• Proper positioning of the baby with a roll placed under the shoulder and the head turned to the contralateral side
• Deep sedation increases the cannulation success
• Prescanning of veins i.e., RaCeVA: Rapid Central Vein Assessment
• Size measurement of the targeted vein sonographically because the caliber of the catheter must not exceed ⅓ of the vessel lumen in order to avoid thrombosis
• Maximal barrier precautions including skin antisepsis with 2% chlorhexidine in 70% isopropilic alcohol
• USG venipuncture by using a high-quality ultrasound machine with a small broadband linear array transducer providing a resolution between 13-22MHz

• Seldinger technique by inserting a soft tipped, straight 0.018-inch (0.46mm) Nitinol guidewire
• Ultrasound assessment of the direction of the guidewire into the vasculature i.e., tip navigation
• Insertion of preferably power injectable 2-4 Fr catheters made from silicone or polyurethane
• Tip location by intracavitary ECG and/or transthoracic echocardiography
• Consider subcutaneous tunneling of the catheter to the infraclavicular area if the catheter is to remain in place for a longer period of time
• Securement by sutureless devices such as Securcath®, Grip-Lok®, or StatLock®
• Cyanoacrylate glue for the closure of the puncture site and for the sealing of the exit site
• Coverage of the exit site with semipermeable transparent membrane

While holding the US transducer in one hand, the IV cannula is maneuvered by the other hand. Using the IP approach, the IV cannula is advanced from lateral to medial under the US transducer. The tip of the IV cannula is then guided under real-time USG into the BCV (Figure 3). This requires a perfect alignment of probe, vessel, and cannula. If the advancement of the cannula cannot be seen on the screen (more frequently observed for the right BCV due its steep caudad course) the author advises to move the cannula in-plane towards the clavicle until it can be recognized on the screen (Figure 4). As soon as the cannula tip appears inside the vein with or even without spontaneous blood reflux the ultrasound probe is turned aside. The stylet of the IV cannula is slightly withdrawn and the cannula fully slided into the vein. A syringe is attached, and blood aspirated. If blood cannot be aspirated because of the cannula tip abutting the wall of the tiny vessel as frequently observed in babies weighing less than 1kg, the cannula is slowly withdrawn under gentle negative pressure via the attached syringe until blood can be aspirated. If blood can still not be aspirated, the cannulation procedure is repeated from the start by piercing the skin again lateral to the long axis of the repositioned ultrasound probe. Positive blood aspiration is followed by Seldinger technique with guide-wire and catheter insertion (Figure 5). Noteworthy, the left BCV is usually easier to cannulate than the right one. The reason for this is the different anatomy. The left BCV runs nearly horizontally whereas the right one often takes a steep caudad direction [23]. At times the optimum obtainable sonographic view of the right BCV only shows a circular appearance of the vein, presenting just the initial part without demonstrating its path caudally alongside the pleura because the right BCV quickly disappears behind the sternoclavicular joint [23,22,4]. In this case, the in-plane cannulation can be expected to be particularly difficult or maybe even impossible. So, it can be said that the sonographic appearance of the right BCV prior to cannulation already predicts the cannulation difficulty demonstrating the importance of RaCeVa (Figure 6).

FEMORAL VEIN CANNULATION (FICC, FEMORALLY INSERTED CENTRAL CATHETER)

A towel is folded and placed under the pelvic region to eliminate any inward flexion of the hips or concavity to the area. The US probe is placed so as to obtain a good short-axis view of the femoral vein. By using usually an OOP technique which can also include a DNTP technique the needle is inserted into the vein. After successful puncture of the vein Seldinger technique is applied. Femoral venous cannulations can be difficult in neonates because of the small size of the vein, its collapse, and the narrow angle making sometimes the insertion of the guide-wire difficult. High catheter related obstruction, infection, and thrombosis rates have been described, however, recently Ostroff [26] has reported the successful long-term use of tunneled femoral venous catheters in neonates [15,25].

COMPLICATIONS

Due to the meticulous use of real-time USG cannulation techniques including a proper training in this field fatal puncture complications should not occur any more. Inadvertent arterial injuries are now reported to be below 1% [1-3]. Likewise, by applying the previously mentioned insertion bundles, long term complications in particular catheter related infections, and thrombosis should also be avoided nearly completely. However, it has to be said that catheter dwell time, small size of the veins, and overall extreme fragility of these babies will remain constant risk factors for complications. Apart from this ultrasound has also become the first choice to diagnose/exclude pneumothorax, pericardial effusion, and thrombotic events [27]. The latter one must not be confounded with the harmless fibroelastic sheaths frequently detected in vessels after catheter removal.

CONCLUSION

The most appropriate access in neonates seems to be the supraclavicular, USG in-plane cannulation of the BCV. By using the insertion bundles meticulously fatal catheter complications should not occur any more.