Conditions: Pain
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 75
Healthy volunteers: no

Brief summary:
Interscalene brachial plexus block provides excellent but time limited analgesia. Intravenous dexamethasone increases the analgesic duration of a single-shot interscalene block with ropivacaine for shoulder arthroscopic surgery. We want to evaluate the effect of two different doses (dexamethasone 10 mg i.v. vs 4 mg i.v. vs placebo) on the analgesic duration of a single-shot inter scalene block. Our study hypothesis is that dexamethasone 4 mg i.v. is equivalent to dexamethasone10 mg i.v. in prolonging the analgesic duration of a single-shot interscalene block with ropivacaine.

Detailed description:
75 patients will be randomly assigned to three groups:

* D10: dexamethasone 10 mg I.V. diluted in normal saline 20cc, immediately after inter scalene block
* D4: dexamethasone 4 mg I.V. diluted in normal saline 20cc, immediately after inter scalene block
* C: control: Normal saline 20cc I.V., immediately after inter scalene block. These patient will be recruited from 3 hospitals, with two surgeons performing the surgeries.

All patients will have their surgery under regional anesthesia only provided by the inter scalene plexus block, with ropivacaine 0.5% 20cc.

In the postoperative period, patients will be given analgesic medication on an as needed basis. They will be instructed to take the first analgesic medication once postoperative shoulder pain has reached \>3/10. They will note the time and day at which this outcome occurs.

Arms:
arm 1: Dexamethasone 10 mg diluted with Normal Saline 17,5 mL i.v. (20 mL total) injected slowly during 30 seconds immediately after performing interscalene brachial plexus block arm 2: Dexamethasone 4 mg diluted with Normal Saline 19 mL i.v. (20 mL total) injected slowly during 30 seconds, immediately after performing interscalene brachial plexus block arm 3: Normal saline 20 mL injected slowly during 30 seconds, immediately after performing interscalene brachial plexus block

Interventions: intervention 1: Dexamethasone intervention 2: Normal Saline
Intervention descriptions: intervention 1: After the performance of inter scalene plexus blockade, patients will either receive dexamethasone 10 mg i.v. (diluted with 17.5 mL normal saline), dexamethasone 4 mg i.v. (diluted with 19 mL normal saline), or normal saline 20 ml i.v. intervention 2: None

Protocol document: