CASE STUDY 12 History
A 55-year-old man was working at a textile manufacturing site and developed shortness of breath and a “dusky” skin color. The man had a history of a Barrett’s esophagus and obstructive sleep apnea and underwent periodic upper gastrointestinal endoscopy as a screening procedure for esophageal cancer. The foreman who called the rapid response reported that the patient had no complaints before this episode but had been splashed with liquid while connecting a hose coupling to a holding tank containing clothing dye. The identification of the dye was not immediately available, but the employee immediately self-decontaminated with water from an emergency shower before the ambulance arrival. The clothes were removed and disposed of at the work site. No other individuals at the site were potentially exposed. Physical Examination
Upon arrival, the patient had blood pressure, 166/112 mm Hg; pulse, 142 beats/min; respiratory rate, 40 breaths/min; and oxygen saturation, 87% on 4 L/min of oxygen via nasal cannula. Physical examination was notable for an ill-appearing man who could only speak in short sentences. His skin and nailbeds were cyanotic; his chest was clear; and his heart was regular and tachycardic without murmurs, gallops, or rubs. Initial Management
The patient received oxygen via a 100% nonrebreather mask, and bilevel positive airway pressure was started while preparations were made for endotracheal intubation. Although his respiratory rate and pulse improved somewhat, his oxygen saturation remained between 86% and 88%. An electrocardiogram (ECG) was obtained and showed sinus tachycardia without ST-segment or T-wave changes suggestive of ischemia or infarction. His clothes were removed and bagged.
A chest radiograph showed no cardiac or pulmonary disease, and an arterial blood gas (ABG) analysis was obtained. The resident commented that although she was certain that the blood was obtained from an artery, it looked dark as if it were venous blood. The results demonstrated the following: pH, 7.32; PCO2, 33 mm Hg; PO2, 426 mm Hg, and oxygen saturation, 100%. The results were interpreted as a primary metabolic acidosis with respiratory compensation (respiratory alkalosis). This corresponded to a serum bicarbonate concentration of approximately 16 mEq/L (Chap. 12) and reinforced the clinical impression that the patient was significantly ill. What Is the Differential Diagnosis?
This patient presented with hypertension, tachycardia, tachypnea, cyanosis, and decreased oxygen saturation. The most common causes of these findings in a nonindustrial environment 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. 16 and 28). The absence of underlying heart disease, an unremarkable ECG, pulse and blood pressure that are adequate for tissue perfusion, and clear chest examination essentially excludes these disorders, although laboratory ultrasonographic and radiologic confirmation should be obtained.
The combination of cyanosis with a low oxygen saturation by pulse oximetry, failure to respond to supplemental oxygen, dark-colored blood, ...