Brain death still a vexing issue
The death of comedy legend Joan Rivers has once again raised the difficult issue of brain death — a concept that entered clinical practice more than 50 years ago, when mechanical ventilators made it possible to artificially sustain patients after brain function ceased. Today, questions and misunderstandings about the determination, and even the definition, of brain death continue to plague both the public and providers.
Accepted medical standards for the declaration of brain death in the United States are based on the 1981 Uniform Determination of Death Act (UDDA) which defines death as the irreversible loss of all brain functioning, including the brain stem. In 1987, the American Academy of Pediatrics issued guidelines detailing the clinical findings needed to make a determination of brain death in infants and children. An updated version appeared in the journal Pediatrics in 2011.
In 1995, the American Academy of Neurology (AAN) published similar guidelines for determination of brain death in adults. The recommendations were updated 15 years later, (Neurology, 2010), providing more information to guide clinical decision-making. The update also attempted to answer five questions commonly related to brain death determination, including whether patients who fulfill the clinical criteria for brain death can potentially recover brain function. According to the report, no patients have recovered after a brain death declaration using AAN guidelines.
Determining brain death
All U.S. brain death guidelines are based on the principle that death can be diagnosed by neurological criteria. To verify the loss of all brain functions, physicians must determine:
- The presence of unresponsive coma
- The absence of brainstem reflexes
- The absence of respiratory drive after a CO2 challenge
To ensure that the loss of brain function is irreversible, physicians must determine the cause of the coma, exclude conditions that might mimic it and observe patients for a period of time to ensure that recovery isn't possible.
Establishing the cause and irreversibility of coma is crucial, says David S. Morris, M.D., a trauma surgeon intensivist and member of the Organ, Tissue & Eye Donation Committee at Mayo Clinic's campus in Minnesota.
"There can't be any diagnostic uncertainty. Hypotension, hypothermia and metabolic disturbances — particularly severe electrolyte, acid-base or endocrine disturbances — must be corrected before going ahead with the neurological evaluation," he explains. "We also need to rule out factors such as locked-in syndrome, epilepsy, alcohol or drug intoxication, and the presence of neuromuscular blocking agents, antidepressants, barbiturates and other confounding drugs."
After the clinical evaluation, patients undergo an extensive neurological exam to evaluate brain stem and respiratory function. Eelco F. Wijdicks, M.D., Ph.D., lead author of the AAN guidelines and a noted authority on brain death at Mayo Clinic, says, "The brain death diagnosis can be made only after a comprehensive evaluation and often involves more than 25 separate assessments." (A link to a list of the 25 assessments used at Mayo Clinic and many other centers appears at the end of this article).
In most states, including Minnesota, only one neurological exam is needed to pronounce brain death in adults. Two examinations, separated by an observation period, are required for infants and children.
Most states also allow all clinicians to determine brain death, although many hospitals require a neurologist, neurosurgeon or neurocritical care specialist to make the determination because of their clinical expertise. "Trauma patients often have substance intoxication or a history of substance abuse, so we involve neurocritical care specialists because drugs and other medical conditions can confound the diagnosis," Dr. Morris explains. "And neurosurgeons are often involved due to the presence of a head injury. There is a lot of discussion between neurosurgery and neurocritical care — we feel this is important."
The challenges surrounding brain death are intensified in smaller hospitals with fewer resources. In such cases, Dr. Morris says, a neurologist in the community may feel comfortable making the declaration. Mayo Clinic specialists also are available for consultations.
"Our neurocritical care specialists are very involved in the community and experienced in the rapid treatment and transfer of stroke patients and are willing to help," he says. "The trauma surgeon on call can also answer questions. I think the most important thing for providers in smaller hospitals is to understand the general guidelines and how brain death is determined and not to be afraid to call for an expert opinion and consultation, if only by phone. That can be very helpful for people who don't do this every day."
For providers in any institution, the challenge of determining brain death is often matched by the challenge of helping families understand it. "Traditionally, a patient was considered alive until the heart stopped, but with the advent of modern life support techniques, the heart can continue to beat even when there is irreversible cessation of brain function. It can be very difficult for families to accept that a ventilator is making the chest rise and fall, Dr. Morris says. "Part of our job is to help families understand what brain death means."
Even more challenging are patients with nonsurvivable head injuries who, for some reason, don't meet all the criteria for brain death. "These are very difficult situations," Dr. Morris says, "but in most cases, once the family realizes there is no chance for a meaningful recovery, they will decide to switch from the ventilator to comfort care. Fortunately, more people are starting to have conversations about end-of-life care. Sometimes it takes a high-profile case to prompt those discussions."
For more information
Nakagawa TA, et al. Guidelines for the determination of brain death in infants and children: An update of the 1987 task force recommendations. Pediatrics.
Wijdicks EFM, et al. Evidence-based guideline update: Determining brain death in adults. Neurology. 2010;74:1911.
The diagnosis of brain death (25 assessments to declare a patient brain dead). Mayo Clinic. 2011.