Comparison of the Modified Approach and Conventional Approach of Radial Artery Cannulation Under Short-axis Ultrasound Guidance in Intensive Care Unit(ICU) Hypotensive Patients: a Randomized Controlled Study.

Hypotensive patients in the intensive care unit may have extremely unstable hemodynamics. Blood pressure is the most important outcome in the diagnosis and treatment of shock. Vasopressor drugs are often required to maintain blood pressure in addition to fluid infusion. Noninvasive blood pressure measurement is unable to meet the clinical requirements. It is necessary to establish an invasive blood pressure monitoring method as soon as possible that can observe the real-time pressure. Radial artery cannulation has become the most commonly used due to its superficial location and less severe complication. However, radial artery cannulation is difficult to achieve in hypotensive patients due to weak radial artery pulsation, small arterial diameter, and peripheral vasospasm as blood flow is directed toward central vessels.

Some studies have shown that ultrasound-guided cannulation is more successful than the palpation technique. However, the success rate is largely dependent on the ultrasound operator's experience and skills. The operator requires good hand-eye coordination, technical skills, and some experience to overcome this shortcoming of ultrasound, which limits the advantages of ultrasound-guided vascular puncture, especially for operators with insufficient experience. There are 2 basic approaches in needling techniques: short-axis out-of-plane(SA-OOP) and long-axis in-plane(LA-IP) techniques.

In-plane technology requires the operator to be very skilled at ultrasound technology, which is more dependent on experience and can be difficult for novices to master; on the other hand, given that the long axis is subject to slice-thickness artifacts, due to the measurable thickness of the ultrasound beam itself, the cannula in the long axis appears to be in the same plane as the extremely small radial artery, even when the cannula has not been successfully inserted into the artery. Therefore, we prefer the out-of-plane technique.

The short-axis view has the advantages of providing better visualization of the surrounding structures and easier imaging which is convenient for novices to master. The procedure of radial artery puncture can be divided into 3 steps. The first step is to locate the puncture site, the second step is the puncture, and the last step entails the insertion of the cannula into the radial artery.

The first step is particularly important because appropriate localization facilitates the success of the puncture and insertion. The first difficulty encountered during radial artery puncture is the exact positioning of the puncture point. Ultrasound with developing lines guided by dynamic ultrasound has achieved a good effect in patients without hypotension. In the group with the modified technique, we use the developing line to locate the puncture site.