CARLOS EDUARDO REIS

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Brain Death

Definition

Brain death is the cessation and irreversibility of all brain function, including brain stem.

Historical Aspects

In 1564, Versalius a famous anatomist is said to have conducted an autopsy in Madrid on a nobleman who had been his patient. This autopsy was carried out in front of a large crowd of citizens and when the torax of the body was opened the heart was beating. After that Versalius was compelled to leave Spain. This and others episodes problably have made it necessary to have physicians pronunce the death of patients.

The Need of the Determination of Brain Death

Nowadays, modern ressucitative devices and technics can maintain the function of the heart, lungs and visceral organs for a period of time(hours or days) after the life-maintaining centers of the brain stem tissue have stopped function, which results in a medical dilema of a dead brain in a otherwise living body. In the other hand, the development of transplant surgery and the need of viable organs have focused ethical and legal attention on the desirability of agreeing on the medical criteria of brain death.

Criteria For Diagnosis of Brain Death

In 1981, the President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research (USA) developed standards for the determination of brain death which with some modifications are accepted worlwide.

Some steps are imortant to be followed:

• Unresponsiveness
  • The patient is completely unresponsive to external visual, auditory, and tactile stimuli and is incapable of communication in any manner.

• Absence of cerebral and brain stem function
  • Pupillary responses are absent, and eye movements cannot be elicited by the vestibulo-ocular reflex or by irrigating the ears with cold water.
  • The corneal and gag reflex are absent, and there is no facial or tongue movement.
  • The limbs are flaccid, and there is no movement, although primitive withdrawal movements in response to local painful stimuli, mediated at a spinal cord level, can occur.
  • Apnea Test: An apnea test should be performed to ascertain that no respirations occur at a PCO2 level of at least 60 mmHg. The patient oxygenation should be maintained with giving 100% oxygen by a cannula inserted into endotracheal tube as the PCO2 rises. The inability to develop respiration is consistent with medullary failure.
• Nature of coma must be know
  • Known structural disease or irreversible systemic metabolic cause that can explain the clinical picture.
• Some causes must be ruled out
  • Body temperature must be above 32 C to rule out hypothermia
  • No chance of drug intoxication or neuromuscular blockade
  • Patient is not in shock
• Persistence of brain dysfunction
  • Six hours with a confirmatory isoelectric EEG or electrocerebral silence, performed according to the technical standards of the American Electroencephalographic Society
  • Twelve hours without a confirmatory EEG
  • Twenty-four hours for anoxic brain injury without a confirmatory isoeletric EEG

• Confirmatory tests (are not necessary to diagnose brain death)
  • EEG with no physiologic brain activity
  • No cerebral circulation present on angiographic examination( is the principal legal sign in many European countries)
  • Brain stem-evoked responses with absent function in vital brain stem structures

References

Guidelines for the determination of death. Report of the medical consultants on the diagnosis of death to the President's Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research. JAMA, 246, 1981.

Coma. In Aminoff MJ, Greenberg DA, Simon RP(eds): Clinical Neurology, Third edition. Appleton & Lange, 1996.

Brain death. In Wynngaarden JB, Smith LH, Bennet JC(eds): Cecil Textbook of Medicine, 20th edition. W B Saunders Company, 1996.

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