Ultrasound-guided Nerve Block: Determination of the Minimal Effective Volume of Local Anesthetic

Recruitment & Eligibility

Inclusion Criteria

aged 18 years from 18 to 80 years with an ASA (American Society of Anesthesiologists) physical status I-II
elective hand ambulatory surgery with a maximum duration of 30 minutes involving the median nerve and performed with elbow nerve blocks

Exclusion Criteria

pregnant or lactating women,
contra-indication to regional anesthesia
diabetes mellitus,
effective anticoagulation or antiplatelet therapy, laboratory evidence of abnormal bleeding
neurological disease ( including carpal tunnel syndrome or neuromuscular disease detected by preoperative neurological examination in the median nerve)
infection at the puncture site
contra-indication to the administration of lidocaine, notably allergy
contra-indication to the administration of lidocaine with epinephrine
not speaking French

Exclusion from the study:

patient having an intraneural injection of the median nerve defined by swelling appearance are excluded from analysis

Study & Design

Arm && Interventions

Group	Intervention	Description
median nerve block	median nerve block	An ultrasound-guided nerve block with dextrose 5% hydrodissection is performed in each case. The first patient will receive a 2 mL local anesthetic solution. For following patients, the volume of local anesthetic depends on the clinical result of the previous patient: * increase of the volume (0.5 mL) in case of failure, * no change or decrease (0.5 mol) in case of success; a randomization is made in this case (BCD method, Stylianou M, Flournoy N. Dose finding using the biased coin up-and-down design and isotonic regression. Biometrics 2002;58:171-7)

Primary Outcome Measures

Name	Time	Method
Minimal effective volume of local anesthetic	1 hour	Effective volume of local anesthetic to obtain a successful median nerve block block in 95% of patients defined as complete light touch block at the palmar aspect of the 2 distal phalanges of the index finger during a 30 minute evaluation period (mL)

Secondary Outcome Measures

Name	Time	Method
Success rate of the median nerve block	1 hour	Success rate concerns: * success rate of sensitive block: complete cold and light touch block at 30 min and 45 min at the palmar aspect of the 2 distal phalanges of the index finger and on the thenar eminence * success rate of motor block: complete motor block at 30 min and 45 min
Duration of the block	1 day	Delay between the completion of the block and the returned to normal onset of sensory and motor recovery of the first three fingers of the hand) (minutes)
Nerve block onset time	1 hour	Onset time for complete cold light touch and motor block at 30 min and 45 min.
Complications	1 month	* complications occurring during the procedure (pain, paresthesia, intraneural injection and vascular puncture), * complications noticed at the first postoperative month (residual pain, paresthesia, dysesthesia, weakness)
Block procedure time	One hour	Time taken to perform hydrodissection with dextrose 5% and inject the local anesthetic (min)
Additional local anesthetic	2 hours	* Percentage of cases where additional local anesthetic was necessary before the incision (%), i.e; performed by anesthesiologist * Percentage of cases where additional local anesthetic was necessary after the incision (%), i.e; performed by surgeon
Duration of analgesia	1 day	Time to first analgesic requirement (minutes)

Recruitment & Eligibility