A new formula for estimating insertion length of umbilical catheters in neonates: an observational study

Objective: We aimed to derive a new model that would improve accuracy in estimating the insertion length of umbilical catheters. Study Design This was a multi-centre prospective observational study of neonates admitted to neonatal units and needing umbilical line(s) inserted for clinical reasons. Demographic data, catheter-related measurements and the new external length measurement were collected at three tertiary-level neonatal units in South Wales, UK. Generalised linear models were used to estimate fits of the external length, birthweight, gestation and head circumference with catheter length and to derive a formula. The best fit was estimated by comparing r 2 values for each equation. Results Data from 113 infants for each venous and arterial line were analysed for the new mathematical formulae. For both UAC and UVC, a quadratic model based on birthweight was found to have the best fit for predicting the insertion length of the catheters, although the overall fit for UVCs was poorer for all explanatory variables. Conclusion Our prospective multi-centre observational study identified a quadratic model based on birthweight as the best fit for estimating the insertion length of umbilical lines in neonates.