290 likes | 589 Views
REPONSE OF BRAIN TISSUE TO TRAUMA. INTRACRANIAL PRESSURE. Intracranial Pressure. Response of brain tissue to trauma occurs at the cellular level: Injury: massive vasodilation Cerebral edema: increase in size and volume of brain Increased ICP:
E N D
REPONSE OF BRAIN TISSUE TO TRAUMA INTRACRANIAL PRESSURE
Intracranial Pressure • Response of brain tissue to trauma occurs at the cellular level: • Injury: massive vasodilation • Cerebral edema: increase in size and volume of brain • Increased ICP: • Increase in pressure exerted within the cranial cavity
Intracranial Pressure • Skull has three essential components: - Brain tissue = 78% - Blood = 12% - Cerebrospinal fluid (CSF) = 10% • Any increase in any of these tissues causes increased ICP
Components of the Brain Fig. 55-1
Intracranial Pressure • Normal ICP = 4 -15 mmHg • Factors that influence ICP • Arterial pressure • Venous pressure • Intraabdominal and intrathoracic pressure • Posture • Temperature • Blood gases (CO2 levels)
Intracranial Pressure • The degree to which these factors ICP depends on the ability of the brain to accommodate to the changes
Intracranial PressureRegulation and Maintenance • Normal intracranial pressure • The pressure exerted by the total volume from the brain tissue, blood, and CSF • If the volume in any one of the components increases within the cranial vault and the volume from another component is displaced, the total intracranial volume will not change
Intracranial Volume-Pressure Curve Fig. 55-2
Intracranial PressureRegulation and Maintenance • Normal compensatory adaptations • Alteration of CSF absorption or production • Displacement of CSF into spinal subarachnoid space • Dispensability of the dura
Intracranial PressureCerebral Blood Flow • Definition • The amount of blood in milliliters passing through 100 g of brain tissue in 1 minute • About 50 ml/min per 100 g of brain tissue
Intracranial PressureImportance of ICP to BP and CPP • Brain needs constant supply O2 and Glucose • BP: heart delivers blood to brain at an average BP of 120/80 (Mean BP = 100); this mean arterial pressure (MAP) must be higher than ICP • CPP (Cerebral Perfusion Pressure): is the pressure needed to overcome ICP in order to deliver O2 & nutrients
Intracranial PressureImportance of ICP to BP and CPP • MAP is the DRIVING FORCE • ICP is the RESISTENCE • CPP = MAP – ICP = 100 mmHg – 15 mmHg = 85 mmHg (Normal) CPP < 50 mmHg→ cerebral ischemia CPP < 30 mmHg → brain death
Intracranial Pressure:Regulatory Mechanisms ofCerebral Blood Flow • Autoregulation of cerebral blood flow • Metabolic Regulation of cerebral blood flow
Intracranial Pressure:Regulatory Mechanisms ofCerebral Blood Flow • Autoregulation • The automatic alteration in the diameter of the cerebral blood vessels to maintain a constant blood flow to the brain • Maintains CPP regardless of changes in BP
Intracranial Pressure:Regulatory Mechanisms ofCerebral Blood Flow • Problem: Autoregulation is limited • If BP and/or ICP rises: Autoregulation fails • When autoregulation fails, blood flow to brain increases or deceases → poor perfusion and cellular ischemia or death
Intracranial Pressure: Regulatory Mechanismsof Cerebral Blood Flow • Metabolic Regulation of cerebral blood flow Factors affecting cerebral blood flow • PCO2 • PO2 • Acidosis
Increased Intracranial PressureMechanisms of Increased ICP • Causes • Mass lesion • Cerebral edema • Head injury • Brain inflammation • Metabolic insult
Increased Intracranial PressureMechanisms of Increased ICP • Sustained increases in ICP result in brainstem compression and herniation of the brain from one compartment to another
Increased Intracranial Pressure Fig. 55-3
Herniation Fig. 55-4
Increased Intracranial PressureNursing Care: Assessment • Change in level of consciousness • Changes in vital signs (Cushing triad) • Widening pulse pressure • Tachy/Bradycardia • Increased systolic BP • Irregular respirations
Increased Intracranial PressureNursing Care: Assessment • Ocular signs • Decrease in motor strength and function • Assess movement • Assess response to stimuli • Assess: • Decerebrate posturing (extensor) • Indicates more serious damage • Decorticate posturing (flexor)
Decorticate and Decerebrate Posturing Fig. 55-6
Increased Intracranial PressureNursing Care: Assessment • Headache • Often continuous and worse in the morning • Vomiting • Not preceded by nausea • Projectile
Increased Intracranial PressureCollaborative Care • Hyperventilation therapy: suctioning → hyperventilate with 100% oxygen • Adequate oxygenation • PaO2 maintenance at 100 mm Hg or greater • ABG analysis guides the oxygen therapy • May require mechanical ventilator
Increased Intracranial PressureCollaborative Care • Drug therapy • Mannitol • Loop diuretics • Corticosteroids • Barbiturates • Antiseizure drugs
Increased Intracranial PressureCollaborative Care • Nutritional therapy • Patient is in hypermetabolic and hypercatabolic state • Need for glucose • Keep patient normovolemic • IV 0.45% or 0.9% sodium chloride
Increased Intracranial PressureNursing Management Overall goals: • ICP WNL • Maintain patent airway • Normal fluid and electrolyte balance • No complications secondary to immobility • Respiratory function • Fluid and electrolyte balance
Increased Intracranial PressureNursing Management Overall goals (cont’d) • Body position maintained in head-up position: elevate HOB 30° • Protection from injury: positioning/turning • Pain control • Psychologic considerations