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28. Central Venous and Arterial Access for Children
Keywords
Central venous access in childrenUltrasound for arterial cathetersPediatric central venous access devicesBroviac catheterPediatric infusaportThis chapter focuses on advanced vascular access techniques in children, and assumes that the reader is familiar with these techniques in adults. The intraosseous route is recommended for emergency resuscitation if peripheral IV access cannot be obtained, and both of these routes are discussed elsewhere in this book.
28.1 Central Venous Access in Children
Central venous access is challenging in children compared to adults because of their small-sized central veins, proximity to major structures and variation in their anatomical position. The success rate is lower and there are more complications compared to adults. Anesthesia or sedation is usually required for their insertion in children.
Ultrasound guidance and careful positioning of the child and equipment are important for insertion. The ultrasound probe, syringe and needle are held stabilized against the child’s body and equipment is positioned so there is no need to move or look away from the child or ultrasound screen. The child’s vein is small, superficial, mobile and easily collapsed by the needle so aspiration of blood is sometimes only seen when the needle is withdrawn. Arterial puncture is difficult to detect, especially in infants with cyanotic heart disease. Pressure transduction is the best technique to distinguish between vein and artery.
The risk of local complications with central venous catheter (CVC) insertion is higher in children than adults, primarily due to the proximity of structures. Central venous anatomy may vary, especially in children with congenital heart disease who are more likely to have a left-sided superior vena cava. Children, like adults, are at risk of infection while their CVC is in situ. The smallest diameter catheter with the minimum number of ports required reduces the risk of infection, as well as thrombosis of the vein. Although antimicrobial-impregnated catheters are sometimes recommended for adults, there is no firm evidence to support their use in children. Antibiotic prophylaxis is not needed at the time of insertion. Routine central catheter replacement is not generally recommended for children in critical care.
28.1.1 Position of the Catheter Tip
Desired tip position on chest X-ray for central catheters in children is 1–2 vertebral bodies below the carina
(a) The distal part of right-sided catheters is usually parallel to the SVC wall. (b) The distal part of left-sided catheters can push against the vein wall and perforate the SVC (dashed line). Advancing the catheter so the tip is in the correct distal position ensures the distal part of the catheter is parallel to the SVC wall (solid line)
28.2 Internal Jugular Vein CVC
The internal jugular vein (IJV) is often used in children for CVC insertion because it has the lowest risk of complications. The vein is more variably sized, smaller and closer to the carotid artery in children compared to adults. Its position relative to the carotid artery may vary—it is most commonly antero-lateral and partly overlapping the carotid artery. The amount of overlap may increase when the head is rotated to the side. It is completely lateral to the carotid artery in less than a quarter of children, and occasionally it is even medial to the carotid. It is usually at a depth of less than 1 cm, and is only about 5 mm in diameter in infants.
28.2.1 Technique
A shoulder roll extends the child’s neck and allows better access. The head is turned slightly so the needle will be clear of the chin. A head-down tilt usually has minimal effect on the size of the IJV in infants but reduces the risk of venous air embolism. Maneuvers to increase the diameter of the vein are not usually required. Simulated valsalva is probably the most effective. When it is combined with liver pressure and head-down tilt, the vein size increases about 65%. The effect of these maneuvers can be observed on ultrasound to assess any benefit.
Most commonly, a high approach to the IJV is used with the needle insertion lateral to the carotid pulsation at the level of the cricoid. The advancing needle can compress the vein, and blood is often aspirated only as it is being withdrawn. After entering the vein with the needle, the guide wire is passed gently to avoid perforating the vein. The J-tip of the wire has a curve larger than the vein diameter of infants and will either traumatize the vein or not advance into the vein. To overcome this problem, the stiffer, straight end of the wire may be inserted, or a short soft straight wire followed by a catheter long enough to act as a conduit into a larger, distal part of the vein for the J-wire. The length of the catheter inserted depends on the size of the child—4–5 cm for a right IJV insertion in a neonate, a little longer when inserted on the left side. The smallest 2-lumen catheter currently available is 4F and 5 cm long.
Tip
The length of catheter to insert (in cm) for the right IJV (high approach) equals one tenth of the child’s height.
The external jugular vein is an unreliable route for central access because it has valves and an angled course that usually prevents a guidewire or catheter advancing. It can be useful however, for peripheral venous access.
28.3 Subclavian Vein CVC
Subclavian vein catheters have a higher risk of pneumothorax and arterial puncture during insertion. However, they are popular postoperatively because they are more comfortable and better tolerated by awake children, and less likely to kink with head movement. They may be preferable in trauma cases when urgent access is required but the neck needs to remain in a neutral position or is in a cervical collar. Subclavian insertion is also easier than IJV insertion using local anesthesia in the older, awake child. Although they are associated with a lower infection rate, they have a higher thrombosis and occlusion rate compared to internal jugular catheters.
28.3.1 Technique
The right subclavian approach may be preferable to avoid injury to the thoracic duct on the left. For insertion, the child is positioned with the head in a neutral position. The landmark-based infraclavicular approach is similar to adults with needle insertion at the midclavicular point where the clavicle bends sharply, aiming the needle medially and slightly cephalad towards the contralateral shoulder or sternal notch. Inserting the needle too far laterally increases the risk of pneumothorax. The guidewire should be relatively straight after insertion to avoid kinking when dilating the vein. Tips to achieve this include a slight laterally and inferiorly placed skin puncture with minimal skin traction and then advancing needle behind clavicle in a consistent direction. Real-time ultrasound guidance assists successful cannulation in less time, and reduces the risk of inadvertent subclavian artery puncture and pneumothorax. With the supraclavicular approach, the subclavian vein is accessed more medially where it joins the internal jugular vein to form the brachiocephalic vein. This approach was less popular in the past due to the greater risk of pneumothorax, however real-time ultrasound may reduce the risk of such complications and increase the safety of this approach.
Keypoint
Subclavian catheters have several advantages over IJV catheters in children. The IJV route, however, is most commonly used in children to reduce the risks of arterial puncture and pneumothorax.
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