Iowa Neonatology Fellows
Revised John Dagle MD, PhD
Peer Review Status: Internally Peer Reviewed
YouTube video for umbilical line placement
- Umbilical artery catheters (UAC) are used primarily for monitoring blood pressure and obtaining samples for blood gases. In order to maintain the patency of the catheter, a saline solution containing heparin (0.25 U/ml) is infused through the line. Medications and other solutions, including parenteral nutrition solutions, should be given through a venous line (peripheral or central), unless discussed with the staff neonatologist.
- Umbilical vein catheters (UVC), are used for exchange transfusions, monitoring of central venous pressure, and infusion of fluids (when passed through the ductus venosus and near the right atrium); and for emergency vascular access for infusions of fluid, blood products or medications.
- Before the procedure is begun, the correct depth of the umbilical artery catheter insertion should be estimated (see #6 below). Sterile gowns and gloves should be worn, as well as a head cover and a mask. A sterilized umbilical catheterization tray with the necessary instruments and drapes is available in the nursery. After opening the tray, alcohol and sterile syringes, stopcocks, catheters and saline will be placed on it. Sterile technique must be observed; the use of goggles (or eyeglasses) is recommended.
- An umbilical catheter with a single end hole may be used for the catheterization of either umbilical artery or vein. On most occasions, it is advantageous to place a double lumen UVC. Infants with a birth weight of less than 1.5 kg will usually require a 3.5-Fr catheter for arterial catheterization. 5-Fr catheters are used for arterial placement in larger infants. In general, umbilical venous catheters are 5 Fr. For babies less than 500 grams, 3.5 Fr double lumen catheters are available.
- A sterile stopcock is attached to all ports on all lines and the system is flushed with saline to remove all air bubbles.
- External measurements are made to determine how far the catheter should be inserted. In a high setting, the arterial catheter tip (UAC) should be positioned between the sixth and tenth thoracic vertebrae on chest x-ray. This can be achieved by inserting the catheter 1 cm more than the infant's umbilical-to-shoulder length or 2 cm more for term infants or 9 cm + (3 cm x wt in kg). This placement is traditionally preferred. A low-lying arterial catheter should have the tip at the third to fourth lumbar vertebra calculated at 2/3 the infant's umbilical-to-shoulder length.
- The infant's abdomen and cord are cleaned with alcohol. The alcohol should be sparingly applied to prevent pooling under the infant's back and buttocks. In infants less than 1.5 kg, only the cord is cleaned to avoid chemical injury to the abdominal skin. The area is then draped so that only the cord is exposed.
- Tie a piece of umbilical tape around the base of the umbilical cord tightly enough to minimize blood loss but loosely enough so that the catheter can be passed easily through the vessel.
- Using a scalpel, the cord is cut cleanly 1.0 cm from the skin. An alternative method is to hold the cord with a hemostat and gently twist back to expose the cord. A scalpel is used to cut about 2/3 of the way through the cord.
- The cord is stabilized with a forceps or hemostat, and the vessels identified. The single, large, thin walled oval vein can readily be distinguished from the two smaller, thick-walled round arteries (see diagram). If the cord is cut close to the skin the 2 arteries tend to be located more caudally, while the large single vein tends to be located more cephalad.
- The arteries are usually constricted, so that the lumens appear pin-point in size. By gently inserting the closed tips of the curved iris forceps into the lumen of the artery until the cut end of the artery is at the bend in the forceps, and then allowing the spring of the forceps to gently spread the tips, the artery can be carefully dilated.
- Grasping the catheter with a forceps or between the thumb and forefinger, the catheter can be inserted into the lumen of the dilated artery. Supporting the stump is usually necessary. Once the catheter has been inserted, it may encounter resistance at the level of the anterior abdominal wall or at the bladder. This resistance can usually be overcome by application of gentle, steady pressure. Repeated probing movements or excessive pressure must be avoided to prevent pushing the catheter outside of the vessel lumen (false tracking). If unsuccessful, wait 2-3 minutes until the vasospasm ceases, or attempt the other umbilical artery.
- After the catheter is advanced the appropriate distance, the position of the catheter should be confirmed by x-ray.
- Observe both legs for evidence of blanching, cyanosis or mottling. If a "blue leg" develops (presumably from vasospasm), the catheter should be removed or carefully observed for a short period of time to allow for resolution of the impaired circulation.
- After placement of the catheter, a purse-string suture is placed around the umbilicus taking care not to puncture the catheter.
- The procedure for catheterization of the umbilical vein (UVC) is similar; differences are as follows:
- Remove any visible clots from the lumen of the vein with forceps.
- Never leave the catheter open to atmospheric pressure. The abdominal venous system is under negative pressure; with a deep inspiration air can enter the catheter with resultant air embolism.
- For administration of fluid, the venous catheter must be in the inferior vena cava, just below the right atrium. Inserting the catheter two-thirds of the shoulder-to-umbilicus distance is a good estimate. A catheter in the portal venous system must not be used for the long-term administration of fluids or medications and should be removed once better central access can be obtained.
- For the purpose of an exchange transfusion, the catheter should be advanced only until there is a free flow of blood, but never more the 8 cm in the full term infant. This catheter should be used only for withdrawal of blood (see section on Exchange Transfusion).
- If code medications and/or fluid need to be given in the delivery room, a UVC should be placed and advanced only until there is a free flow of blood as in "D" above.
- To sample blood from an umbilical catheter, withdraw 1 ml of blood into a sterile syringe, keeping the syringe perpendicular to the infant. This will cause the blood to settle near the tip of the syringe. The tip of the syringe should be kept sterile, and not placed in the infant's incubator or bed.
- The blood sample is then withdrawn into a second syringe and the initially withdrawn blood reinfused and the system flushed with a small amount of saline until free of blood.
- The alcohol should be washed off with sterile water after the procedure is completed. This is important to prevent clinical burns, especially in very small infants.
- The umbilical artery catheter is removed slowly (~1cm/minute after withdrawing to 6 cm) when it is no longer needed. With proper care, the catheter need not be changed for the duration of its use.