Height-based formulas for predicting intravascular length of tunnelled neck central venous catheter in paediatric population.

Introduction: Central venous catheter (CVC) placement is commonly performed in children. We aim to develop simple formulas to predict CVC intravascular length to minimise radiation exposure associated with the procedure.

Methods: 124 paediatric patients who received tunnelled neck CVCs and subsequent CT thorax at Hong Kong Children's Hospital from January 2020 to July 2022 were reviewed retrospectively. Formula development cohorts were subdivided by insertion sites-9 right external jugular vein (REJV), 41 right internal jugular vein (RIJV), 14 left external jugular vein (LEJV), 10 left internal jugular vein (LIJV). Using measurements from CT by two radiologists, formulas predicting the CVC intravascular length based on height and insertion sites were developed using a linear regression model. These formulas were tested with validation cohorts (10 randomly selected cases in REJV and RIJV groups respectively). Validation cohorts were not available for LEJV and LIJV groups due to small sample sizes.

Result: The goodness-of-fit (R^2) of all formulas are above 0.8. In the validation cohorts, the REJV formula was predictive of intravascular CVC length within 1 cm in 70% of CVC with mean absolute difference of 0.63 cm (SD 0.48 cm), and the RIJV formula was predictive of intravascular CVC length within 1 cm in 80% of CVC with mean absolute difference of 0.67 cm (SD 0.53 cm).

Conclusion: Intravascular CVC length can be estimated using simple formulas based on height and insertion sites. Further prospective validation of the LEJV and LIJV formulas is needed.