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Brain Death Anatomy and Physiology. Joel S. Cohen, M.D. Associate Professor of Clinical Neurology Albert Einstein College of Medicine. Historical Perspective. Prior to the advent of mechanical respiration, death was defined as the cessation of circulation and breathing .

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Brain DeathAnatomy and Physiology

Joel S. Cohen, M.D.

Associate Professor of Clinical Neurology

Albert Einstein College of Medicine


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Historical Perspective

Prior to the advent of mechanical respiration, death was defined as the cessation of circulation and breathing


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Historical Perspective

  • 1959 Coma de’passe’ Mollaret and Goulon

  • 1968 Irreversible Coma/Brain Death Harvard Medical School Ad Hoc Committee

  • 1981 Uniform Determination of Death Act - President’s Commission for the Study of Ethical Problems in Medicine

  • 1994 American Academy of Neurology Guidelines for the determination of Brain Death

  • 2005 NYS Guidelines for Determining Brain Death


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Brain Death Current Consensus

  • Absent Cerebral Function

  • Absent Brainstem Function

  • Apnea



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Normal Brain Anatomy

Cerebral Cortex

Reticular Activating System

Brain Stem


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Cerebral Cortex

  • Cognition

  • Voluntary Movement

  • Sensation



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Brain Stem

Midbrain

Cranial Nerve III

  • pupillary function

  • eye movement


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Brain Stem

  • Pons

  • Cranial Nerves IV, V, VI

    • conjugate eye movement

    • corneal reflex


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Brain Stem

  • Medulla

    Cranial Nerves IX, X

    • Pharyngeal (Gag) Reflex

    • Tracheal (Cough) Reflex

  • Respiration


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    Reticular Activating System

    • Receives multiple sensory inputs

    • Mediates wakefulness


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    Causes of Brain Death

    Cerebral Anoxia

    Normal


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    Causes of Brain Death

    Normal

    Cerebral Hemorrhage


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    Causes of Brain Death

    Subarachnoid Hemorrhage

    Normal


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    Causes of Brain Death

    Normal

    Trauma


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    Causes of Brain Death

    Meningitis

    Normal


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    Mechanism of Cerebral Death

    ICP>MAP is incompatible with life

    Increased Intracranial

    Pressure


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    Conditions Distinct From Brain Death

    • Persistent Vegetative State

    • Locked-in Syndrome

    • Minimally Responsive State


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    Persistent Vegetative State

    • Normal Sleep-Wake Cycles

    • No Response to Environmental Stimuli

    • Diffuse Brain Injury with Preservation of Brain Stem Function


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    Locked-in Syndrome

    Ventral Pontine Infarct

    • Complete Paralysis

    • Preserved Consciousness

    • Preserved Eye Movement


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    Minimally Responsive State

    Static Encephalopathy

    • Diffuse or Multi-Focal Brain Injury

    • Preserved Brain Stem Function

    • Variable Interaction with Environmental Stimuli


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    Brain Death Neurological Examination

    Clinical Prerequisites:

    • Known Irreversible Cause

    • Exclusion of Potentially Reversible Conditions

      • Drug Intoxication or Poisoning

      • Electrolyte or Acid-Base Imbalance

      • Endocrine Disturbances

    • Core Body temperature > 32° C


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    Brain Death Neurological Examination

    • Coma

    • Absent Brain Stem Reflexes

    • Apnea


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    Coma

    No Response to Noxious Stimuli

    • Nail Bed Pressure

    • Sternal Rub

    • Supra-Orbital Ridge Pressure


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    Absence of Brain Stem Reflexes

    • Pupillary Reflex

    • Eye Movements

    • Facial Sensation and Motor Response

    • Pharyngeal (Gag) Reflex

    • Tracheal (Cough) Reflex


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    Pupillary Reflex

    Pupils dilated with no constriction to bright light


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    Eye Movements

    Occulo-Cephalic Response

    “Doll’s Eyes Maneuver”


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    Eye Movements

    Oculo-Vestibular Response

    “Cold Caloric Testing”


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    Facial Sensation and Motor Response

    • Corneal Reflex

    • Jaw Reflex

    • Grimace to Supraorbital or

      Temporo-Mandibular Pressure


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    Apnea Testing

    Prerequisites

    • Core Body Temperature > 32° C

    • Systolic Blood Pressure ≥ 90 mm Hg

    • Normal Electrolytes

    • Normal PCO2


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    Apnea Testing

    1. Pre-Oxygenation

    • 100% Oxygen via Tracheal Cannula

    • PO2 = 200 mm Hg

      2. Monitor PCO2 and PO2 with pulse oximetry

      3. Disconnect Ventilator

      4. Observe for Respiratory Movement until PCO2 = 60 mm Hg

      5. Discontinue Testing if BP < 90, PO2 saturation decreases, or cardiac dysrhythmia observed


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    Confounding Clinical Conditions

    • Facial Trauma

    • Pupillary Abnormalities

    • CNS Sedatives or Neuromuscular Blockers

    • Hepatic Failure

    • Pulmonary Disease


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    Observations Compatible with Brain Death

    • Sweating, Blushing

    • Deep Tendon Reflexes

    • Spontaneous Spinal Reflexes- Triple Flexion

    • Babinski Sign


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    Confirmatory Testing

    Recommended when the proximate cause of coma is not known or when confounding clinical conditions limit the clinical examination


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    Confirmatory Testing

    EEG

    Normal

    Electrocerebral Silence


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    Confirmatory Testing

    Cerebral Angiography

    Normal

    No Intracranial Flow


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    Confirmatory Testing

    Technetium-99 Isotope Brain Scan


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    Confirmatory Testing

    MR- Angiography


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    Confirmatory Testing

    Transcranial Ultrasonography


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    Confirmatory Testing

    Somatosensory Evoked Potentials


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    Concern for man and his fate must always form the chief interest of all technical endeavors. Never forget this in the midst of your diagrams and equations.

    Albert Einstein


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