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.

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.

Inclusion Criteria:

• The investigators will identify patients 0 to 14 years of age who are classified as ASA physical status ≤4 and scheduled to have surgery under general anesthesia

Exclusion Criteria:

• History of vasculitis, autoimmune disease, Reynauds phenomenon or disease
• History of no collateral perfusion
• The absence of an upper extremity artery to cannulate such as a bilateral amputee
• A child in DHS custody
• Infection at the site of insertion
• Patient refusal.