Comparison of ultrasound-guided oblique-axis versus short-axis approaches for right internal jugular vein cannulation in the left decubitus position: a prospective, randomized, single-center trial
In a prospective randomized trial of patients requiring right internal jugular vein cannulation in the left decubitus position, the ultrasound-guided oblique-axis approach demonstrated a higher first-time puncture success rate and fewer mechanical complications compared to the short-axis approach, although the evidence for the primary endpoint was borderline.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In hospitals, doctors often need to thread a thin tube into a large vein near the heart to deliver life-saving medicines, monitor pressure, or provide fluids. This procedure, known as central venous cannulation, is a routine but delicate task. The most common spot for this is the right internal jugular vein, a large vessel running up the side of the neck. While doctors usually perform this with the patient lying flat on their back, surgery sometimes requires patients to be positioned on their side. In this sideways position, the anatomy shifts, the vein can collapse slightly, and the usual landmarks doctors use to find the vein become hidden. To make this difficult job safer and more accurate, doctors now use ultrasound machines. These devices act like a flashlight, letting the doctor see the vein and the needle in real time as they work. However, there is a debate about the best way to hold the ultrasound probe. One method looks at the vein from directly above, like a cross-section, while another looks at it from an angle that shows the needle's path more clearly. It has been unclear which of these two ways works better when the patient is lying on their side.
A team of researchers at Shanghai Tongren Hospital decided to settle this question with a direct comparison. They recruited seventy-four patients who were scheduled for elective surgery requiring them to lie on their left side. All these patients needed a tube placed in their right neck vein. The researchers randomly assigned each patient to one of two groups. In the first group, the doctors used the traditional short-axis approach, where the ultrasound probe sits flat across the neck, showing the vein as a round circle. In the second group, they used an oblique-axis approach, where the probe is tilted to an intermediate angle. This tilt allows the doctor to see the needle entering the vein from the side while still keeping the vein and the nearby artery visible next to each other. The doctors performing the procedures were highly experienced specialists, and a separate observer recorded every attempt and the time it took, ensuring the data was precise.
The results showed a clear advantage for the angled, or oblique-axis, method. When using this tilted view, the doctors successfully placed the needle on the very first try in twenty-seven out of thirty-seven patients, which is about seventy-three percent. In contrast, the traditional flat view succeeded on the first try in only eighteen out of thirty-seven patients, or roughly forty-nine percent. Beyond just getting it right the first time, the angled method also led to fewer complications. In the group using the traditional flat view, six patients experienced mechanical issues, such as the needle accidentally piercing the back wall of the vein or hitting the artery. In the group using the angled view, there were zero such complications. The total time to complete the procedure was slightly faster with the angled approach, though the difference was small enough that it could have been due to chance.
The study suggests that tilting the ultrasound probe to see the needle's path more clearly is a safer and more effective way to access the vein when a patient is lying on their side. This method helps the doctor keep the needle tip in sight as it travels through the skin and into the vein, reducing the risk of missing the target or damaging surrounding tissue. While the statistical evidence for the first-attempt success was strong, the researchers noted that the study was relatively small and that the results for the primary goal were on the edge of significance. This means that while the findings are promising and point in a clear direction, larger studies involving more patients and different hospitals will be needed to confirm that this angled technique is definitively the new standard of care. For now, the data indicates that changing the angle of the ultrasound probe can make a difficult medical procedure significantly easier and safer for patients who cannot lie flat.
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