A head injury patient has an ICP of 28 mmHg and a mean arterial pressure of 80 mmHg. His cerebral perfusion pressure is calculated as 52 mmHg. On CT, there is no significant midline shift. Cerebral autoregulation is intact. Which of the following interventions will MOST specifically reduce ICP without reducing CPP further?
- A Hyperventilation to PaCO2 30 mmHg: cerebral vasoconstriction reduces CBV and ICP
- B Hypertonic saline 3% IV: osmotic extraction of water from brain parenchyma reduces cerebral edema and ICP ✓
- C Elevate head of bed to 30° to enhance jugular venous drainage, reducing cerebral venous blood volume
- D Mannitol 1 g/kg IV: osmotic agent drawing water out of brain, reducing ICP
Explanation
CPP = MAP − ICP = 80 − 28 = 52 mmHg. Hypertonic saline (3% NaCl) creates an osmotic gradient between plasma and brain parenchyma, drawing free water out of edematous brain cells and reducing ICP while simultaneously expanding intravascular volume (which supports MAP, thereby increasing CPP). It does not cause rebound cerebral edema and has a more sustained effect than mannitol. Hyperventilation (option A) reduces ICP but causes cerebral vasoconstriction that may reduce CBF; it is a temporizing measure and can worsen ischemia with sustained use. Mannitol (option D) is also effective but can cause rebound edema and osmotic diuresis may reduce MAP. Head elevation (option C) helps venous drainage but has modest effect on ICP and may reduce MAP in a hypovolemic patient. Hypertonic saline is increasingly preferred as the first-line osmotherapy.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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Written and medically reviewed by the StethoPrep medical team.