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A rapid response team (RRT) was called to the endoscopy suite because a patient developed shortness of breath and decreased oxygen saturation. On arrival, the responders found a 55 year-old man with the following vital signs: blood pressure, 166/112 mm Hg; pulse, 142 beats/min; respiratory rate, 40 breaths/min; oxygen saturation, 87% on 4 liters/minute of oxygen via nasal cannula. The man had a history of Barrett's esophagus and obstructive sleep apnea (OSA) and had to undergo periodic upper gastrointestinal endoscopy as a screening procedure for cancer.

The gastroenterologist who called the RRT reported that the patient had no complaints during the pre-procedural time out and that the following vital signs had been recorded: blood pressure, 142/88 mm Hg; pulse, 88 beats/min; respiratory rate, 16 breaths/min; tympanic temperature, 97.6°F (36°C); and oxygen saturation, 99% on room air. Just prior to administration of conscious sedation, the patient became uncomfortable and complained of shortness of breath. Within a few minutes his vital signs deteriorated and he became cyanotic.

Immediate Assessment and Management

The patient was immediately given high flow oxygen via a 100% nonrebreather mask, and although his respiratory rate and pulse improved somewhat, his oxygen saturation remained between 86% and 88%. Physical examination was notable for an ill appearing man who could only speak in short sentences. Although he denied chest pain, review of systems was positive for headache and nausea. His skin and nailbeds were cyanotic, his chest was clear, and his heart was regular and tachycardic without extra sounds. The patency of his intravenous line was confirmed, and an electrocardiogram was obtained and showed sinus tachycardia without ST segment or T wave changes suggestive of ischemia or infarction. When he failed to respond to supplemental oxygen, he was moved to the emergency department (ED).

On arrival to the ED, the following vital signs were obtained: blood pressure, 152/104 mm Hg; pulse, 122 beats/min; respiratory rate, 32 breaths/min; tympanic temperature, 97.8°F (36.5°C); oxygen saturation, 88% on 100% oxygen; and end tidal CO2, 28 mm Hg.

What Is the Differential Diagnosis?

This patient presented with hypertension, tachycardia, tachypnea, cyanosis, and decreased oxygen saturation. The most common causes for these findings are cardiac and pulmonary disease. Hypoxia and cyanosis in a normal environment (breathing a normal FiO2) can result from a shunt, ventilation-perfusion mismatch, diffusion abnormalities, or pump failure (Chaps. 17 and 29). The absence of underlying heart disease, unremarkable electrocardiogram, pulse and blood pressure that is adequate for tissue perfusion, and clear chest examination essentially excludes these disorders, although laboratory and radiologic confirmation should be obtained (see following sections). When cardiac and pulmonary disorders are excluded, dyshemoglobinemias should be considered, specifically methemoglobinemia and sulfhemoglobinemia (Chap. 127).

What Immediate Diagnostic and Therapeutic Interventions Are Indicated?

The patient was maintained on 100% oxygen, and bilevel positive airway pressure (BiPAP) was started while preparations were made for endotracheal intubation. Reasonable initial testing would include a chest radiograph, bedside echocardiogram, and an arterial blood ...

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