This definition of death is a medical definition which may differ from religious, ethical, philosophical or cultural definitions of death.

Modern anesthesia techniques can render a person without brain activities (flat EEG), totally paralyzed (with neuromuscular blocking agents), and with no cardiac (heart) activity (with cardioplegic solutions), such as is the case when a patient is undergoing extracorporeal circulation during cardiac anesthesia. In this case, despite that the patient physically resembles that of a dead person, the condition is reversible.

Therefore, to declare brain death, one must follow a protocol of clinical testing as well as preclude anesthetic causes and hypothermia.

Traditionally, a physical examination of the patient confirming the absence of clinical signs (pulses, respiration, movements, pupillary size and reactions to light) is sufficient prior to a declaration of death.

Three major considerations lead to a more elaborate set of criteria for the clinical definition of death:

1. Complete absence of clinical signs on a patient can be maintained with modern anesthetic techniques.
2. Some patients found with no pulse or respiration due to exposure to hypothermia can be later resuscitated.
3. A patient without integrated brain function may be mechanically ventilated, have a strong pulse and good circulation, as is often found in patients of trauma, or patients with intracerebral hemorrhage, despite the fact that there is no expectation of the patient ever regaining brain function.