Cerebral perfusion pressure (CPP) = MAP − ICP. In a patient with ICP = 35 mmHg and MAP = 75 mmHg, what is CPP and what pharmacological intervention best improves it without raising ICP?
- A CPP = 40 mmHg; administer sodium nitroprusside to raise MAP
- B CPP = 110 mmHg; no intervention needed
- C CPP = 40 mmHg; administer norepinephrine to raise MAP while avoiding cerebral vasodilation ✓
- D CPP = 40 mmHg; administer hydralazine to lower ICP
Correct answer: C. CPP = 40 mmHg; administer norepinephrine to raise MAP while avoiding cerebral vasodilation
Explanation
CPP = MAP − ICP = 75 − 35 = 40 mmHg, which is critically low (target CPP in TBI is 60–70 mmHg per Brain Trauma Foundation guidelines). To improve CPP, MAP must be raised. Norepinephrine is the vasopressor of choice as it raises MAP through alpha-1 agonism without crossing the blood-brain barrier to cause cerebral vasodilation. Sodium nitroprusside and hydralazine cause cerebral vasodilation which increases CBV and worsens ICP, further reducing CPP — they are contraindicated in raised ICP. The target is CPP 60–70 mmHg; values >70 mmHg may worsen ARDS in polytrauma.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
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