Determining Brain Death

Neurocritical Care
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Sep 7, 2021
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  • Permanent, irreversible termination of cerebral and brainstem functions including the ability to regulate respiratory activities.

Reason for Diagnosing Brain death

  • Emotional closure for family
  • Organ Donation


Causes of Brain Death
Devastating brain injury due to
  • Trauma
  • Subarachnoid hemorrhage
  • Intracerebral hemorrhage
  • Hypoxic-ischemic encephalopathy
  • Ischemic stroke
  • Any condition causing permanent gross brain injury

Brain death diagnosis criteria by American Academy of Neurology

Of Note: Most states and hospitals have their own criteria based on the following. Please make sure to use your local criteria if that is available.


  • Irreversible coma with a known cause
  • Neuroimaging showing coma
  • Evidence (clinical or neuroimaging) of acute central nervous system (CNS) injury
  • Elimination of other potentially confounding medical conditions like severe electrolyte, acid-base, endocrine, or circulatory disturbances e.g, shock)
  • Core temperature >36°C (97°F)
  • Exclusion of possible drug intoxication or poisoning, which includes any sedative drug administered in hospital
  • Systolic blood pressure >100 mmHg
  • No spontaneous respirations

Examination findings

  • Absence of motor response originating from brain which includes response to pain stimulus above neck and other movements arising from brain eg, decerebrate or decorticate posturing, seizures
  • Absence of pupillary light reflex
  • Absence of corneal reflexes: Swing light test shows no response
  • Absence of oculocephalic (doll's eyes) and oculovestibular reflexes (caloric responses)
  • Absence of jaw jerk
  • Absence of gag reflex
  • No facial movement to noxious stimuli at supraorbital nerve, temporomandibular joint
  • Absence of motor response to noxious stimuli in all four limbs (spinally mediated reflexes are permissible)
  • Absence of cough with tracheal suctioning
  • Absence of sucking or rooting reflexes (in neonates)

Apnea test

  • Ventilator adjusted to provide PaCO2 35–45 mm Hg (normocarbia).
  • Patient
    • hemodynamically stable
    • preoxygenated with 100% FiO2 for >10 minutes to PaO2>200 mm Hg
    • well-oxygenated with a positive end-expiratory pressure (PEEP) of 5 cm of water.
  • Provide oxygen via a suction catheter to the level of the carina at 6 L/min or attach T-piece with continuous positive airway pressure (CPAP) at 10 cm H2O.
  • Disconnect ventilator.
  • Spontaneous respirations absent
  • Arterial blood gas drawn at 8–10 minutes, patient reconnected to ventilator.
  • PCO2 ≥60 mm Hg, or 20 mm Hg rise from normal baseline value.
  • Positive apnea test results show no respiratory response to a PaCO2 >60 mmHg or 20 mmHg greater than baseline values and arterial pH of <7.28.

Ancillary/Confirmatory tests

  • Not compulsory but preferred in patients where clinical testing can not be performed reliably or at all.
  • Any of the mentioned tests may produce similar results in patients with severe brain damage but who have not yet fulfilled the clinical criteria of brain death.
  • Tests are listed in order of their sensitivity

Conventional angiography

  • No intracerebral filling at the level of the carotid bifurcation or circle of Willis.


  • At least 30 minutes of recording showing no electrical activity
  • Minimal technical criteria for EEG recording in suspected brain death as adopted by the American Electroencephalographic Society.

Transcranial Doppler ultrasonography

  • Initial absence of Doppler signals cannot be interpreted as consistent with brain death as a small percentage of patients may not have temporal insonation windows due to skull thickness.
  • Markedly increased intracranial pressure indicated by small systolic peaks in early systole without diastolic or reverberating flow that indicate notably high vascular resistance

Technetium-99m hexamethylpropyleneamineoxime brain scan

  • “Hollow skull phenomenon” i.e, no uptake of isotope in brain parenchyma.

Somatosensory evoked potentials

  • Bilateral absence of N20-P22 response with median nerve stimulation

Movements and clinical observations compatible with brain death diagnosis

  • Occasional manifestations.
  • Should not be misinterpreted as evidence for brainstem function.
  • Movements stemming from spinal cord or peripheral nerves may occur in brain dead patients
  • Triggers can be tactile stimuli or occur spontaneously
  • Examples include:
    • Faint, semi-rhythmic movements of muscles innervated by facial nerve ( due to denervated facial nerve).
    • Flexor movements of fingers.
    • Tonic neck reflexes.
    • Lazarus sign: Neck flexion may be accompanied by complex extremity and truncal movements, mimicking sitting up type movements and neck-abdominal muscle contraction or head turning to one side.
    • Foot stimulation can induce triple flexion response with flexion at the hip, knee, and ankle .
    • Asymmetric opisthotonic posturing of the trunk.
    • Preservation of superficial and deep abdominal reflexes.
    • Positive Babinski sign.
    • Undulating toe sign:
      • Passive displacement of foot causing alternating flexion-extension of toes
    • Upper limb pronation extension reflex.
    • Widespread trunk and extremities fasciculations.
  • Respiratory-like movements without significant tidal volumes
  • Blushing, sweating
  • Tachycardia
  • Normal blood pressure without pharmacologic support or sudden increases in blood pressure
  • No diabetes insipidus

Confounders of brain death diagnosis

  • Conditions that may interfere with clinical diagnosis of brain death.
  • Clinical assessment is not enough in such cases to definitively diagnose brain death. Confirmatory tests are recommended
Box 1: Confounders in Brain Death Diagnosis
  • Severe facial trauma
  • Preexisting pupillary abnormalities
  • Toxic levels of:
    • Sedative drugs
    • Aminoglycosides
    • Tricyclic antidepressants
    • Anticholinergics
    • Antiepileptic drugs
    • Chemotherapeutic agents
    • Neuromuscular blocking agents
  • Chronic CO2 retention due to severe pulmonary disease or sleep apnea

Standard medical record documentation

  • Etiology and irreversibility of condition
  • Absent brainstem reflexes
  • Absent motor response to pain
  • Absent respiration with PCO, 260 mm Hg
  • Confirmatory test justification and result, if used
  • Repeat neurologic examination.

Box 2: Brain Death Determination Note (Example)

Brain Death Determination Note (*** designated input required)
Patient Identification Information:
Insert NAME, Medical Record number, Age, Date of Birth
Etiology of Coma:
Insert cause of Irreversible Cause
Prerequisite Conditions:
State (***) No below or explain if there are any prerequisite not met or expected
Major Electrolyte Abnormality: ***
Major EndocrineAbnormality: ***
Major Acid Base Abnormality: ***
Toxins or Drugs: ***
Hypothermia (Temp < 36): ***
SBP > 100 mm Hg: ***
Sedative Medications: ***
Other Confounding Variables: ***
Intubated and not sedated; does not follow commands. No vertical gaze or blinking to command. Pupils fixed bilaterally size (INSERT Size). No gaze deviation or dysconjugate gaze. Corneal Reflex; Absent. Facial Grimace, Absent. Gag/Cough: absent
VOR: (Cold Calorics) no response of eye movements
Motor Exam: RUE - No movement to central and peripheral noxious stimulation LUE - No movement to central and peripheral noxious stimulation RLE - No movement to central and peripheral noxious stimulation LLE - No movement to central and peripheral noxious stimulation
Respiratory Drive: NOT overbreathing the ventilator Ventilator: Turned to pressure support without autoflow and elevated flow trigger. No respirations or diaphragmatic movement seen
Apnea Test:
Insert pre and post ABG finding here
No respiratory effort noted during the apnea testing
Confirmatory Test: A confirmatory test is not needed Or a confirmatory test was done and consistent with brain death diagnosis
Autopsy: Discussed with next of kin and family but they declined.
Medical Examiner: Indicate here if a case for medical examiner to review
Time of Death 1/1/2024 at 0001. Recorded and Certified. Next of Kin notified

Further Reading

  • Young, GB. (2021). Diagnosis of brain death. In Wilterdink, JL, UpToDate. Retrieved September, 06, 2021, from
  • Wijdicks EF, Varelas PN, Gronseth GS, Greer DM; American Academy of Neurology. Evidence-based guideline update: determining brain death in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2010 Jun 8;74(23):1911-8. doi: 10.1212/WNL.0b013e3181e242a8. PMID: 20530327.


  • Practice parameters for determining brain death in adults (summary statement). The Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 1995 May;45(5):1012-4. doi: 10.1212/wnl.45.5.1012. PMID: 7746374.
  • Goila AK, Pawar M. The diagnosis of brain death. Indian J Crit Care Med. 2009 Jan-Mar;13(1):7-11. doi: 10.4103/0972-5229.53108. PMID: 19881172; PMCID: PMC2772257.
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