Simple measurements to place umbilical catheters using surface anatomy

To use external anatomical landmarks to determine a new method for the estimation of appropriate insertion length of umbilical catheters, suitable for newborn infants of varying birth weight (BW) and gestational age.Neonates who had umbilical venous (UVC) or arterial (UAC) catheters placed soon after birth were included in the study. Catheters were placed using formulas derived by Shukla (1986) and/or Wright (2007), and adjusted to appropriate positions confirmed radiologically: UAC tip between T6-T10 vertebral bodies and UVC at the level of the diaphragm±0.5 cms. Final catheter length was compared with the length estimated by Shukla/Wright formulas and to four additional morphometric measurements: umbilicus to nipple (UN), umbilicus to midpoint of inter-mammary distance, umbilicus to xiphoid process and umbilicus to symphysis pubis (USp).Of 216 infants, 32 were excluded; UVC was placed in 170 infants and UAC in 125 infants. Among the morphometric measurements, UN-1 cm ( UN distance minus 1 cm) provided the best estimate of accurate insertion length of UVC, (r=0.984, P<0.001) and estimated correct insertion length of 94% of UVCs compared with 57% accuracy with Shukla formula for all BW categories (P<0.001). Morphometric measurement UN-1+2 USp (UN distance minus 1 cm plus twice the distance from umbilicus to symphysis pubis) showed significantly better correlation with appropriate insertion length of UAC (r=0.985, P<0.001) and estimated correct insertion length of 92% of UACs in all infants as compared with 57% accuracy with Shukla formula (P<0.001), and the correct insertion length in 94% of very low BW infants as compared with 68% accuracy with Wright formula (P<0.001).Simple and intuitive morphometric measurements UN and USp provide more accurate estimates of appropriate insertion lengths for umbilical catheters in infants with all BWs than commonly used BW-based formulas.