Vascular access in ill neonates who present to the ED can be challenging. Umbilical vein catheterization can be a life-saving option. The umbilical vein remains patent and viable for cannulation until approximately 1 week after birth.
On a sterile field use betadine or chlorhexidine to sterilize the tip of the umbilical cord stump. Tie a 4-0 nylon suture around the cord, approx 1.5 cm from the abdominal wall. Trim the end cord off, horizontally with a scalpel, just distal to the suture. Dilate and de-clot the umbilical vein (there is only one and it’s slightly larger than the two arteries).
Use a 3.5-French catheter for preterm newborns, and a 5-French catheter for full-term newborns.
Gently insert the catheter with the tip aimed toward the right shoulder. Advance 1-2 cm beyond the point at which good blood return is obtained (~4-5 cm in a full-term neonate). If resistance is encountered, loosen the suture. Avid forcing the catheter. If oozing occurs after placement, tighten the suture.
http://emedicine.medscape.com/article/80469-overview#a01