Impact on Sensitivity and Motor Block Duration of an Intravenous Dexamethasone an Axillary Block With Mepivacaine.

Overview

Intravenous dexamethasone is used to increase the duration of analgesia of interscalene bloc for shoulder surgery: it extends from 11h to 23h the sensitivity block in shoulder area. However, the time of dexamethasone intravenous injection has not been studied. In all studies, dexamethasone was injected right after the achievement of loco regional anesthesia. The main objective is to demonstrate that intravenous injection of dexamethasone delayed at 90 minutes in patients who received an axillary block with mepivacaine prolongs the duration of the motor block by 40 minutes.

In orthopedic surgery, most of procedures are made under loco regional anesthesia. For a surgery of hand, wrist or forearm, an axillary block is made to obtain an insensitivity (sensitivity block) and an unability to move from elbow to fingers (motor block). Depending on the duration of surgery, less or more than 2 hours, a choice of anesthetic has to be made. For short surgeries, mepivacaine is taken on, but for longer ones, local anesthetics like ropivacaine or levo bupivacaine are recommended. Nevertheless, once surgery started, there isn't any possibility to extend the anesthesia duration in case of an unexpected increase of surgery length. A general anesthesia will therefore be required. Intravenous dexamethasone is used to increase the duration of analgesia of interscalene bloc for shoulder surgery: it extends from 11h to 23h the sensitivity block in shoulder area(1). However, the time of dexamethasone intravenous injection has not been studied. In all studies, dexamethasone was injected right after the achievement of loco regional anesthesia. The investigator hypothesized that intravenous dexamethasone could extend anesthetic duration of a mepivacaine axillary block (motor and sensitivity block length) even though dexamethasone was injected 90 min after the achievement of block and could be a good option in case of an unexpected extended surgery. In orthopedic surgery, most of procedures are made under loco regional anesthesia. For a surgery of hand, wrist or forearm, an axillary block is made to obtain an insensitivity (sensitivity block) and an unability to move from elbow to fingers (motor block). Depending on the duration of surgery, less or more than 2 hours, a choice of anesthetic has to be made. For short surgeries, mepivacaine is taken on, but for longer ones, local anesthetics like ropivacaine or levo bupivacaine are recommended. Nevertheless, once surgery started, there isn't any possibility to extend the anesthesia duration in case of an unexpected increase of surgery length. A general anesthesia will therefore be required. Intravenous dexamethasone is used to increase the duration of analgesia of interscalene bloc for shoulder surgery: it extends from 11h to 23h the sensitivity block in shoulder area(1). However, the time of dexamethasone intravenous injection has not been studied. In all studies, dexamethasone was injected right after the achievement of loco regional anesthesia. The investigator hypothesized that intravenous dexamethasone could extend anesthetic duration of a mepivacaine axillary block (motor and sensitivity block length) even though dexamethasone was injected 90 min after the achievement of block and could be a good option in case of an unexpected extended surgery. 52 patients will be randomly assigned to two groups: * DEXA: dexamethasone 8 mg/2cc I.V. 90 minutes after axillary block * Control: Normal saline 2cc I.V., 90 minutes after axillary block These patients will be recruited during the anesthesia interview from 1 hospital, with 5 surgeons performing the surgeries and 15 anesthetists performing the axillary block 1. After written consent, all patients will have their surgery under regional anesthesia only provided by the axillary block, with mepivacaine 1.5% 25cc. 2. Time of complete motor and sensitivity block will be monitored and recorded 3. 80 minutes after achievement of axillary block, if the surgery is not ended, patients will be randomly assigned to one of the two groups : DEXA or Control 4. Injection will be done 90minutes after achievement of axillary block 5. Monitoring of motor block and sensitivity block recovery will be done : * during the surgery by nurse and surgeon * after the surgery in recovering room by nurses each 15min. 6. Patients will be called on post operative day one for pain evaluation and detection of adverse effects.