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1 May 2023 brain death
Brain death
Brain DeathOut line What is brain death? Causes of Brain Death Clinical evaluation of brain death Brain Death Diagnosis
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Normal Brain Anatomy
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Cerebral Cortex
Brain Stem
Reticular Activating
System
Receives multiplesensory inputs
&Mediates
Consciousness(wakefulness)
Cerebral Cortex: Function
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Cognition Voluntary Movement Sensation
Brain Stem : Functions
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MedullaCranial Nerve IX, X
Pharyngeal (Gag) Reflex
Tracheal (Cough) Reflex
Respiration
Death : Definition Thanatology
Branch of science dealing with study of death
Death is the complete and irreversible stoppage of Circulation Respiration Brain function (Tripod of life)
As long as oxygenated blood reaches brain stem, Life exists ….
Mechanical Ventilator use in ICU Brought concept of “Brain Death”1 May 2023 brain death
Brain Death
Ireversible destruction of the brain,with the resulting total absence of all cortical and brainstem functions,although spinal cord refleves may remain
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Conditions Distinct fromBrain Death
Coma
Persistent Vegetative State
Locked in Syndrome
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3 clinical findings necessary to confirm irreversible cessation of all functions of the entire brain, including brain stem
Coma (with a known cause)Absence of brainstem reflexesApnoea
Causes: Brain Death
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Normal Cerebral Anoxia
Causes: Brain Death
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Normal Cerebral Haemorrhage
Causes: Brain Death
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Normal Cerebral Trauma
Brain Death : Mechanism
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Neuronal Injury
Decreased Intracranial Blood Flow
Neuronal Swelling
Increased Intracranial
Pressure
ICP > MAP is incompatible
with life
4 Steps in Determining Brain Death
The Clinical Evaluation
The Neurologic Assessment
Ancillary Test
Documentation
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Clinical evaluation of brain death
Irreversible coma Known etiology and or reversible causes ruled out
Must have an absence of
Hypothermia (>32.50C)
Neuromuscular blockade and Shock
Significant levels of sedatives
Severe metabolic distrubance and Endocrine
abnormalities
Poisoning
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Absence of cortical functions
No spontaneous movement, eye opening, or movement or response after auditory, verbal, or visual commands
Cerebral motor response to pain Supraorbital ridge, the nail beds,
trapezius Motor responses may occur
spontaneously during apnea testing (spinal reflexes)
Spinal arcs are intact!
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Absence of brain stem function-
1)Pupillary reflex
2)Corneal reflex
3)Gag reflex
4)Cough reflex
5)Oculocephalic reflex (doll’s eye reflex)
6)Oculovestibular reflex (caloric reflex)
7)No integrated motor response to pain
8)Apnea testing
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Pupillary reflex-
pupils may be midposition or dilated (4 to 9 mm)
Absent pupillary light reflex IV atropine does not markedly affect
response Paralytics do not affect pupillary size Topical administration of drugs and eye
trauma may influence pupillary size and reactivity
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Corneal reflex- Corneal reflexes are absent in brain death
Corneal reflexes - tested by using a cotton-tipped swab
.
There is no blink response to direct corneal stimulation.
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Oculocephalic reflex
Rapidly turn the head 90° on both sides Normal response = deviation of the
eyes to the opposite side of head turning
Brain death = oculocephalic reflexes are absent (no Doll’s eyes) = no eye movement in response to head movement
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Vestibularocular reflex
No eye movements within 3 mints after irrigating each tympanic membrane (if intact) sequentially with 50 ml ice water for 30 to 45 seconds while the head of the supine patient is elevated 30 degrees
Retained vestibulocular reflex
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Cold calorics interpretation
Not comatose Nystagmus; both eyes slow toward cold, fast
to midline Coma with intact brainstem
Both eyes tonically deviate away cold water No eye movement
Brainstem injury / death Movement only of eye on side of stimulus
Internuclear ophthalmoplegia Suggests brainstem structural lesion
Brain Death : Apnoea Test
Pre-requisites Body Temperature > 36° C Systolic Blood Pressure ≥ 100 mm Hg Normal Electrolytes profile Normal PaCO2 (35-45 mm Hg)
Pre-Oxygenation 100% Oxygen via Tracheal Cannula for 10 min Achieve PaO2 = 200 mm Hg
Monitor PaO2 with pulse oximetry
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Brain Death : Apnoea Test
Reduce Ventilation frequency to 10/min Reduce PEEP to 5 Cm H2O Take 1st Blood sample for Blood Gas
analysis Disconnect Ventilator Deliver 100% O2 by catheter through ET
tube @ 6 L/min
Observe for Respiratory Movement Atleast for 8 – 10 min
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Interpreting the test The apnea test is POSITIVE (i.e.,
supports the diagnosis of brain death) if: There are no respiratory efforts during
the test AND Repeat ABG shows PCO2 > 60 mm Hg.
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Interpreting the test The apnea test is INDETERMINATE
if: after 10 minutes, the patient
demonstrates no respiratory effort, but the PCO2 is < 60 mm Hg.
The apnea test is NEGATIVE (i.e., does NOT support the diagnosis of brain death) if: the patient demonstrates any
respiratory effort at any time during the test.
Cease the test and reconnect the ventilator immediately upon observing respiratory effort.
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The Apnea Test If the patient becomes unstable at
any point during the Apnea Test (i.e. SBP drops less than 90, significant desaturation on pulse-oximetry, observance of cardiac arrhythmias, etc.), the test should be aborted. The Apnea Test should not “induce a
code!”
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Movements originating from the spinal cord or peripheral nerve
which occur in brain death Spontaneous 'spinal' reflexes in the
limbs Respiratory-like movements Sweating, blushing, tachycardia Normal BP Normal osmolar control mechanism Deep tendon reflexes, Babinski's reflex Facial myokymias
Brain DeathAncillary Confirmatory Testing
Recommended when Proximate cause of coma is not known or When confounding clinical conditions
limit clinical examination EEG Cerebral Angiography PET : Glucose Metabolic Studies Dynamic Nuclear Scan Somato-Sensory Evoked Potential
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Brain DeathConfirmatory Testing
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Electro-Cerebral Silence
Normal
EEG
Brain DeathConfirmatory Testing
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No Intra- Cranial Flow
Normal
Cerebral Angiography
PETGlucose Metabolism Studies
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“Hollow-skull sign” of brain death
Cerebral metabolism globally reduced ~50%
Normal
Nature Rev Neurosci 2005;6:899-909
Dynamic Nuclear Brain Scan
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“Hollow-skull sign” of brain death
NEJM 2001;344:1215-1221