Challenges in diagnosing brain death

Abstract

Recognizing that the nature of the practice of clinical medicine involves areas of uncertainty, death is one diagnosis that doctors must not be allowed to miss. The concept of brain death, which originates from the Harvard Criteria, has allowed development of cadaveric organ transplantation programs. Over the years, the definition of brain death and the criteria for the neurological determination of death (NDD) have been updated. The Universal Determination of Death Act provides a definition of death but leaves the determination process to accepted medical standards (national, provincial, or even local), which can entail a high variability. In April 2003, in response to a perceived need in the general medical and critical care community, the Canadian Council for Donation and Transplantation (CCDT) held a national forum to revisit the process of declaring brain death and to propose updated recommendations. These are the current guidelines used by organ donation and transplantation organizations across Canada. The CCDT recommendations have the virtue of having brought uniformity to the process of NDD. Still, several of its recommendations are somewhat vague and open the door to clinical judgement and interpretation, a situation that is highly undesirable when facing potential organ donation. In this issue of the Journal, Roberts et al. report two cases where experienced physicians faced challenges in the clinical NDD. In both cases, it appears that several of the criteria for NDD were either misinterpreted or overlooked. Although they are usually not reported in the medical literature, similar incidents occur more than occasionally. This is somewhat disturbing. The existence of cadaveric organ donation and transplantation programs relies on the Dead Donor Rule that dictates that a patient’s death must be confirmed before any attempt at organ preservation or harvesting for the purpose of transplantation. Before a patient is dead, ethical principles mandate that medical care must be directed toward the sole and only benefit of this patient, even in a situation that could be perceived as ‘‘almost dead’’. Brain death is a complex concept that is very difficult for the general public to understand. Patients and their families place their trust in their treating physician. In organ donation, they trust that physicians will strictly abide by the Dead Donor Rule. Therefore, the process for NDD must be watertight. The CCDT recommendations define neurological death as the irreversible loss of all brain stem functions. The minimum criteria for clinical NDD are: 1) an established etiology capable of causing neurological death in the absence of reversible conditions capable of mimicking neurological death; 2) a deep unresponsive coma with bilateral absence of motor responses (excluding spinal reflexes); 3) absent brain stem reflexes, as defined by absent gag and cough reflexes, and the bilateral absence of corneal responses, pupillary responses to light (with pupils at mid-size or greater), and vestibulo-ocular responses; 4) absent respiratory effort based on the apnea test; and 5) absence of any confounding factors. Minimum means that at least all of these criteria must be met for clinical NDD. Confusion may arise regarding the first criterion. An etiology ‘‘capable of causing’’ neurological death is not the same as ‘‘sufficient to account for’’ the absence of clinical signs of brain function. For example, brain trauma is an M. R. Lessard, MD (&) J. G. Brochu, MD Department of Anesthesia and Critical Care, Centre hospitalier affilie universitaire de Quebec, Universite Laval, 1401, 18e rue, Quebec, QC G1J 1Z4, Canada e-mail: martin.lessard@anr.ulaval.ca