To the Editor: We read the randomized, controlled trial on ultrasound-guided umbilical venous catheter (UVC) insertion in neonates with great interest [1]. We applaud the authors for a pertinent study in the current era that will contribute to reducing radiation exposure in neonates. The authors showed that ultrasound-guided UVC insertion significantly reduced the rate of catheter tip malposition. Index study considered plain radiographs as a gold standard which are less sensitive and specific than ultrasound in identifying catheter tip position. In a recent systematic review comparing radiographs with ultrasound for UVC tip position verification, the overall diagnostic sensitivity and specificity (with 95% CI) of plain radiographs were 0.90 (0.71–0.97) and 0.82 (0.53–0.95), respectively [2]. Therefore, the cases where the radiograph classified the tip position as too high or too low may be incorrect in many cases. Recent literature suggests ultrasound with saline contrast injection should be the gold standard for catheter tip localization [2, 3].

During ultrasound-guided UVC insertion, the tip is placed at the inferior cavoatrial junction, which a trained person can easily visualize. Hence, the chances of putting the catheter tip too high (into the right atrium) or too low is negligible, provided the tip is well visualized. In the index study, 7 of 11 neonates have either high-placed or low-placed UVC, probably due to poor visualization on ultrasonography (which is quite common). In such cases, saline contrast injection (popularly known as agitated saline contrast) can help localize the tip [4]. This technique was initially used to identify the cardiac shunts and has been recently used for identifying central venous catheter tip position. Using agitated saline contrast might improve the successful UVC catheter placement rates, hence further improving the efficacy of ultrasound-guided catheter insertion.