Transcript Coma & Brain Death

Coma & Brain Death
Brain Death
• Defined by documentation of irreversible
coma and irreversible loss of brainstem reflex
responses and f(x) of respiratory centre
• OR by the demonstration of the cessation of
intracranial flow
Brain Death
• 2 Clinical examinations must be performed by
2 medical practitioners 6 hours apart;
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Response to painful stimulation within cranial nerve distribution
Pupillary responses to light
Corneal reflexes
Gag reflex
Cough reflex
Vestibulo-ocular reflexes
Respiratory function
 Apnoea test – Preoxygenation with 100% O2 followed by cessation of ventilation
 While mechanical ventilation is stopped O2 is supplied through tracheal catheter
 AT the end of the period w/o O2 apnoea must persist in the presence of adequate
stimulus to spontaneous ventilation PCO2 > 60mmHg and arterial pH < 7.30
Brain Death
• If this assessment is not possible then
radiocontract angiography can be used to look
at intracranial blood flow
• Flow should be absent in the supratentorial &
vertebro-basilar circulation to show brain
death
• NB: All reversible causes should be ruled out
Coma
• A state of unconsciousness where patient cannot
be wakened or aroused by external stimuli
• Occurs from damage to brain regions that control
consciousness;
• Brainstem reticular activating system above midpons &
Both cerebral hemispheres
• Defined a;
1. Not opening eyes
2. Not obeying commands
3. Not understanding words
Persistent Vegetative State
• Coma has progressed to wakefulness without
detectable awareness
• Usually just need feeds, no ventilation
• May open eyes and have sleep cycles
Causes of Coma
• Diffuse Brain Dysfunction (generalised metabolic
toxic injury/widespread inflammation)
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Hyperglycaemia (DKA)/Hypoglycaemia
ETOH
Drug intoxication
Hypoxic/IBI
Electrolyte imbalances
Acidosis (resp or metabolic)
SAH
Encephalitis
Cerebral Malaria
Endocrine (hypothroidism/hypoadrenalism)
Causes of Coma
• Direct Effect within Brain Stem
• Trauma
• Brainstem haemorrhage/infarction
• Neoplasm
• Pressure effect of the Brain Stem
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Hemisphere tumour or abscess
Cerebellar mass lesion
Trauma (SDH/EDH)
Encephalitis
Assessment
• Signs of Trauma
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Swelling of soft tissues
Racoon eyes – periorbital eccymoses
Blood behind the tympanic membrane (haemotypanum)
Battle’s sign – discoloured swelling over the mastoid bone behind
the ear
• CSF Rhinorrhoea/Otorrho
Assessment
Vital Signs
- BP
o HT may indicate intracerebral haemorrhage or stroke
o May also give clue to the cause of the coma (SAH?)
- Temp
o Hypothermia – ETOH, sedatives, hypoglycaemia
o Hyperthermia – heat stroke, infection, hypothalamic lesions
- Respiration
o Cheyne- Stokes (periodic respiration with hyperpnoea & apnoea due to
delay in medullary chemoreceptor response – LVF, brain damage, altitude)
o Kussmaul (acidotic) – deep sighing hyperventilation due to stimulation of
inspiratory centres – DKA, uraemia, metabolic acidosis
o Ataxic – shallow, halting irregular respiration in response to medullary
respiratory centre damage
Assessment
Pupils
Normal
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3-4mm in diameter, equal bilaterally
Constrict briskly+ symmetrically to light
Metabolic acidosis & CNS depressant drugs (not opiates)
Pin-point
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1-1.5mm in diameter
Opioid overdose
Pontine lesions, organophosphate poisoning
Pupils
Fixed Dilated
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7mm or more and fixed (not reactive to light
Results from compression of CN III
Common in herniation of the medial temporal lobe
- Fixed Mid-size
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5mm in diameter & fixed
Commonly from brainstem lesion at midbrain level
Anisocoria (Assymetrical)
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Less than 1mm difference in normal people (20% cases)
Pupil that has reduced constriction – lesion affecting midbrain or CNIII
Assessment
Optic Fundi
- Papilloedema/retinal haemorrhages – HT or raised ICP
- Subhyaloid (superficial retinal) haemorrhages – SAH
Ocular Movements
- Ocular Axes
o Usually slightly divergent in coma
o Slow, roving, side to side eye movements in light coma
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Doll’s Eye Reflex (Vestibulo-ocular reflex)
o Passive head turning produces ocular deviation away from the direction of head
rotation
o Lost in very deep coma and brainstem lesions
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Calorics Testings
o Ice water is irrigated into the tympanic membrane
o Slow tonic ocular deviation towards irrigated ear (intact brainstem)
o Commonly used to Dx brainstem death
GCS
Eye Opening
-None
-To Pain
-To speech/verbal command
-Spontaneous
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Verbal
Response
-None
Incomprehensible sound
Inappropriate words
Confused/disoriented
Talking & orientated
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Motor
Response
None
Extension
Flexion
Withdrawal
Localised pain
Obeys commands
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CGS
• 8 is the critical score
• 90% less than 8 – coma
• After 6 hours at 8 50% death rate
Investigations
• FBE
• Biochemistry – U&E’s, Glucose, Ca, LFt’s
• Drugs screen – salicylates, benzodiazepines,
narcotics, amphetamines
• TFT’s
• Blood cultures
• CT or MRI – mass leson or intracranial haemorrhage
• CSF
• EEG – metabolic coma, encephalitis, brain death
Management (ED)
• DRABC
• IV catheter and Bloods
• IV infusion (routine)
o Thiamine 100mg + dextrose 25g
o Thiamine always precedes dextrose as dextrose along can worsen
Wernicke’s encephalophaty
o Naloxone 0.4-1.2mg (routine)
Management (LT)
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Fluids & Feeding (NGT or paraenteral)
Skin Care (Pressure sores)
Oral Hygiene (mouth washes + suction)
Eye care – tape eye lids
Physiotherapy – muscles + joints
TED stockingss/heparin – DVT risk
Sphincter Control – Catherisation, rectal evacuation
Family Wishes
References: Acknowledgment J Koh & D Cheng
Case
• Mr GF, 75 y/o retired cook
• Wife found him slumped over table
– Unable to speak, but could undertand
– Right side of face drooping, weak right arm
• Presented to ED 2 hours later
• O/E: unable to speak, obeys simple commands
– Right facial droop (pronounced in lower part of face)
– Vision & Visual fields intact
– Power reduced in right arm, only weak elevation of
shoulder and shoulder adduction
– Mild weakness of right hip flexion
– Soft bruit on auscultation of left carotid artery
– BP 165/100
• PHx:
– HT (on ACE inhibitors)
– Ex-smoker (40 pack/years)
• Quit 10 years ago
• FHx
– Father, also smoker, died of stroke at 65
• Tests:
– Haem/biochemical screens normal
– Coag screen normal
– CT brain reported as normal
– MRI: shows area of diffuse restriction in anterior portion of
left middle cerebral artery
– Repeated CT scan done 48 hours later shows area of low
attenuation in same region
• Speech therapy shows dysphagia w/ uncoordinated
swallowing
• Made ‘nil by mouth’ + nasogastric tube
• Given aspirin
• Physio commenced next day
• Becomes febrile
– Right lower lobe consolidation detected clinically, seen on
CXR
– Antibiotic & chest physiotherapy
• Over next week, return of speech & right arm weakness
improves
• Carotid doppler shows 80-90% occlusion left carotid
– Vascular surgery consulted
– Left carotid endarterectomy planned in 6 weeks