Death and Post-Mortem Changes

Nature and Definition of Death

• Death is the irreversible cessation of life in a previously viable organism.
• A dead person is an individual who has sustained irreversible cessation of:
  • Circulatory and respiratory functions, or
  • All functions of the entire brain (cortex and brain-stem)

Phases of Death

• Somatic death: a person irreversibly loses their personality, becoming unconscious, unable to communicate with their environment, and unable to receive sensory stimuli or initiate voluntary movement, but reflexes and circulatory/respiratory functions may persist.
• Cellular or molecular death: cessation of respiration and metabolism of body tissues and their constituent cells, followed by autolysis and decay.
• Brain death:
  • Cortical death: irreversible coma and failure of spontaneous breathing, leading to hypoxic cardiac arrest and cellular death.
  • Brainstem death: irreversible damage to the brainstem, marking the end of somatic life, but not yet cellular death.

Diagnosis of Somatic or Clinical Death

• Cessation of circulation:
  • Absent pulsations in big arteries (carotid or femoral).
  • Undetected blood pressure.
  • Absent heart beats.
  • Flat ECG on all leads.
• Cessation of respiration:
  • Apnea as checked by careful auscultation.
  • Severe hypoxia and hypercapnea inconsistent with life in Arterial Blood Gas Analysis.

Diagnosis of Brain Stem Death

• Clinical tests:
  • Absent pupilary response to light.
  • Absent corneal reflex.
  • Oculocephalic reflex (doll's eye) is absent.
  • Vestibulo-ocular reflex is negative when icewater is introduced into the ears.
  • Pharyngeal and tracheal reflexes are absent (gagging and coughing).
  • Testing for apnea (failure of spontaneous respiration) if all previous clinical tests are lost.
• Exclusions:
  • All reversible causes.
  • Primary hypothermia.