A 32-year-old woman is brought to the emergency department after being stuck in a malfunctioning elevator for 45 minutes. The patient says she felt extremely anxious in the closed space of the elevator and experienced dizziness, shortness of breath, generalized weakness, and blurred vision. She has no other medical conditions and takes no medications. She does not use tobacco, alcohol, or illicit drugs. Which of the following is the most likely cause of this patient's symptoms?

Question

A 32-year-old woman is brought to the emergency department after being stuck in a malfunctioning elevator for 45 minutes.  The patient says she felt extremely anxious in the closed space of the elevator and experienced dizziness, shortness of breath, generalized weakness, and blurred vision.  She has no other medical conditions and takes no medications.  She does not use tobacco, alcohol, or illicit drugs.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3ce8_21eb_9249_aff12f6f4ef7_MD0001_00 This patient most likely had a panic attack while trapped in the elevator. Panic attacks are typically accompanied by hyperventilation with a resulting decrease in arterial partial pressure of CO₂ (PaCO₂). This hypocapnia can cause decreased cerebral perfusion with consequent neurologic sequelae, including generalized weakness, blurred vision, presyncope (ie, dizziness, lightheadedness), and syncope. Cerebral blood flow (CBF) remains relatively constant over a wide range of perfusion pressures (cerebrovascular autoregulation) and is mainly influenced by arterial blood gas levels, particularly changes in PaCO₂. Hypercapnia triggers an increase in CBF (to aid in removal of toxins), and hypocapnia triggers a decrease in CBF. In fact, because hypocapnia decreases CBF, mechanically ventilated patients with cerebral edema are often hyperventilated to decrease intracranial pressure and help prevent brain herniation. CBF is less sensitive to the arterial partial pressure of oxygen (PaO₂). PaO₂ has little influence on CBF until the level drops below 50 mm Hg, at which point a rapid increase in CBF is triggered. (Choices B and D) The total blood O₂ content is predominantly made up of hemoglobin-bound O₂ (determined by the blood hemoglobin level and PaO₂) plus a small contribution of dissolved O₂. Hyperventilation increases the alveolar partial pressure of O₂ and should somewhat increase (rather than decrease) both PaO₂ and total blood O₂ content. (Choice C) Hyperventilation produces respiratory alkalosis, marked by an increase in arterial pH. (Choice E) Disturbances that increase the alveolar-arterial O₂ gradient include V/Q mismatch (eg, pulmonary embolism), diffusion limitation, and right-to-left shunting (eg, Eisenmenger syndrome). Changes in ventilation rate (ie, hypo- or hyperventilation) have no effect on the alveolar-arterial O₂ gradient. (Choice F) Increased arterial lactic acid content is a sign of tissue hypoxia (eg, due to sepsis or ischemia), which is unlikely in the setting of hyperventilation from a panic attack. Educational objective: Panic attacks are typically accompanied by hyperventilation, leading to hypocapnia. Cerebral blood flow is directly related to the arterial partial pressure of CO₂; therefore, hypocapnia can lead to reduced cerebral blood flow and symptoms of cerebral hypoperfusion (eg, blurred vision, dizziness, lightheadedness).

A 32-Year-Old Woman Is Brought to the Emergency Department After