The Retroclavicular Approach for Regional Anesthesia of the Upper Limb in Obese Patients

Success rate is defined as the completion of the intended surgery under regional anesthesia with retroclavicular block without the need for a rescue technique. These techniques are defined as: adding local anesthetic locally by surgeon, rescue intravenous narcotics in excess of 1 microgram per kilogram of patient weight, need for general anesthesia, rescue distal neural blockage by anesthesiologist. Patient sedation with midazolam 1 to 2 mg IV or propofol perfusion up to 50 mcg/kg/min is allowed for patient comfort during the surgery and is not considered a rescue technique.

Progress of the sensory block in the distribution of the radial, median, ulnar, musculocutaneous, and medial cutaneous nerves of the forearm and hand at 10, 20 and 30 minutes after block completion (mepivacaine-ropivacaine mixed injection). The scale used is: 0:no sensitive block, 1:analgesia (loss of pain but not tactile sensation), 2:anesthesia (loss of pain and tactile sensation).

Progress of the motor block in the distribution of the radial, median, ulnar, musculocutaneous nerves of the forearm and hand at 10, 20, and 30 minutes after block completion (mepivacaine injection). The scale used is: 0: no motor block, 1: paresis, 2: paralysis. No units are attached to this scale

Number of seconds needed to complete the block, from time of local skin anesthesia until regional block needle removal (local skin anesthesia plus injection of mepivacaine-ropivacaine mixture)

Using the Likert standardized scale, two evaluators will individually quantify the ease of needle visualization using the video footage recorded by the ultrasound machine from all the retroclavicular blocks. Likert scale for visualization, is defined as: 1:very bad, 2: bad, 3: adequate, 4:good, 5: very good.

Using a Visual Analog Scale (VAS), patients will quantify the discomfort they experienced during the block. This assessment will take place in the minutes following mepivacaine injection and block needle withdrawal. The VAS scale is rated from 1-10, 1 being almost no pain and 10 being the worst pain ever.

Using a VAS, patients will quantify their satisfaction with the retroclavicular technique throughout the study period.

With a phone call to the patient at 48 hours after injection of mepivacaine-ropivacaine mixture, complications will be searched for (pain at puncture site, paresthesia or paresis in the operated arm, signs of infection at puncture site such as redness or purulent discharge). Response is classified as YES or NO. No units attached to this scale. If patient reports paresthesia or paresis, further questioning over the phone will determine which nerve or cord is involved.

Duration of the block will be evaluated using 3 criteria: patient's subjective opinion of when the block receded (time of the day), time at which first oral analgesia is taken, and time of first onset of pain. Units involved is time (for example "3 pm".)

If at any point during the surgery, patient complains of tourniquet pain, this will be noted as well as the analgesia given. Units is time of pain ("3 pm") and analgesia given ("micrograms of fentanyl").

At the discretion of the anesthesiologist performing the block, neurostimulation can be used to supplement ultrasound guidance. This will be recorded as a YES or NO (neurostimulation used or not). No units attached to this rate.

If, for a given patient, during ultrasound guidance the anatomic structure are too poorly visualized to safely perform the block, no puncture will be attempted and the technique will be considered a failure; an alternative anesthesia technique will be proposed to the patient.

Immediate and early complications (vascular puncture, pneumothorax, paresthesia during block performance, pain during infection of the local anesthetics, Horner's syndrome) will be assessed throughout the patient's stay in the OR and PACU. Immediate and appropriate treatment will be provided if necessary.