Duration of Sciatic Nerve Block After Injection of Local Anesthetic In or Around the Nerve

Study Overview
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Brief Summary
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This study was designed to assess whether the injection of local anesthetic into the nerve (intraneural), as opposed to around it (perineural), leads to longer anesthesia and analgesia of the leg. Some reports of accidental intraneural injection mention an extremely long duration. When different drugs and doses were evaluated in a clinical trial of intraneural injection, a longer-than-expected duration was reported. The investigators will compare the two types of injection using the same drug, so as to determine if there is an actual difference in duration.

Detailed Description
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This randomized, controlled trial will investigate prospectively for differences in sensory and motor block duration after intra- or perineural injection of 1.5% (wt/vol) mepivacaine, a short-acting local anesthetic.

Official Title
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Duration of Subgluteal Sciatic Nerve Block After Intra- or Perineural Injection of Mepivacaine: a Randomized, Controlled Trial

Conditions
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Orthopedic Surgical Procedures, Postoperative Pain

Intervention / Treatment
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* Procedure: Intraneural Injection for Subgluteal Sciatic Nerve Block
* Procedure: Perineural Injection for Subgluteal Sciatic Nerve Block
* Procedure: Femoral Nerve Block
* Procedure: Patient-controlled postoperative analgesia
* Drug: Mepivacaine


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Undergoing non-emergent orthopedic procedure of knee, leg, foot with thigh tourniquet ASA Physical Status Class I-III Consenting to surgery under peripheral nerve block anesthesia (sciatic + femoral/saphenous block) Exclusion Criteria: Unable to understand or communicate for the purpose of the study Exhibiting signs of neuropathy in the ipsilateral extremity Inability to satisfactorily image the sciatic nerve in the opinion of the attending anesthesiologist

Ages Eligible for Study
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Minimum Age: 18 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: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Perineural<br>Patients in this group will receive a perineural injection of mepivacaine for subgluteal sciatic nerve block, in addition to a femoral nerve block and patient-controlled postoperative analgesia. | Procedure: Perineural Injection for Subgluteal Sciatic Nerve Block<br>* The injection will start as the needle indents the outermost discernible layer of the nerve (epineurium) under ultrasound guidance. The injection will be adjudicated as intraneural if the drug infiltrates the space between the epimysium of the surrounding muscles and the outer epineurium of the sciatic nerve. Short-axis real-time ultrasound imaging will be used, with an in-plane needle approach.<br>* Other names: Extraneural injection;Procedure: Femoral Nerve Block<br>* Patients will receive an ultrasound-guided femoral nerve block using a short- or long-acting local anesthetic, as deemed indicated.<br>Procedure: Patient-controlled postoperative analgesia<br>* Patients will receive a patient-controlled intravenous or perineural catheter-based analgesia, depending on their preference and the anesthesiologist's indication.<br>* Other names: Patient-controlled continuous peripheral nerve block;Drug: Mepivacaine<br>* Thirty milliliters of 1.5% (wt/vol) mepivacaine will be used for the sciatic nerve block.<br>* Other names: Carbocaine;|
| Experimental: Intraneural<br>Patients in this group will receive an intraneural injection of mepivacaine for subgluteal sciatic nerve block, in addition to a femoral nerve block and patient-controlled postoperative analgesia. | Procedure: Intraneural Injection for Subgluteal Sciatic Nerve Block<br>* The injection will start as the needle penetrates the outermost discernible layer of the nerve (epineurium) under ultrasound guidance. The injection will be adjudicated as intraneural if nerve cross section expansion and a reduction in echogenicity are observed. Short-axis real-time ultrasound imaging will be used, with an in-plane needle approach.<br>* Other names: Subparaneural injection;Procedure: Femoral Nerve Block<br>* Patients will receive an ultrasound-guided femoral nerve block using a short- or long-acting local anesthetic, as deemed indicated.<br>Procedure: Patient-controlled postoperative analgesia<br>* Patients will receive a patient-controlled intravenous or perineural catheter-based analgesia, depending on their preference and the anesthesiologist's indication.<br>* Other names: Patient-controlled continuous peripheral nerve block;Drug: Mepivacaine<br>* Thirty milliliters of 1.5% (wt/vol) mepivacaine will be used for the sciatic nerve block.<br>* Other names: Carbocaine;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Differences in Time to Resolution of Sciatic Nerve Block | The time at which sensory and motor function of the sciatic nerve have recovered at least to the following criteria: Sensory: patients feel discomfort when pricked with a thin needle (25G) Motor: patients may move both toes and ankle, albeit with reduced strength This outcome measure will be examined by an investigator every 30-60 min and reported by patients as time to return of sensation and movement. The investigator-reported value will be preferred if both are available. | <12 h | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Block Onset Time | Time to onset of sciatic nerve anesthesia, defined as meeting at least the following criteria: Sensory: does not feel pain or discomfort when pricked with a 25G needle. Motor: able to slightly curl toes; unable to flex the ankle. | ≤30 min | 
| Success Rate of Anesthetic Nerve Blocks | The percentage of patients who attain the criteria for block success within 30 minutes of the injeciton. Investigators will also report the percentage of patients who successfully complete surgery without significant additional analgesia (see below); this will be defined as clinical success rate. | ≤30 min | 
| Incidence and Prevalence of Neurologic Disturbances | Patients will be interviewed at  4 h (block resolution visit), 7 days and (if necessary) at 30 days to assess for residual neurologic disturbances in the sciatic nerve territory. The incidence/prevalence of these phenomena will be noted. | 30 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Lower Extremity, Sciatic Nerve, Anesthesia, Regional, Anesthetics, Local, Mepivacaine, Ultrasonography