Influence of Ultrasonographic Hydro-dissection With Glucose 5% on Nerve Block Efficiency (Hydro-Echo)

• Onset time of sensory blockade (cold test at index finger and thenar eminence) [ Time Frame: 30 minutes after injection ] [ Designated as safety issue: No ]
• Onset time (light touch test at thenar eminence) [ Time Frame: 30 minutes after injection ] [ Designated as safety issue: No ]
• Onset time for motor blockade [ Time Frame: 30 minutes after injection ] [ Designated as safety issue: No ]
• Success rate (% of patients with total light touch block at index finger within 30 min evaluation period) [ Time Frame: 30 minutes after injection ] [ Designated as safety issue: No ]
• Successful surgical anesthesia [ Time Frame: 30 minutes after injection ] [ Designated as safety issue: No ]
• Duration of nerve blockade [ Time Frame: 12 hours ] [ Designated as safety issue: No ]
• Nerve block complication [ Time Frame: one month ] [ Designated as safety issue: Yes ]
• Duration of the puncture procedure [ Time Frame: 30 minutes after the beginning of the procedure ] [ Designated as safety issue: No ]

The real-time visualization of a needle and nerve during an ultrasound-guided nerve block can be challenging. These difficulties may partly explain the systemic complications of local anesthetics under ultrasound. Injection of small amounts of a solution around the anesthetized nerve (hydro-dissection) has been proposed to enhance contrast outlining its borders and also to improve the visualization of the needle tip. The glucose solution 5% solution is interesting because it allows, unlike saline, to maintain the motor response with neurostimulation. The hydro-dissection can be particularly useful when one suspect hypoechoic vessels near the nerve to be anesthetized. Thereby, the nerve well demarcated and separated from the vessels, injection of local anesthetic is performed in the circumferential diffusion space (like a small pocket) without redirecting needle.

The influence of this hydro-dissection on the nerve block efficiency is unknown. The nerve block quality can be improved because the entire anesthetic is injected in contact with the nerve, but it can also be reduced due to the dilution of the local anesthetic by the glucose solution.

In this randomized study, the investigators test the hypothesis that hydro-dissection does not alter the nerve block onset time.

• Procedure: median nerve block
  median nerve block performed using ultrasound guidance
• Procedure: median nerve block after hydro-dissection
  median nerve block performed after hydro-dissection (glucose 5% solution), both using ultrasound guidance

• Active Comparator: nerve block
  median nerve block (6 ml lidocaine 1.5 % with adrenalin 1:200000)
  Intervention: Procedure: median nerve block
• Experimental: median nerve block after hydro-dissection
  median nerve block (6 ml lidocaine 1.5 % with adrenalin 1:200000) after hydro-dissection (glucose 5% solution)
  Intervention: Procedure: median nerve block after hydro-dissection

Inclusion Criteria:

• Adult patients with an ASA physical status I-II scheduled for elective ambulatory surgery of the hand or wrist involving the median nerve

Exclusion Criteria:

• Patients with type 1 or 2 diabetes mellitus,
• History of clinical or laboratory evidence of abnormal bleeding,
• Infection at the injection site,
• Allergy to local anesthetic,
• Preexisting central or peripheral muscular or neurological disease (for example: carpal tunnel syndrome)