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PATIENT
Ms. M is a 70-year-old woman who arrives at the emergency department complaining of shortness of breath and dizziness. On physical exam, her pulse is 105 bpm, BP 75/45 mm Hg, and her skin exam is notable for hives. She is warm and has bounding pulses. The patient recently underwent surgery to have a mechanical mitral valve placed and took amoxicillin for the first time as prophylaxis for an upcoming dental procedure.
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As noted above, the first step in the evaluation of the hypotensive patient is the recognition of shock. The patient’s profound hypotension, particularly at this age, and dizziness suggest symptomatic hypotension and inadequate cerebral perfusion diagnostic of shock. The first pivotal diagnostic step is to consider whether the history and physical exam suggest 1 of 3 leading causes of shock: septic shock, hypovolemic shock, or cardiogenic shock. Her bounding pulses and warm extremities suggest distributive shock, a high output form of shock. As mentioned above, the most common form of distributive shock is septic shock, a must not miss hypothesis. However, her hives and recent use of amoxicillin is a pivotal clue that suggests another cause of distributive shock, anaphylactic shock. This is both the leading and must not miss hypothesis. Table 25-6 lists the differential diagnosis.
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Anaphylactic shock was quickly recognized, and Ms. M promptly received an IM injection of epinephrine as well as fluids. Her BP and shortness of breath quickly improved.