The Impact of Nerve Cross Section Area on Sensory Block Onset

Study Overview
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Brief Summary
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The study aims to describe a correlation between the nerve cross section and the sensory or motor block onset time. Therefore, different nerve cross sections with their Motor and sensory onset times are compared in order to find a correlation. In the case of discovering a correlation, this could be translated into clinical practice, where a more tailored and individualized approach to performing peripheral nerve blocks would be possible, thus lowering the risks of adverse events occurring.

Official Title
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The Impact of Nerve Cross Section Area on Sensory Block Onset. A Prospective, Monocentric Crossover Study on Volunteers

Conditions
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Regional Anesthesia

Intervention / Treatment
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* Procedure: Dominant Arm
* Procedure: Non-dominant arm


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: ASA I - II, both sexes ≥ 18 years old < 65 years old Written informed consent as documented by signature Exclusion Criteria: Known allergy or hypersensitivity to a study drug or class of drug. Severe coagulopathy. History of alcohol abuse or the intake of psychotropic drugs. Pregnancy. Infection at the injection site or a systemic infection. Fever of unknown origin. Motor or sensory abnormalities in the arm. Previous enrollment into the current study

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 64 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Dominant Arm<br>Two ultrasound guided nerve blocks (block of the ulnar and median nerve) on the dominant forearm | Procedure: Dominant Arm<br>* The volume of local anesthetic used for the block of the ulnar and median nerve will be 5 times the estimated 95% effective dose (ED 95 ) of LA needed to block the nerve relative to the nerve cross-sectional area. The ED 95 for the ulnar nerve has been elucidated to be 0,11ml/mm2. The same ED 95 will be used for the median nerve.<br>|
| Active Comparator: Non-dominant arm<br>Two ultrasound guided nerve blocks (block of the ulnar and median nerve) on the non-dominant forearm. | Procedure: Non-dominant arm<br>* The volume of local anesthetic used for the block of the ulnar and median nerve will be 5 times the estimated 95% effective dose (ED 95 ) of LA needed to block the nerve relative to the nerve cross-sectional area. The ED 95 for the ulnar nerve has been elucidated to be 0,11ml/mm2. The same ED 95 will be used for the median nerve.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Correlation between nerve cross-section and time to complete sensory block of a nerve | Correlation between the nerve cross-section in mm2 of both nerves (median and ulnar) measured with an ultrasound system and time in minutes from the moment the investigator starts injecting the local anesthetic (LA) around the respective nerves to complete sensory loss in the innervation area of the blocked nerve, assessed by response to light touch, pinprick and cold sensation. This correlation will be expressed in min/ mm2. | Sensory evaluation will be carried out before the block and every 2 minutes after the start of the injection of LA until complete sensory loss to both cold and pinprick. Expected time frame: 10-60 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Correlation between nerve cross-section and time to complete motor block of a nerve | The correlation between the nerve cross-section area in mm2 of both nerves (median and ulnar) measured with an ultrasound system and time in minutes from the start of the LA injection around the nerve median and ulnar nerves to the respective onset of the motor block, assessed with a numerical scale ranging from 0 to 5 (0-no muscle contraction visible, 5-normal muscle strength, maximal force against resistance and gravity). This correlation will be expressed in min/ mm2. | Motor evaluation will be carried out before the block and every 2 minutes after the start of the injection of LA until complete motor block. Expected time frame: 10-100 minutes | 
| Correlation between nerve cross-section and the duration of sensory nerve block | The correlation between the nerve cross-section area in mm2 of both nerves (median and ulnar) measured with an ultrasound system and the duration of the respective sensory block in minutes, as reflected by the return of normal sensation in the innervation area of the respective nerve. This correlation will be expressed in min/ mm2. | The evaluation of the duration of block will start one hour after the determined complete sensory loss and will be tested every 10 minutes until complete resolution of the sensory block. Expected time frame: 10-300 minutes | 
| Correlation between the nerve cross-section and duration of motor nerve block | The correlation between the nerve cross-section area in mm2 of both nerves (median and ulnar) measured with an ultrasound system and the duration of the respective motor block in minutes, as reflected by the return of normal muscle strength in the innervation area of the respective nerve. This correlation will be expressed in min/ mm2. | The evaluation of the duration of sensory block will start one hour after the determined complete motor loss and will be tested every 10 minutes until complete resolution of the motor block. Expected time frame: 10-300min | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Ultrasound-guided regional anesthesia