Determining Brain Death in the Emergency Department

By Sean Weaver, DO MPH
Emergency Medicine Resident

Brain death accounts for 1-2% of all deaths in the United States (1).  Depending on where you practice this number may seem too high or too low.  Regardless, patients may present to your emergency department clinically brain dead.  While neurologists, neurosurgeons and intensivists may have more experience in determining brain death, all physicians have the legal authority to determine brain death (2).  As emergency medicine physicians we need to know how to properly evaluate these patients, assess their level of brain function, guide their disposition and prepare the family or loved ones for the eventual outcome.

Legal Definition (3)
The legal definition of death was established in 1980 under the Uniform Determination of Death Act (UDDA) by the Presidentially appointed National Conference of Commissioners on Uniform State Law.  This group met for 7 days in Kauai, Hawaii and came up with the follow definition of brain death:

“An individual who has sustained either:

1. Irreversible cessation of circulatory and respiratory function.
   
2. Irreversible cessation of all functions of the entire brain, including the brain stem, is dead.
   

A determination of death must be made with acceptable medical standards.” (3)

While this law adopted a legal term of death there was, appropriately so, no clarification regarding “acceptable medical standards”.

Determining Acceptable Medical Standards for Declaring Brain Death (4)
In 1995 the American Academy of Neurologists published practice parameters regarding declaration of brain death.  These guidelines are worth knowing and have been upheld in subsequent studies.  Here is a summary of their recommendations:

Brain Death Criteria
Definition: absence of clinical brain function when the proximate cause is known and demonstrably irreversible.

• Clinical or neuroimaging evidence of acute CNS catastrophe
  
• No confounding medical condition
  
• No drug intoxication
  
• Core temp > 90 deg F
  

Three Cardinal Signs of Brain Death: coma, absence of brain stem reflexes and apnea
1.  Coma or unresponsiveness: no cerebral motor response to pain
2.  No brain stem reflexes

• No occulocephalic testing- dolls eye
  
• No deviation of eyes to 50 mL of cold water irrigation in each ear
  

3.  Lack of facial sensation and facial motor response

• No corneal reflex to touch
  
• No jaw reflex
  
• No grimace to deep pressure of the supraorbital ridge or TMJ
  

4.  Pharyngeal and tracheal reflexes

• No response after stimulation of posterior pharynx with a tongue blade
  
• No cough to bronchial suctioning
  

5.  Apnea testing: prerequisites

• Core temp ≥ 36.5 deg C or 97 deg F
  
• SBP ≥ 90 mmHg
  
• Euvolemic
  
• Normal PCO2: option of arterial PCO2 >40 mmHg
  
• Normal PO2: option of preoxygenation to obtain arterial PO2 ≥ 200 mmHg
  
  

6.  Apnea Testing: process

• Deliver 100% O2 either directly into the trachea or by placing a cannula at the level of the carina
  
• Connect a pulse ox (if not done already) and disconnect the ventilator.
  
• Get an ABG 8 minutes after the ventilator has been disconnected. Goal is to obtain PaO2, PaCO2 and pH.
  
• Reconnect the ventilator.
  
• If respiratory movements are absent and PaCO2 is  ≥ 60 mmHg the apnea test is positive
  
• If respiratory movements are observed or PaCO2 is < 60 mmHg , the apnea test result is negative.  Repeat the test if appropriate.
  
• If during testing the SBP is ≤ 90 mmHg or pulse ox indicates significant O2 desaturation or if cardiac arrhythmias develop immediately obtain an ABG.  If PaCO2 is ≥ 60 mmHg or PaCO2 is increased ≥ 20 mmHg over baseline the apnea test is positive. If PaCO2 is < 60 mmHg or PaCO2 is < 20 mmHg over baseline normal PaCO2 the test is indeterminate.

7.  Pitfalls

• Severe facial trauma
  
• Preexisting pupillary abnormalities
  
• Toxic levels of sedative drugs, aminoglycosides, TCA’s, etc.
  
• Sleep apnea or severe pulmonary disease resulting in chronic CO2 retention.
  

Observations That Do Not Exclude Brain Death

• Spontaneous movement of limbs
  
• Respiratory like movements
  
• Sweating, blushing, tachycardia
  
• Normal blood pressure or sudden increases in blood pressure
  
• DTR’s
  
• Babinski reflex
  

2010 Evidence-Based Guideline Update: Determining brain death in Adults (2)
In 2010 the American Academy of Neurology published an evidence-based review of the 1995 guidelines.  They reviewed the existing literature and sought to answer five questions listed below. This is a brief summary of their conclusions.

1.  Are there patients who fulfill the clinical criteria of brain death who recover brain function?

• No.  At the time of publication there were not any published cases in which the patient recovered neurologic function after being declared brain dead using the AAN guidelines.  This only applies to adult patients.  
  

2. What is an adequate observation period to ensure that cessation of neurologic function is permanent?

• There is insufficient evidence to make a recommendation.
  
  

3.   Are complex motor movements that falsely suggest retained brain function sometimes observed in brain death?

• Multiple studies have documented spontaneous and reflex movements in patients meeting criteria for brain death, sometimes even up to 32 hours after determination of brain death.  Additionally, ventilators can sometimes misinterpret ET tube pressure or changes in transpleural pressure due to heartbeat that inappropriately trigger the ventilator.
  
  

4.  What is the comparative safety of techniques for determining apnea?

• Comparative studies evaluating the safety of apneic oxygenation diffusion have not been performed.  However, there is no evidence to suggest that apneic oxygenation diffusion is unsafe.
  

5.   Are there new ancillary tests that accurately identify patients with brain death?

• At the time of the review, available studies showed a “high risk of bias and inadequate statistical precision.”  Therefore, the authors concluded there was insufficient evidence to answer the question.
  

Typically, only one neurologic exam is sufficient to pronounce brain death.  There is some state to state variation so it is important that you become familiar with state laws guiding this issue.

The 2010 evidence based guidelines provide an outline of the suggested neurologic assessment in someone suspected of brain death.  These recommendations do not differ significantly from the 1995 recommendations with the exception of the following:

• Preoxygenation for ≥ 10 minutes with 100% O2 to a PaO2 of > 200 mmHg is required
  
• Reduce PEEP to 5 cm H2O
  
• Abort the apnea test if pulse ox is < 85% for > 30 seconds.  Retry procedure with T-piece, CPAP at 10 cm H20 and 100% O2 12 L/min.
  
• If the test is inconclusive but the patient is hemodynamically stable it can be repeated for 10-15 minutes after the patient is adequately preoxygenated.
  
  

Ancillary Testing
The following contains short description of ancillary tests that an emergency medicine physician may be asked to order in potentially brain dead patients.  This is not a comprehensive list (2, 1).

• Cerebral angiography: contrast is used to evaluate anterior and posterior cerebral circulation. A positive test includes a lack of intracerebral filling at the level of entry of the carotid or vertebral artery to the skull.  Historically, 4-vessel cerebral angiography is the “gold standard” but CTA is emerging as a viable alternative. 
  

• Transcranial Doppler Ultrasound: This test is useful only if a reliable signal is found.  The test examines abnormalities of flow including backflow or reverberation abnormalities in flow due to the increased resistance from a brain-dead brain (1).  Insonation must be done bilaterally, anteriorly and posteriorly.
  

• EEG and nuclear scan cerebral scintigraphy as also options for evaluating a potentially brain dead patient.  They were not covered in this review due to their lack of utility in emergency medicine management.
  

Ancillary tests, while helpful do not replace a neurologic exam.  Clinicians ordering the ancillary tests need to be aware of the false positive rates and understand that in the presence of an unclear clinical neurologic exam ancillary testing may not be appropriate (1).

References

1. Spinello IM. Brain Death Determination. J Intensive Care Med. 2013.
   
   
2. Wijdicks EF, Varelas PN, Gronseth GS, Greer DM. Evidence-based guideline update: determining brain death in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2010;74(23):1911-8.
   
   
3. Available at: http://pntb.org/wordpress/wp-content/uploads/Uniform-Determination-of-Death-1980_5c. Accessed June 27, 2014.
   
   
4. Practice parameters for determining brain death in adults (summary statement). The Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 1995;45