Must the entire brain be dead to diagnose brain death?

Abstract

To the Editor: The June 2006 issue of the Canadian Journal of Anesthesia contains four excellent articles dealing with brain death.1–4 In 1981 the President’s Commission for the Study of Ethical Problems in Medicare and Biomedical and Behavioral Research published a landmark report intended to establish a common ground for American law related to brain death.5 The commission defined brain death as the “irreversible cessation of all functions of the entire brain, including the brain stem”. Since that time, this seminal report has been used as the basis for much of the discourse on brain death, especially in the United States. Similarly, the World Medical Association has written that “it is essential to determine the irreversible cessation of all functions of the entire brain, including the brain stem”.6 The purpose of this letter is to point out that, while these bodies have defined brain death in terms of “irreversible cessation of all functions of the entire brain,” in the years since this definition has been widely adopted it has become very clear that many (perhaps most) patients diagnosed with brain death do not actually meet this requirement. In particular, many patients diagnosed with brain death still synthesize arginine vasopressin (which regulates serum osmolality), implying the presence of residual function in the hypothalmus. Indeed, evaluation of hypothalamic function is not part of any brain death protocol with which I am familiar. It may be time for the World Medical Association and other authorities to reformulate the definition of brain death to reflect current clinical realities.