Check Yourself # 6
Neurologic
While we may (un-) lovingly deride the NCLEX for its structure (the most correct answer, anyone?), it does do a good job of evaluating nursing judgement and showing what/how you should be thinking while nursing.
And it doesn’t stop with the NCLEX. Every certification exam you take is built on the same structure. Yay. So, let’s practice and check our knowledge at the same time.
Which of the following is an accurate restatement of the Monro-Kellie hypothesis?
 A. If one of the three intracranial volumes goes down, one of the other two intracranial volumes will go up to prevent a decrease in intracranial pressure (ICP).
 B. If one of the three intracranial volumes goes up, one of the other two intracranial volumes will go down to prevent an increase in ICP.
 C. If one of the three intracranial volumes goes up, there will be a resultant vasoconstriction to normalize blood flow.
 D. If one of the three intracranial volumes goes down, there will be a resultant vasodilation to normalize blood flow.
Source: Dennison ‘Pass CCRN!’ 4th Edition, online resources
Ta-da! You get a double brain week. If you haven’t read the Nurse-Files on the Monroe-Kellie Hypothesis, go back and review. You’ll be able to get the answer easy-peasy.
Now, I know question this reads like a Dr. Suess book. So, let’s weed out the wrong answers one by one.
(Quick review: the three intracranial volumes are blood, cerebral spinal fluid, and brain tissue. They exist in a finite space determined by the skull.)
First out is D. If one of the volumes goes down (decreased ICP), then why the heck would we need vasodilation? That would drop blood pressure, which would decrease the volume of blood getting into the brain and decrease CSF production. Wrong, wrong, wrong.
Likewise, we can cross out C. If the ICP goes up, we don’t want to also increase BP with more vasoconstriction! Get it together, brain.
Now, this is truly a tricky question. A and B say the same thing, technically. And yes, your body will autoregulate via vasoconstriction if there is a sudden drop in cerebral BP, such as if you stand suddenly after sitting for a long time. But the Monroe-Kellie Hypothesis specifically deals with an increase in brain volumes and the subsequent increase in intracranial pressure.
The ‘most correct’ answer is B. (Curse you, NCLEX!)
References
Porth’s Pathophysiology: Concepts of Altered Health States (9th Edition). Grossman, S.C., Porth, C.M.
Wikipedia: Intracranial Pressure
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Enjoy!
Anna, RN, BSN, CCRN
Necessary disclaimer: I am discussing medications and medical conditions in this article based on my personal experiences as a nurse. Your facility may have different requirements and resources. Use your own nursing judgement to assess and treat your patients according to your governing body and facility guidelines. All information within this article is correct to the best of my knowledge, but should be confirmed through verified evidence-based sources. I am not responsible for any clinical decisions made based on this article.