Nerve stimulator versus ultrasound guidance for placement of popliteal catheters for foot and ankle surgery

Study ObjectiveTo determine whether ultrasound guidance improves the quality of continuous popliteal block when compared with a nerve stimulator after major foot and ankle surgery.DesignProspective, randomized, double-blinded clinical trial.SettingOperating room, Postanesthesia Care Unit (PACU), and hospital wards of a university-affiliated hospital.Patients45 ASA physical status 1, 2, and 3 patients undergoing elective major foot and ankle surgery.InterventionsPlacement of a popliteal sciactic nerve catheter using either nerve stimulator or ultrasound guidance. In the PACU, a continuous infusion of ropivacaine 0.2% was started at a basal rate of 4 mL/hr and adjusted in a standardized fashion to maintain visual analog scale (VAS) pain scores < 4. All patients also received intravenous (IV) patient-controlled analgesia with hydromorphone and oral opioids.MeasurementsVAS pain scores at rest and with physical therapy, ropivacaine use, opioid use, and opioid-related side effects were recorded.Main ResultsCummulative ropivacaine use was lower in patients whose catheter was placed by ultrasound than by nerve stimulator guidance (mean 50 vs 197 mL, P < 0.001). Pain scores at rest and during activity were similar between groups. Cumulative opioid consumption (mean 858 vs 809 mg oral morphine equivalents) and daily frequencies of nausea (5% to 33% vs 0 to 24%) and pruritus (0 to 21% vs 0 to 24%) were similar between groups. Length of hospital stay was similar between groups (3.5 vs 3.7 days).ConclusionsUltrasound guidance was associated with less local anesthetic consumption than with the nerve stimulator; however, there was little clinical benefit, as all other outcomes were similar between groups.