Umbilical Vessel Catheterization
Aris C. Garro
James G. Linakis
Introduction
Umbilical vessel catheterization is used frequently in the newborn period for transfusion therapy, blood pressure monitoring, emergency delivery of medications and fluids, delivery of parenteral nutrition, and blood sampling. Although most likely to be performed in the neonatal ICU setting, arterial or venous catheterization also can be performed in the emergency department (ED) for the resuscitation of infants delivered in the prehospital or ED setting. Peripheral intravenous access should be attempted first; however, such access can at times be difficult to obtain. Umbilical vessel catheterization provides a reliable means of emergency vascular access in the newborn. In addition, the umbilical vein should be considered as an option for emergency access in the neonate up to 2 weeks of age. Although it is associated with a higher complication rate, this method has the advantage of providing central venous access and allowing direct visualization of the vessels to be catheterized.
Anatomy and Physiology
The fetal cardiovascular system serves prenatal needs and allows for modifications after birth that lead to a postnatal circulatory pattern (Fig. 38.1) (1). In the fetal circulatory system, well-oxygenated blood (∼80% saturated) returns from the placenta through the umbilical vein, which courses through the hepatic sinusoids and ductus venosus to the inferior vena cava. High pressure in the fetal pulmonary vascular system results in the majority of blood being shunted from the right atrium across the foramen ovale into the left atrium. One third of the blood that reaches the right ventricle is distributed to the lungs, while two thirds is shunted to the aorta by way of the ductus arteriosus. Umbilical arteries receive approximately 40% to 50% of the mixed blood in the descending aorta (∼58% saturated with oxygen) and return it to the placenta, where O2, CO2, nutrients, and waste products are exchanged. The remainder of the blood from the descending aorta circulates through the gut, kidney, and lower extremities.
Numerous changes occur in the circulatory system following birth. With the first breath and the inflation of alveoli, pulmonary vascular resistance falls. Elevations in PaO2 and pH contribute to pulmonary vasodilation and further reduction of pulmonary vascular resistance. In contrast, neonatal systemic resistance is immediately increased when the umbilical cord is clamped. These dramatic changes in pressure result in a reversal of the gradient across the atrial septum and closure of the foramen ovale.
The ductus arteriosus begins to constrict almost immediately following birth, stimulated by increased oxygen tension and decreased circulating prostaglandins. Functional closure generally occurs 1 to 2 days after birth. The ductus venosus also closes once the umbilical cord is clamped. The umbilical arteries begin to constrict within minutes of birth and close before the umbilical vein. The umbilical vein may retain some degree of patency for up to 2 weeks after the cord is clamped and cut.
The umbilical arteries and vein can be differentiated in a cross section of the umbilical cord based on a number of characteristics. The vein is generally located on the cephalad end of the umbilicus. It is thin walled, with a large lumen, and only a single vein is present within the cord. The umbilical artery possesses a thicker wall and a smaller lumen and may appear slightly protuberant above the cut umbilical surface. Two arteries generally are present in the umbilical cord; however, approximately 0.5% of newborns will have only one umbilical artery. A patent urachus is a persistent embryologic connection to the bladder that may rarely be present and can appear similar to the umbilical vein but without bleeding.
 Figure 38.1 The fetal cardiovascular system illustrating the course of the umbilical vessels. Structures marked with an asterisk (*) close soon after birth. |
Indications
Umbilical artery catheterization is indicated for newborns with severe cardiopulmonary insufficiency requiring mechanically assisted ventilation. The umbilical artery catheter allows for frequent arterial blood gas determinations and can be used for administration of fluids, medications, and exchange transfusion. It is usually quite simple to catheterize the umbilical artery in a sick infant during the first hour of life, and most infants can be catheterized within the first 24 hours. Occasionally this route can be used up to 7 days of age.
Umbilical vein catheterization in the ED or delivery room is recommended for emergent situations in which delivery of resuscitative medications, volume expanders, or blood products is the desired goal. Catheterization of the umbilical vein is easiest in newborns but has been successful in infants up to 2 weeks of age.
An umbilical vessel catheter (arterial or venous) should never be inserted in the presence of omphalitis or impetiginous skin lesions. It is also generally contraindicated when a possibility of intestinal hypoperfusion or necrotizing enterocolitis exists, both of which are often suggested by abdominal distention. Finally, inserting an umbilical catheter for routine administration of parenteral fluids or medications or for routine blood sampling is inappropriate.
Equipment
Radiant warmer with light source
Prep solution (povidone-iodine), sterile drape, gauze pads
Mask, cap, goggles, sterile gloves, gown
Scalpel (No. 11 or 15)
Curved, nontoothed iris forceps (4″) or pointed, solid metal dilator
Small, smooth curved hemostat(s)
Straight Crile forceps
Iris scissors
Needle holder
Nonthrombogenic, molded-tip umbilical catheters (3.5, 4, 5, and 8 French with end hole)
3.0 or 4.0 silk suture on curved or straight needle
Linen umbilical tape (∼15″)
Adhesive tape
10-cc syringe filled with normal saline (NS) (with or without heparin 1 unit/mL)
D5W (5% dextrose in water), D10W (10% dextrose in water), or NS infusion setup (with heparin 1 unit/mL, unless medications incompatible with heparin)
Fluid chamber, i.v. tubing, infusion pump, 0.22-μm filter
Three-way stopcock, cardiac monitor, pulse oximeter
Procedure
Preparation
Treatment for cardiorespiratory disturbances should begin before commencing the procedure. The child is placed beneath a radiant warmer and the extremities are restrained in a supine frog-leg position (Fig. 38.2). The cardiac rate should be monitored, and adequate oxygenation should be made available throughout the procedure. The clinician performing the procedure should wear a surgical gown, gloves, cap, mask, and goggles (Chapter 7). The infant’s abdomen and remaining umbilical cord is scrubbed with a bactericidal solution, such as povidone-iodine, from the xiphoid process to the symphysis pubis. Pooling of solution at the infant’s side should be avoided because this may result in skin blistering. The umbilical area is draped in a sterile fashion, and the infant’s head is left exposed for observation.
A purse-string suture or umbilical tape loosely tied with a surgeon’s knot is placed at the base of the umbilical cord to provide hemostasis and an anchor after line placement.
The umbilical tape or suture that is secured at the base of the umbilicus should provide hemostasis but should not be tight enough to result in tissue ischemia. The cord is grasped full thickness with forceps between 0.5 to 2 cm from its base and cut transversely at the top edge of the forceps using the scalpel (Fig. 38.3A). The cord should be transected in a plane perpendicular to the cord axis to preserve recognizable vessel orientation and anatomy. It is prudent to make initial cuts as far from the base of the umbilical cord as possible to provide residual cord length if further attempts are required. A forceps or thumb and index finger are used to grasp the umbilical stump, and the vessels are identified.
The umbilical tape or suture that is secured at the base of the umbilicus should provide hemostasis but should not be tight enough to result in tissue ischemia. The cord is grasped full thickness with forceps between 0.5 to 2 cm from its base and cut transversely at the top edge of the forceps using the scalpel (Fig. 38.3A). The cord should be transected in a plane perpendicular to the cord axis to preserve recognizable vessel orientation and anatomy. It is prudent to make initial cuts as far from the base of the umbilical cord as possible to provide residual cord length if further attempts are required. A forceps or thumb and index finger are used to grasp the umbilical stump, and the vessels are identified.
 Figure 38.2 Positioning and restraint of the neonate for umbilical vessel catheterization. Note shoulder to umbilicus and crown to heel (total body length) measurements. Shading represents area to be cleansed with bactericidal solution. |
 Figure 38.3 Introduction of the umbilical artery catheter. |
Arterial Catheterization
A curved hemostat is used to grasp the cut edge of the cord near the artery selected for catheterization, or two hemostats are used to grasp opposite sides of the umbilicus. The edges are then everted (Fig. 38.3B). Using curved iris forceps without teeth, approximately 1 cm of arterial lumen is gently dilated by repetitively introducing and opening the tips of the forceps within the lumen. A pointed, solid metal dilator can be used in place of the iris forceps, with careful attention directed toward not tearing the arterial wall.
The catheter, previously flushed with heparinized solution, is grasped approximately 1 cm from its tip with thumb and index finger or with small forceps, and the tip is inserted into the arterial lumen (Figs. 38.3C–D). A 3.5 to 4 French catheter is used for infants weighing less than 2 kg, and a 5 French catheter for infants weighing more than 2 kg. During insertion, tension is placed cephalad on the cord so that the catheter can be advanced more directly toward the feet. The catheter is passed using gentle, constant pressure to overcome resistance, which is usually felt at two points. Slight resistance is first
met at 1 to 2 cm, where the umbilical artery curves toward the feet; placing tension cephalad on the cord helps to reduce this resistance. The clinician will feel greater resistance at the junction of the internal iliac artery at 5 to 6 cm, where the artery turns upward (Fig. 38.1). A slight twisting motion of the catheter will help to overcome resistance. Resistance during arterial catheter insertion may occur as a result of vasospasm. This can sometimes be relieved by removing the catheter, filling its tip with 0.1 to 0.2 mL of 2% lidocaine, reinserting the catheter to the point of resistance, flushing the lidocaine into the vessel, and waiting 1 to 2 minutes before reattempting to advance the catheter.
met at 1 to 2 cm, where the umbilical artery curves toward the feet; placing tension cephalad on the cord helps to reduce this resistance. The clinician will feel greater resistance at the junction of the internal iliac artery at 5 to 6 cm, where the artery turns upward (Fig. 38.1). A slight twisting motion of the catheter will help to overcome resistance. Resistance during arterial catheter insertion may occur as a result of vasospasm. This can sometimes be relieved by removing the catheter, filling its tip with 0.1 to 0.2 mL of 2% lidocaine, reinserting the catheter to the point of resistance, flushing the lidocaine into the vessel, and waiting 1 to 2 minutes before reattempting to advance the catheter.
Resistance at 4 to 5 cm generally indicates that a false tract has been created, with subintimal cannulation. If this occurs to both arteries, a vessel may still be cannulated by performing a subumbilical cutdown. This latter procedure does, however, carry the risk of hemorrhage and accidental entry into the peritoneum and should therefore only be performed by personnel experienced with the procedure.
 Figure 38.4 Nomograms for estimating umbilical artery catheter length based on total body or shoulder to umbilicus measurement. (Adapted from Dunn PM. Localization of the umbilical catheter by postmortem measurement. Arch Dis Child. 1966;41:69.) |
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