Coma and Related Disorders of Consciousness Flashcards
apnea test
test is conducted by first employing preoxygenation for several minutes with high inspired oxygen tension
the patient can then be disconnected from the respirator for several minutes during which time 100 percent oxygen is being delivered by cannula or ventilator that has its pumping mechanism turned off, this allows the arterial pCO2 to ruse to 50-60 mmHg,
the hypercarbia serves both as a stimulus to breating and a confirmation that spontaneous ventilation has failed.
other ancillary tests for BD
atropine test
inability to produce tachycardia in response to injection of atropine
this reflects the loss of innervation of the heart by the medullary vagal neurons
define electrocerebal silence in EEG in BD
no electrical potential of more than 2 mV during a 30-min recording except for artifacts created by the ventilator, ECG and surrounding electrical devices
Alpha coma in EEG
not limited to the posterior cerebral regions
not monorhythmic like normal alpha activity
displays no reactivity to sensory stimuli
associated with pontine or diffuse cortical lesions and has a poor prognosis
T/F
The anatomic boundaries of the upper brainstem Reticular activating system are distinct.
False
p366
indistinct
acute drop of cerebral blood flow from ____ to ____ mL/min/100g brain tissue causes slowing of the EEG, syncope, impaired consciousness
55 to 25
drop in CBF below ______ causes elctrocerebral silence, coma, cessation of most neuronal metabolic and synaptic functions
12-15mL/min/100g
Neurons cannot survive when CBF is
below 8-10 mL/min/100g
T/F
The ipsilateral pupillary dilatation from pinching the side of the neck (ciliospinal reflex) is usually lost in brainstem lesions.
true
“Wrong-way eyes” a paradoxical conjugate deviation to the side opposite the lesion may sometimes occur with
thalamic and upper brainstem lesions
caloric test
oculovestibular
irrigation of one ear with 10mL of cold water causes slow conjugate deviation of eyes toward the irrigated ear, followed in a few seconds by compensatory nystagmus (fast component away from the stimulated side)
One mnemonic used to remember the FAST direction of nystagmus is COWS.
COWS: Cold Opposite, Warm Same.
Cold water = FAST phase of nystagmus to the side Opposite from the cold water filled ear
Warm water = FAST phase of nystagmus to the Same side as the warm water filled ear
what does Cheyne-stokes breathing pattern signify
bilateral dysfunction of cerebral structures, usually deep in the hemispheres or diencephalon
breathing pattern in lesions of the lower mibrain-upper pontine tegementun eithe rprimry or secondary to transtentorial herniation
Central Neurogenic Hyperventilation
increased in the rate and depth of respiration to an extent that produces advanced respiratory alkalosis
breathing pattern in low pontine lesions
apneustic breathing
a pause of 2 to 3 seconds in full inspiration
breathing pattern in lesions of dorsomedial part of medulla
chaotic rhythm of breathing
Biot breathing or ataxic
