Arterial Cannulation With Ultrasound

A drop in blood pressure during anaesthesia for a surgical procedure has been associated with worse patient outcomes, including complications such as damage to the heart, brain and kidneys. Continuous blood pressure monitoring prior to the start of anaesthesia alerts the anaesthetist to drops in blood pressure and allows this to be treated promptly. This may help to avoid the complications described above. Continuous blood pressure monitoring is carried out by inserting a small plastic tube (cannula) into an artery. In this study, the investigators propose inserting a cannula into the radial artery in the wrist before a patient is anaesthetised for surgery. The usual technique for insertion of this cannula is for the anaesthetist to identify the site of the radial artery by feeling for an arterial pulse with the fingertips (palpation). An alternative technique for identification is to use ultrasound. Ultrasound creates a two-dimensional image of the area under the skin on a screen, enabling the operator to visualise the artery being targeted. This may reduce the number of cannulation attempts required, reducing patient discomfort.