Brain Death

Definitions

Clinical Patterns of Brain Dysfunction

  • Akinetic Mutism
  • Brain Death (see Brain Death, [[Brain Death]])
  • Coma (see Obtundation-Coma, [[Obtundation-Coma]])
  • Dementia (see Dementia, [[Dementia]])
  • Locked-In Syndrome (see Locked-In Syndrome, [[Locked-In Syndrome]])
  • Persistent Vegetative State: term was first used in 1972
  • Minimally Conscious State

BRAIN INJURY


Considerations

  • The Criteria for the Determination of Brain death Given in the 1995 AAN Neurology Practice Parameter Have Not Been Invalidated by Published Reports of Neurologic Recovery in Patients Who Fulfill These Criteria (Level U Recommendation)
  • There is Insufficient Evidence to Determine the Minimally Acceptable Observation Period to Ensure that Neurologic Functions Have Irreversibly Ceased (Level U Recommendation)
  • Complex Spontaneous Motor Movements and Fase-Positive Triggering of the Ventilator May Occur in Patients Who are Brain Dead (Level C Recommendation)

Criteria 1: Presence of Coma

  • Patients Must Lack All Evidence of Responsiveness
    • Eye opening or eye movement to Noxious Stimuli is Absent
    • Noxious Stimuli Should Not Produce a Motor Response Other than Spinally-Mediated Reflexes
    • The Clinical Differentiation of Spinal Responses from Retained Motor Responses Associated with Brain Activity Requires Expertise

Criteria 2: Absence of Brainstem Reflexes

Absence of Pupillary Response to Bright Light in Both Eyes

  • Usually the Pupils are Fixed in a Midsize or Dilated Position (4–9 mm)
    • Constricted Pupils Suggest the Possibility of Drug Intoxication
    • When Uncertainty Exists, a Magnifying Glass Should be Used

Absence of Ocular Movements with Oculocephalic Reflex Testing and Oculovestibular Reflex Testing

  • Technique of Oculocephalic Reflex Testing: once the integrity of the cervical spine is ensured, the head is briskly rotated horizontally and vertically
    • There Should Be no Movement of the Eyes Relative to Head Movement
  • Technique of Oculovestibular Testing: irrigate each ear with ice water (caloric testing) after the patency of the external auditory canal is confirmed
    • The Head is Elevated to 30 Degrees
    • Each External Auditory Canal is Irrigated (1 Ear at a Time) with Approximately 50 mL of Ice Water
    • Movement of the Eyes Should be Absent During 1 min of Observation
    • Both Sides are Tested, with an Interval of Several Minutes

Absence of Corneal Reflex

  • Technique of Corneal Reflex Testing: touching the cornea with a piece of tissue paper, a cotton swab, or squirts of water
    • No Eyelid Movement Should Be Seen

Absence of Facial Muscle Movement to Noxious Stimuli

  • Technique: deep pressure on the condyles at the level of the temporomandibular joints and deep pressure at the supraorbital ridge
    • No Grimacing or Facial Muscle Movement Should Be Seen

Absence of Pharyngeal and Tracheal Reflexes

  • Technique of Pharyngeal/Gag Reflex Testing: stimulation of the posterior pharynx with a tongue blade or suction device
  • Technique of Tracheal Reflex Testing: most reliably tested by examining the cough response to tracheal suctioning -> the catheter should be inserted into the trachea and advanced to the level of the carina followed by 1 or 2 suctioning passes

Criteria 3: Absence of Breathing with Apnea Test

Considerations

  • There is Insufficient Evidence to Determine the Comparative Safety of Techniques Used for Apnea Testing (Level U Recommendation)

Prerequisites

  • Normothermia: core temperature at least 36.5 C (97 F)
  • Normotension: SBP >90 mm Hg (with or without pressors)
  • Euvolemia: corrected diabetes insipidus (positive fluid balance)
  • Eucapnia: normal PCO2 (arterial PCO2 of 35-45 mm Hg) and no prior evidence of CO2 retention

Procedure

  • Adjust Pressors to Achieve SBP >100 mm Hg
  • Preoxygenate >10 min with 100% O2 to Achieve pO2 >200 mm Hg
  • Adjust Ventilator RR to Achieve Eucapnia (pCO2: 35-45)
  • Reduce PEEP to +5 cm H2O (oxygen desaturation with decreasing PEEP may predict difficulty with performing the apnea test)
  • If SpO2 Remains >95%, Obtain Baseline ABG
  • Disconnect Patient from Ventilator -> Place a Cut-Off Nasal Cannula Catheter (at 6 L/min) Through the ETT and Close to the Level of the Carina
  • Monitor for 10 min -> Look Closely for Respiratory Movements
    • Respiration is Defined as Abdominal or Chest Excursions and May Include a Brief Gasp
    • Abort (and Check ABG) if Systolic Blood Pressure Decreases to <90 mm Hg
    • Abort (and Check ABG) if SpO2 Decreases to <85% for at Least 30 sec
    • If Apnea Test is Aborted for Hypoxemia, May Retry Procedure with T-Piece, CPAP 10 cm H2O, and 100% Oxygen at 12 L/min
  • If No Respiratory Movements are Observed, Repeat ABG at 10 min and Reconnect Patient to Ventilator
  • Interpretation of Apnea Test
    • Positive Apnea Test (i.e., supports the clinical diagnosis of brain death)
      • No Respiratory Movements are Observed
      • Arterial PCO2 >60 mm Hg (or >20 mm Hg Increase in PCO2 Over Baseline Normal Arterial PCO2)
    • Inconclusive Apnea Test
      • No Respiratory Movements are Observed
      • Arterial PCO2 is <60 mm Hg (or <20 mm Hg Increase in PCO2 Over Baseline Normal Arterial PCO2)
  • If Apnea Test is Inconclusive: if the patient is hemodynamically stable during the testing, it may be repeated for a longer period of time (10-15 min) after the patient is again adequately preoxygenated

Ancillary Testing

  • Considerations
    • There is Insufficient Evidence to Determine if Newer Ancillary Tests Accurately Confirm the Cessation of Function of the Entire Brain (Level U Recommendation
  • Rationale
    • Ancillary Tests are Used When There is Uncertainty About Reliability of Components of the Neurologic Exam or When the Apnea Test Cannot Be Performed
      • They are Not Required for the Diagnosis of Brain Death in Adults
      • They Should Not Replace a Neurologic Exam
    • Ancillary Tests May Be Used to Shorten the Duration of the Observation Period (in Some Protocols)
    • Interpretation of Ancillary Tests Requires Expertise: results should be correlated with those from neurologic exam (as false-positives may occur in ancillary testing)
    • Rather Than Ordering Ancillary Testing, Physicians May Decide to Not Proceed with the Declaration of Brain Death if Clinical Findings are Unreliable
  • Types of Ancillary Tests

Documentation

  • Time of Brain Death is Documented in the Medical Record
    • Time of Death is the Time that Arterial pCO2 Reached the Target Value
    • In Patients with an Aborted Apnea Test, the Time of Death is When the Ancillary Test Has Been Officially Interpreted
  • Checklist is Completed, Signed, and Dated
  • Federal/State Laws Require the Physician to Contact an Organ Procurement Organization (Lifeshare) Following the Determination of Brain Death

References

  • Evidence-Based Guideline Update: Determining brain death in adults. Neurology 2010;74:1911–1918 [MEDLINE]