Radial arterial cannulation is a common invasive procedure for real-time measurement of arterial blood pressure. Placement of the arterial catheter using conventional palpation is often relatively easy and quick, but this is not always true. A relatively new method for direct visualization of the artery is the use of two-dimensional ultrasound. This technique allows cannulation of the artery to take place under real-time visualization and may increase the success rate of first time pass of the needle. Another technique utilizing Doppler has also proven to be effective in cannulating the radial artery. This technique utilizes changes in acoustic pitch as the probe passes directly over the artery. The primary objective of this study is to compare the first attempt success rate for radial artery cannulation among the palpation, Doppler and U/S guided technique when applied by trainees. Secondary outcomes include: success rate within 5 minutes, successful, number of attempts required, and correlation between success rate and operator experience for successful cannulation of the radial artery.

Radial artery cannulation is a common invasive procedure in the operating room, intensive care unit and emergency department. It allows continuous hemodynamic monitoring and repeated arterial blood sampling. Although severe complications are rare, successful radial artery cannulation can be technically challenging, particularly in hypotensive patients and those with vascular disease. Multiple unsuccessful attempts at arterial cannulation increase patient discomfort, delay timely care and may also contribute to adverse events such as arterial spasm or local hematoma.

The radial artery is traditionally located by palpation. A number of techniques to aid radial artery localization have been described. Doppler-assisted radial arterial cannulation was first described in 1976. Several case reports suggest that Doppler can be helpful in patients with difficult arterial access. More recently, ultrasound-guided radial artery cannulation has been described. In a recent meta-analysis of four randomized controlled trials, ultrasound increased the rate of cannulation on the first attempt by 71% compared with palpation. However, two of the studies were of children and all four were small, with 30-152 participants (311 in total), making the generalizability of these results to adult patients uncertain. Furthermore, variation in the training and experience of the operators was evident within one of the studies.

Accordingly, the aim of this study is to compare three different radial arterial cannulation techniques in adult surgical patients when performed by anesthesia residents: Doppler; palpation; and ultrasound. We think that ultrasound would have a higher rate of cannulation on the first attempt compared with other techniques.

Inclusion Criteria:

• Main OR patients at UIHC who require arterial catheter placement for surgery

Exclusion Criteria:

• The patients who will be excluded from the study include those who have had arterial cannulation in the previous month, infections at site of insertion, and AV shunts in upper extremity.

We are not planning on sharing IPD.

3 days