Flashcards in Coma and End of Life Deck (21):
Coma is defined as a sleep-like, unarousable, unresponsive state.
Persistent Vegetative State
The eyes periodically open or move, sleep and wake cycles occur, and pain responsiveness may return, but meaningful interaction remains absent since severe cortical impairment persists.
What are some possible causes of coma?
- Cerebral Hypotension
- Drug intoxication/overdose
Can a solitary unilateral cerebral lesion cause coma?
No. Unless it affects the opposite hemisphere via brain edema or herniation.
How can a brain stem lesion cause coma?
Coma may be produced by a brain stem lesion if it disrupts the reticular formation.
What are asymmetrical neurological signs suggestive of?
Structural Lesion - ischemic infarction, hemorrhage or tumor
What are symmetrical neurological signs suggestive of?
Toxi-metabolic Process - anoxia
Decorticate posturing is flexion of the upper limbs with extension of the lower limbs associated with a lesion at the level of the cerebral cortex or hemisphere.
Decerebrate posturing is extension of the upper and lower limbs, associated with a lesion at the level of the midbrain (red nucleus).
What is Cheyne-Stokes respiration indicative of?
Bilateral cortical involvement due to metabolic encephalopathy, such as renal failure, a unilateral lesion with severe brain edema, or from bilateral structural lesions in cerebral cortex.
***Elderly patients can have this pattern of breathing as they sleep
Central Neurogenic Hyperventilation
Lesion in the low midbrain to upper pons
Ataxic Respiration Pattern
Variable breaths at an irregular rate from a lesion or edema in the medulla
What happens to the pupillary light reflex in patients with coma from metabolic causes?
Often in coma from metabolic causes the pupillary light reflex is preserved
What can large, blown and fixed pupils be indicative of?
What happens to the pupils with a pontine lesion?
A pontine lesion selectively involves the sympathetic fibers, causing small, pinpoint pupils
Oculocephalic Reflex "doll's eyes"
The eyes should normally move in the direction opposite to the lateral turn of the head.
Oculovestibular Reflex "cold caloric"
Eyes normally move slowly toward the cold (irrigated) ear
What should be immediately ruled out in an emergency coma?
How does hyperventilation decrease ICP?
Intracranial blood volume is reduced since hypocarbia from hyperventilation causes arterial vasoconstriction
Irreversible loss of function for both cerebrum and brain stem, leading to the inevitable failure of other vital organs, including the heart.