Comparing Through-the-Needle With Suture-Method Catheter Designs for Popliteal Nerve Blocks

This investigation will be a randomized, observer-masked, controlled, parallel-arm, human-subjects clinical trial. Of note, the investigators will be using standard-of-care perineural catheters and local anesthetic under their FDA-approved purpose and do not plan to research a possible change of indication or use of these drugs as part of this research project.

Consenting adults undergoing surgery with a planned popliteal-sciatic perineural catheter placement will be offered enrollment. Study inclusion will be proposed to eligible patients prior to surgery. If a patient desires study participation, written, informed consent will be obtained using a current UCSD IRB-approved ICF.

Following written, informed consent, the investigators will collect baseline anthropomorphic information (age, sex, height, and the investigatorsight). Subjects will be then be randomized using a computer-generated list and opaque, sealed envelopes to one of two treatment groups (blocks of 4, no stratification): perineural catheter insertion using (1) through-the-needle technique or (2) suture technique. All catheters will be placed by a regional anesthesia fellow or resident under the direct supervision and guidance of a regional anesthesia attending (or by the attending him/herself).

All subjects will have a peripheral intravenous (IV) catheter inserted, standard noninvasive monitors applied, supplemental oxygen administered via a nasal cannula or face mask, and positioned prone. Midazolam and fentanyl (IV) will be titrated for patient comfort, while ensuring that patients remain responsive to verbal cues. The area that will be subsequently covered by the catheter dressing will be clipped of hair, if necessary. The ultrasound will be placed to visualize the short axis (cross-section) of the sciatic nerve to identify the sciatic nerve bifurcation which will subsequently be marked, as well as the location 5 cm cephalad to the bifurcation. The area will be cleaned with chlorhexidine gluconate and isopropyl alcohol and a clear, sterile, fenestrated drape applied. The ultrasound probe will be placed to visualize the short-axis (cross-section) of the target nerve(s) and the target for the catheter to intercept the nerve may be anywhere between the bifurcation and 5 cm cephalad to the bifurcation. All catheters will be placed using standard UCSD ultrasound-guided perineural catheter techniques as previously described. Normal saline 5-20 mL will be administered via the needle and/or catheter to allow catheter insertion and/or testing of catheter location (viewed with ultrasound).

Local anesthetic (20 mL, lidocaine 2% with epinephrine 1:200,000-400,000) will be administered via the catheter. A "successful" catheter insertion will be defined as sensory-block onset in the tibial nerve distribution within 30 minutes following the local anesthetic injection. If the nerve block fails, the catheter will be replaced or the patient removed from further study.

An infusion pump will be attached to the patient's perineural catheter and initiated within the recovery room. The pump will provide ropivacaine 0.2% at a 6 mL/h basal rate infusion and a 4 mL patient-controlled bolus with a 30 minute lockout (standard at UCSD). Subjects will be discharged with a prescription for oxycodone 5 mg tablets for supplementary analgesia. Subjects will be contacted via phone for 4 days following surgery to collect study outcome measures: worst, average, least, and current surgical pain (Numeric Rating Scale of 0 to 10, with "0" being no pain and "10" being the worst pain ever experienced), analgesic use (oral opioids and infusion boluses), sleep disturbances, opioid and local anesthetic infusion side effects, local anesthetic leakage, gross catheter dislodgement, sensory and motor block, and satisfaction with pain control. Subjects or their caretakers will remove the catheters at home.

Primary endpoint:

Hypothesis 1: Surgical pain will be noninferior within the first 2 days following foot/ankle surgery with a suture-method compared with a through-the-needle perineural catheter when used for a continuous popliteal-sciatic nerve block to provide postoperative analgesia (the mean "average" pain measured daily with a Numeric Rating Scale).

Hypothesis 2: Opioid consumption will be noninferior within the first 2 days following foot/ankle surgery with a suture-method compared with a through-the-needle perineural catheter when used for a continuous popliteal-sciatic nerve block to provide postoperative analgesia (cumulative dose).

Inclusion criteria

• Patients undergoing ambulatory foot or ankle surgery with a popliteal perineural catheter for postoperative analgesia.

Exclusion criteria

• Pregnancy
• Inability to communicate with research staff
• Incarceration
• Clinically apparent neuropathy in the operative extremity
• Chronic high dose opioid use
• History of opioid abuse
• Concurrent surgery outside the block distribution
• Patients with nerves deeper than 5 cm from the skin