Archive Of Standardized Exam Questions: Methemoglobinemia

OVERVIEW

This page is dedicated to organizing various examples of standardized exam questions whose topic is methemoglobinemia. While this may seem a odd practice, it is useful to see multiple examples of how methemoglobinemia will be characterized on standardized exams (namely the boards and the shelf exams). This page is not meant to be used as a traditional question bank (as all of the answers will be the same), however seeing the classic “test” characterization for a topic is quite valuable.

KEY CHARACTERISTICS OF THIS CONDITION (ON EXAMS)

When it comes to standardized exams, each topic has its own “code” marked by key buzzwords, lab findings, clues, etc. If you are well versed in this code you will be able to more quickly identify the condition that is being discussed, and get the right answer on the exam you are taking. Below is the “code” for methemoglobinemia. 

  • Exposure to nitrites: this will cause this condition. 
  • Dusky discoloration of the skin: this is similar to cyanosis, and occurs because methemoglobin is unable to carry oxygen. 
  • Normal partial pressure of oxygen in arterial blood: this value can very likely be in the reference range. 
QUESTION EXAMPLES

Question # 1

 

Explanation # 1

 

Question # 2

 

Explanation # 2

 

TESTABLE FACTS ABOUT THIS TOPIC (BEYOND ITS IDENTIFICATION)

Many questions on standardized exams go beyond simply recognizing the underlying topic. Often there are specific testable facts regarding some aspect of the topic’s pathophysiology/management/clinical implications that are commonly asked. Some of these are listed below:

  • Cause: nitrite exposure can be responsible for this condition. 
  • Consequence: nitrites induce the conversion of heme iron to its oxidized ferric (Fe3+) state, leading to methemoglobin (which is unable to bind to oxygen). Iron in hemoglobin is usually in its reduced ferrous (Fe2+) state which binds oxygen readily. 
  • Does partial pressure of oxygen in blood change: no it does not. 
  • How it is treated: 
    • Vitamin C (ascorbic acid): is the ancillary treatment fro this condition by reducing Fe3+ to Fe2+
    • Methylene blue is also used. 

 

 

Page Updated: 04.26.2017