A 36-Year-Old Woman With Intermittent Cyanosis.

A 36-year-old woman with a medical history of opioid use disorder and frequent urinary tract infections presented to the ED from her opioid use disorder clinic, where she was found to have an oxygen saturation by pulse oximetry (Spo2) of 82% on room air. Starting 3 days before presentation, the patient's family noted worsening pale complexion and blue lips at rest. These findings of cyanosis had occurred a few times before and always resolved within a couple days without any medical intervention. She had no pulmonary symptoms outside of long-standing dyspnea with moderate exertion when at work or doing chores around the house. Her medications included methadone 160 mg daily, acetaminophen 650 mg nightly as needed, and phenazopyridine 199 mg three times daily as needed for increased urinary frequency and urethral discomfort that lasted a maximum of 4 days at a time. She confirmed she had started taking a new course of phenazopyridine 4 days before presenting to the ED. She had no dietary restrictions, had been eating her normal diet, and lived in a mobile home with her family, two dogs, and a gerbil. The patient reported using less than 10 tobacco cigarettes per day, one marijuana cigarette nightly, and no alcohol or other drugs. She worked in a warehouse stacking prepackaged bread.