Motor-Sparing Femoral Nerve Block Dose
Motor-Sparing Femoral Nerve Block Dose
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.
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.
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