This research study is to determine the relative times for perineural catheter placement with the use of ultrasound versus electrical stimulation. The perineural catheter is placed next to the nerves through which local anesthetic is placed to provide pain control following surgery. This study may determine if one method is associated with increased success rate and patient comfort.

Primary Specific Aim: To determine if the relative times for perineural catheter placement with the use of ultrasound versus electrical stimulation.

Hypothesis: Compared with the use of electrical stimulation, the use of ultrasound guidance when inserting a perineural catheter is associated with a decreased time of placement.

Secondary Specific Aim: To determine if other possible benefits of perineural catheter placement associated with the use of ultrasound guidance versus electrical stimulation.

Hypothesis: Compared with the use of electrical stimulation, the use of ultrasound guidance when inserting a perineural catheter is associated with an increased surgical block success rate and catheter-placement success rate, as well as decreased patient discomfort and incidence of venous puncture.

Inclusion Criteria:

• undergoing surgery with a planned perineural catheter for postoperative analgesia
• catheter in the interscalene, infraclavicular, popliteal, or femoral anatomic location
• age 18 years or older

Exclusion Criteria:

• pregnancy
• inability to communicate with the investigators and hospital staff
• incarceration