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Content covers the skull, Factors Affecting Cerebral Blood Vessel Tone, Intracranial Pressure (ICP), Glasgow Coma Scale, Hematomas, Hemodynamic monitoring, Arterial Line Monitoring, Pulmonary Artery Pressure, Shock, Burns, Sepsis, and DIC
Skull
● Bony vault with brain, CSF, & blood
● Cerebrospinal fluid: 10%
● Intravascular blood: 12%
● Brain tissue: 78%
● Posterior pituitary secretes ADH (vasopressin)
○ Responsible for holding water in the body
○ Not enough ADH → Diabetes Insipidus
● Brainstem
○ Midbrain
■ Cranial nerves 3-4 → control movement of eye muscles
■ Relay center for impulses from body going to and from brain
○ Pons
■ Cranial nerves 5-8
■ Cranial nerve 5 → trigeminal
■ Cranial nerve 7 → facial
■ Cranial nerve 8 → auditory
■ Reticular activating system- controls sleep wake cycles
● Important part of circadian rhythm
● Responsible for wakefulness, ability to focus, fight or flight
response, & how the world is perceived
● Patients with head injury are asked if they had any loss of
consciousness to see if the reticular activating system was affected
○ Medulla oblongata
■ Cranial nerves 9-12
■ Control mouth, throat, tongue, swallowing, & neck
■ Contains both motor & sensory pathways that help unite the brainstem,
cerebellum, & cerebrum to coordinate information coming back to the
brain/going to the body
■ Controls heart rate & respiratory rate
Factors Affecting Cerebral Blood Vessel Tone
● CO2
, ○ Hypercapnia (increased CO2) → dilates cerebral vessel → increased cerebral blood
flow
○ Hypocapnia (decreased CO2) → constricts cerebral vessel → decreased cerebral
blood flow
● O2
○ Low O2 → dilates cerebral vessel → increases cerebral blood flow
● H+ Ion
○ Byproduct of low O2 is lactic acid → increased H+ ions → dilates cerebral vessel →
increased cerebral blood flow
○ Can be an issue if the patient has increased ICP
● Temperature
○ High temperature/fever → dilates cerebral vessel → increased cerebral blood flow
○ High temperature also increases metabolic demand, which consumes more O2
○ Shivering uses a lot of O2 stored in the body & produces CO2 as a byproduct →
dilates cerebral vessel → increased cerebral blood flow
● Increased cerebral blood flow increases ICP
Intracranial Pressure (ICP)
● Monroe-Kellie doctrine
○ CSF, blood, & brain must remain at a relatively constant volume within the skull
○ If the volume of any increases, the volume of one or both of the others will
decrease
○ The volume is constant
○ Only applies when the skull is closed
● Normal ICP 5 to 15 mm Hg
○ Elevated if >20 mm Hg sustained
● Cerebral blood flow (CBF)
○ Amount of blood passing through brain tissue in one minute
● Cerebral perfusion pressure (CPP)
○ Pressure needed to ensure blood flow to the brain
○ CPP= MAP - ICP
○ Normal is 60 to 100 mg Hg
○ <50 mg Hg- ischemia & neuronal death
○ When ICP is elevated, it is important to maintain adequate MAP
, Clinical Manifestations
● Change in level of consciousness
○ Impaired cerebral blood flow & decreased oxygenation
● Change in vital signs due to damage to brainstem
○ Cushing’s triad
■ Bradycardia
■ Cheyne-stokes respirations
■ Increased BP
● Change in body temperature
○ Controlled by hypothalamus, which is compromised by increased ICP
● Compression of oculomotor nerve
○ Controls muscles in the eye
○ Eyes may be sluggish, not respond to light, or have ptosis
● Decrease in motor function
○ Hemiparesis
● A
○ Decorticate
○ Internal rotation, adduction of arms, & flexion of elbows
○ May see extension of the legs
○ Due to the interruption of voluntary motor tracks in cerebral cortex
● B
○ Decerebrate
○ Results from injury of motor fibers in midbrain & brainstem
● C
○ Decorticate on right & Decerebrate on the left
○ Part of cerebral cortex & part of brainstem affected
● D
○ Opisthotonic
○ Similar to Decerebrate, except neck & back are arched posteriorly
● HA
● Vomiting
○ Due to increased pressure in the skull
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