Week 8 - Coma & Brain Death Flashcards
define coma
- state of being unarousable & unresponsive to external stimuli or internal needs
how are the causes of coma categorized (2)
- where they originate
2. structural or metabolic (Nonstructural)
what are the categories of coma based off where they originate
- within the cranium = intracranial
2. outside the cranium = extracranial
what are examples of structural causes of coma (4)
- hemorrhages
- hematoma
- infarction
- tumours
all lead to increased ICP & brain herniation
what are some examples of metbolic causes of coma (3)
- drugs
- hypercalcemia
- uremia
what do nonstructural comas cause
- a confusional state, but if severe, coma
- most are reversible
what signs are seen with a nonstructural coma
- often pupil size is normal, since ICP Is not elevated
- may effect medullary function
is coma irreversible or not?
- can be reservsible or irreversible depending on the cause & severity of brain failure
describe how supratentorial lesions progress? what does it influence?
cranial-to-caudal fashion
- top (cortex) to base (brainstem)
- indicates the degree of cerebral & brainstem dysfunction
what is lock in syndrome
- condition where the pt is aware & capable of thinking, but is paralyzed & unable to communicate
what causes lock in syndrome
- incomplete damage to the cerebrum , where brainstem function is preserved
what does severe cerebral damage result in
a vegetative state:
- all cognitive abilities are lost
- but sleep-wake cycles and brainstem function remains
what occurs when all cortical functions are lost (2)
- the individual assums decorticate or flexor posturing
- cheyne’s stokes respirations
what occurs if the lesions progresses to the midbrain & pons (3)
- pupils become fixed (bc the oculomotor nerve is in the midbrain)
- decerebrate or extensor posturing occurs
- oculocephalic reflex is impaired
what is the oculocephalic reflex
- aka doll’s eyes reflex
- normally, when you move a pts head to the side quickly, the eyes remain fixated on one position in place (ex. continue looking at a board in the middle of the room)
what happens if the oculocephalic reflex is impaired
- when turning the pt’s head quickly to one side, the eyes remain mid position
what do medullary lesions result in (3)
- flaccididty
- loss of gag & cough reflex
- apnea
what assessment is used to determine the severity of a coma
- the glascow coma scale
what is the glascow coma scale based on
- the cranial to caudal progression
what 3 areas does the glascow coma scale measure
- eye opening
- motor response
- verbal response
what does the glascow coma scale determine
- what parts of the brain are effected
- specifically, if the brain stem functions are involved
what does a high glascow coma score mean? low?
- high = little brainstem involvement
- low = medullary reflexes impaired
define brain death
- irreversible loss of brain & brainstem function
what does “life support” do
- keeps cells of the body alive & functional despite complete failure of the brain
what is a key cause of brain death? what causes it? (3)
- severe cerebral ischemia resulting from increased ICP, cardiac or resp arrest, or severe metabolic disturbance
when is determination of brain death required
- whenever an artificial ventilator is required for respiration, but cardiac function is preserved
what is the 7 criteria for diagnosis of brain death
- no spontaneous movements, seizures, or posturing
- no response to any kind of painful stimuli in the innervated area of nerves
- absence of brainstem reflex
- no spontaneous reaction to a PCO2 of 60 mmHg
- rule out possible contributing factors
- confim that it is due to irreversible brain damage
- verify that findings are unchanged up to 24 h later
what might still be intact during brain death
- spinal reflexes
what types of brainstem reflexes must you assess for diagnosis of brain death
- pupillary reflex to light
- gag reflex
- oculocephalic reflex
what are possible contributing conditions to brain death (4)
- drugs that depress the CNS or block neuromuscle junction
- hypothermia
- hypoglycemia
- electrolyte disturbances
