Syringe-free technique in children: Comment on: Ultrasound-guided supraclavicular brachiocephalic vein catheterization in children: Syringe-free in-plane technique with micro-convex probe

We read the article by Balaban et al. ¹ with great interest and appreciated their work that highlighted the importance of visualizing the guidewire advancement through the needle tip into the central vein. They suggested the use of syringe-free technique, in which the plastic cover holding the guidewire inside is attached to the needle during real-time ultrasound (US)-guided in-plane brachiocephalic vein access, to be advantageous in paediatric patients. ¹ The syringe-free technique first defined in adult patients was reported to facilitate the cannulation by bypassing the aspiration of blood in the standard Seldinger technique used in combination with real-time US guidance. ² In the real-time US-guided central cannulation, the needle is inserted through the skin into the vein visualizing the needle tip either in in-plane or out-of-plane view. Although it is necessary and sufficient to visualize the needle tip inside the vein to advance the guidewire, verification of the placement of the needle tip may still be needed to avoid the beam width artefact. This artefact may cause a misleading view of the needle inside the vein when it is not, especially in small babies that very often have a brachiocephalic vein barely reaching 3 mm. Hence, a syringe is often attached to the needle to aspirate blood in order to confirm the needle is in the vein. On the other hand, a spontaneous return of blood to the bevel of the needle (without any syringe attached) is an alternative technique to avoid misinterpretation of unsuccessful aspiration of blood due to collapsing vascular wall. Following either of these techniques used for verification, it is inevitable that the non-dominant hand puts away the ultrasound probe to hold the needle firmly in place to enable the dominant hand advancing the guidewire through the needle. This hand work may cause the needle to change its position either by resulting an injury in the posterior wall or totally dislodge from the vein. Moreover, putting away the probe to advance the guidewire results in blind advancement which may result in mechanical guidewire complications. The guidewires of small diameters may kink or damage easily even when small forces exerted on them; hence, any difficulty in advancing the guidewire requires checking first with ultrasound without applying any force. We experienced such an extravascular advancement of guidewire resulting in a kink subcutaneously in a neonate, eventually retrieved by skin incision. The syringe-free technique enabling the visualization of guidewire coming out from the needle tip into the vein evidently may prevent such complications. In addition, it may still be possible to verify the placement of the needle tip in the vein by visualizing the spontaneous return of blood to the bevel of the needle, because the plastic cover of the guidewire attached to the needle will not prevent it. However, in the small neonates the verification of the needle tip inside the vein requires both visualization with ultrasound and aspiration of blood. Because, even in case of failure to see spontaneous return of blood to the bevel, aspiration of blood is recommended to verify the placement of the needle tip.^3,4 It is especially recommended in small neonates including the preterms due to their low central venous pressure to provide spontaneous return into the bevel. ⁴

The syringe-free technique to visualize the advancement of the guidewire through the needle tip into the vein may be advantageous in avoiding any extravascular misplacement and mechanical complications related to guidewire, and also allowing the operator to control how far the guidewire is introduced to prevent deep insertions triggering arrhythmias. However, as Balaban et al. also pointed out, the technique will need clinical trials with larger group of patients to be suggested for use in children, especially in small infants and neonates.