Authors: Missouri S et al.
Cureus, June 15, 2026.
Summary
This case report describes a 33-year-old man who developed significant but transient postoperative hypoxemia after an otherwise uncomplicated general anesthetic.
The patient had obesity with a body mass index of 35 kg/m², no known cardiopulmonary disease, and a history of heavy cannabis exposure. He reported vaping cannabis two to four times daily and smoking cannabis on the morning of surgery.
He underwent robotic excision of a small oropharyngeal mass. General anesthesia was induced with lidocaine, fentanyl, propofol, and rocuronium. Anesthesia was maintained with propofol and remifentanil infusions, with additional ketamine and dexmedetomidine.
The intraoperative course was stable. Oxygen saturation remained between 96% and 98%, ventilation was adequate, and there were no signs of aspiration, bronchospasm, airway obstruction, or hemodynamic instability.
Neuromuscular blockade was reversed with sugammadex, and quantitative monitoring showed adequate recovery before extubation.
After extubation, the patient’s oxygen saturation fell to approximately 80%. He continued to breathe spontaneously with large tidal volumes, and ventilation remained preserved. Recruitment maneuvers improved his oxygen saturation, but he still required 8 L/min of supplemental oxygen by face mask.
In the recovery unit, the patient continued to require oxygen despite being awake, ambulatory, and free of shortness of breath. Incentive spirometry did not correct the hypoxemia.
Chest radiography showed no acute pulmonary disease, although increased pulmonary vascular markings were present. Arterial blood gas analysis demonstrated:
• pH: 7.36
• pCO2: 42 mmHg
• pO2: 57 mmHg
• Oxygen saturation: 88%
The normal carbon dioxide level and preserved respiratory effort argued against opioid-induced hypoventilation.
The patient was admitted for observation, continued incentive spirometry, and received albuterol as needed. His oxygen requirement resolved completely within 24 hours, and he was discharged without complications.
The authors proposed that chronic cannabis vaping may have produced subclinical pulmonary inflammation and impaired gas exchange. General anesthesia may then have worsened these abnormalities through atelectasis, reduced functional residual capacity, altered pulmonary perfusion, and increased ventilation-perfusion mismatch.
Potential cannabis-related pulmonary mechanisms include airway inflammation, bronchial hyperreactivity, oxidative stress, alveolar injury, impaired surfactant function, increased alveolar-capillary permeability, and endothelial dysfunction.
Alternative causes of postoperative hypoxemia were considered less likely. There was no evidence of aspiration, negative-pressure pulmonary edema, opioid-induced respiratory depression, pulmonary embolism, or overt structural lung disease.
Although the patient had a STOP-Bang score of 5 and possible undiagnosed obstructive sleep apnea, the persistent hypoxemia while fully awake and ambulatory made obstructive sleep apnea an unlikely primary explanation.
What You Should Know
Heavy cannabis vaping may cause clinically silent pulmonary inflammation and impaired oxygen exchange.
These abnormalities may become evident only after general anesthesia.
Patients may have significant postoperative hypoxemia despite normal ventilation, minimal symptoms, and little or no abnormality on chest imaging.
Preoperative evaluation should specifically ask about cannabis use, route of administration, frequency, duration, and use on the day of surgery.
Cannabis vaping should not be considered harmless simply because the patient is young and has no diagnosed pulmonary disease.
Patients with heavy or recent cannabis exposure may require more cautious postoperative respiratory monitoring.
Cannabis use on the morning of elective surgery may increase perioperative risk and should prompt reconsideration of proceeding, depending on the patient’s condition and urgency of surgery.
The rapid resolution within 24 hours suggests a reversible disturbance in gas exchange rather than permanent structural lung injury.
This was a single case report, so it cannot prove that cannabis caused the hypoxemia.
Prospective studies are needed to determine how long patients should abstain before surgery and which cannabis users are at greatest risk for postoperative respiratory complications.
Thank you to Cureus for allowing us to summarize this article.