Discussion
COMPLICATIONS
This prospective, randomized clinical study revealed that CVCs with the x-plane approach yielded a significantly higher first-puncture success rate, operator confidence score, and shorter catheterization time, along with a lower incidence of immediate complications compared to the single-plane approach.US-guided CVCs are recommended for routine use in ICU. However, there is no consensus on the application of in- or out-of-plane approaches, because each method has its own set of disadvantages. The out-of-plane technique requires users to follow the needle tip with the US probe, which is not intuitive for novice users and requires a significant learning curve because the needle is generally not visible until it traverses the axial imaging plane. Moreover, it requires the sliding or tilting of the transducer to follow the needle tip in real time and project the needle path, which is difficult to operate, particularly for novice operators [Our study shows that the first-puncture success rate was higher for the x-plane approach than for the single-plane approach for both IJVC (91.6% vs. 74.7%) and FVC (90.9% vs. 68.3%), although the overall success rate for US-guided CVCs was 100%. The higher first-puncture success rate, fewer puncture attempts, and shorter catheterization time were mainly attributed to the advantages of the x-plane approach, which overcame the limitations of the single-plane approach and allowed users to visualize both the transverse and longitudinal views simultaneously.The real-time biplane imaging technique offers visualization of the trajectory of the needle tip, which was confirmed by the long-axis view, and the confirmation of the needle tip inside the lumen, as well as the relationship of the target vessel to adjacent structures, which was offered by the short-axis view. This explains the higher first-puncture success rate (87.4% vs. 69.0% for IJVC and 90.9% vs. 68.3% for FVC, respectively) and shorter time (205 s vs. 311 s for IJVC and 228 s vs. 340 s for FVC, respectively) needed for CVCs in the x-plane group than that in the single-plane group. Meanwhile, the confidence score of the operator during the cannulation procedure was higher in the x-plane group (2 points for IJVC and 3 points for FVC, respectively), which could be another reason for the shorter catheterization time. Our results prove that the biplane approach optimizes the chances of successful cannulation and minimizes the risks to the surrounding structures.The higher incidence of immediate complications in the single-plane approach (28.7% vs. 10.5% for IJVC and 34.1% vs. 9.1% for FVC, respectively) was mainly due to undesired punctures with multiple skin breach to redirect the needle. This is explained by the fact that the operator cannot line up the thin US beam with the entire length of the needle, and both have the midline axis of the vessel longitudinal plane. During CVC positioning, the hand of the operator can slide by a few millimeters, and the three axes can move out of alignment with each other, thus allowing visualization of the artery. In this context, information regarding the location of the artery and target vein is lost, and the continuous display of the needle leads to a misleading sense of safety that may ultimately lead to redirection and repuncture of the needle, as well as arterial puncture. This also caused the high rate of arterial puncture when using single-plane approach for FVC. The biplane approach allows for the visualization of the needle path in the long-axis view, as well as the needle tip, target vessel, and surrounding structures in the short-axis view, as long as the probe is positioned perpendicular to the course of the vessel. Even if the needle path cannot be clearly displayed in the long-axis view, the position of the needle tip can be visualized in the short-axis view to ensure that the needle is inserted into the vascular lumen. Using this technique, the needle tip can be observed directly, and its progression can be inferred from the movements of the surrounding tissues, even if minimal probe adjustments are required in rare cases. This could be the reason why a higher rate of first-puncture success and a shorter insertion time were achieved in the biplane approach than those in the single-plane approach in the present study.Previous researches have reported the efficacy and safety of US-guided venous catheterization using the biplane approach [