Pathophysiology-process of increasing intracranial pressure & complications

Supratentorial processess that cause a decreased level of consciousness are caused by injury somewhere above the tentorium. In this case, Ms. Spinosa suffered diffuse bilateral cortical dysfunction that caused widespread injury throughout the cerebral cortex & in the subcortical white matter. IN Ms. Spinosa's injury, her intracranial pressure increased from a normal 5 to 15 mmHg because of intracerebral hemorrhage or edema. The brain tissue is displaced, & the blood vessels are distorted...In stage 1 the increasing pressure forces the cerebrospinal fluid out of the cranial vault, compresses the intracranial veins, & increases venous vasoconstriction. Often intracranial pressure will not change during this stage b/c blood volume & CSF volumes are reduced...Stage 2 occurs when pressure is not relieved. Arterial blood vessels constrict, compromising oxygen supply. The systemic arterial system will also constrict to increase BP. There elevated system BP is an attempt to overcome the intracranial pressure...When intracranial pressure increases & approaches arterial pressure, stage 3 intracranial hypertension occurs. During the stage tissue hypoxia, hypercapnia, & acidosis occur. Autoregulation of blood vessel diameter is lost. Hypercapnia causes local vasodilation w/ subsequent increasing capillary permeability. As increasing cerebral edema occurs., ICP increases. Small changes in volume cause dramatic increases in pressure w/ decreased cerebral perfusion pressure...Stage 4 is characterized by herniation of the brain from the compartment of greater pressure to one of lower pressure. In Ms. Spinosa's case, the brain herniated downward (supratentorial herniation), causing central or uncal herniation. Blood supply & brain tissue are markedly compromised or completely cut off, causing further ischemia, hypoxia & hemorrhage in the herniated portion of the brain. When mean systolic pressure equals ICP, the blow to the brain sops