This is a randomized controlled trial evaluating the impact of interscalene block on worsening of upper airway collapse in sleep disordered breathing for patients undergoing ambulatory shoulder surgery.

Sleep disordered Breathing (SDB), closely associated with obesity, is a highly prevalent, serious, and often unrecognized breathing disorder resulting from repeated upper airway collapse, decreased oxygen levels, and a very high risk of life threatening complications at the time of surgery. Current guidelines recommend using regional as opposed to general anesthesia in SDB patients to minimize risks and the use of strong narcotic medications. It is unclear whether interscalene block in use for analgesia (pain relief) may actually worsen the severity of SDB by invariably freezing the phrenic nerve, thereby temporarily paralyzing the diaphragm.

This novel clinical trial will examine whether or not ISB increases the rate of upper airway obstruction or collapse during sleep and other dangerous postoperative complications seen in patients with SDB following shoulder surgeries.

The Primary Objective of the study is to evaluate the impact of ISB on the oxygen desaturation index (sleep apnea severity) in untreated SDB patients undergoing ambulatory shoulder surgery compared to patients who do not receive ISB.

Secondary Objectives are: 1) To evaluate the impact of hemidiaphragmatic paresis on impairment in pulmonary function; 2) To evaluate the impact of impairment in pulmonary function on the oxygen desaturation index (ODI); 3) To assess the incidence of important perioperative clinical outcomes such as hypoxemia, recurrent respiratory events, delayed discharge, and resource utilization in SDB patients undergoing ambulatory shoulder surgery compared to patients who do not receive ISB; and 4) To assess important analgesia related outcomes such as: time to onset of pain, intraoperative and postoperative opioid consumption, hourly and daily VAS pain scores, opioid related side effects, patient satisfaction with analgesia, and presence/absence of nerve block complications.

Inclusion Criteria:

• Adult patients ( >18 to 80 years);
• American Society of Anesthesiology (ASA) physical status I-IV;
• Undergoing elective ambulatory shoulder surgery such as shoulder replacement, acromioplasty, rotator cuff repair, or Bankart procedure under general anesthesia.

Exclusion Criteria:

• Past history of head, neck or thoracic surgery (e.g., OSA corrective surgery);
• Pregnancy or lactation;
• Phrenic nerve stimulators;
• Local anesthetic allergy;
• Previous diaphragmatic paralysis;
• Inability to communicate with health care providers or the research personnel, inability to perform breathing maneuvers such as spirometry, or inability to follow instructions.

On the day of surgery, patients will be randomly assigned (1:1) to one of two groups according to a computer-generated list. The patients, the clinical care team (anesthesiologist providing intraoperative care, nurses, and surgeons), data collectors, outcome adjudicators, and the study statisticians will all remain blinded to randomization and group allocation. The anesthesiologist who will perform the intervention will be aware of group allocation, but the anesthesiologist providing intraoperative care will remain blinded. Situations such as patient refusal at any time of the study, any adverse event or complication necessitating withholding the intervention would result in voluntary un-blinding of study investigators.