APPENDIX C: Clinical criteria for neurologic determination of death
Clinical criteria for neurologic determination of death
• Presence of Central Nervous System (CNS) catastrophe that is compatible with brain death.
• Absence of complications that may confound assessment of brain death including hypotension and metabolic derangements.
• Absence of drug intoxication or poisoning, absence of sedation and neuromuscular blockage.
• Core temperature > 32oC (90oF).
2. CARDINAL SIGNS OF BRAIN DEATH
• Coma: Coma is defined as having no cerebrally mediated motor response to noxious stimuli. A patient in coma will show no response to nail-bed pressure in any extremity, or to supraorbital or temporomandibular joint pressure.
• Absence of brainstem reflexes
- Pupils: Both pupils show no response to bright light. Size of the pupils may vary from 4 mm to 9 mm. They may be round, oval or irregular. Preexisting pupillary abnormalities must be ruled out.
- Ocular Movement: Occulocephalic reflex is absent giving the impression of doll’s eyes. Occulovestibular reflex is also absent .
• Facial sensation and facial motor response
- No corneal reflex to touch with a cotton swab or gauze.
• Pharyngeal and tracheal reflexes
- No response to stimulation of posterior pharynx with tongue blade
- No cough response to bronchial suctioning
- Apnea is defined as the absence of respiratory movement and exchange of gases.
- Following conditions must be met prior to performing the apnea test.
• Core temperature ≥ 36.5°C or 97.7°F
• Arterial PCO2 ≥ 40 mm Hg
• Arterial PO2 ≥ 100 mm Hg
- Testing procedure: PO2 and PCO2 are measured before the test to ensure that requirements have been met. The patient is pre-oxygenated for 10 minutes with 100 percent oxygen via the ventilator. Apnea testing is done with pre-oxygenation to eliminate respiratory nitrogen stores, accelerate oxygen transportation, and decreases the risk of hypoxic complications during apnea testing. The ventilator is removed and the patient receives 100 percent oxygen passively. The patient is monitored for any signs of chest movement. Arterial blood gases are measured every two minutes until one of the following occurs: 1) PCO2 is greater than or equal to 60 mm of Hg; 2) PCO2 is 20 mm Hg greater than pre-test level; or 3) patient becomes unstable. At the end of the apnea testing the patient is placed back on the ventilator at the previous settings.
3. CONFIRMATORY TESTING
Sometimes the patient is unstable before apnea testing or may become unstable during the test compelling the physician-on-call to abort the test. In such cases, alternative tests may be performed to determine brain death although some hospitals may require both apnea testing and confirmatory testing before pronouncing a patient dead by neurological criteria. Tests that may be used for alternative testing include Cerebral Flow Scan, Transcranial Doppler Ultrasonography, Electroencephalography, and Cerebral Scintigraphy . Electroencephalography was once the gold standard for determining brain death. However, EEG frequently gives false positive results and is therefore less accurate. The general trend across the country today is to use the cerebral flow scan.
Cerebral Flow Scan: This test provides unequivocal evidence of brain death. The test involves intravenous injection of radioactive isotope and taking static images at several time intervals including immediately after isotope injection, and between 30 and 60 minutes. To confirm that the isotope was injected into the blood stream, additional liver images may be taken to demonstrate uptake. If the images do not reveal blood perfusion in the brain, the patient is brain dead. Many hospitals however do not perform cerebral flow scans. A limitation of this test is that it may be false positive for patients who have undergone craniotomy or in children as they have a well-perfused scalp.
APPENDIX C: References
4 - Must assure that the spinal cord is intact prior to performing this examination.
5 - Occulovestibular reflex is the deviation of the eyes to irrigation in each ear with 30-50 ml of ice water. Observe for 1 minute after irrigation and wait at least 5 minutes before testing on the opposite side.
6 - Department of Surgical Education, Orlando Regional Medical Center.