Coma and Brain Death Flashcards
Coma is defined as….
Which reflexes are the one clinically testable reflexes?
Treatment
Patients could recover or transition to:
Coma is defined as sleep-like, unarousable, unresponsive state
[other pt with impaired consciousness but some limited degree of responding are described as obtunded or stuporous]
ONLY BRAIN STEM REFLEXES are clinically testable, since cortical function is absent
Treatment: finding and treating the cause of coma
Patients could recover or transition to persistent vegetative state [eyes may move, sleep/wake cycles can occur, pain responsiveness may return but meaningful interaction remains absent since severe cortical impairment persists]
What are causes of coma?
Can cerebral lesions cause coma?
What area of the brain is important for wakefulness and arousal?
Severe metabolic or systemic conditions that diffusely depress cortical function may cause coma
DIRRECT impairment to brain function: hypoxia, inadequate cerebral blood flow, hypoglycemia and drug intoxication/overdose
INDIRECT impairment: systemic infections, metabolic disturbances, hepatic or renal failure
**TIMELY CORRECTION CRITICAL esp for the hypo’s (hypotension, hypoxia, hypoglycemia)
bilateral lesions could produce a coma
a solitary, unilateral cerebral lesion does NOT produce coma, unless it adveresely affects the opposite hemisphere via brain edema or herniation.
The tegmental brain stem reticular formation, projecting to thalamic and subcortical nuclei, is important for wakefulness and arousal; thus a coma could be prouced by a brain stem lesion if it disrupts the reticular formaiton.
What limited neurological exams can be evaluated in a comatose patient? (4)
What would asymmetrical neurological signs suggest?
What would progressive loss of neurological function and brain stem reflexes indicate?
What would symmetrical abnormalities suggest?
Motor responses, breathing patterns, pupil size and reactivity, and reflexive ocular movements
Asymmetrical neurological signs –> suggestive of a structural lesion (ischemic infarction, hemorrhage or tumor)
Symmetrical abnormalities –> more diffuse or toxi-metabolic process (anoxia)
Progressive loss of neurological function and brain stem reflexes suggestive of a rostral to caudal deterioration due to edema or inflammation
Do motor responses occur in coma?
What is DECORTICATE posturing?
What is DECEREBRATE posturing?
Motor responese to COMMAND / WITHDRAWL to painful stimuli DO NOT OCCUR in coma, since an appropriate, localizing response to a noxious stimulus requires some cortical function.
DECORTICATE posturing: 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: extension of the upper AND lower limbs, associated with a lesion at the elvel of the midbrain/red nucleus
What type of breathing pattern is Cheyne-Stokes respiration?
This pattern is produced from what cortical involvement?
what are the causes of this?
Can Cheyne-Stokes respiration be seen in non-comatose patients?
Cheyne-Stokes respiration is a very distinctive patter of ALTERNATING TACHYPNEA and APNEA (crescendo-decrescendo respiration)..pt takes progressively deeper, often faster, breaths followed by slower and shallower breathing leading to a period of apnea, after which the cycle repeats.
This pattern is produced from the BILATERAL CORTICAL INVOLVEMENT due to metabolic encephalopathy (renal failure, unilateral lesion with severe brain edema, or from bilateral structural lesions in the cerebral cortex)
CAN be seen in non-comatose patients: CHF where slowed circulation time creates delayed feedback to the carotid chemorreceptors influencing the respiration rate. Elderly, otherwise healthy individuals, can have Cheyne-Stokes breahting while they sleep
An ataxic respiration pattern consist of….
from a lesion or edema in the ________ involving what control centers?
What could this respiratory pattern signify?
An ataxic respiration pattern consist of VARIABLE BREATHS AT AN IRREGULAR RATE
from a LESION or EDEMA in the MEDULLA involving the cariorespiratory control centers
**ominous sign- signaling IMPEDING RESPIRATORY ARREST and the EMERGENT NEED to INTUBATE AND MECHANICALLY VENTILLATE the patient**
Eye exams:
Coma due to metabolic causes the pupillary light reflex is__
A tectal/dorsal midbrain lesion, cuases ________ pupils due to unopposed _____ fibers
Larger, “blown”, fixed pupils (unreponsive to consensus/direct) is often due to compression of the ipsilateral ___________ from a swollen _______ lobe = _______ herniation
Potine lesion —-> ________ pupils
Eye exams:
Coma due to metabolic causes the pupillary light reflex is PRESERVED
A tectal/dorsal midbrain lesion, causes LARGE, FIXED pupils due to unopposed SYMPATHETIC fibers
Larger, “blown”, fixed pupils (unreponsive to consensus/direct) is often due to compression of the ipsilateral CN III from a swollen TEMPORAL lobe = UNCAL herniation
Potine lesion —-> PINPOINT pupils (unopposed parasympathetic fibers)
Central neurogenic hyperventilation may result form a lesion or edema in the ______ to _____.
Is this often or rarely seen?
Central neurogenic hyperventilation may result form a lesion or edema in the LOW MIDBRAIN TO UPPER PONS
Is this often or rarely seen? RARELY SEEN (hyperventilation more likely due to anxiety, fear or reflexive from pulmonary congestion)
In the absence of a brain stem lesion, reflexive eye movements may be suppressed by _______
The oculocephalic reflex, aka ________ reflex, is a reflex mediated by _____; eyes should normally move in the direction _____ to the lateral turn of the head.
The oculovestibular reflex, aka _____reflex, is meadiated by _______. What should be excluded before the oculovestiular reflex is tested? How is the oculovestibular reflex tested? The eyes normally would move _____ towards the ____ ear. How would a conscious patient’s response differ from an unconcious pt’s response?
What are two other reflexes that should also be tested?
In the absence of a brain stem lesion, reflexive eye movements may be suppressed by vestibulotoxic drugs (ie-benzos)
The oculocephalic reflex, aka DOLL’S EYES REFLEX, is a reflex mediated by BRAINSTEM; in a comatose pt, eyes move in the direction OPPOSITE to the lateral turn of the head.
The oculovestibular reflex, aka COLD CALORIC REFLEX, is meadiated by BRAINSTEM.
Exclude ear canal blockage or ruptured tympanic membrane prior to mediating reflex.
Elevate pt head about 30degrees above the horizontal, then irrigate one ear canal with up to 100 cc of ice water –> induced convection movement of cooled endolymph creates reduced vestibular activity from that ipsilateral semicanal…
The eyes normally would move SLOWLY TOWARDS TO COLD/irrigated EAR.
(conscious pt will also have nystagmus, with the eyes beating towards the opposite, non-irrigated ear)
Also, helpful to check corneal and palpebral reflexes
1 that should be ruled out is ______, by what methods (2)
EMERGENCY treatment of the comatose pt:
Emergent care of coma invovled the ______ of:
1 that should be ruled out is HYPOGLYCEMIA, by fingerstick testing OR empirically give IV 50% dextrose
EMERGENCY treatment of the comatose pt:
Emergent care of coma invovled the ABCs of AIRWAY, BREATHING, CIRUCLATION
A structural cause of coma, ie) hemorrhage, ishcemic infraction or mass lesion is likely to present as ______ (asymmetrical/symmetrical) neurological signs?
What should always be suspected until ruled out?
A structural cause of coma, ie) hemorrhage, ishcemic infraction or mass lesion is likely to present as ASYMMETRICAL neurological signs?
Suspect INTRACRANIAL bleeding unless ruled out via CT/MRI
(RX of brain edema and surgical removal of a hematoma may be needed)
What are general measures that could be used to reduce increased intracranial pressure in comatose patients?
Mechanical hyperventilation
intracranial blood volume is reduced since hypocarbia causes arterial vasoconstriction;
Osmotic diuretics (ie- mannitol)
cerebral water volume is reduced by the effect of osmotic diuretics on the intact BBB in normal brain tissue
What could be used to counteract cerebral edema?
IV corticosteriods such as dexamethasone can counteract the edema produced by a cerebral tumor, abscesses or encephalitis; specific treatment for these lesions should follow
HOWEVER, brain edema due to ischemic infarction or hemorrhage is UNAFFECTED BY CORTICOSTEROIDS, but these pt may survive after decompressive craniectomy or hematoma removal
If the coma produces systemic neurological signs, it is likely that the coma is caused by _______, in which the patient should be evaluated for (6):
Also, while waiting for results, administer drugs such as (2)_____, in case of drug intoxication.
If the coma produces systemic neurological signs, it is likely that the coma is caused by TOXIMETABOLIC causes, in which the patient should be evaluated for (6): electrolyte abnormalities, hypothermia, hepatic or renal failure, carbon monoxide poisoning, drug intoxication or overdose
Also, while waiting for results, administer drugs such as narcotic or benzzodiazepine antagonist, in case of drug intoxication.
In brain death, there is irreversible loss of function for both _____ and ______, leading to the inevitable failure of other vital organs
In brain death, there is irreversible loss of function for both CEREBRUM and BRAIN STEM, leading to the inevitable failure of other vital organs
