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Pathophysiology of BrainInjury•Hypercarbia (hypoventilation)–Causes cerebral vasodilation–Results in increased blood volume–Which results in increased ICP•Hypotension –Results in decreased CPP–Which results in cerebral vasodilation–Which results in increased blood volume–And leads to increased ICP
The Endless Cycle . . .•With increasing ICP, this vicious cycle ensues•When ICP = MAP, cerebral blood flow ceases
Intracranial Pressure: ClinicalEffects(1 of 3)•Clinical effects of increased ICP will result from pressure exerted down on the brain–Cerebral cortex and reticular activating system (RAS)•Altered level of consciousness–Hypothalamus•Vomiting
•Brain stem–BP increases in an effort to maintain cerebral blood flow against increasing ICP–Bradycardia develops from vagal stimulation and increased BP –Respirations become: •Irregular, causing increased carbon dioxide (CO2), or •Fast (tachypnea), causing a decrease in CO2Intracranial Pressure: ClinicalEffects(2 of 3)
•Brain stem (cont’d)–Cranial nerve III (oculomotor) compression leads to unequal or unreactive pupils –Abnormal posturing (flexion or extension)–Seizures •Herniation of the brainIntracranial Pressure: ClinicalEffects(3 of 3)
Clinical Effects of IncreasedICP
Patient Assessment: Primary Assessment•Determine the mechanism of injury and the need to consider the possibility of spinal injury•Is there:–Airway compromise?–Ventilatory compromise?–Adequate oxygenation?–Adequate circulation and perfusion?
Patient Assessment•Neurologic assessment for disability–The complete neurologic exam consists of six components:•Mental status (MS)•Cranial nerves (applicable cranial nerves only)•Motor function•Sensory function•Coordination•Reflexes–In most cases, only the first four are completed in the prehospital setting
Patient Assessment: MentalStatus(1 of 3)•AVPU–Provides an initial impression•Alert•Responds to Verbal stimulus•Responds to Painful stimulus•Unresponsive
•Glasgow Coma Scale (GCS)–The GCS should be scored afterthe correctible causes of altered mental status have been addressed–Use the modified GCS for pediatricsPatient Assessment: MentalStatus(2 of 3)
Patient Assessment: MentalStatus(3 of 3)
Patient Assessment•Assessing for symmetry of function (movement and sensation) is key•Asymmetry is abnormal until proven otherwise•In some people, asymmetry is a normal or baseline finding–Always ask, “Is this normal for you?”
Patient Assessment: CranialNerves •Cranial nerves (CNs)–12 pairs•Not all CNs are evaluated in the prehospital setting–Most important are CNs responsible for evaluation of eye dysfunctions –CN II, III, IV, and VI
Patient Assessment: Pupils •Normally equal, round, and 3 to 5 mm in size•Anisocoria (unequal pupils) suggests CNS disease or traumatic injury–Difference of > 1 mm is abnormal–5–10% of people are estimated to have anisocoria as a normal variant•Pupils + light constrict•Light in one pupil should constrict both–Consensual light reflex tests CNs II and III