Arora et al in 2020 compared the rate of first pass radial artery cannulation using out- of plane vs in-plane imaging. It was a prospective, randomised, observational study carried out in a tertiary care centre. They compared 84 adult patients undergoing cardiac surgery after dividing them into out-of-plane USG group (n=42) and in-plane USG group (n=42). In each approach, the number of times first pass success was achieved, number times the cannula was redirected, number of skin punctures, incidence of hematomas, and number of failed attempts were noted. The first-pass success rate was statistically significant (p=0.007) in the In-Plane USG group. A larger number of patients in the Out-of-Plane group required redirection of cannula (p= 0.002). The number of times skin needed to be punctured was also greater in the Out-of-plane group as compared to the In-Plane group (p= 0.002). The time taken for completion of cannulation and the incidence of hematomas were similar in both the groups. They concluded that the In-plane Ultrasound technique was superior in achieving a higher first pass success rate and also ensuring minimal redirections and reduced number of skin punctures. 

 Sethi et all in 2016 also did a comparison of the Short- axis out-of-plane (SA-OOP) and the long-axis in-plane (LA-IP) USG guided radial artery cannulation in adult patients. It was a prospective, randomized controlled trial. 150 patients of ASA class 1- 3 and between the age group of 18-70 were included. They were randomized into two groups of 75 each. The primary out come was successful cannulation in the first attempt. First attempt arterial cannulation was successful in 80% of patients in the SA-OOP group when compared to 82.6% in the LA-IP group. Time to successful cannulation of the artery was similar in the two groups. But time to localize the artery was higher in the LA-OOP technique (p>0.001).  Hence they concluded that the rate of first pass success and the time taken for completion of arterial cannulation was similar in both the techniques.

 Zeng et all in 2020 did a study comparing Oblique axis/In-plane (OA-IP) versus longitudinal axis/in-plane (LA-IP) approach for ultrasound guided radial artery cannulation. 60 surgical patients in the age group of 18-70 years, and falling in ASA class 1-3 were selected. They required invasive arterial line for monitoring. The primary objective was to compare the first attempt success rate in OA-IP as compared to LA-IP. They inferred thar the first attempt success rate was higher (93.3% vs 60%, p= 0.005) in the OA-IP technique when compared to the LA-IP technique. The OA-IP technique was also associated with shorter cannulation time and fewer injuries.

 Wilson Et all in 2019 did a comparison between ultrasound guided vs traditional palpation technique which was carried out by residents. 60 patients above the age of 18 requiring arterial cannulation for invasive monitoring or frequent blood sampling were recruited. The were randomized in to either groups. Their results showed that the ultrasound guided arterial cannulation group required fewer attempts as compared to the palpation technique group (96% vs 47%). They concluded that the residents were more successful and had fewer cannulation attempts with the ultrasound guided technique when compared to traditional arterial cannulation after standard intern-level ultrasound training. 

 Hansen Et all in 2014 compared Ultrasound guided dynamic needle tip positioning radial artery cannulation to traditional landmark technique. It was a randomized, patient blinded, crossover study. The patients underwent bilateral radial artery cannulation using both techniques. The primary objective was to determine the difference in needle manipulation time. Forty patients were analyzed. There was no significant difference in the needle manipulation time. In the traditional palpation technique there was use of a higher number of skin perforations, catheters and attempts at targeting the vessel. First attempt success was significantly higher in the ultrasound dynamic needle tip positioning group. They concluded that the ultrasound dynamic needle tip positioning technique significantly improves the clinically relevant parts of the procedure.