Brain Death

Brain death is the complete and irreversible neurological cessation of brain activity. It is often characterized by a patient in a coma and who does not have brainstem reflexes. Brain death often occurs by:

• Increase in intracranial pressure leading to decreased cereral perfusion and cytotoxic brain injury.
  • herniation of the brain tissue can also occur leading to sudden death.
• Direct cytotoxic cellular injury to nervous tissue

Patient's often do not protect their airway, and if not intervened upon, the patient will become apneic and death will occur secondary to respiratory failure and ultimately cardiorespiratory collapse.

The clinical criteria for diagnosis brain death are:

• clinical and radiographic evidence of a neurologic catastrophe
• hemodynamic stability (systolic blood pressure >100 mm Hg)
• body temperature > 36 C (96.8 F)
• lack of another cause to explain patient's neurologic stats (e.g. metabolic or electrolyte abnormalities, intoxication, infection/sepsis, etc.)

Exam findings suggesting irreversable brain injury include:

• lack of brainstem reflexes
  • oculocephalic, pupilary, caloric testing
  • gag reflex
• extensor posturing

Respiratory drive is a higher level function, often controlled by the brainstem. A positive apnea test can confirm brain death:

• No respiratory response for 8-10 minutes while off mechanical ventilation
• PaCO2 > 60 mm Hg (or >20 mmHg from baseline)
• arterial pH <7.28