Calculate the cerebral perfusion pressure of a client whose mean arterial pressure is 72 mmHg and intracranial pressure is 24 mmHg.

Appeared in: NORCET-11 Mains

Explanation

The formula to determine Cerebral Perfusion Pressure (CPP) is Mean Arterial Pressure (MAP) minus Intracranial Pressure (ICP).
Using the provided values: CPP = 72 mmHg (MAP) – 24 mmHg (ICP).
The correct calculation yields a CPP of 48 mmHg.
This value is below the normal range of 60-100 mmHg, indicating compromised brain perfusion and risk of ischemia.

Option A: This value is incorrect. It does not result from the correct formula (MAP - ICP). It might be confused with a normal CPP value, but it is not the calculated result.
Close distractor alert - Option C: This is the result of incorrectly adding the MAP and ICP (72 + 24 = 96). The formula requires subtraction, not addition.
Option D: This value is incorrect. It may be the result of a miscalculation, such as dividing the MAP by 2 (72 / 2 = 36), which is not related to the CPP formula.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation and interpretation of Cerebral Perfusion Pressure (CPP) as background academic context rather than a clinical decision trigger.
Monitoring CPP is a fundamental nursing responsibility in neurocritical care to prevent secondary brain injury from ischemia or hyperemia.
A CPP below 50-60 mmHg is a critical finding that requires immediate intervention. The nurse must be prepared to administer medications to increase MAP (vasopressors) or implement measures to decrease ICP (e.g., head of bed elevation, administering osmotic diuretics).
What if? If the client's MAP was 94 mmHg and the ICP was 14 mmHg, the CPP would be 80 mmHg (94 - 14). This falls within the normal range of 60-100 mmHg, indicating adequate cerebral perfusion, and would not require immediate intervention.

How to Approach the Question

First, identify that the question asks for a calculation based on provided physiological parameters.
Recall the specific formula for Cerebral Perfusion Pressure (CPP), which is CPP = Mean Arterial Pressure (MAP) - Intracranial Pressure (ICP).
Extract the values given in the question: MAP = 72 mmHg and ICP = 24 mmHg.
Substitute these values into the formula: CPP = 72 - 24.
Perform the subtraction to get the result: 48.
Compare your calculated result with the given options to find the correct answer.

Concept Tested & Keywords

Concept Tested: Calculation and interpretation of Cerebral Perfusion Pressure (CPP).
Stem keywords: cerebral perfusion pressure, mean arterial pressure, intracranial pressure, 72 mmHg, 24 mmHg
Lead-in keywords: Calculate
Negative lead-in flag: false

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E6 Medicine Davidson Principles Practice 24e p. 228-230

E6 Nursing Brunner Adult Health 3SA Vol 2 Part 2 p. 30-32

E6 Medicine Harrison 22e Part 2 p. 247-249

Practise the full NORCET-11 Mains

Attempt every question from this paper in a timed mock, then review the full solution for each one.