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COMA AND BRAIN DEATH
Introduction
Coma – clinical state in which patients have impaired responsiveness
(or are unresponsive) to external stimulation and are either difficult
to arouse or are unarousable.
Stupor, lethargy and obtundation – states between alertness and
coma.
An alteration in arousal – acute, life treating emergency
Etiologies and pathophysiology
• ARAS (ascending reticular activating system)
• Tegmentum (upper pons and midbrain) –diencephalon (thalamus &
hypothalamus) – cerebral cortex
• Cerebral hemispheres – must be bilateral/or large unilateral
• Toxic, metabolic, infection, hypothermia
• Multiple medical conditions
• ER presentation: TBI, stroke, intoxications, infections, metabolic
disturbance
History
• History from witnesses, friends, family members
• The patient’s personal belongings (bracelet, wallet, list of
medications)
• Old hospital chart
General examination
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Vital signs (HTN-PRES, ICH, hypotension-sepsis, cardiac failure)
Ventilatory pattern
Hyperthermia (infection, heat stroke, anticholinergic)
Hypothermia (accidental, primary-hypothalamic dysfunction-Wernicke,
secondary-adrenal failure, hypothyroidism, sepsis, EtOH, drugs)
Cutaneous and mucosal abnormalities, bullous lesions- barbiturate
Perspiration (fevers, hypoglycemia, pheochromocytoma)
Jaundice, cherry red color-CO, pallor – uremia, anemia, myxedema
Needle tracks
CSF rhinorrhea
Neurologic examination
• Level of consciousness
• Motor responses
• Cranial nerves
• Brainstem reflexes: pupillary light, extraocular and corneal
• Coma syndromes
• Herniation syndromes
• Brainstem lesions
• Metabolic coma
• Toxic syndromes
Coma syndromes
Herniation syndromes
• Transtentorial herniation (expanding mass lesions)
• Horizontal shifts- pineal body >8mm (some impairment of
consciousness), >11 mm = usually comatose
• Papilledema
• Cushing’s triad: HTN, bradycardia, irregular respiration
• CENTRAL HERNIATION
• UNCAL HERNIATION (ipsilateral III -mydriasis, downward and
outward eye deviation. Loss of contralateral pupil
reactivity=brainstem lesion
Brainstem lesions
• Infarction or hemorrhage of the upper pons and/or midbrain
• Osmotic demyelination syndrome (CPM)
• Brainstem encephalitis
• Asymmetric eye movements, small pupils
Metabolic coma
• Symmetrical nature of neurologic deficits
• Exceptions: hypo or hyperglycemia-lateralized motor findings
• Tremor, asterixis, multifocal myoclonus
• Decreased muscle tone
• Less common cerebrate posturing
• Pupils abnormal, symmetric, constrict with light
Toxic syndromes
Conditions mistaken for coma
• Locked-in syndrome
• Akinetic mutism
• Psychogenic unresponsiveness
Locked-in syndrome
• Focal injury to the base of the pons (BA embolic occlusion)
• Consciousness is preserved
• Can voluntary blink and vertical eye movements
Akinetic mutism
• A lack of motor response in an awake individual
• Prefrontal or premotor (supplementary motor) areas –executive
problem
• The patient follows with the eyes but does not initiate other
movements or obey commands
• Muscle tone, reflexes and postural reflexes usually intact
Psychogenic unresponsiveness
• Resist passive eye opening
• Roll over when tickled
• Turn the eyes towards the floor
• Nonepileptic seizures
• Catatonia-preserved ability to maintain posture (sitting or
standing)
Diagnosis
• Laboratory tests
• Neuroimaging
• Lumbar puncture
• EEG
Management
Prognosis
• Coma – transitional state that rarely lasts > several weeks (except
in cases of ongoing sedative therapies or protracted sepsis)
• Recovery of brain death/persistent vegetative or minimally
conscious state
• Depends on the underlying etiology, severity of the insult and
other premorbid factors, including age
Brain death
Death is an irreversible, biological event that consists of permanent
cessation of the critical functions of the organism as a whole.
Brain death qualifies as death, as the brain is essential for integrating
critical functions of the body.
Permanent absence of cerebral and brainstem functions.
1959 – the first concept of irreversible coma or brain death
TBI and SAH, ICH, hypoxic ischemic encephalopathy, ischemic
stroke
Clinical criteria
• Clinical setting
• Neurological examination
• Apnea test
• Observation period
• Examiner(s)
Clinical setting
• Clinical or neuroimaging evidence of an acute CNS catastrophe
• Exclusion of complicating medical conditions (no severe
electrolyte, acid-base, endocrine or circulatory disturbance)
• No drug intoxication or poisoning
• Core temperature >36C (97F)
• Normal SBP>100 mm Hg (vasopressors may be required)
Neurologic examination
It must demonstrate absent cerebral or brainstem function with all of the
following findings:
• Coma
• Absent brain-originating motor response, including response to pain above
the neck or other brain-originating movements (seizures, decerebrate or
decorticate posturing)
• Absent pupillary light reflex (midposition or dilated (4-9 mm)
• Absent corneal reflexes
• Absent oculovestibular reflexes (caloric responses)
• Absent jaw reflex
• Absent gag, sucking or rooting reflex
• Absent cough with tracheal suctioning
Neurologic examination
Movements originating from the spinal cord or peripheral nerve may
occur in brain death – common- 33-75%
• Semi-rhythmic facial movements
• Finger flexor movements
• Tonic neck reflexes – “Lazarus sign”
• Triple flexion response – plantar response
• Asymmetrical opisthotonic posturing of the trunk
• Alternating flexion-extension of the toes
• Upper limb pronation extension reflex
• Widespread fasciculations of trunk and extremities
Apnea test
• Performed after all other criteria for brain deathhave been met
• Core temperature >36C
• SBP>100 mm Hg
• Absence of hypoxia
• Euvolemia
Not valid in patients with chronic >PaCO2, neuromuscular paralysis or
high cervical spinal cord lesion.
Preoxygenation
POSITIVE TEST: no respiratory response to a PaCO2>60 mm HG or 20
mm Hg greater than baseline values and a final arterial pH<7.28. 8-10 min
Observation period
• Varies extensively
• 24 hours for adults
• 48 hours for children
Examiner(s)
• Varies by the state and country
Ancillary tests
Brain blood flow
• Cerebral angiography
• TCD
• MRA
• CTA
• Nuclear medicine
Electrophysiology
• EEG
• EP
Other tests
• Atropine test (3mg IV, >HR<3%)
Brain death mimics
• Locked-in syndrome
• Neuromuscular paralysis (acute, severe PN or with neuromuscular
blocking agents)
• Hypothermia
• Drug intoxication
• Guillain-Barre syndrome