Ultrasound guided infraclavicular block for forearm or hand surgery

Corresponds to the time elapsed between the penetration of the skin with the needle until the complete removal of the needle from the tissues.

Sensory loss will be assessed in the territory of the radial (lateral aspect of the dorsum of the hand), median (volar aspect of the index), ulnar (volar aspect of the fifth finger), musculocutaneous (lateral aspect of the forearm), and medial cutaneous nerve of the forearm (medial aspect of the forearm) distributions using a 3-point score, where 0 = normal sensation, 1 = diminished sensation to pinpricks (hypoesthesia), and 2 = loss of sensation to pinpricks (analgesia). The sum of five scores on a maximum of 10 will be the sensory loss final score. An independent, blinded, research assistant will complete the sensory assessment at 10, 20 and 30 minutes after procedure

Motor function will be tested (0 = normal strength, 1 = weakness, 2 = paralysis) for the radial (wrist extension), median (thumb-fifth finger opposition), ulnar (fifth finger abduction), and musculocutaneous (elbow flexion) nerves. The sum of the four scores on a maximum of 8 will be the motor block final score. An independent, blinded, research assistant will complete the motor assessment at 10, 20 and 30 minutes after procedure

Success is defined as the completion of surgery without the need for additional local anesthetics infiltration, intravenous narcotics, or general anesthesia. However, light sedation is allowed if deemed necessary by the anesthesiologist. Light sedation includes midazolam 1 to 4 mg intravenously, fentanyl up to 1 mcg/kg. A minimum sensory score of 9/10 will be necessary to proceed to surgery without additional local anesthetics infiltration. Patients with an overall sensory score less than 9/10 at 30 minutes will be offered general anesthesia or supplemental blocks.

Measured in minutes and defined as the sum of performance time and time to achieve a minimum sensory score of 9/10. It is the time for readiness for surgery.

Defined as a unit of 1,2,3, etc. The number of times the block needle will have to be realigned at the skin in order to achieve its final positioning goal under the axillary artery.

Procedures will be videotaped and reviewed simultaneously after study completion by 2 independent anesthesiologists skilled in US-guided regional anesthesia using a 5-point Likert scale to rate needle visibility (1=very poor,2=poor,3=fair,4=good,5=very good). Needle visibility will be evaluated twice. First, for the retroclavicular approach, assessment will be done when needle tip is seen 1cm after crossing the clavicle acoustic shadowing. For the coracoid infraclavicular approach, the first assessment will be at a needle tip depth of 1 cm. Second needle visibility assessment will be immediately before local anesthetic injection when block needle is positioned under axillary artery (when the visibility is theoretically optimized)

Using the same videotape that investigators used for the evaluation of the needle visibility, the angle between the needle and the upper side of the ultrasound image will be noted. It will be a continuous outcome ranging from 0 to 90 degrees.

Neurostimulation is accepted if needed. However, its use other than for safety sentinel (defined by <0,3 mA) will be recorded for subsequent analysis. It will be a dichotomic outcome.

Immediately after block completion, patients will be asked to rate their discomfort associated with the procedure using a 10-cm visual analogue scale (0 = no pain, 10 = worst pain imaginable) by an independent and blinded outcome assessor.

The incidence of needle-induced paresthesia, vascular puncture, Horner syndrome, dyspnea, and symptoms of local anesthetics toxicity will be noted. All patients will be contacted 48 hours after surgery to ask for any delayed complications, such as dyspnea, paresthesia, weaknesses, pain at the puncture site, hematoma.