Intracranial Pressure - University of Windsor顱內(nèi)壓-溫莎大學

1、REPONSE OF BRAIN TISSUE TO TRAUMAINTRACRANIAL PRESSUREIntracranial 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 cavityIntracra

2、nial Pressure Skull has three essential components:- Brain tissue = 78%- Blood = 12%- Cerebrospinal fluid (CSF) = 10% Any increase in any of these tissues causes increased ICPFig. 55-1Intracranial Pressure Normal ICP = 4 -15 mmHg Factors that influence ICP Arterial pressure Venous pressure Intraabdo

3、minal and intrathoracic pressure Posture Temperature Blood gases (CO2 levels)Intracranial Pressure The degree to which these factors ICPdepends on the ability of the brain to accommodate to the changesIntracranial PressureRegulation and Maintenance Normal intracranial pressure The pressure exerted b

4、y 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 changeFig. 55-2Intracranial PressureRegulation and Maintenance Normal comp

5、ensatory adaptations Alteration of CSF absorption or production Displacement of CSF into spinal subarachnoid space Dispensability of the duraIntracranial 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 10

6、0 g of brain tissueIntracranial 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 pressur

7、e needed to overcome ICP in order to deliver O2 & nutrientsIntracranial 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 ischemiaCPP 30 mmHg brain deathIntracranial Pressure:Regulatory Mecha

8、nisms of Cerebral Blood Flow Autoregulation of cerebral blood flow Metabolic Regulation of cerebral blood flowIntracranial Pressure:Regulatory Mechanisms of Cerebral Blood Flow Autoregulation The automatic alteration in the diameter of the cerebral blood vessels to maintain a constant blood flow to

9、the brain Maintains CPP regardless of changes in BPIntracranial Pressure:Regulatory Mechanisms of Cerebral 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 ische

10、mia or deathIntracranial Pressure: Regulatory Mechanisms of Cerebral Blood Flow Metabolic Regulation of cerebral blood flowFactors affecting cerebral blood flow PCO2 PO2 AcidosisIncreased Intracranial PressureMechanisms of Increased ICP Causes Mass lesion Cerebral edema Head injury Brain inflammatio

11、n Metabolic insultIncreased Intracranial PressureMechanisms of Increased ICP Sustained increases in ICP result in brainstem compression and herniation of the brain from one compartment to anotherFig. 55-3Fig. 55-4Increased Intracranial PressureNursing Care: Assessment Change in level of consciousnes

12、s Changes in vital signs (Cushing triad) Widening pulse pressure Tachy/Bradycardia Increased systolic BP Irregular respirationsIncreased Intracranial PressureNursing Care: Assessment Ocular signs Decrease in motor strength and function Assess movement Assess response to stimuli Assess: Decerebrate p

13、osturing (extensor) Indicates more serious damage Decorticate posturing (flexor)Fig. 55-6Increased Intracranial PressureNursing Care: Assessment Headache Often continuous and worse in the morning Vomiting Not preceded by nausea ProjectileIncreased Intracranial PressureCollaborative Care Hyperventila

14、tion 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 ventilatorIncreased Intracranial PressureCollaborative Care Drug therapy Mannitol Loop diuretics Corticosteroids Barbit

15、urates Antiseizure drugsIncreased 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 chlorideIncreased Intracranial PressureNursing ManagementOverall goals: ICP WNL Maintain patent airway Normal fluid and electrolyte balance No complications secondary to immobility Respiratory function F