Brain Death

Brain Death (Death by Neurologic Criteria)

David Ray Velez, MD

Table of Contents

Diagnosis
Cranial Nerve Reflexes
Apnea Test

Diagnosis

Definition: A Permanent, Irreversible, and Complete Loss of Brain Function

Determination of Brain Death is Primarily a Clinical Diagnosis and Can Be Done with a Clinical Exam that Demonstrates Coma, Brainstem Areflexia, and Apnea

Mandatory Criteria to Consider the Diagnosis

  • Must Have Neuroimaging Consistent with the Mechanism and Severity
  • No Spontaneous Respirations
  • No Response to Pain/Noxious Stimulation
  • No Cranial Nerve Reflexes
  • *Can Still Have Spinal Cord/Deep Tendon Reflexes

Criteria that Exclude the Diagnosis

  • Hypothermia
  • Hypotension (Stable Dose Vasopressors are Acceptable)
  • Significant Metabolic Derangements (Electrolytes, Acid-Base, or Endocrine)
  • Depressant Drugs

Definitive Testing (If All Other Criteria are Met)

  • Preferred Definitive Test: Apnea Test
  • Ancillary Testing:
    • Indications:
      • Unstable and Unable to Tolerate Time Off Ventilator (Hypoxic Respiratory Failure, etc.)
      • High Cervical Spine Injury that May Inhibit Phrenic Nerve Function
      • Unable to Perform All Cranial Nerve Reflexes (C-Spine Fracture, Severe Eye/Ear Injury, etc.)
    • Acceptable Testing:
      • Four-Vessel Cerebral Angiogram
      • Nuclear Cerebral Scintigraphy
      • Transcranial Doppler
    • Unacceptable Tests: EEG, CTA, MRI/MRA

Note: Laws are Different in Different States and Physicians Should Be Aware of State, Local, and Facility Regulations

Pediatrics Often Have Additional Requirements Such as a Second Examiner with Mandatory Time Between Examinations

Brain Death by Nuclear Cerebral Scintigraphy

Cranial Nerve Reflexes

Pupillary Light Reflex

  • Test: Light Shown into the Eye
  • Normal Reflex: Prompts Pupil Constriction
  • Absent Reflex: Pupil Does Not Constrict

Corneal Reflex

  • Test: Cornea Touched with Cotton Swab or Saline
  • Normal Reflex: Prompts Blinking
  • Absent Reflex: Does Not Blink

Gag Reflex

  • Test: Touching the Posterior Pharyngeal Wall
  • Normal Reflex: Prompts Palate Elevation
  • Absent Reflex: No Palate Elevation

Cough Reflex

  • Test: Tracheal Suctioning
  • Normal Reflex: Prompts Coughing
  • Absent Reflex: Does Not Cough

Oculocephalic (Doll’s Eyes) Reflex

  • Test: With Eyes Held Open the Head is Briskly Turned Side-to-Side and Held at the End of the Turn
  • Normal Reflex: Eyes Rotate to the Opposite Side of Head Rotation (Continue to Look Forward)
  • Absent Reflex: Eyes Do Not Rotate
  • *Must First Ensure that the Cervical Spine is Clear and May Be Unable to Perform if a Collar is in Place

Oculovestibular (Cold Caloric) Reflex

  • Test: With Head Elevated at 30 Degrees, 200 cc of Ice Water is Instilled into the External Ear Canal
  • Normal Reflex: Nystagmus with Eye Deviation to the Tested Ear
  • Absent Reflex: No Nystagmus Seen

Apnea Test

Test

  • Preoxygenate with 100% O2 for at Least 10 Minutes Before Starting
  • Ensure CO2 Normal (35-45 mmHg) by ABG Before Starting
  • Disconnect the Ventilator for 10 Minutes
    • Continue to Deliver O2 During the Test
  • Monitor for Spontaneous Respirations During the Test
  • Repeat an ABG After 10 Minutes

Positive Test Result (Requires All for Diagnosis of Brain Death)

  • (1) No Respirations are Seen
  • (2) Arterial pH < 7.30
  • (3) PaCO2 ≥ 60 mmHg AND Increases by ≥ 20 mmHg
    • If Known the Have Chronic CO2 Retention: Increase by ≥ 20 mmHg Above the Known Chronic Elevated Level
    • *Previously “OR” Prior to 2023 Guidelines
  • *Can Continue Testing Beyond 10 Minutes and Repeat ABG Every 2 Minutes if ABG Thresholds are Not Met

Indications to Abort Apnea Testing

  • Hemodynamic Instability: SBP < 100 mmHg or MAP < 75 mmHg Despite Titration of Vasopressors, Inotropes, or Fluids
  • Hypoxia: Progressive Decrease in SpO2 < 85%
  • Cardiac Arrhythmia with Hemodynamic Instability