Trial

Introduction: This study evaluates the effect of transverse (TO) and longitudinal (LO) ultrasound transducer orientation on saphenous vein cannulation during endovenous ablation. Aim: To determine whether probe orientation effects speed and pain in venous cannulation Methods: A single-blinded, multicentre, randomised controlled trial was performed in patients undergoing ultrasound guided venous cannulation for saphenous ablation. The primary outcomes were overall cannulation success and time to successful cannulation. Results: In total 100 patients were assigned to parallel LO and TO groups. Cannulation success was 100%. There was no significant variation in time to cannulation detected between the TO and LO (85seconds vs. 71seconds, p=0.314). Longitudinal orientation was associated with significantly fewer needle passes [median 3 (IQR 1-5) vs. 2 (IQR 1-3), p=0.026] and less pain (Median Visual Analogue Scale score 1 vs. 2.5, p=0.039) than those in the TO group. Conclusion: This trial has shown that while LO is associated with less procedural pain it has no significant effect on time to target vein cannulation during endovenous ablation.