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Brain Death Anatomy and Physiology

Brain Death Anatomy and Physiology

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Brain Death Anatomy and Physiology

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  1. Brain DeathAnatomy and Physiology Joel S. Cohen, M.D. Associate Professor of Clinical Neurology Albert Einstein College of Medicine

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

  3. 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

  4. Brain Death Current Consensus • Absent Cerebral Function • Absent Brainstem Function • Apnea

  5. Normal Brain Anatomy

  6. Normal Brain Anatomy Cerebral Cortex Reticular Activating System Brain Stem

  7. Cerebral Cortex • Cognition • Voluntary Movement • Sensation

  8. Brain Stem

  9. Brain Stem Midbrain Cranial Nerve III • pupillary function • eye movement

  10. Brain Stem • Pons • Cranial Nerves IV, V, VI • conjugate eye movement • corneal reflex

  11. Brain Stem • Medulla Cranial Nerves IX, X • Pharyngeal (Gag) Reflex • Tracheal (Cough) Reflex • Respiration

  12. Reticular Activating System • Receives multiple sensory inputs • Mediates wakefulness

  13. Causes of Brain Death Cerebral Anoxia Normal

  14. Causes of Brain Death Normal Cerebral Hemorrhage

  15. Causes of Brain Death Subarachnoid Hemorrhage Normal

  16. Causes of Brain Death Normal Trauma

  17. Causes of Brain Death Meningitis Normal

  18. Mechanism of Cerebral Death ICP>MAP is incompatible with life Increased Intracranial Pressure

  19. Conditions Distinct From Brain Death • Persistent Vegetative State • Locked-in Syndrome • Minimally Responsive State

  20. Persistent Vegetative State • Normal Sleep-Wake Cycles • No Response to Environmental Stimuli • Diffuse Brain Injury with Preservation of Brain Stem Function

  21. Locked-in Syndrome Ventral Pontine Infarct • Complete Paralysis • Preserved Consciousness • Preserved Eye Movement

  22. Minimally Responsive State Static Encephalopathy • Diffuse or Multi-Focal Brain Injury • Preserved Brain Stem Function • Variable Interaction with Environmental Stimuli

  23. 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

  24. Brain Death Neurological Examination • Coma • Absent Brain Stem Reflexes • Apnea

  25. Coma No Response to Noxious Stimuli • Nail Bed Pressure • Sternal Rub • Supra-Orbital Ridge Pressure

  26. Absence of Brain Stem Reflexes • Pupillary Reflex • Eye Movements • Facial Sensation and Motor Response • Pharyngeal (Gag) Reflex • Tracheal (Cough) Reflex

  27. Pupillary Reflex Pupils dilated with no constriction to bright light

  28. Eye Movements Occulo-Cephalic Response “Doll’s Eyes Maneuver”

  29. Eye Movements Oculo-Vestibular Response “Cold Caloric Testing”

  30. Facial Sensation and Motor Response • Corneal Reflex • Jaw Reflex • Grimace to Supraorbital or Temporo-Mandibular Pressure

  31. Apnea Testing Prerequisites • Core Body Temperature > 32° C • Systolic Blood Pressure ≥ 90 mm Hg • Normal Electrolytes • Normal PCO2

  32. 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

  33. Confounding Clinical Conditions • Facial Trauma • Pupillary Abnormalities • CNS Sedatives or Neuromuscular Blockers • Hepatic Failure • Pulmonary Disease

  34. Observations Compatible with Brain Death • Sweating, Blushing • Deep Tendon Reflexes • Spontaneous Spinal Reflexes- Triple Flexion • Babinski Sign

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

  36. Confirmatory Testing EEG Normal Electrocerebral Silence

  37. Confirmatory Testing Cerebral Angiography Normal No Intracranial Flow

  38. Confirmatory Testing Technetium-99 Isotope Brain Scan

  39. Confirmatory Testing MR- Angiography

  40. Confirmatory Testing Transcranial Ultrasonography

  41. Confirmatory Testing Somatosensory Evoked Potentials

  42. 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