A study of insertional length of umbilical artery catheters in newborns

To correlate the neonatal body measurements that best predict insertional length of the umbilical artery catheter (UAC), we performed this study with two separate parts. In part I, we collected 120 cases with indication for umbilical artery catheterization from Mackay Memorial Hospital during December 1986 to November 1987. They were randomly divided into 4 groups and in each group the internal catheter length of UAC was calculated with formula of: Gr. 1. 3 birth weight (BW) (Kg) + 9 (cm), Gr. 2. suprasternal notch to public symphysis length (SSL) (cm), Gr. 3. 1/3 total body length (TBL) (cm), Gr. 4. shoulder to umbilicus length (SUL) + 2 (cm). The accuracy was 90% in BW group, 90% in TBL group, 70% in SSL group and 70% in SUL group respectively, and there was no statistical difference between any two groups. However, BW and TBL formula were clinically more practical than the other two (SUL and SSL). In part II of our study, out of 120 cases we selected 63 appropriate for gestational age (AGA) cases with catheter tips placed between the 7th and 9th thoracic vertebra. Correlation coefficients (rs) between inserted length of UAC and each of the four parameter (BW, TBL, SSL, and SUL) were shown to have statistically significant correlation. There was no statistical difference among those correlation coefficients. Modified regression equations derived from BW, SSL, TBL and SUL were 1.7BW (kg) + 2 (cm). 2. SSL (cm). 3. 1/3 TBL (cm) + 0.5 (cm). 4. SUL (cm) + 1 (cm). Further study would be necessary for establishing a more widely adaptable equation.