Chapter 24: Hypoxia & Ischemic Brain Injury Flashcards
DEFINITION:
Most typically defined as a complete lack of oxygen in arterial blood, due to a profound and sudden medical event such as cardiac arrest or loss of perfusion pressure
Anoxia
DEFINITION:
A deficient amount of oxygen availability in the blood supply to the brain. It is distinguished from anoxia, but the two are often used interchangeably in the literature and medical reports
Hypoxia
DEFINITION:
Another term commonly used to refer to reduced partial pressure oxygen in arterial blood (<60 mm Hg).
Hypoxemia
Note: Hypoxemia can lead to hypoxia
DEFINITION:
The failure of perfusion of blood through the cerebral vessels to tissue (e.g., lack of blood supply).
Ischemia
Note: Both ischemia and anoxia are usually involved in cases of profound and sudden cardiac arrest
What ACUTE conditions may cause hypoxic-ischemic brain damage?
- Cardiac Arrest
- Acute respiratory distress syndrome (ARDS)
- Carbon monoxide poisoning
- Suffocation, drowning, hanging
- Massive blood loss due to trauma
- Prolonged seizures
- Anesthesia accidents in surgical procedures
What CHRONIC conditions may cause hypoxic-ischemic brain damage?
- Chronic obstructive pulmonary disease (COPD)
- Obstructive sleep apnea (OSA)
- Asthma
- Conditions that paralyze the respiratory system (e.g.,, amyotrophic lateral sclerosis, myasthenia gravis, etc.)
What brain regions show vulnerability to hypoxia/ischemia?
- Neocortex (layers 3, 5, 6)
- Hippocampus (pyramidal cells in CA1)
- Basal ganglia (striatum, globus pallidus)
- Cerebellar regions (Purkinje cells)
- Visual cortex
- Thalamus
DEFINITION:
Apoptosis
Programmed cell death.
Apoptosis is part of normal regulation and turnover of cells, but can also result from pathologic processes such as ischemic.
DEFINITION:
Adenosine Triphosphate
Adenosine Triphosphate (ATP) is a chemical compound that provides energy for cells/neurons.
Note: under anoxic/hypoxic conditions, less ATP becomes available in the neuron, leading it to catabolize itself.
DEFINITION:
Chronic obstructive pulmonary disease (COPD)
A term that encompasses several conditions of pulmonary disease (e.g., emphysema, bronchitis) in which there is progressive obstruction of expiration; COPD can produce chronic hypoxia and, depending on the severity, may result in cognitive impairment.
DEFINITION:
Glutamate
The most common excitatory neurotransmitter in the brain. Under conditions of anoxia/hypoxia, excessive amounts of glutamate are released into the synaptic cleft, and it becomes excitotoxic, as well as contributing to further deleterious processes in the neuron.
DEFINITION:
Ischemic-hypoxic encephalopathy
Refers to the encephalopathy resulting from the combined effects of anoxia/hypoxia and ischemia. In their purest presentations, anoxia/hypoxia and ischemia may produce somewhat different neuropathology, but most cases in which the brain suffers marked disruption of oxygen supply inolve both processes.
DEFINITION:
Necrosis
Refers to the death of tissue or neurons, typically due to insufficient blood supply.
DEFINITION:
Obstructive sleep apnea (OSA)
a disorder that involves recurrent episodes of blood oxygen desaturation and also disrupts normal sleep architecture. During episodes of total breathing cessation (apnea) or partial (hypopnea), blood oxygen saturation can fall to harmfully low levels, resulting in repeated hypoxic periods.
DEFINITION:
Partial pressure of oxygen (PaO2)
Partial pressure refers to the pressure exerted independently by a specific gas within a larger mix of gases. The partial pressure of arterial oxygen (PaO2) in healthy adults at sea level is typically 95-100 mm Hg. When this level rapidly drops, complex cognitive processes, memory, and judgment show impairment.
