Final answer:
An arterial catheter is used to monitor intra-arterial pressure in critically ill children or those undergoing major surgery, providing real-time data for accurate blood pressure measurements and blood gas analysis.
Step-by-step explanation:
An arterial catheter is often inserted to monitor a child's intra-arterial pressure for accurate and continuous blood pressure measurements in critical care settings. This procedure is vital for patients who are hemodynamically unstable or undergoing significant surgeries and require close monitoring of their blood pressure and arterial blood gas analyses. Arterial catheters provide real-time data, allowing for prompt adjustments in therapy to manage the patient's condition effectively.