Science Museum. Brought to Life: Exploring the History of Medicine.

How do we know if someone is really dead? Defining the moment of death can be surprisingly difficult.

llustration from a book warning of the dangers of pronouncing death prematurely, 1746.

Credits:Wellcome Library, London

Looking for signs of life

Medical approaches to death were in keeping with popular ones until recently. Breathing was checked for on a body, perhaps using a mirror. A pulse was sought. Eyes were examined to see if the pupils had become fixed and unresponsive.

These checks were not foolproof. There are many folk stories about the dead rising from their funeral shrouds. They also tell of coffin lids marked by the desperate clawing of their revived occupants. The ‘dead’ could return. Body warming, electrical stimulation and mouth-to-mouth resuscitation were occasionally successful. Other methods, including a tobacco enema for reviving the drowned, were less so.

Confirming death with technology

Despite such anomalies, a medical consensus developed from the 1700s. It said death was the complete failure of the heart. Lungs stopped taking in air, the heart stopped beating and the circulation of vital fluids halted. The invention of the stethoscope in 1816 and later the ECG machine accurately tested for these key signs of life.

Throughout the 20th century, developing technologies as well as refined and widely practised life-saving techniques cast doubts on this situation. An individual might be revived and kept alive from a state previously defined as death. Cardio-pulmonary resuscitation (CPR) and defibrillation could sustain circulation and restart the heart. Life support machinery could artificially maintain a patient who would otherwise die. Cardiac pacemakers and organ transplants further blurred the picture. The connection between life, death and the cardio-respiratory system became less clear cut. Death was re-evaluated.

Patient on life support machinery which has taken over the functioning of heart and lungs, 2002.

Credits:Wellcome Photo Library, London

Redefining the nature of death

A committee at Harvard Medical School redefined death according to brain activity. Subsequent decades established thorough methods for diagnosing brain death. However, death only became more complex and controversial.

Current neurological criteria say death is preceded by irreversible damage to the brainstem. Without it, unassisted breathing is impossible and organs malfunction. This is known as ‘whole-brain death’. ’Higher-brain death’ can occur should the brainstem survive but the cerebellum be damaged. The cerebellum is responsible for reasoning, cognition and personality. The ambiguity of higher-brain death presents dilemmas.

Patients damaged in this way can enter a persistent vegetative state (PVS), a state of medical and often legal limbo. Higher brain functions cease, but an active brainstem and life support equipment oversee respiration, digestion and circulation. Given food and water, an individual can remain in this state for long periods; the longest on record is 37 years. Is this living? Some argue instead of viewing death in purely biological terms, the loss of that very essence defines us as individuals.

The ambiguous line between life and death

Cultural and religious beliefs can present further complications. Consider two patients with severe head injuries. One has undergone whole-brain death. His doctor declares him dead, but his beating heart indicates to his grieving Catholic parents he is alive. The second patient is in a PVS. Her body could function for years and legally she is alive. However, to her loved ones, the woman they knew is dead. They may have to enter a legal battle to remove her feeding tube.

Defining your own death

Interpreting whole-brain death is controversial despite legal approval. Patients declared brain dead can still exhibit neural activity if not every cell has ceased to function. This fuzziness results in different interpretations of brain death. Such interpretations are important for organ donation, where organs are ideally harvested minutes after death is declared.

These ethical and biological uncertainties have prompted calls for people to be able to pre-define their death. They might choose either whole- or higher-brain death. Or they may opt for when their unaided heart simply stops beating.

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