A 55-year-old man is brought to the emergency department by his wife due to sudden-onset confusion. The couple lives on the coast, and the patient was on his boat this morning performing recreational diving with 2 of his friends. Shortly after returning home, the patient reported shortness of breath, as well as tingling and weakness of the left arm. He attempted to walk to a chair but stumbled and fell. His speech then began to slur, and he could not answer questions appropriately. Medical history includes hypertension and diet-controlled type 2 diabetes mellitus. Temperature is 37.2 C (99 F), blood pressure is 102/68 mm Hg, and pulse is 104/min. Physical examination shows moderate respiratory distress. Heart sounds are normal with no murmurs. There are faint lung crackles bilaterally. Neurologic examination reveals reduced muscle strength in the left arm and no other focal findings. Mottling of the skin of the hands and feet is also noted. Which of the following is the most likely cause of this patient's presentation?

Question

A 55-year-old man is brought to the emergency department by his wife due to sudden-onset confusion.  The couple lives on the coast, and the patient was on his boat this morning performing recreational diving with 2 of his friends.  Shortly after returning home, the patient reported shortness of breath, as well as tingling and weakness of the left arm.  He attempted to walk to a chair but stumbled and fell.  His speech then began to slur, and he could not answer questions appropriately.  Medical history includes hypertension and diet-controlled type 2 diabetes mellitus.  Temperature is 37.2 C (99 F), blood pressure is 102/68 mm Hg, and pulse is 104/min.  Physical examination shows moderate respiratory distress.  Heart sounds are normal with no murmurs.  There are faint lung crackles bilaterally.  Neurologic examination reveals reduced muscle strength in the left arm and no other focal findings.  Mottling of the skin of the hands and feet is also noted.  Which of the following is the most likely cause of this patient's presentation?

Quizplus · Accepted Answer

This patient is most likely experiencing the effects of vascular air embolism. Deep underwater diving (ie, scuba diving) is associated with a risk of decompression sickness ("the bends"), which can result from the formation of nitrogen gas bubbles within the body when a diver ascends too rapidly from the high ambient pressure of the deep water to the lower ambient pressure at the surface. Symptoms usually begin within 12 hours of surfacing. Small air bubbles in the venous bloodstream can lodge in the capillaries of the skin to cause pruritus or mottling and cyanosis of the extremities. The air bubbles can also lodge in the pulmonary capillaries to cause respiratory distress and localized ischemia, with resulting pulmonary edema. A relatively large volume of coalesced air (eg, 50 mL) can lodge in the right ventricular outflow tract and cause obstructive shock. Air can also pass into the arterial circulation by overwhelming the pulmonary capillary filtering capacity or via a right-to-left-shunt (eg, patent foramen ovale). Small air bubbles in the arterial circulation can travel to the brain to cause confusion, gait ataxia, and dysarthria. A small volume (eg, 1-2 mL) of coalesced air can cause localized stroke (eg, left arm weakness) or myocardial infarction. Emergency treatment involves intravenous hydration, Trendelenburg positioning, and the immediate administration of 100% oxygen to facilitate absorption of nitrogen gas from the bloodstream. Optimal management is with hyperbaric oxygen therapy. (Choice A) Carbon monoxide poisoning most often occurs due to exposure to smoke or faulty heating systems in a closed space and usually presents with headache, nausea, dizziness, and confusion. Focal neurologic deficits are not typical. (Choice B) Cerebral artery plaque rupture is a common mechanism of stroke, and this patient has risk factors for atherosclerotic disease (eg, diabetes mellitus, hypertension). However, plaque rupture would not explain this patient's respiratory symptoms. (Choice C) Cocaine intoxication can present with chest pain and respiratory distress and can increase the risk of stroke; however, confusion, gait ataxia, and dysarthria are not typical. (Choice D) Severe hyponatremia can occur following intense exertion with ingestion of hypotonic fluid. It typically presents with confusion but would not explain this patient's respiratory distress or focal neurologic findings. Educational objective: Vascular air embolism can occur due to decompression sickness following deep underwater diving. Venous air embolism can cause skin cyanosis, respiratory distress, and obstructive shock, whereas arterial air embolism can cause confusion, gait ataxia, dysarthria, and stroke. References: Diving emergencies. (http://www.ncbi.nlm.nih.gov/pubmed/14625107)

A 55-Year-Old Man Is Brought to the Emergency Department by His