Chapter 45

Umbilical vessel catheterization can be used as a reliable method of obtaining rapid vascular access in the neonate. Umbilical vessel catheters may be used for fluid resuscitation, blood transfusion, medication administration, frequent blood sampling, and cardiovascular monitoring.1–4 Either the umbilical artery or vein may be used for vascular access. The artery can usually be accessed within the first 24 hours of life. It is occasionally possible to use the umbilical artery up to 7 days after birth.1 The umbilical vein can be accessed for up to 2 weeks of age.1,5

Umbilical artery catheterization is more desirable than umbilical vein catheterization because it allows frequent arterial blood gas sampling and continuous blood pressure monitoring, in addition to fluid, blood, and medication administration. Unfortunately, umbilical artery catheterization is more difficult and time consuming to perform, especially in unskilled hands. Therefore, umbilical vein catheterization is the preferred procedure for the infant in shock and in need of rapid resuscitation. Arterial access can be obtained later in a more controlled environment, such as in the neonatal intensive care unit. Umbilical vessel catheterization can lead to serious complications and should be reserved for the patient in whom peripheral venous access attempts have been unsuccessful.4,6

The fetal circulatory system is quite different from that of the neonate or infant (Figure 45-1). Oxygenated blood from the placenta travels via the umbilical vein, through the ductus venosus in the liver, to the inferior vena cava, and into the right atrium. Oxygenated blood from the inferior vena cava preferentially enters the left atrium through the foramen ovale. It then enters the left ventricle, then the aorta. This oxygen-rich blood supplies the brain prior to mixing with the oxygen-poor blood coming through the ductus arteriosus. Deoxygenated blood from the superior vena cava enters the right ventricle and is pumped to the pulmonary artery. It then passes through the ductus arteriosus to meet the oxygenated blood in the aorta.

###### FIGURE 45-1

The fetal circulation.

Pulmonary vascular resistance decreases dramatically as the infant takes its first breaths. The systemic vascular resistance increases when the umbilical cord is clamped. The foramen ovale closes with the combination of decreased pulmonary artery pressure and increased systemic resistance. The ductus arteriosus closes within 24 to 48 hours due to the release of prostaglandins and increased oxygen tension. The ductus venosus closes when the umbilical cord is clamped.

The umbilical vein and arteries can easily be differentiated by examination of a cross section of the umbilical cord (Figure 45-2). The umbilical vein is a single vessel with thin walls and a large lumen. It is usually flattened in one direction. There are two thick-walled umbilical arteries that are significantly smaller in diameter than the umbilical vein. Occasionally, only a single umbilical artery is present.

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