Neonatal 4:
Umbilical Artery and Vein Cannulation Portal
The umbilicus contains two arteries and a vein. As seen below, the large vein connects with the portal vein on its way to the liver and continues on to the vena cava. When an infusion catheter is inserted into the umbilical vein, it should reach just into the abdomen or all of the way to the vena cava to avoid harming the liver with injected medications.
The two small arteries course downward on the inner aspect of the abdominal wall to connect with the left and right internal iliac arteries in the pelvis. When an infusion catheter is placed in one of the arteries, it should reach just above the bifurcation of the aorta or in the aorta above the diaphragm.
In an emergency situation, it is easiest and safest to cannulate the umbilical vein, placing the end of the cannula just within the abdominal wall. For longer term use, it is best to place the end of the umbilical vein cannula in the vena cava above the liver.
An umbilical artery catheter is valuable when frequent blood gases need to be obtained and when arterial blood pressure needs to be closely monitored. It is not used for the infusion of drugs.
To determine the length of the venous or arterial catheter to be inserted to reach the vena cava above the liver or the aorta above the diaphragm, measure the distance between the center of a line drawn between the shoulders and the umbilicus in cm.
The estimated length of catheter can now be read from a chart (check with an x-ray):
Length of catheter in cm |
Shoulder-umbilicus distance in cm | Add the lengh of the umbilical stump to these lengths | |
| Venous cath | 6.5 | 10 | |
7.2 | 11 | ||
7.9 | 12 | ||
8.6 | 13 | ||
9.3 | 14 | ||
10.1 | 15 | ||
10.8 | 16 | ||
11.5 | 17 | ||
| Arterial cath | 5.3 | 10 | |
6.1 | 11 | ||
6.9 | 12 | ||
7.7 | 13 | ||
8.5 | 14 | ||
9.3 | 15 | ||
10.1 | 16 | ||
10.9 | 17 |
Technique: Use sterile technique. Wear a mask, gloves, and gown if time allows. Prep the cord and surrounding skin with povidone solution. Place sterile towels on the field. Place a twill tape around the base of the umbilical cord to use as a tourniquet if bleeding occurs. Use one throw of a knot on the twill to hold it in place. Divide the cord with a scalpel or sterile scissors near the umbilical clamp. Identify the two arteries and the vein. Have an assistant hold the selected vessel for you using fine curved pickups.
Attach a three-way stopcock to the selected cannula and fill it with saline. Umbilical catheters have markings at 5 cm intervals. Use a 3.5 French catheter for an arterial line and a 5.0 French catheter for venous cannulation.
When an arterial line is inserted, slight resistance may be felt at the abdominal wall and again at the junction with the iliac artery branch. Twisting the catheter gently and applying gentle pressure or injecting 0.5 mL of 0.5% lidocaine to relieve spasm will usually allow successful advancement of the catheter. Insert the line to the desired length and obtain an x-ray to confirm correct placement of the T6-T10 level above the diaphragm or at the L3-L4 level just above the bifurcation of the aorta.
When a venous line is inserted, resistance may be felt as the catheter reaches its juncture with the portal vein. Gently twisting the catheter will usually allow it to reach the vena cava. Insert the line to the desired length and obtain an x-ray to confirm correct placement in the right atrium or vena cava above the diaphragm.
In the emergency situation, use the vein and insert the catheter only to 3 to 4 cm. Good back bleeding should be obtained if it has been inserted far enough. The catheter may be replaced with a longer one later.
To secure the catheter in place, tighten the twill tape and add another throw to the knot. Place a ooo or oooo silk suture in the skin and tie it down. Now use the long limbs of this suture to wrap around the catheter at the umbilicus and tie it in place. Place a clear plastic dressing on the abdominal wall on either side of the umbilicus to protect the skin.
Complications include infection, air embolism, and thrombus formation. Perforation of the vessels may result in internal hemorrhage, so do not use excessive force when passing the lines. The lines can come apart with resulting bleeding, so be sure the IV connections are secure. Iliac artery spasm can occur resulting in a poorly perfused, blue leg. Treat by wrapping the other leg in a warm towel. The spasm should relent within 15 minutes. If it does not, remove the catheter. Hepatic necrosis may occur if hypertonic meds are injected in to the portal system. To avoid this complication, the venous catheter tip must either be just in the abdomen or in the vena cava.
To remove an arterial umbilical catheter, withdraw the catheter until it is just outside of the abdominal wall. Introduce a small bubble of air at the catheter tip. Watch the pulsations of the bubble caused by the arterial pressure. When the pulsations stop, in about 3 to 5 minutes, remove the catheter entirely and put pressure on the artery to stop any bleeding. The baby can kick the catheter out before you are ready, so restrain the legs.
To remove a venous umbilical catheter, withdraw the catheter until it is just outside of the abdominal wall. Wait for clotting, then remove the catheter entirely. Be careful to occlude the vein because air embolism may result if the vessel remains open.