Revised formula to determine the insertion length of umbilical vein catheters.

UNLABELLED: The method of Shukla is commonly used to predict the insertion length of umbilical vein catheters (UVCs) but often leads to over-insertion. Malposition of UVCs can lead to complications. In this study, we compared the formula of Shukla, i.e., (3 x birthweight in kg + 9) / 2 + 1 cm with a revised formula, i.e., (3 x birthweight in kg + 9) / 2 cm in determining the insertion length of UVCs. A cohort where the revised formula was used for UVC placement (revised group) was compared with a historical cohort using the conventional formula (Shukla group). We evaluated the position of UVCs stated as the corresponding vertebra level with a radiograph of the infant's chest and abdomen immediately after insertion in both groups. Positioning of the catheter tip above the ninth or below the tenth thoracic vertebra was considered too high or too low, respectively. Median position of 93 UVCs placed according to Shukla was lower (seventh thoracic vertebra, interquartile range (IQR) 6-9) when compared to 92 UVCs placed according to the revised formula (eighth thoracic vertebra (IQR 7-9)). UVCs were more often over-inserted using the Shukla formula (73%) when compared to the revised formula (54%). One UVC in the Shukla group (1%) and two UVCs in the revised group (2%) were placed too low (p = NS).
CONCLUSION: The revised formula reduces the rate of over-insertion of UVCs without increasing the rate of inadequate lower positioning.