Motor-Sparing Femoral Nerve Block Dose

Study Overview
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Brief Summary
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Femoral nerve blocks are commonly used to provide pain control for total knee replacement, anterior cruciate ligament (ACL) reconstruction. Commonly employed local anesthetic concentrations result in motor block of the quadriceps and constitute an inherent risk factor for patient fall. The aim of this study is to determine the minimum effective concentration of bupivacaine in 90 % of patients (MEC90) required for a motor-sparing, successful sensory block of the femoral nerve.

Detailed Description
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With the approval of Ethics Committee of the University of Chile Clinical Hospital, approximately 60 patients undergoing ACL repair or TKR will be recruited. All blocks will be conducted preoperatively in an induction room.Dose assignation will be done using an up-and-down sequential method, where the dose of each subsequent patient depends on the response of the previous patient, called the Biased Coin Design. The assignment of each subsequent concentration will be based on the response of the previous patient.As soon as we recruit 45 patients with random dose assignment, we will terminate the enrollment procedure. The injectate will be prepared and administered by a research assistant using syringes connected to the block needle. The operator and the patient will be blinded to the concentration injected.

Official Title
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Minimum Effective Concentration of Bupivacaine for Motor-Sparing Femoral Nerve Block

Conditions
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Osteoarthritis, Knee, Knee Injuries

Intervention / Treatment
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* Drug: Same Bupivacaine Concentration
* Drug: Lower Bupivacaine Concentration


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age between 18 and 75 years American Society of Anesthesiologists classification 1-3 Body mass index between 20 and 35 Exclusion Criteria: Adults who are unable to give their own consent Pre-existing neuropathy (assessed by history and physical examination) Coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. platelets≤ 100, International Normalized Ratio≥ 1.4 or partial prothrombin time ≥ 50) Renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. creatinine ≥ 100) Hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up i.e. transaminases ≥ 100) Allergy to LA Pregnancy Prior surgery in the inguinal region Chronic pain syndromes requiring opioid intake at home

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Supportive Care
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: same dose<br>patient is exposed to the same previously successful dose | Drug: Same Bupivacaine Concentration<br>* patient is exposed to the same concentration than previously successful one<br>|
| Experimental: lower dose<br>patient is exposed to a lower concentration dose | Drug: Lower Bupivacaine Concentration<br>* patient is exposed to a lower concentration than previously successful one<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Minimum Bupivacaine Analgesic concentration preserving quadriceps strength analgesia |  | 5 months |