Ch 28 Hypoxic and Ischemic brain injury Flashcards
Definition of anoxia
Complete lack of oxygen in blood due to profound and sudden medical events such as cardiac arrest, loss of perfusion pressure
Hanging, strangulation
Definition of hypoxia
Deficient amount of oxygen available in the blood supply to the brain.
Hypoxemia definition
Reduced partial pressure of oxygen in blood.
(Low levels of oxygen in blood)
Hypoxemia can lead to hypoxia
Ischemia definition
Failure of perfusion of blood through the cerebral vessels to tissue.
Ischemia and anoxia are usually involved in sudden cardiac arrest
What is the partial pressure of arterial oxygen and healthy adults?
95 to 100 mm Hg
What happens when partial pressure of arterial oxygen drops or is disrupted?
Homeostatic protective mechanisms are triggered
Which parts of the brain regions are more vulnerable to hypoxia and ischemia?
Brain regions with high metabolic demands
Those that are at the distal end of cerebral arteries, watershed regions
Sample of brain regions that are highly vulnerable to hypoxia and Ischemia?
Neo cortex Hippocampus Basal ganglia Cerebellar regions Visual cortex Thalamus
What is a common response of the brain following anoxic or hypoxic insult?
Edema
What else may happen during anoxia and hypoxia?
Edema, a series of metabolic events which lead to
Wallerian degeneration
Accelerated apoptosis
Atrophy
Does atrophy and degeneration happen acutely or span over a longer period?
It evolves over the course of many weeks and months
Neural imaging findings in apraxia or hypoxia
Loss of distinction between white and gray matter in the cortex
Damage of basal ganglia in neo cortex regions
Results that come later-
Hippocampal damage
Diffuse atrophy
White matter tracks vulnerable to carbon monoxide poisoning
What used to be considered the hallmark feature of hypoxic damage
Hippocampal damage.
This has been refuted in studies.
Other areas that are frequently damaged?
Watershed cortex
basal ganglia
Most energy required by neurons is derived from hydrolysis of what chemical
Adenosine triphosphate ATP
Does the brain have any inherent energy stores?
No, so it’s critically dependent on uninterrupted flow of oxygen and glucose
When there is a critical shortage of oxygen and glucose supply to neurons, what would result
Neuronal death
Describe the secondary toxic process that is triggered as a result of neuronal death?
Sodium and calcium pumps fail
depolarization of neuronal membrane and release of excessive glutamate.
How is glutamate related to toxic process in hypoxia and anoxia
Glutamate is the most common excitatory neurotransmitter, but at excessive levels it could be toxic to neurons
What else is involved in the toxic process?
Lactic acidosis
Wallerian degeneration
Necrosis
Apoptosis
Additional potential sources of damage to the brain after circulation is restored?
Secondary hypoxia
-after circulation returns, blood flow may go through a period of 30 to 50% reduction
Reperfusion injury
-After re-perfusion, some processes happen that may cause further damage such as
1 free radical formation
2 nitric oxide toxicity,
3 additional glutamate release,
4 edema and micro hemorrhages,
5 impaired ability to remove toxic metabolic stuff
What shares many of the same affects as hypoxia and ischemia?
Carbon monoxide poisoning
Carbon monoxide has a very high for affinity for binding with what
Hemoglobin
After carbon monoxide binds with hemoglobin, what would be formed?
Carboxyhemoglobin
Once carboxyhemoglobin rises above 20 to 30% of total hemoglobin in the blood, what happens
Levels above 50% will result in coma and other severe CNs effects
What else happens with carbon monoxide poisoning?
Delayed neurologic deterioration which happens 1 to 3 weeks after severe exposure.
Basal ganglia damage
Hippocampal atrophy and generalized brain atrophy
Neuropsych deficits including attention, processing, executive functions, memory
Incidence rates for hypoxia and ischemia
Extremely difficult to estimate
Percentage of people surviving with permanent brain damage after anoxic or hypoxic injury
50%
Hypoxia that does not involve collapse or cessation of functioning of the circulatory system will typically result in less or more damage?
If it does not involve the collapse of circulatory system, damage is less
Under what circumstance is hypoxia not going to damage CNS?
If it is not severe enough to disrupt consciousness
Examples of severe hypoxia cases
Sudden cardiac arrest
Acute respiratory distress syndrome
What happens after a loss of consciousness happens?
Once the brain is deprived of oxygen for several minutes, damage progresses rapidly, and if the underlying condition is not quickly reversed, brain death or minimally conscious state would result.
What happens when someone wakes up from a prolonged coma after hypoxia or ischemia?
Long lasting cond of functional disability
extrapyramidal syndrome’s such as parkinsonism
What environmental factor can help reduce likelihood of permanent damage the brain after hypoxia?
If event Occurs in a hospital setting and receives rapid and effective resuscitation
Examples of chronic disease related to chronic hypoxic an ischemic conditions
Obstructive sleep apnea and COPD
Chronic obstructive pulmonary disease COPD symptoms
Emphysema, neural muscular weakness, fibrosing lung disease
Persistent respiratory acidosis with reduced oxygen saturation an elevator carbon dioxide
Cognitive deficits may not occur in mild cases they do not produce persistent hypoxia
Severe COPD cases result in cognitive impairment
Obstructive sleep apnea symptoms
Recurrent episodes of blood oxygen desaturation due to total apnea or partial apnea breathing cessation
Neurological correlates of COPD
Greater risk for a white matter hyperintensities and cognitive impairment.
How does CPAP machine help with COPD
Reduces episodes of breathing disruption
Reduces oxygen desaturation during sleep
Improves daytime sleepiness
Factors that are associated with poor outcome after hypoxic and ischemic event
GCS score of 3 to 5 after 24 hours post onset
No pupillary response on Day 3 post injury
Sustained abnormal EYE functions
Lower cranial nerve or brainstem dysfunction
Seizures or Myoclonus
Alpha coma EEG pattern
Relationship between Age and recovery after hypoxic or anoxic event
Negatively correlated
Do patients with severe hypoxic ischemic injury return to independence?
No, recovery curves are flat
Delayed Post hypoxic leukoencephalopathy DPHL
Condition that is sometimes seen after anoxia or hypoxia.
Commonly seen after CO poisoning
Can occur due to any etiology producing prolonged hypo oxygenation
Patient initially makes a good recovery and could resume normal functioning followed by an abrupt onset of progressive neurologic decline involving parkinsonism or akinetic mutism with prominent cognitive impairment.
What can you expect on imaging studies for delete posts hypoxic leukoencephalopathy?
Prominent white matter demyelination in frontal parietal region
Comparison of outcomes between TBI and Hypoxia anoxia
Difference
Amount of tissue loss is more critical in anoxia (than TBI) in determining outcome
Hypoxia cases are more likely to be referred to residential care than TBI
Hypoxia cases perform worse on all measures of functional outcome than TBI
Hypoxia cases have significantly lower FIM gains relative to TBI
Same
Measures of memory correlate with hippocampal atrophy in both conditions
Intelligence correlates with whole brain volume in both
Assessment of hypoxia anoxia
CT, MRI of the brain do not reveal significant changes initially.
Abnormalities often take weeks or months to show on scans:  White matter changes Corpus callosum atrophy Cortical edema Cerebellar lesions Basal ganglia lesions Thalamic lesions Hippocampal atrophy
Which cognitive domain is less likely a problem for anoxia
Aphasia
Outcomes of sudden cardiac arrest and ARDS
More than 30% With sudden cardiac arrest and ARDS show generalized cognitive impairment
Memory, attention, processing speed
Outcomes of severe hypoxia and anoxia
More than 50% of people have changes in memory,
30% show personality changes
What percent of people can regain full independence after hypoxia ischemia
<50%
Neuropsychological assessment results in hypoxic ischemic injury
Memory is most common Attention Executive dysfunction Visual spatial deficits Overall decline
Do pure amnestic syndromes happen often following anoxia hypoxia?
No, rarely happens
Cognitive impairment is typically more extensive due to diffuse cerebral injury
Do all patients suffer from memory impairment?
No a subset of patients do not have memory impairment but display motor or cognitive impairments and other domains
Which parts of the brain are at high-risk for injury in hypoxia and anoxia?
Basal ganglia and cerebellum
Describe sensorimotor functioning after hypoxia and anoxia
Severe hypoxic injury can cause spastic Quadripareais
Ataxia
Parkinsonism syndromes
Emotion and personality changes after hypoxic an anoxic injury?
Anosognosia, self awareness impairment
Depression
Emotional and behavioral dysregulation
PTSD may be seen in mild hypoxia and anoxia injuries following traumatic event
Example of medication for hypoxia anoxia
Methylphenidate
Stimulants
Acetylcholinesterase inhibitor (aricept)
SSRIs or anti-convulsant for mood stabilization
Brains of infants and children require higher or lower percentage of oxygen than adults?
Infants to kids age 4 need
> 30% total body oxygen consumption in their brains
Outcomes of perinatal anoxic hypoxic injury?
Later development of ADHD
Outcome of neonatal hypoxia
Developmental disorder and impaired cognition
What is the strongest predictor of long-term outcome in brain injury in neonates?
If there is injury in basal ganglia and thalamus
 Are older brains more or less able to recover from hypoxic brain injury?
Older people are less likely to repair or recover from hypoxic brain injury,
permanent and severe cognitive deficits due to reduce cerebral reserve
Definition of acute respiratory distress syndrome ARDS
Severe, life-threatening medical condition in which lungs are compromised or damaged and are unable to supply enough oxygen to arterial blood.
Result in anoxic hypoxic damage to the brain
