NCLEX-PN® ExaminationPhysiological AdaptationMedium
A client is admitted to the intensive care unit with a severe traumatic brain injury (TBI). The nurse understands that maintaining a cerebral perfusion pressure (CPP) between 60-70 mmHg is crucial. If the client's intracranial pressure (ICP) is 20 mmHg and the mean arterial pressure (MAP) is 80 mmHg, what is the client's current CPP?
- A40 mmHg
- B60 mmHg
- C70 mmHg
- D100 mmHg
Show answer & explanationAnswer & explanation
Correct answer: B. 60 mmHg
Cerebral perfusion pressure (CPP) is calculated as Mean Arterial Pressure (MAP) minus Intracranial Pressure (ICP). In this case, CPP = 80 mmHg (MAP) - 20 mmHg (ICP) = 60 mmHg. This value is at the lower end of the desired range (60-70 mmHg), indicating the need for careful monitoring and potential interventions.
Why the other options are wrong
- A. 40 mmHg would result from MAP 60 - ICP 20, or MAP 80 - ICP 40.
- C. 70 mmHg would result from MAP 90 - ICP 20, or MAP 80 - ICP 10.
- D. 100 mmHg would result from MAP 120 - ICP 20, or MAP 80 + ICP 20 (incorrect formula).
Cerebral Perfusion Pressure (CPP) Calculation
Cerebral Perfusion Pressure (CPP) is the net pressure gradient causing cerebral blood flow to the brain, calculated as Mean Arterial Pressure (MAP) minus Intracranial Pressure (ICP).
- Formula: CPP = MAP - ICP.
- Normal CPP is 70-100 mmHg; desired for TBI is often 60-70 mmHg.
- Maintaining adequate CPP is vital to prevent cerebral ischemia.
Memory trick: MAP minus ICP, gives the brain its blood, you see!