Coma End of Life Flashcards
coma
sleep-like unarousable nonresponse state
- only brain stem reflexes are clinically testable
- cortical function absent
persistive vegetative state
eyes periodically open or move, sleep and wake cycles occur, and pain responsiveness my return but meaningful interaction remains absent since sever cortical impairment persists
What things directly/indirectly cause affect the cerebral cortex?
Directly 1.hypoxia 2. inadequate cerebral blood flow 3. hypoglycemia 4. drug intoxication Indirectly 1. systemic infection 2. metabolic disturbances 3. hepatic or renal failure
A solitary, unilateral cerebral lesion does not produce a coma unless what?
it adversely affects the opposite hemisphere via brain edema or herniation
What type of brainstem lesion can lead to a coma?
disruption of the reticular formation
- responsible for wakefulness and arousal
- projects from tegmental brainstem to thalamus and subcortical nuclei
What do asymmetrical neurological signs suggest?
structural lesion
-ischemic infarction, hemorrhage, or tumor
What do symmetrical neurological signs suggest?
more diffuse or toxi-metabolic process
-such as anoxia
Do motor responses to command or withdrawal to pain stimuli occur in coma?
no because localizing response to a noxious stimulus requires some cortical function
-may show certain stereotyped or automatic movements spontaneously or after painful stimulus such as decorticate or decerebrate
Decorticate posturing
flexion of the upper limbs with extension of the lower limbs
-associated with lesion at the level of :
cerebral cortex or hemisphere
Decerebrate posturing
extension of the upper and lower limbs
-associated with lesion at the level of :
midbrain (red nucleus)
cheyne-stokes respiration
alternating tachypnea and apnea (crescendo-decrescendo respiration)
- bilateral cortical involvement due to metabolic encephalopathy
- such as from: renal failure, unilateral lesion with severe brain edema, or from bilateral structural lesions in cerebral cortex
What does central neurogenic hyperventilation result from?
lesion or edema in the low midbrain to upper pons
Ataxic respiration patttern
variable breaths at an irregular rate from lesion or edema in the medulla
-bad
What type of coma results in the pupillary light reflex being preserved despite loss of other brainstem or cranial nerve reflexes ?
metabolic causes
A tectal midbrain lesion selectively involves the parasympathetic fibers causing what?
large, fixed pupils
The presence of a larger blown fixed pupil which is unresponsive to consensual or direct light is often due to what?
compression of the ipsilateral oculomotor nerve CN3 from a swollen temporal lobe (uncal herniation)
A pontine lesion selectively involves what lading to small pinpoint pupils?
sympathetic fibers
oculocephalic reflex
dolls eyes reflex
-brainstem mediated reflex
eyes should move in the opposite direction of the turned head
(if doesn’t move brainstem depressed)
oculovestibular reflex
(cold caloric)
-brainstem mediated
-eyes to turn toward cold ear
(if doesn’t move brainstem depressed)
What does dexamethasone do?
counteract the edema produced by a cerebral tumor, abscess or encephalitis
(doesn’t affect edema from ischemia infarction or hemorrhage)
Brain Death
Irreversible loss of function of both the cerebrum and brainstem
What do you need to declare brain death?
- apparent cause should be known
- must be sufficient to account for the irreversible coma
- bedside neuro exam should not show any hint or suggestion of cerebral function in a comatose patient unresponsive to painful stimuli
- no decorticate or decerebrate post, seizures, swallowing yawning, or vocalizations
- —except some spinal cord mediated movements may still persist (stretch reflex and babinski) - all cranial nerves or brainstem reflexes must be absent
- apnea can be verified by specific testing
- confirmation tests of brain death are not required-radioisotope brain scan-absence of cerebral blood flow
