Bupivacaine-Lidocaine vs Bupivacaine for Ultrasound-Guided Popliteal Sciatic Nerve Block

This prospective, randomized, double-blind clinical trial aims to compare the efficacy of two local anesthetic regimens for ultrasound-guided popliteal sciatic nerve block in adult patients undergoing elective distal lower extremity surgery. Eligible participants (ages 18-65, ASA physical status I-III, BMI 18-35 kg/m²) will be randomized into two equal groups of 20. Patients in Group BL will receive a combination of 10 mL 2% lidocaine and 10 mL 0.5% bupivacaine, while patients in Group B will receive 20 mL 0.5% bupivacaine alone, administered via ultrasound-guided popliteal sciatic nerve block prior to surgery. The primary outcome is the onset time of sensory and motor blockade. Secondary outcomes include block success rate, duration of sensory and motor block, postoperative opioid consumption, pain scores assessed by the Numeric Rating Scale (NRS) at 2, 4, 8, 12, and 24 hours postoperatively, Quality of Recovery-15 (QoR-15) score, and incidence of rebound pain. The study is conducted at Ataturk University Research Hospital, Department of Anesthesiology and Reanimation, Erzurum, Turkey.

Background and Rationale Peripheral nerve blocks have become an increasingly preferred technique for both anesthesia and analgesia in distal lower extremity surgery, offering advantages such as reduced opioid consumption, stable intraoperative hemodynamics, lower rates of postoperative nausea and vomiting, and enhanced early mobilization. The popliteal approach to the sciatic nerve provides effective surgical anesthesia for foot, ankle, and distal leg procedures, with high patient satisfaction and a low complication profile. Ultrasound guidance further improves block success rates by enabling direct visualization of perineural anatomical structures. The choice of local anesthetic plays a critical role in determining block onset time, duration of sensory and motor blockade, and overall analgesic duration. Lidocaine offers rapid onset and short-to-intermediate duration, while bupivacaine provides prolonged sensory and motor blockade, thereby reducing postoperative opioid requirements. The combination of these two agents theoretically enables simultaneous achievement of rapid onset and prolonged analgesia; however, the net effect of this combination on block characteristics remains inconclusive in the current literature. Study Design This is a prospective, randomized, double-blind, single-center, two-arm parallel-group clinical trial conducted at Ataturk University Research Hospital, Department of Anesthesiology and Reanimation, Erzurum, Turkey. Participants A total of 40 adult patients scheduled for elective distal lower extremity surgery will be enrolled. Inclusion criteria: age 18-65 years, ASA physical status I-III, body mass index (BMI) 18-35 kg/m², and written informed consent. Exclusion criteria include inability to provide informed consent, coagulopathy, sepsis, hepatic or renal insufficiency, known allergy to local anesthetics, prior surgery or significant scar tissue in the popliteal fossa, pregnancy, and chronic opioid use at home. Randomization and Blinding Eligible patients will be randomized in a 1:1 ratio using a computer-generated random number list into two groups of 20. Study solutions will be prepared by a dedicated investigator not involved in block performance or outcome assessment. Patients, the anesthesiologist performing the block, and the outcome assessor will all be blinded to group allocation (triple-blind). Block procedures will be performed by an anesthesiologist with a minimum of two years of experience in ultrasound-guided regional anesthesia who is not involved in patient care. Intervention All patients will receive an ultrasound-guided popliteal sciatic nerve block using a total volume of 20 mL local anesthetic solution. Patients will be positioned prone or in lateral decubitus with the operative limb uppermost and the knee in slight flexion. Under aseptic conditions, a high-frequency linear ultrasound probe will be placed transversely over the popliteal fossa to visualize the popliteal artery and the tibia trial.show_full_description

Inclusion Criteria: * Age between 18 and 65 years * American Society of Anesthesiologists (ASA) physical status classification I, II, or III * Scheduled for elective distal lower extremity surgery (below-knee) * Body mass index (BMI) between 18 and 35 kg/m² * Provision of written informed consent Exclusion Criteria: * Refusal to participate in the study * Morbid obesity (BMI ≥35 kg/m²) * Known allergy or hypersensitivity to any local anesthetic agent * Severe cardiac, hepatic, or renal disease * Pre-existing neurological deficits or peripheral neuropathy * Use of anticoagulant therapy * History of prior surgery or significant scar tissue in the popliteal fossa * Pregnancy * Chronic opioid use at home