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34 Cards in this Set

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  • Back
Define coma.
An unarousable state where the patient is completely unresponsive to deep noxious stimuli and shows no sign of interaction with his/her environment.
What neural structures are neccessary for the maintenance of consciousness?
1. Cerebral Hemisphere
2. brainstem (Ascending recticular activating system)
3. connecting fibers of both structures
Structurally, what aspect of the brain is depressed in coma?
1. Both cerebral hemispheres
2. ARAS at the level of the midbrain/diencephalon/pons
...due to either a structural, metabolic lesion or psychogenic causes.
What are the three common processes leading to coma?
1. Supratentorial mass lesions
2. Subtentorial mass lesions (posterior fossa)
3. metabolic disturbances-responsible for 2/3 of coma (anoxia, ischemia, hemorrhage, toxins) often reversible.
What five physiological variables are essential for the localization of mass lesions in coma?
1. state of consciousness
2. breathing pattern
3. pupillary reactivity
4. eye movements (oculovestibular activity)
5. motor response
Discuss uncal herniation and its clinical presentation.
hemispheric mass lesion unilaterally compressing the edge of the uncus through the tentorial notch manifesting as initial III nerve palsy...or a unilateral dilated (blown) pupil.
Discuss central herniation and its clinical presentation.
Conus pressure transmitted to diencephalon and eventually brainstem resulting in progressive decrease of consciousness, and bilateral pupillary dilitation.
What clinical evaluation is vital to determination of the etiology of coma?
1. History
2. ABC's (airway, breathing, circulation)
3. Blood Glc, CBC drug toxicity panel.
What is the definition of "death?"
1. cessation of cardiac/respiratory function
2. Irreversible destruction of neuronal contents of the intracranial compartment resulting in loss of BOTH cortical and brain stem activity.
Define Brain death?
Absence of clinical brain function when cause is known and determined to be irreversible.
What are the prerequisites for "clinical" Dx of brain death?
1. Clinical/neuroimaging evidence of acute CNS injury.
2. Exclusion of complicating confounding conditions (electrolyte imbalance)
3. absence of drug intoxication/poisoning
4. core body temp > 32 degrees celsius
What are the three cardinal reflexes associated with brain death?
1. Coma/unresposiveness- lack of response to deep noxious stimuli (sternal rub)
2. Absent brainstem reflex- unreactive pupils, absence of occulocephalics (cold calorics), occulovestibular reflexes (dolls eyes), gag and cough
3. Apnea- absence of respiratory movments and arterial pCO2 > 55mmHg after 5-8 min. of passive delivery of 1000% oxygen.
List reflexive manifestations occasionally seen and commonly mis-interpreted as evidence for brainstem funciton?
1. Spontaneous movt of extremities
2. respiratory-like movt
3. sweating, blushing, tacchycardia
4. normal bp
5. presence of deep tendon reflexes
6. Babinski reflex
Discuss structural vs. metabolic lesions.
Structural lesions include strokes, tumors, hemorrhage & trauma, hyrdrocephalus, infection. Whereas metabolic lesions can be temp disorders, thiamine/b12 def, electrolyte/base disturbance, diabetic ketoacidosis.
What are the two top causes of supratentorial mass lesions?
1. Subdural hematomas
2. Intracerebral hemorrhage
What is emergency treatment for comatose patient?
1. Thiamine (alcoholic, B12 def)
2. Dextrose (hypoglyemia)
3. Naloxone or Narcan for opiod OD
4. Flumazenil- for benzodiazepene OD
Why is thiamine administered before glucose in emergent situations?
Thiamine is a cofactor in Glc metabolism, glucose will precipitate all thiamine and intesify the thiamine deficiency.
What is the Glasgow Coma Scale (GCS)?
three point scale utilized to assess level of consciousness. (eye, response, motor response, verbal response)
15 normal
Comatose if <8
True coma is 3
***Characterize the locale of the lesion in a patient looking away from the side of the weakness.
Hemispheric lesion (RMCA stroke weakness in the left field thus eyes gaze to right side)
***What eye movt are characteristic of brainstem stroke?
Weakness in left field eyes gaze towards same side as weakness....thus pt looking to the left.
List your differential for a comatose patient with pinpoint amd reactive pupils?
1. Pontine coma, Metabolic Coma & Opiod Overdose
What is the oculocephalic reflex? What are dolls eyes?
Movt of eyes in direction with fast head movement. Dolls eyes are a manifestation of intact brainstem functionality- eyes lag slightly behind directional/rotational movement of head so that it appears that they oppose head movement. Dolls eyes are a function of the brainstem ONLY IF HEMISPHERES are not working.
What is the oculovestibular reflex?
COWS (cold opposite warm same) for a person awake and alert/
Name the loci of the neural generator for the fast/slow component of nystagmus.
Fast component is mediated by the hemispheres
Slow component is mediated by the brainstem
What is your prediction for the outcome of Left eart cold water calorics vs. eye movt in comatose patient with intact brainstem?
Eyes drift to left due to absence of hemispheric input.
Discuss decorticate posturing and its clinical implication.
Arms flex and legs extend in response to sternal rub (noxious stimuli) indicatiev of a lesion above the red nucleus...intact brainstem
Discuss decerebrate posturing and its clinical implications.
Extension of legs and arms in response to noxious stimuli. Ominous finding that little brain function is left.
What type of breathing pattern is typically a sign of impending herniation?
Cluster breathing
What type of breathing would be characteristic of a patient suffering a leison in the lower pons?
apneustic breathing...taking a deep breath, hold and release. Square wave breathing
What type of breathing is characteristic of a person suffering from a lesion in the diencephalon?
Cheyenne-Stokes- crescendo/decrescendo breathing pattern
What clinical manifestations are characteristic of pschogenic coma (psuedocoma)?
1. Often reversible with pain...patients resistant to noxious stimuli
2. Saccadic eye movements-strip of paper with stripes will induce nystagmus if not comatose
3. Drop arm towards face and hand will never hit face
What reflexive activities are typically exhibited by patients in a persistent vegitative state after 2-4weeks?
Return of diurnal rhythm, chewing, yawning...etc.
True/False. Decorticate and decerebrate posturing are frequently observed in brain dead patients.
False. Both forms of posturing are indicative of brainstem functionality.
What clinical work-up is necessary for the declaration of brain death?
Two neurological exams...the second usually 2-6 hours after the initial exam and the apnea test (pCO2>55).
**Confirmatory/ancillary tests are not neccessary