Accuracy of five formulae to determine the insertion length of umbilical venous catheters

Introduction Umbilical venous catheter (UVC) placement is a common neonatal procedure. It is important to position the UVC tip accurately at the first attempt to prevent complications and minimise handling. Catheters positioned too low need to be removed, but catheters positioned too high may be withdrawn in a sterile fashion to a safe position. We aimed to determine the precision and accuracy of five published formulae developed to guide UVC placement. Methods This was a prospective observational study. Following UVC insertion, anteroposterior and lateral X-rays were performed to identify catheter tip position. Parameters required to apply the five formulae were recorded. Insertion lengths were then calculated and compared with the gold standard (UVC tip at the level of the diaphragm on the lateral X-ray). They were also used to classify predicted UVC tip position as either correct (UVC tip at or up to 1 cm above the diaphragm), too high or too low. Results Of 118 eligible infants, 70 had the UVC tip in a position where measurements could be used. Their median (IQR) gestational age and weight were 28.5 (26-36) weeks and 1035 (745-2788) g, respectively. The predicted success rate for each formula ranged from 44.9% to 55.7%. A formula based on birth weight had the highest rate of either correct or high position (95.8%). Conclusions Inserting a UVC into a safe position on first attempt is difficult and low tip placement is common. Around half of UVCs need to be manipulated to achieve the desired position.