Understanding Brain Death
Brain Death is defined as the irreversible loss of all functions of the brain, including the brainstem. The three essential findings in Brain Death are Coma, absence of Brainstem Reflexes, and Apnoea. An evaluation for Brain Death should be considered in patients who have suffered a massive, irreversible brain injury of identifiable cause. A patient determined to be Brain Dead is legally and clinically dead. There is a clear difference between severe brain damage and Brain Death; Brain Death is the principal prerequisite for the donation of organs for transplantation. The 1994 Transplantation of Human Organ Act defines brain stem death in India, as opposed to the whole brain dead in many countries like United States.
Evolution of Brain Stem Death
Historically, death was defined by the presence of putrefaction or decapitation, failure to respond to painful stimuli, or the apparent loss of observable cardio respiratory action. The widespread use of mechanical ventilators that prevent respiratory arrest has transformed the course of terminal neurologic disorders. Vital functions can now be maintained artificially after the brain has ceased to function. In 1968, an ad-hoc committee at Harvard Medical School reexamined the definition of Brain Death and defined irreversible coma, or brain death, as unresponsiveness and lack of receptivity, the absence of movement and breathing, the absence of brain-stem reflexes, and coma whose cause has been identified.
Brain Death Certification
(1) Identification of history or physical examination findings that provide a clear etiology of brain dysfunction.
The determination of Brain Death requires the identification of the proximate cause and irreversibility of Coma. Severe head injury, Hypertensive Intracerebral Hemorrhage, Aneurysmal Subarachnoid Hemorrhage and Hypoxic-ischemic Brain Insults are potential causes of irreversible loss of brain stem function.
The evaluation of a potentially irreversible coma should include, as may be appropriate to the particular case; clinical or neuro-imaging evidence of an acute CNS catastrophe that is compatible with the clinical diagnosis of brain death.
(2) Exclusion of any condition that might confound the subsequent examination of cortical or brain stem function.
- Shock or Hypotension
- Hypothermia with temperature < 32°C
- Drugs known to alter Neurologic, Neuromuscular function and Electroencephalographic testing, like Anaesthetic agents, Neuroparalytic drugs, Methaqualone, Barbiturates, Benzodiazepines, high dose Bretylium, Amitryptiline, Meprobamate, Trichloroethylene, alcohols.
- Brain stem encephalitis
- Guillain- Barre syndrome
- Encephlopathy associated with Hepatic Failure, Uraemia and Hyperosmolar Coma
- Severe Hypophosphatemia
Brain Death Examination
Test all the three components of coma, loss of brain stem reflexes and Apnoea.
Before starting ensure the following
- Pre Oxygenation with 100% Oxygen for 15 min.
- Core temperature ≥ 36.5°C or 97.7°F
- Euvolemia- positive fluid balance in the previous 6 hours
- Normal PCO2 – arterial PCO2 ≥ 40 mm Hg
- Normal PO2 – pre-oxygenation to arterial PO2 ≥ 200 mm Hg
Demonstration of Coma
- Absence of movement/ grimace to central deep painful stimuli in cranial nerve distribution Supraorbital Ridge, Temporo – Mandibular Joint (afferent V and efferent VII) or Trapezes Muscle squeeze (afferent and efferent spinal accessory nerve)
- Painful stimuli in spinal dermatome distribution will not test response to central pain
- Patient may have spinal reflexes present in brain stem death
Absence of Brain Stem Reflexes
- Pupils- no response to bright light Size: mid-position (4 mm) to dilated (9 mm) (absent light reflex – cranial nerve II and III)
- Ocular movement- cranial nerve VIII, III and VI
- No Oculocephalic Reflex (testing only when no fracture or instability of the cervical spine or skull base is apparent)
- No deviation of the eyes to irrigation in each ear with 50 ml of cold water (tympanic membranes intact; allow 1 minute after injection and at least 5 minutes between testing on each side)
- Facial sensation and facial motor response
- No corneal reflex (cranial nerve V and VII)
- No jaw reflex (Cranial Nerve IX)
- Pharyngeal and tracheal reflexes (cranial nerve IX and X)
- No response after stimulation of the posterior pharynx
- No cough response to Tracheo-bronchial suctioning
Demonstration of Apnoea.
- Complete monitoring and disconnect the ventilator
- Deliver 100% O2, 6 l/min, into the trachea. Option: place a cannula at the level of the carina.
- Look closely for any respiratory movements (abdominal or chest excursions that produce adequate tidal volumes).
- Measure arterial PO2, PCO2, and pH after approximately 8 minutes and reconnect the ventilator
- If respiratory movements are absent and arterial PCO2 is ≥ 60 mm Hg (option: in carbon di oxide retainers 20 mm Hg increase in PCO2 over a baseline PCO2 ), the apnoea test result is positive (i.e. it supports the diagnosis of brain death)
- If respiratory movements are observed, the apnoea test result is negative (i.e. it does not support the clinical diagnosis of brain death)
- Connect the ventilator, if during testing
- The systolic blood pressure becomes < 90 mm Hg (or below age appropriate thresholds in children less than 18 years of age)
- or the pulse oximeter indicates significant oxygen desaturation,
- or cardiac arrhythmias develop;
- Immediately draw an arterial blood sample and analyze arterial blood gas.
- If PCO2 is ≥ 60 mm Hg or PCO2 increase is ≥ 20 mm Hg over baseline normal PCO2, the apnoea test result is positive (it supports the clinical diagnosis of brain death).
- If PCO2 is < 60 mm Hg and PCO2 increase is < 20 mm Hg over baseline normal PCO2, the result is indeterminate and a confirmatory test can be considered. (not allowed in |Indian law)
When two doctors either Neurologist, Intensivist, Anesthesiologist or Physician who are nominated by appropriate authority, perform the test independently at least 6 hours apart, and if both tests are positive for brain death, the patient is declared as Brain Dead. The complete process is also observed by primary admitting doctor of the patient and the hospital head, who along with the two doctors complete the Form 10 and certify death. The time of death is end of second apnoea test.
Once death is declared the next of kin of patent are informed and counseling for organ donation should be done.