Intravenous Dexamethasone to Increase the Analgesic Duration of Interscalene Block

Impact of Two Doses of Intravenous Dexamethasone on the Analgesic Duration of a Single-shot Interscalene Block With Ropivacaine for Shoulder Arthroscopy; a Prospective, Randomized, Placebo-controlled Study

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.

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.

Inclusion Criteria:

• Elective shoulder arthroscopy under ropivacaine single-shot interscalene brachial plexus block anesthesia (rotator cuff repair and shoulder decompression)
• ASA I-III
• Age 18-80 years old

Exclusion Criteria:

• Any contraindication to interscalene brachial plexus block anesthesia
• Interscalene brachial plexus block failure
• Known local anesthetics allergy
• Dexamethasone allergy or intolerance
• Any contraindication to acetaminophen
• Any contraindication to morphine or hydromorphone
• Brachial plexus neuropathies
• Chronic pain syndrome other than shoulder pain
• Routine use of opioid medication
• Routine use of systemic corticosteroid
• Pregnancy
• Weight below 50 kilograms
• Incapability to understand a numeric verbal pain scale
• Incapability to consent
• Patient refusal