Determining Brain Death: Updated Guidelines and Ancillary Testing

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Author: Sean Weaver, DO MPH
Emergency Medicine Resident
University of Nevada, School of Medicine

The following blog post appeared initially at www.lasvegasemr.com/foam-blog and is reproduced with the permission of the author.



Introduction
Last week we reviewed the original 1995 criteria for declaring brain death. This week we are reviewing updated standards as outlined by the American Academy of Neurologists (AAN). Also, this post reviews some of the ancillary tests that EM physicians may be asked to order in order to evaluate for possible brain death.

Updated Evidence-Based Guideline: Determining Brain Death in Adults[1]
In 2010 the American Academy of Neurology published an evidence-based review of the original 1995 guidelines on determining brain death. 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. This applies only to adult patients. 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.
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 up to 32 hours after determination of brain death. Additionally, ventilators can sometimes misinterpret ET tube pressure or changes in transpleural pressure due to heartbeats and inappropriately trigger a ventilation.
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.

Summary
Typically a single neurologic exam is sufficient to pronounce brain death. There is state-to-state variation, so it is important that you become familiar with your state laws regarding this issue.

The 2010 evidence-based guidelines support the importance of neurologic assessment in patients suspected of brain death. These recommendations do not differ significantly from the original 1995 recommendations with the exception of the following:

• Preoxygenation for ≥ 10 minutes with 100% O2 to a PaO2 of  >200mmHg is required
• Reduce PEEP to 5cmH2O 
• Abort the apnea test if pulse ox is <85% for >30 seconds. Retry procedure with T-piece, CPAP at 10cmH20 and 100% O2 12 L/min.
• If the test is inconclusive, but the patient is hemodynamically stable, the test can be repeated for 10-15 min 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.[1,2]

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.[2] Insonation must be done bilaterally, anteriorly and posteriorly.

EEG and nuclear scan cerebral scintigraphy as also options for evaluating the brain dead patient. They were not covered in this review due to the decreased likelihood of them being ordered from the ED.

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.[2]

References

1. 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.
2. Spinello IM. Brain Death Determination. J Intensive Care Med. 2013.