More than half of organ transplants in the world are carried out on organs obtained from deceased donors. In 1959 the term brain death came into vogue to describe patients who have a permanent cessation of brainstem or brain functions which are required to integrate functioning of the organism as a whole. Some tissues may still be “live” and can continue to grow in laboratories for indefinite periods. However, the organism as a whole does not live once brain death has occurred.
Conventionally brain death had been ascertained once the heart has stopped beating. However, a few heartbeats may occur for some time after the cessation of cardiac function and a few gasps may be seen. This criterion of clinical death has been replaced in most countries of the world by the concept of brain death.
In modern ICUs once brain death has occurred, spontaneous breathing does not occur. Hence patients are on ventilators and most require support to maintain blood pressure ( vasopressors).
What is brain death?
Brain death is the cessation of brain function and almost always accompanied by the stoppage of blood flow to the brain. This is in most cases due to injury as in road traffic accidents, falls or elsewhere. It is also a common result of subarachnoid bleed (bleeding inside the covering of brain in the cranial cavity).
How is brain death diagnosed?
Diagnosis of brain death requires expertise and experience.
Prerequisites for diagnosing brain death are
- Cause of injury to the brain should be known and compatible with brain death.
- Poisoning and drug intoxication should be excluded
- The body temp should be above 36 C.
- There should be no severe electrolyte or metabolic state (sugar, sodium, CO2 and O2 level)
- Blood pressure should be >100 mm systolic
Clinical Examination :
Neurological examination reveals coma,
The absence of all reflexes originating from the brain stem.
The absence of motor activity originating from the brain (spinal cord reflexes and some involuntary movements may be seen)
Apnea test may be carried out by stopping mechanical ventilation, waiting for CO2 levels to rise and observing for spontaneous breathing. Oxygen is usually given at a high pressure before carrying out this test.
Tests to see absent blood flow. The methods employed may be MR Angiography, CT angiography, Nuclear scans, Trans Cranial Doppler etc
EEG and brain stem evoked potentials to ascertain activity.
These tests are usually carried out by more than one clinician. Neurologists, neurosurgeons, physicians, intensive care doctors, anesthesiologists are usually experienced in these tests. These tests are repeated after a time interval to ensure that the changes are indeed reproducible and permanent.
Most countries have their own definitions, examination patterns and requirements before brain death is declared including the qualifications of doctors declaring the same. It is equated with clinical death in most countries. However, the lack of clarity is apparent as yet there are no universally applicable guidelines.
Organs for various transplantation purposes can be obtained once brain death is declared and other laws and relatives permitting the same. The organs thus retrieved are in a reasonably healthy state as organ perfusion has continued till the retrieval and ischemia time is least.