Optimal Location of Local Anesthetic Injection for Ultrasound Guided Interscalene Block

Inclusion Criteria: ASA I-II patients who are 18 years and older and who are scheduled for shoulder arthroscopy are eligible for enrollment provided they do not have any of the following exclusion criteria. Exclusion Criteria: * chronic pain * high preoperative opioid requirement * age \< 18 years old * non-English speaking * contraindication to regional anesthesia (allergy to local anesthetics, coagulopathy, severe thrombocytopenia, pre-existing neuropathy in operative limb, infection at puncture site) * need for postoperative nerve function monitoring * patient refusal * dementia * pulmonary disease or low baseline oxygen saturation