Intravenous Oliceridine and Opioid-related Complications

Inclusion Criteria: * ≥18 years old * American Society of Anesthesiologists physical status 1-4 * Scheduled for major noncardiac surgery expected to last at least 2 hours * Expected to remain hospitalized at least two postoperative nights * Scheduled for general endotracheal, spinal anesthesia, or the combination * Expected to require substantial opioid analgesia, defined as ≥20 mg morphine equivalents * Expected to have patient-controlled intravenous analgesia. Exclusion Criteria: * Are demented or otherwise cannot provide valid consent * Have contraindications to oliceridine * Used legal or illegal opioids chronically, defined as \>15 mg morphine equivalents for \>15 days during the month before consenting by history * Have language, vision, or hearing impairments that may compromise continuous ventilation monitoring * Have planned epidural anesthesia/analgesia * Planned spinal morphine administration * Are designated Do Not Resuscitate, hospice, or receiving end of life therapy * Are expected to require postoperative mechanical ventilation or ICU admission * Are expected to receive intrathecal opioids * Are expected to receive gabapentin, pregabalin or other analgesic adjuvants * Use oxygen at home * Are unwilling or unable to comply fully with study procedures (including not tolerating the capnography cannula) * Are known to be pregnant or breastfeeding * Use CPAP at home * Have previously participated in the trial