Nitroprusside/NTG and Methemoglobinemia

[drlee]

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1994 ITE Question 163 (K-type):

A 32yo woman is scheduled for emergency craniotomy after sustaining a closed head injury in a motorcycle accident. Effects of nitroprusside to control hypertension include:

1) Increased ICP
2) methemoglobinemia
3) decreased PaO2
4) increased serum creatinine concentration

Answer: B

According to my previous readings, nitroprusside can lead to methemoglobinemia. The answer contradicts this. Nitroglycein in high-doses also can cause methemoglobinemia. Does anyones else agree?

 

[Bougie]

1994 ITE Question 163 (K-type):

A 32yo woman is scheduled for emergency craniotomy after sustaining a closed head injury in a motorcycle accident. Effects of nitroprusside to control hypertension include:

1) Increased ICP
2) methemoglobinemia
3) decreased PaO2
4) increased serum creatinine concentration

Answer: B

According to my previous readings, nitroprusside can lead to methemoglobinemia. The answer contradicts this. Nitroglycein in high-doses also can cause methemoglobinemia. Does anyones else agree?

Not sure I follow your logic. Nitroprusside can cause methemoglobinemia. It can also technically cause increased ICP (answer A) in normocapnic patients due to vasodilation and expansion of cerebral volume. Another reason I highly discourage use of questions 15 years old. You may get a physiological tidbit here and there but you are wasting your time with management issues since the material on those exams are very dated and are full of mistakes. Stick with Hall and the ACE questions.

 

[pgg]

1994 ITE Question 163 (K-type):

A 32yo woman is scheduled for emergency craniotomy after sustaining a closed head injury in a motorcycle accident. Effects of nitroprusside to control hypertension include:

1) Increased ICP
2) methemoglobinemia
3) decreased PaO2
4) increased serum creatinine concentration

Answer: B

According to my previous readings, nitroprusside can lead to methemoglobinemia. The answer contradicts this. Nitroglycein in high-doses also can cause methemoglobinemia. Does anyones else agree?

Nitroprusside metabolism produces 1 methemoglobin (from 1 oxyhemoglobin) and 5 CN-. One of those CN- immediately combines with the methemoglobin to produce cyanomethemoglobin.

Methemoglobin is an intermediary; there's no net production of it.


Bougie - I disagree about the utility of old exams. I reviewed the 94-95 exams in great detail prior to the last ITE, and I thought the overwhelming majority of the current questions had close analogues to old questions ... some were repeated verbatim. Some drugs come & go, some doctrine & dogma change, but the vast majority of the content tested hasn't really changed in 13 years.

If nothing else, working through old questions like this to figure out why the board answer is (usually) right and I was wrong is a good learning opportunity.

I've also used Hall (great book) and several other Q&A books. The old ITEs are IMO a great tool.