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34 Cards in this Set
- Front
- Back
Define coma.
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An unarousable state where the patient is completely unresponsive to deep noxious stimuli and shows no sign of interaction with his/her environment.
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What neural structures are neccessary for the maintenance of consciousness?
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1. Cerebral Hemisphere
2. brainstem (Ascending recticular activating system) 3. connecting fibers of both structures |
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Structurally, what aspect of the brain is depressed in coma?
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1. Both cerebral hemispheres
2. ARAS at the level of the midbrain/diencephalon/pons ...due to either a structural, metabolic lesion or psychogenic causes. |
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What are the three common processes leading to coma?
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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. |
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What five physiological variables are essential for the localization of mass lesions in coma?
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1. state of consciousness
2. breathing pattern 3. pupillary reactivity 4. eye movements (oculovestibular activity) 5. motor response |
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Discuss uncal herniation and its clinical presentation.
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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.
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Discuss central herniation and its clinical presentation.
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Conus pressure transmitted to diencephalon and eventually brainstem resulting in progressive decrease of consciousness, and bilateral pupillary dilitation.
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What clinical evaluation is vital to determination of the etiology of coma?
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1. History
2. ABC's (airway, breathing, circulation) 3. Blood Glc, CBC drug toxicity panel. |
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What is the definition of "death?"
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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. |
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Define Brain death?
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Absence of clinical brain function when cause is known and determined to be irreversible.
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What are the prerequisites for "clinical" Dx of brain death?
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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 |
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What are the three cardinal reflexes associated with brain death?
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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. |
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List reflexive manifestations occasionally seen and commonly mis-interpreted as evidence for brainstem funciton?
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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 |
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Discuss structural vs. metabolic lesions.
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Structural lesions include strokes, tumors, hemorrhage & trauma, hyrdrocephalus, infection. Whereas metabolic lesions can be temp disorders, thiamine/b12 def, electrolyte/base disturbance, diabetic ketoacidosis.
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What are the two top causes of supratentorial mass lesions?
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1. Subdural hematomas
2. Intracerebral hemorrhage |
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What is emergency treatment for comatose patient?
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1. Thiamine (alcoholic, B12 def)
2. Dextrose (hypoglyemia) 3. Naloxone or Narcan for opiod OD 4. Flumazenil- for benzodiazepene OD |
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Why is thiamine administered before glucose in emergent situations?
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Thiamine is a cofactor in Glc metabolism, glucose will precipitate all thiamine and intesify the thiamine deficiency.
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What is the Glasgow Coma Scale (GCS)?
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three point scale utilized to assess level of consciousness. (eye, response, motor response, verbal response)
15 normal Comatose if <8 True coma is 3 |
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***Characterize the locale of the lesion in a patient looking away from the side of the weakness.
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Hemispheric lesion (RMCA stroke weakness in the left field thus eyes gaze to right side)
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***What eye movt are characteristic of brainstem stroke?
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Weakness in left field eyes gaze towards same side as weakness....thus pt looking to the left.
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List your differential for a comatose patient with pinpoint amd reactive pupils?
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1. Pontine coma, Metabolic Coma & Opiod Overdose
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What is the oculocephalic reflex? What are dolls eyes?
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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.
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What is the oculovestibular reflex?
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COWS (cold opposite warm same) for a person awake and alert/
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Name the loci of the neural generator for the fast/slow component of nystagmus.
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Fast component is mediated by the hemispheres
Slow component is mediated by the brainstem |
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What is your prediction for the outcome of Left eart cold water calorics vs. eye movt in comatose patient with intact brainstem?
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Eyes drift to left due to absence of hemispheric input.
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Discuss decorticate posturing and its clinical implication.
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Arms flex and legs extend in response to sternal rub (noxious stimuli) indicatiev of a lesion above the red nucleus...intact brainstem
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Discuss decerebrate posturing and its clinical implications.
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Extension of legs and arms in response to noxious stimuli. Ominous finding that little brain function is left.
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What type of breathing pattern is typically a sign of impending herniation?
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Cluster breathing
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What type of breathing would be characteristic of a patient suffering a leison in the lower pons?
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apneustic breathing...taking a deep breath, hold and release. Square wave breathing
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What type of breathing is characteristic of a person suffering from a lesion in the diencephalon?
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Cheyenne-Stokes- crescendo/decrescendo breathing pattern
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What clinical manifestations are characteristic of pschogenic coma (psuedocoma)?
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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 |
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What reflexive activities are typically exhibited by patients in a persistent vegitative state after 2-4weeks?
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Return of diurnal rhythm, chewing, yawning...etc.
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True/False. Decorticate and decerebrate posturing are frequently observed in brain dead patients.
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False. Both forms of posturing are indicative of brainstem functionality.
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What clinical work-up is necessary for the declaration of brain death?
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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 |