Innovative Probe With Laser on Radial Artery Puncture and Catheterisation in Paediatric

Following induction of anaesthesia in the paediatric patient, position one arm in slight abduction with a thin rolled bandage placed beneath the wrist to maintain mild dorsal extension. Disinfect the radial artery puncture site with povidone-iodine solution and drape the area. Select the appropriate ultrasound system and probe according to the assigned group (T-shape ultrasound guidance group or out-of-plane ultrasound guidance group).

T-shaped probe ultrasound guidance Group:

Fit the 3D-printed housing, which contains a laser emitter, onto the T-shaped ultrasound probe. The laser emitter is positioned directly above the mark on the short-axis plane of the T-shaped ultrasound probe. Instruct the assistant to apply an appropriate amount of coupling gel evenly to the ultrasound probe. Working in conjunction with the assistant, the operator should cover the entire assembly-comprising the 3D-printed, three-axis adjustable support arm and the ultrasound probe-with a sterile sleeve, expel any air from between the probe and the sleeve, and apply sterile coupling gel evenly to the outer surface of the sleeve where it will come into contact with the child's skin to complete the preparation of the equipment. To begin positioning, the operator uses the support arm to gently place the T-shaped ultrasound probe 0.5 cm below the child's wrist crease, with the short axis at the distal end and the long axis at the proximal end. The support arm and rotation axis are adjusted so that the midline of the short-axis ultrasound image passes through the centre of the radial artery's cross-section. Subsequently, with the short axis as the centre, the long axis is swivelled in a fan-shaped pattern from side to side to achieve optimal visualisation of the radial artery in the long-axis ultrasound image. At this point, the laser beam is directed towards the superficial projection of the target radial artery beneath the ultrasound probe. Once the support arm has been adjusted to ensure the probe rests stably against the skin surface, a stable, fully visualised ultrasound-guided procedure is established that can be performed by a single operator using both hands. The operator holds the ultrasound probe steady with their left hand, whilst holding a 24G arterial puncture cannula in their right hand, ensuring the laser fully covers the needle shaft and inserting the needle at an angle of approximately 30° to the skin (the insertion point is 0.5 cm from the ultrasound probe). Once the needle tip has entered the subcutaneous tissue, if deviation is observed on the short-axis ultrasound image, the angle of insertion may be adjusted, with the number of adjustments recorded. The needle should penetrate the anterior wall directly above the radial artery; whilst the right hand maintains the position of the cannula, the left hand slides the probe towards the proximal end and, using the short-axis image, determines the position of the needle tip prior to cannula insertion according to the 'dynamic needle tip method'. A screenshot is retained for scoring the needle tip position on the first attempt. Upon observing backflow, move the ultrasound probe distally along the course of the artery by approximately 0.5 cm; once the needle is shown to have entered the vessel in the long-axis view, advance the needle at an appropriate angle under ultrasound guidance. When the position is satisfactory, withdraw the needle core; if backflow is unobstructed, insert the introducer sheath. If resistance persists, the operator shall decide, based on clinical experience, whether to employ the penetration technique. If insertion fails, withdraw the needle from the radial artery and apply pressure to the puncture site with sterile gauze. After approximately 3 minutes, when there is no significant bleeding at the puncture site, proceed to the next attempt. During this time, the procedure timer shall not be paused, and the number of times the ultrasound probe is repositioned and the needle tip is adjusted shall be recorded throughout the procedure.

Out-of-plane ultrasound guidance Group:

The assistant applies coupling gel to the surface of the ultrasound probe. Working together, the operator and assistant cover the probe with a sterile sleeve, expel any air from between the probe and the sleeve, and evenly apply sterile coupling gel to the outer surface of the sleeve where it will come into contact with the child's skin, thereby completing the preparation of the equipment. To begin positioning, the operator gently places the ultrasound probe 1 cm below the child's wrist crease, ensuring that the short-axis midline of the ultrasound image passes through the radial artery at the centre of the image. The left hand stabilises the ultrasound probe, and positioning is complete. Adjust the ultrasound probe to form an angle of approximately 90° with the skin. Once the midpoint of the probe's short-axis plane aligns with the marked point, insert the 24G arterial puncture cannula with the right hand at an angle of approximately 30° to the skin. Upon observing blood return, capture a screenshot to score the needle tip position for the first attempt. Use the 'dynamic needle tip method' to guide the advancement of the puncture needle. Once the position is correct, withdraw the needle core; if blood return is unobstructed, insert the cannula. If resistance persists, the operator shall decide, based on their experience, whether to use the penetration technique. If insertion fails, withdraw the needle from the radial artery and apply pressure to the puncture site with sterile gauze. After approximately 3 minutes, when there is no significant bleeding at the puncture site, proceed to the next attempt. During this time, the operation timer shall not be paused, and the number of times the ultrasound probe is repositioned and the number of needle tip adjustments shall be recorded throughout the procedure.

Inclusion criteria

• The paediatric patient's family fully understands and voluntarily participates in this study, having signed the informed consent form.
• Paediatric patients undergoing critical surgery requiring radial artery puncture and catheterisation for continuous blood pressure monitoring are selected.
• ASA physical status classification of I-IV.
• Age ≤ 24 months, gender not restricted.

Exclusion criteria

• Paediatric patients who have undergone radial artery puncture within the past month.
• Paediatric patients with abnormal development of the radial or ulnar arteries, peripheral vascular disease at the radial puncture site, congenital heart disease, or haemorrhagic or cardiogenic shock.
• Paediatric patients with wounds, infections, or haematomas near the radial puncture site.
• Ultrasound imaging demonstrating inadequate collateral circulation or a negative Allen test.
• Cases where the paediatric patient's guardian refuses to sign the informed consent form for study participation.
• Other circumstances deemed unsuitable for trial participation by the investigator.