Fifteen years after the AAN published its practice parameter on brain death comes a new report from the AAN Quality Standards Subcommittee in the June 8 issue of Neurology. The new parameter provides an evidence-based review of the recent literature and guidance on how to diagnose brain death accurately.
The 1995 AAN guideline has stood the test of time, but further refinements were needed to assist physicians, said the senior author of the new parameter Eelco Wijdicks, MD, PhD, professor of neurology at the Mayo Clinic in Rochester, MN. Dr. Wijdicks, an authority on critical care neurology and neurologic complications of medical and surgical critical illness, described the panel's findings in a telephone interview with Neurology Today. Dr. Wijdicks has authored many papers on brain death and coma, and is the editor of the classic monograph “Brain Death”; a new edition will be published in 2011.
WHAT CHANGES HAVE BEEN MADE SINCE THE PUBLICATION OF THE 1995 AAN GUIDELINE?
The new AAN guideline is an improvement over the prior 1995 guideline and incorporates recent studies on clinical determination. The diagnosis of brain death can be made only after a comprehensive clinical evaluation and often involves more than 25 separate assessments. The new AAN guideline will help physicians with that. The guideline also includes a critical review of current ancillary tests. We have included a checklist that clinicians can use to help them establish brain death.
WHY WAS THE 1995 GUIDELINE NECESSARY IN THE FIRST PLACE?
The President's Commission on determining brain death published a report in 1981 that recommended a proposed legal definition based on “an acceptable medical standard,” but it did not define that standard. That report led to passage of the 1993 Uniform Determination of Death Act (UDDA). Under the law, brain death can be established only if an individual “has sustained either 1) irreversible cessation of circulatory and respiratory functions, or 2) irreversible cessation of all functions of the entire brain, including the brain stem.” Most state laws have adopted the UDDA, and some have added their own amendments. Nonetheless, institutional policies vary greatly, even within certain states, despite the 1995 practice parameter.
In leading US hospitals, variations have been found in brain death prerequisites, the lowest acceptable core temperature, and the number of required examinations. Also, audits of charts of patients diagnosed with brain death showed common deficiencies in documentation. We hope this new guideline will foster review of hospital policies and appropriate revision. The AAN guideline may also prompt a review of guidelines by countries outside the US.
ARE THERE SUFFICIENT PUBLISHED STUDIES TO DRAW CONCLUSIONS OR RECOMMENDATIONS?
The literature on clinical testing and its pitfalls in brain death determination remains meager. Many studies have concentrated on the validity of new ancillary (confirmatory) tests. We found the literature on these tests unsupportive in many instances. Brain death remains a clinical assessment, and no laboratory test can refute or prove this condition.
WHAT DID THE PANEL FIND ABOUT RECOVERY?
The first question was whether patients who fulfill the clinical criteria of brain death ever recover neurologic function. In adults we found no reports in peer-reviewed medical journals of recovery of brain function after a determination of brain death using the 1995 AAN practice parameter as a yardstick.
WHAT DID THE EVIDENCE SUGGEST ABOUT DECIPHERING ‘MIMICS’ FROM REAL BRAIN DEATH?
With regard to conditions that might be mistaken for brain death, so-called brain death mimics, we identified and reviewed nine Class IV studies. These included fulminant Guillain-Barré syndrome, organophosphate intoxication, high cervical spinal cord injury, lidocaine toxicity, baclofen overdose, and delayed vecuronium clearance. The description of the examinations provided in these studies indicated that a complete brain death examination was not performed in any of the patients.
WAS THERE A RECOMMENDED TIME PERIOD SUGGESTED FOR OBSERVATION BEFORE ESTABLISHING BRAIN DEATH?
Recommendations for the length of observation periods have varied extensively throughout the world and the US, and there are no detailed studies on serial examinations in adult patients who have been declared brain dead. We concluded that there is insufficient evidence to determine the minimally acceptable observation period to ensure that neurologic functions have ceased irreversibly. A reasonable time should be allowed before proceeding on a comprehensive clinical examination, but once established there is no evidence this should be followed by a second examination.
WHAT ABOUT THE COMPLEX MOTOR MOVEMENTS OBSERVED IN SOME PATIENTS?
These are occasionally observed in patients who are brain dead. They continue to create interest and have been better characterized over the years. Additionally, ventilator autocycling may falsely suggest patient-initiated breathing, and this needs to be recognized. Failure to appreciate these signs may unnecessarily delay the determination of brain death.
WAS APNEA TESTING FOUND SAFE?
We looked at the comparative safety of various methods for apnea testing. There have been four published studies on the technique of apnea tests, none of which compared one technique to another. In a recent series, done by experienced physicians, the apneic oxygenation-diffusion test to determine apnea was found to be safe, but there is insufficient evidence to determine the comparative safety of techniques used for apnea testing.
WAS THE EVIDENCE DEFINITIVE TO SUPPORT ANY ANCILLARY TESTING?
We examined the literature on new ancillary techniques to assess brain death and found a number of studies of new tests; however, because of a high risk of bias and inadequate statistical precision, there is insufficient evidence to determine if any new ancillary tests accurately identify brain death. These studies have examined such techniques as bispectral index, somatosensory evoked potentials, CT angiography, and MRI and magnetic resonance angiography (MRA).
Many of the details of a clinical neurological examination to determine brain death cannot be established by evidence-based methods. The examination can be defended both on empirical and neurobiological grounds. The new parameter includes the detailed brain death evaluation protocol, or checklist, that is intended as a tool for clinicians.
WHAT ADDITIONAL RESEARCH IS NEEDED IN THIS AREA?
What we all would need to see is a national or international consensus on brain death. This is something that organizations like the AAN or the World Federation of Neurology could work toward.
CHECKLIST FOR DETERMINATION OF BRAIN DEATH
The following must all be checked off from this checklist to determine brain death:
• Practice Parameter Update: Determining brain death in adults (an evidence-based review). Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology
• Guidelines for the determination of death. Report of the medical consultants on the diagnosis of death to the President's commission for the study of ethical problems in medicine and biochemical and behavioral research. JAMA
• Practice parameters for determining brain death in adults (summary statement). The Quality Standards Subcommittee of the American Academy of Neurology. Neurology