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Acute Intracranial Problems

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Biological Sciences
Stephen Reid

Chapter 57: Acute Intracranial Problems NORMAL INTRACRANIAL PRESSURE  Intracranial pressure (ICP) is the hydrostatic force measured in the brain CSF compartment. Normal ICP is the total pressure exerted by the three components within the skull: brain tissue, blood, and CSF.  If the volume of any one of the three components increases within the cranial vault and the volume from another component is displaced, the total intracranial volume will not change.  ICP can be measured in the ventricles, subarachnoid space, subdural space, epidural space, or brain parenchymal tissue using a pressure transducer. Normal intracranial ICP ranges from 0 to 15 mm Hg.  A sustained pressure above the upper limit is considered abnormal. ICP may rise due to head trauma, stroke, subarachnoid hemorrhage, brain tumor, inflammation, hydrocephalus, or brain tissue damage from other causes. CRANIAL BLOOD FLOW  Cerebral blood flow (CBF) is the amount of blood in milliliters passing through 100 g of brain tissue in 1 minute.  Through a process known as autoregulation, the brain has the ability to regulate its own blood flow in response to its metabolic needs despite wide fluctuations in systemic arterial pressure.  The cerebral perfusion pressure (CPP) is the pressure needed to ensure blood flow to the brain. As the CPP decreases, autoregulation fails and CBF decreases, which can lead to ischemia and neuronal death.  Compliance is the expandability of the brain. With low compliance, small changes in volume result in greater increases in pressure. INCREASED INTRACRANIAL PRESSURE  Increased ICP is a life-threatening situation that results from an increase in any or all of the three components (brain tissue, blood, CSF) within the skull. Cerebral edema is an important factor contributing to increased ICP.  Elevated ICP is clinically significant because it diminishes CPP, increases risks of brain ischemia and infarction, and is associated with a poor prognosis.  The clinical manifestations of increased ICP can take many forms, depending on the cause, location, and rate at which the pressure increase occurs. Complications of ICP include changes in the level of consciousness, changes in vital signs, dilation of pupils, decrease in motor function, headache, and vomiting.  The earlier the condition is recognized and treated, the better the patient outcome.  The major complications of uncontrolled increased ICP are inadequate cerebral perfusion and cerebral herniation.  ICP monitoring is used to guide clinical care when the patient is at risk for or has elevations in ICP. It may be used in patients with a variety of neurologic insults, including hemorrhage, stroke, tumor, infection, or traumatic brain injury.  The “gold standard” for monitoring ICP is the ventriculostomy, in which a specialized catheter is inserted into the right lateral ventricle and coupled to an external transducer. Other devices now allow for an indirect assessment of cerebral oxygenation and perfusion.  With the ventricular catheter and certain fiberoptic systems, it is possible to control ICP by removing CSF. The level of the ICP at which to initiate drainage, amount of fluid to be drained, height of the system, and frequency of drainage are ordered by the physician.  The goals of collaborative care are to identify and treat the underlying cause of increased ICP and to support brain function.  Drug therapy plays an important part in the management of increased ICP. An osmotic diuretic, corticosteroids, and barbiturates may be prescribed.  All patients must have their nutritional needs met, regardless of their state of consciousness or health. Early feeding following brain injury may improve outcomes.  The Glasgow Coma Scale is a quick, practical, and standardized system for assessing the degree of impaired consciousness that should be used during nursing assessment. Also during assessment, the pupils are compared to one another for size, shape, movement, and reactivity.  The overall nursing goals are that the patient with increased ICP will (1) maintain a patent airway, (2) have ICP within normal limits, (3) demonstrate normal fluid and electrolyte balance, and (4) have no complications secondary to immobility and decreased level of consciousness.  Maintenance of a patent airway is critical in the patient with increased ICP and is a primary nursing responsibility. As the level of consciousness decreases, the patient is at increased risk of airway obstruction from the tongue dropping back and occluding the airway or from accumulation of secretions.  The patient with increased ICP should be maintained in the head-up position. The nurse must take care to prevent extreme neck flexion, which can cause venous obstruction and contribute to elevated ICP.  The patient with increased ICP and a decreased level of consciousness needs protection from self-injury. Confusion, agitation, and the possibility of seizures increase the risk for injury. HEAD INJURY  Head injury includes any trauma to the scalp, skull, or brain. The term head trauma is used primarily to signify craniocerebral trauma, which includes an alteration in consciousness, no matter how brief.  Scalp lacerations are an easily recognized type of external head trauma. Because the scalp contains many blood vessels with poor constrictive abilities, the major complications associated with scalp laceration are blood loss and infection.  Skull fractures frequently occur with head trauma. There are several ways to describe skull fractures: (1) linear or depressed; (2) simple, comminuted, or compound; and (3) closed or open.  A concussion is a sudden transient mechanical head injury with disruption of neural activity and a change in the LOC and is considered a minor head injury.  A contusion, a major head injury, is the bruising of the brain tissue within a focal area. A contusion may contain areas of hemorrhage, infarction, necrosis, and edema and frequently occurs at a fracture site.  Lacerations, another major head trauma, involve actual tearing of the brain tissue and often occur in association with depressed and open fractures and penetrating injuries.  Complications from a head injury may include an epidural hematoma, a subdural hematoma, and intracerebral hematoma.  CT scan is considered the best diagnostic test to evaluate for craniocerebral trauma because it allows rapid diagnosis and intervention in the acute setting. MRI, PET, and evoked potential studies may also be used in the diagnosis and differentiation of head injuries.  The most important aspects of nursing assessment are noting the GCS score, assessing and monitoring the neurologic status, and determining whether a CSF leak has occurred.  The overall nursing goals are that the patient with an acute head injury will (1) maintain adequate cerebral oxygenation and perfusion; (2) remain normothermic; (3) achieve control of pain and discomfort; (4) be free from infection; and (5) attain maximal cognitive, motor, and sensory function.  Management at the injury scene can have a significant impact on the outcome of the head injury. The general goal of acute nursing management of the head-injured patient is to maintain cerebral oxygenation and perfusion and prevent secondary cerebral ischemia.  The major focus of nursing care for the brain-injured patient relates to increased ICP. However, there may be other specific problems that require nursing intervention, such as hyperthermia.  Once the condition has stabilized, the patient is usually transferred for acute rehabilitation management to prepare the patient for reentry into the community. Many of the principles of nursing management of the patient with a stroke are appropriate. BRAIN TUMORS  Brain tumors can occur in any part of the brain or spinal cord. Tumors of the brain may be primary, arising from tissues within the brain, or secondary, resulting from a metastasis from a malignant neoplasm elsewhere in the body.  Brain tumors are generally classified according to the tissue from
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