This prospective, sequential dose-finding clinical observational study aims to estimate the median effective concentration (EC50) and the 95% effective concentration (EC95) of liposomal bupivacaine for ultrasound-guided femoral nerve block. Sensory and motor block endpoints are evaluated separately at 30 minutes after block placement using a modified up-and-down (sequential allocation) design, with trial termination after eight reversal points.
This prospective clinical observational, sequential dose-finding study is designed to determine the effective concentrations of liposomal bupivacaine for ultrasound-guided femoral nerve block in patients undergoing lower limb surgery or related procedures. All patients receive ultrasound-guided femoral nerve block performed by an experienced anesthesiologist using a standardized technique. A fixed injection volume of liposomal bupivacaine is administered, while the drug concentration is adjusted according to a modified up-and-down sequential method. The concentration for each subsequent participant is determined based on the response of the preceding participant. Following a positive response, the concentration is decreased; following a negative response, the concentration is increased by a pre-specified step size. The study is terminated after eight reversal points (crossovers) are observed. To independently characterize sensory and motor block dose-response relationships, participants are allocated into two endpoint-specific observation groups: Sensory block group Sensory function in the femoral nerve distribution is assessed 30 minutes after block placement using standardized sensory testing. Complete loss of sensation at 30 minutes is defined as a positive response, while preserved sensation is defined as a negative response. Motor block group Motor function of the quadriceps muscle is evaluated 30 minutes after block placement using a standardized motor strength assessment. The successful (positive) quadriceps motor block is defined as a decrease of ≥1 grade in the muscle strength of the quadriceps compared with that before the block. The primary objective of this study is to estimate the EC50 and EC95 of liposomal bupivacaine for:femoral nerve sensory blockade, and femoral nerve motor blockade, based on sequential allocation data and appropriate dose-response modeling. Secondary objectives include describing the differential sensory-motor block profile of liposomal bupivacaine and evaluating its clinical feasibility and safety for femoral nerve block applications. All patients are monitored for block-related adverse events, including signs of local anesthetic systemic toxicity, nerve injury, and other complications throughout the perioperative period.
Study Type
Liposomal bupivacaine administered for ultrasound-guided femoral nerve block at varying concentrations using a modified up-and-down sequential dose-finding design.
Department of Anesthesiology,the Second Affiliated Hospital of Hainan Medical University
Haikou, Hainan, China
EC50 and EC95 for femoral nerve sensory block
The median effective concentration (EC50) and the 95% effective concentration (EC95) of liposomal bupivacaine for ultrasound-guided femoral nerve sensory blockade are estimated using a modified up-and-down sequential dose-finding design. Sensory block is assessed 30 minutes after block placement in the femoral nerve distribution on the blocked side, including the anterior thigh (anterior femoral cutaneous nerve territory) and the medial aspect of the lower leg (saphenous nerve territory). Sensory testing is performed using pinprick testing and/or cold stimulation with an ether-soaked cotton swab, with the contralateral non-blocked limb used as an internal control. Sensory block is graded as follows: 0 = no block (sensation identical to the non-blocked limb); 1 = partial block (reduced sensation); 2 = complete block (absence of pain sensation). A positive sensory response is defined as a sensory block score of 2.
Time frame: 30 minutes after femoral nerve block placement
EC50 and EC95 for femoral nerve motor block
The median effective concentration (EC50) and the 95% effective concentration (EC95) of liposomal bupivacaine for ultrasound-guided femoral nerve motor blockade, estimated using a modified up-and-down sequential dose-finding design. Motor function is evaluated immediately by assessing quadriceps muscle strength. Patients are instructed to perform a straight leg raise in the supine position or actively extend the knee. Muscle strength is graded using the Medical Research Council (MRC) scale (0-5). The successful (positive) quadriceps motor block is defined as a decrease of ≥1 grade in the muscle strength of the quadriceps compared with that before the block.
Time frame: 30 minutes after femoral nerve block placement
Postoperative Resting pain intensity assessed by VAS
Postoperative Resting pain intensity is assessed using the Visual Analog Scale (VAS, 0-10, where 0 indicates no pain and 10 indicates the worst imaginable pain). VAS scores will be recorded while the patient is at rest on postoperative day 1 and postoperative day 2 to evaluate pain at rest following femoral nerve block. A higher score indicates more severe pain.
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INTERVENTIONAL
Allocation
NA
Purpose
HEALTH_SERVICES_RESEARCH
Masking
NONE
Enrollment
79
Time frame: postoperative day 1 and day 2
Postoperative movement-evoked pain assessed by VAS
Movement-evoked pain is assessed using the Visual Analog Scale (VAS, 0-10). VAS scores are recorded during active movement of the operated limb on postoperative day 1 and postoperative day 2 to evaluate pain associated with mobilization following femoral nerve block.
Time frame: Postoperative day 1 and day 2
Quadriceps muscle strength after surgery
Quadriceps muscle strength on the operated side is evaluated using the Medical Research Council (MRC) muscle strength scale (0-5). Assessments are performed on postoperative day 1 and postoperative day 2 to evaluate recovery of motor function following femoral nerve block.
Time frame: Postoperative day 1 and day 2
Length of hospital stay
Length of hospital stay is defined as the number of days from the date of surgery to the date of hospital discharge.
Time frame: From the date of surgery until hospital discharge, assessed up to 30 days postoperatively.
Time to first ambulation after surgery
Time to first ambulation is defined as the time interval from the end of surgery to the patient's first out-of-bed ambulation with or without assistance.
Time frame: From the end of surgery until the first out-of-bed ambulation, assessed up to 72 hours postoperatively.
Intraoperative heart rate
Intraoperative heart rate is continuously monitored and recorded during surgery to assess intraoperative physiological stability.
Time frame: From skin incision to the end of surgery, assessed continuously during the intraoperative period.
Intraoperative mean arterial pressure
Intraoperative mean arterial pressure is continuously monitored and recorded during surgery to assess intraoperative hemodynamic stability.
Time frame: From skin incision to the end of surgery, assessed continuously during the intraoperative period.