Arterial cannulation is a procedure which is very often put into use in acute and critical care settings. It is an invasive means to measure the blood pressure and mean arterial pressure more accurately as well as to provide beat to beat assessment of hemodynamic status in critical situations compared to the non-invasive means. In addition, it is very useful for repeated sampling of ABG in critical care settings.

Continuous invasive blood pressure monitoring is of extreme importance for monitoring patients who are in a critical condition or those who are undergoing a major surgery. Although non-invasive blood pressure measurement is generally safe, it can lead to rare but severe complications. One possibility is that of compartment syndrome, which can develop after prolonged periods of frequent cycling and mostly observed in situations such as trauma to the limb, hypovolemic shock or impaired distal limb perfusion.

Arterial cannulation needs technical expertise for placement and management. Despite drawbacks such as high risk, invasive procedure, associated complications, and high cost involved, it is still the accepted reference standard for blood pressure monitoring. Arterial cannulation is indicated if there is need for continuous, real-time blood pressure monitoring, anticipated pharmacological or mechanical cardiovascular manipulation, need for repeated blood sampling, failure of indirect arterial blood pressure management or requirement of supplementary diagnostic information from arterial waveform.

For invasive blood pressure monitoring, various arteries can be used including the radial, brachial, axillary, femoral and dorsalis pedis arteries. The most common access for real time blood pressure monitoring is gained via radial artery cannulation. This is so because the radial artery runs a superficial course, has fewer complications, and the hand has a dual blood supply. Before cannulating the radial artery, assessment of collateral blood flow by the modified Allen’s test is mandatory. Though Allen’s test is the only tool available for assessment of efficiency of collateral circulation in hand, unfortunately, predictive value of this test has been found to be poor and prognostic value of this test in detecting adequate collateral circulation is unconfirmed.
 Radial artery cannulation by palpatory (conventional) method is achieved mainly by three techniques: direct arterial puncture, guidewire assisted cannulation (Seldinger technique), and the transfixion withdrawal method.

In recent years, ultrasonography-guided radial artery cannulation has become a common method to access the radial artery. Ultrasound guided technique offers a direct view of the vessel lumen followed by guiding the cannula directly inside the lumen avoiding damage either to the vessel or adjacent structures. There are studies that have also shown that ultrasonography-guided radial artery cannulation improves the first attempt success rate for cannula insertion and also consumes less time as compared to the conventional palpatory method. However, there is a learning curve for achieving expertise in the ultrasound guided technique.

On review of literature for studies, we found that there is a paucity of research materials with respect to comparing the conventional and ultrasound guided techniques of arterial cannulation particularly in Indian population. We are undertaking a study comparing conventional palpatory method of radial artery cannulation with that of ultrasound technique for radial arterial cannulation in Indian adults posted for elective major surgical procedures.