If you're preparing for the United States Medical Licensing Examination® (USMLE®) Step 3 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.    

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A 42-year-old woman whom you have been treating for anxiety calls your office demanding to talk to you. The nurse gets you immediately because the woman sounds "out of control." When you finally get to the phone, she is screaming, "A plumber is working in my house and he hurt his eye." You ask for details of the injury and she says that all she knows is that he "got some kind of liquid in his eye and he is freaking out." You instruct her to look at the bottle and read the label to you, but all you can understand from her hysterical speech is "pH of 12.2." You hear a man in the background screaming in pain.

You try to calmly explain to her that the most appropriate immediate management is to do which of the following?

A. Call an ambulance to bring him to the hospital and place a patch over the affected eye while he is waiting for the ambulance.

B. Call an ophthalmologist and schedule an appointment for the next available time.

C. Flush the eye with an acidic substance she may have in her cupboard.

D. Flush the eye continuously with cold running water before going to the hospital.

E. Apply antihistamine eyedrops to the eye before going to the hospital.

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The correct answer is D.

This patient most likely has an alkaline eye burn, which is extremely destructive, and the process of destruction continues as long as the substance is in contact with the tissues. Immediate removal of the offending substance is essential, and the best method is massive irrigation. In the emergency room, sterile saline would be used, but at home, tap water will do. This irrigation is important even before going to the hospital because the alkaline fluid will remain in the eye if irrigation is delayed until the man gets to the ER physicians.

Choice A: It is extremely dangerous to call an ambulance to bring the man to the hospital and place a patch over the affected eye while he is waiting for the ambulance. The alkaline chemical will begin to destroy the eye if irrigation does not begin immediately while he is waiting for help.

Choice B: Alkaline eye burns are emergencies that require immediate irrigation and medical attention. Calling an ophthalmologist and scheduling an appointment for the next available time will leave too much time for the chemical to destroy the eye.

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Choice C: It would be inappropriate to tell the woman to flush the plumber's eye with a substance that she can find in her cupboard that has a pH of 6.9 or lower. Irrigation with cold tap water is the treatment while waiting for additional medical help (in the ambulance or at the hospital).

Choice E: Antihistamine eyedrops play no role in the management of acute caustic injuries to the eye. They are used for allergic conditions of the eye. Also, administration of these drops will only delay treatment and may even cause more damage to the eye.

The most important initial step in management in alkaline eye burns is to flush exposed or irritated eyes with plain water or saline for at least 30 minutes. Do not attempt to neutralize the chemical substance.

For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.

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