In this arm the US transducer, protected with a sterile cover and sterile gel will be placed in the short axis above the distal end of the selected vein, moving the probe to place the vein in the center of the ultrasound screen under the middle mark of the image. The catheter needle will be inserted close to the transducer. The needle tip will be visualized as a white dot on the ultrasound screen. Then, the transducer will be shifted slightly proximally until the white dot disappears from the screen. The needle and the transducer will be moved alternately toward the patient several times to visualize the needle tip in real time. After penetrating the anterior wall of the vein, these steps will be repeated a few more times with a smaller insertion angle to visualize the white dot in the vein. Finally, the outer catheter will be fully advanced and the needle core will be extracted.

For traditional insertion technique insertion attempt will be blind or tactile. Otherwise, the same protocol and measurements as elaborated for the US guided group will be applied.

Catheterizations will be performed by one of three pediatric intensivists with vast experience in both traditional and US guided DNTP techniques for peripheral intravenous access. The operator will be allowed to independently choose which peripheral vein to cannulate. If necessary, patients will be given supplemental dose of sedation and analgesia in addition to the already given continuous infusions for invasive mechanical ventilation. Before puncture, the limb will be taped and maintained in an optimal position. A tourniquet will be placed proximal to the planned cannulation site. The site of puncture will be disinfected with Chlorhexidine gluconate 0.5% w/v, Alcohol 70% v/v. The choice of catheter will be left to the discretion of the operator. Available PIV cannulas include : 14 GA, 2X45 mm; 17 GA, 1.4X45 mm; 18 GA 1.2X45 mm; 20 GA 1X32mm BD Venflon™ and 24 GA, 0.7X19 mm; 26 GA 0.6X19 mm BD Neoflon™ (Becton Dickinson Infusion Therapy AB, Helsingborg, Sweden).

Assessment of peripheral IV cannulation success on first attempt (Yes vs No)

The overall success rate of peripheral intravenous cannulation within 3 attempts.

Defined as the time from first skin puncture to successful cannulation (minutes).

Age in years

Female vs Male