At a time when "donation after cardiac death" (DCD) has become an important approach to increasing the number of transplant organ donors, a provocative new study shows changes in brain activity occurring in response to withdrawal of life support, reports the May issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).
Some transplanted organs come from living donors, while others come from cadaveric donors shortly after brain death. Society has become comfortable procuring organs from donors following brain death, because the person is believed to no longer "exist" when the brain stops functioning.
Donation after cardiac death is a recently revived category of organ donation. These are organ donations from patients with unrecoverable illness, almost always in conjunction with severe brain injury. The key distinction is that these patients are not brain dead. However, because of the terminal nature of their illness, the decision has already been made to discontinue life support. Once this decision is made, the possibility of donation of the organs after death is discussed with the patient's family. If the family consents, the organs are procured only after the patient has been removed from life support and declared dead.
Changes in Brain Activity after Withdrawal of Life Support—but What Do They Mean?
In the new study, researchers at Duke University looked at the processed electroencephalograms (EEGs) at the time that life support was withdrawn. In three patients, they found changes in the processed EEG, reflecting changes in brain electrical activity, immediately in response to withdrawal of life support. The researchers note that the processed EEGs "showed considerable changes traditionally associated with lighter planes of anesthesia immediately after withdrawal of care."
This does not mean that the patient was trying to wake up, the researchers point out. Rather, they contend that there's not enough evidence to interpret the EEG changes in the context of the physiologic changes leading to death. Meanwhile, they suggest it might be sensible to administer some anesthesia to such patients, in view of the fact that they are not brain dead.
An accompanying editorial by Dr. Marie Csete, a transplant anesthesiologist at Emory University, describes the ethical dilemmas faced in donation after cardiac death, including "the ethical imperative to provide the best possible care to donors at the end of life." Clearly the brains of the three patients were generating changing electrical signals. But was the brain processing any information? Even in patients with severe brain injury, "electrical activity in the brain during the dying process is to be expected," Dr. Csete points out. Along with the study authors, she concludes that "more knowledge about the dying process can only help us improve the necessary and important care of DCD donors."
The authors make it clear that the surgery for organ procurement did not begin until about five minutes after circulation had stopped. In each case, there was no EEG activity at the time surgery began, or any evidence that the brain responded to surgery. Instead, the likely explanation is that during the dying process blood flow is temporarily redistributed to areas of the brain that generate the EEG signals.
Dr. Steven L. Shafer, Editor-in-Chief of Anesthesia & Analgesia and Professor of Anesthesiology at Columbia University, takes a pragmatic view. "We don't know what the EEG changes mean, but they probably do not reflect pain or any other conscious process. When my time comes, I want my organs made available to those who might need them, regardless of what happens to my EEG in the final minutes of my life."
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