Ultrasound Guided Arterial Line Placement in Long Axis Versus Short Axis in Pediatric Patients
Condition: General Anesthesia
Study type: Interventional

Summary: 
      The use of ultrasound is becoming widespread to guide the placement of arterial lines for
      both vascular access and regional anesthesia in the field of anesthesia. Arterial line
      placement can be challenging, especially in the pediatric population. Frequently multiple
      attempts are required with relatively high failure rates. This can result in excessive needle
      punctures and extended OR times. A few studies have looked at the use of ultrasound to
      decrease OR time and increase success rates both in adult and pediatric populations. These
      studies compared the traditional palpation method with either short axis or long axis views
      of the vessel using ultrasound guidance. No study to date has compared short axis and long
      axis views for arterial line placement in either the pediatric or adult population. Our study
      compares success rates and OR times when long and short axis methods of arterial line
      insertion are employed in the pediatric population.
    

Detailed description: 
      An Arterial line is an intraoperative monitor that is frequently placed in the pediatric
      population. Due to their smaller anatomy and more compliant skin, arterial lines can be more
      difficult to insert in the pediatric population than in adults. Additionally, lower perfusion
      pressure and larger subcutaneous adipose tissue can make pulse palpation more difficult.
      Ultrasound is a modality that can directly image the radial, ulnar, or brachial artery. Along
      with 2D ultrasound, doppler ultrasound can be utilized to confirm that an artery is not a
      vein. Once the vessel is identified, the vessel can be viewed in either the long or short
      access. The ultrasound beam is only 1 millimeter thick so a practitioner must stabilize the
      probe to view the vessel, especially in the long axis view. Once the artery is viewed in long
      axis, the needle can be directly visualized all the way into the vessel. Visualization of a
      guidewire or catheter in the vessel can confirm proper arterial access. In a short access
      ultrasound view, it is possible to see tissue movement and sometimes a hyperechoic (bright)
      dot which represents the needle. Tissue movement can help confirm the needle is immediately
      above the artery at all times. The advantage of the short axis view is that less precision is
      needed to hold and position the transducer than with the long axis view. The disadvantage of
      the short axis view is that the operator cannot see the tip of the angiocatheter as it enters
      the vessel. As a result, the proximal portion of the angiocatheter can be above the artery
      but the distal tip could be to the side of the artery.
    

Intervention name(s): Arterial line placement
Intervention type(s): Procedure
Intervention description(s): The following measures will be collected and compared.
Time (in seconds) required for successful placement of the arterial line. This is the time elapsed between either palpation or placement of ultrasound probe on the patient's wrist and the successful demonstration of arterial waveform on the anesthesia monitor.
number of attempts, defined as forward advancements of needle, required to cannulate the artery.
number of separate skin punctures.
number of arteries into which entry is attempted.
Other intervention name(s): Ultrasound guided (short vs Long axis)
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Arterial line; Ultrasound; Anesthesia; Pediatric