Unit 5 Ch 44 Acute Disorders of the Brain, pg. 891-911

Unit 5

Ch 44 Acute Disorders of the Brain, pg. 891-911


Acute Disorders of the Brain
 Mechanisms of Brain Injury
 Types of Brain Injuries:

 Primary Injury
 is that which occurs immediately at the onset of
brain injury.




 Secondary injury
 refers to the development of further neurologic
damage and changes subsequent to the primary
injury




 these may progress over days and weeks and continue to
cause changes to the brain for years.
 Vascular compromise
 Reperfusion injury
 Abnormal autoregulation
 Blood flow through the brain
tissue is controlled by
autoregulation of pH, CO2, and
oxygen levels

,  Hypotension predisposes to ischemia, whereas
severe hypertension may lead to vascular
damage and brain edema.




 Anything that interferes with the ability of the
vessels to dilate
 Increased CO2 - causes
vasodilation
 Decreased CO2 - causes
vasoconstrict




 ATP level reduction is a consequence of ischemia and
hypoxia, which accompany many types of acute brain
injury, including trauma and stroke

 Note Mitochondrial failure

, Ischemia and Hypoxia
 Ischemia

 occurs when the delivery of oxygenated
blood is below the level needed to meet
metabolic demands of the brain tissue.
 Can be primary and
secondary
 Hypoxia
 Hypoxia is a deficiency of oxygen at the
cellular level, which may occur as a result
of decreased blood flow (ischemia) or
decreased blood oxygenation
(hypoxemia).

,  Typically occurs with
ischemia


o Compensatory responses

 Keep the MAP at 60 to 140 mmHg
 Cerebral vessels dilate when mean arterial blood pressure falls
(less then 60) or when brain metabolism increases.









o Increased Intracranial Pressure (ICP)

 Pathophysiology: Cranium compartments
 brain tissue
 cerebrospinal fluid (CSF)
 Blood




o normal ICP = 0 to 15 mm Hg

o Monro-Kellie hypothesis