Continuous peripheral nerve blocks (CPNB; also known as "perineural" catheters) provide target-specific pain control for a variety of surgeries. There has been increasing interest in the use of ultrasound guidance for regional anesthesia, and many techniques using ultrasound alone for perineural catheter insertion have been described. Catheters may be placed at various points along the brachial plexus (for upper extremity procedures) or in proximity to the femoral and/or sciatic nerve (for lower extremity procedures). To date, the optimal ultrasound scanning technique, catheter insertion endpoint, catheter placement location per indication, for the majority of ultrasound-guided continuous peripheral nerve blocks remain unknown. This study will help provide important information related to optimal ultrasound scanning techniques and will help identify ways to improve the success rates, onset times, and analgesic effectiveness of these techniques for real patients undergoing surgical procedures.