Arterial Cannulation With Ultrasound

The investigators will test whether ultrasound guidance improves the success rate of radial artery cannulation, compared to palpation alone, in a randomised controlled trial in an NHS hospital. Patients will be over 45 years old, undergoing general or neuraxial anaesthesia for non-cardiac surgery lasting 120 minutes or more. Patients will be randomly assigned to a palpation or ultrasound-guided technique for arterial cannulation. Patients will receive numbing local anaesthetic cream to the area beforehand. A needle is used to introduce the cannula into the artery. There will be a maximum of one attempt allowed. In addition to measuring success rate, we will also compare whether the successfully sited cannula provides an adequate arterial waveform, requires resiting at any point during the surgery and any complications which arise directly related to arterial catheterisation. Patients will receive standard anaesthetic and surgical care in all other respects.