Intracranial Hypertension

Incidence in USA: >50% of pts presenting with head trauma or other intracranial pathology (>600,000/y)

Gender predominance: Only for certain etiologies (i.e., TBI and males)

Increased risk of herniation leading to subsequent brain infarction, disability, coma, and death

Controlling ICP and preventing brain ischemia/herniation

CV and respiratory instability

Coexisting injuries in trauma pts (occult cervical spine and intra-abdominal injuries)

Intracranial compartment has fixed volume with three components (brain = 85%, CSF = 10%, CBV = 5%).

Increased volume of one component (e.g., tumor, hydrocephalus, or hemorrhage) without compensatory decrease in another compartment elevates ICP, leading to ICH (ICP >20 mm Hg for >5 min typically, but individual patients’ threshold for injury varies).

ICH reduces CPP (CPP = MAP – ICP), causing brain ischemia and/or infarction.

ICH causes ICP gradients that may extrude brain parenchyma through dural or bony passages, resulting in herniation. Subfalcine herniation compresses the anterior cerebral artery. Transtentorial herniation compresses the posterior cerebral artery and herniation from cranioectomy may compress the middle cerebral artery.

Some anesthetic agents, hypercapnia, and hypoxemia increase CBF, increasing CBV and ICP. In cases of loss of autoregulation Htn may also increase CBF.