Doctors use brainstem tests to determine if a patient is brain dead. The brainstem controls vital functions such as breathing and heart rate. The most common test is the brainstem auditory evoked response test, which measures the brain’s response to sounds. In the UK, further tests must be performed before declaring a person dead. The tests involve shining a light in the eyes, testing the cornea’s reaction to irritation, measuring pain response, and testing the gag reflex. The final test involves removing the patient from life support to see if they can breathe spontaneously.
Doctors use brainstem tests to determine the general level of functioning within that region of the brain. The brainstem controls several functions vital to survival, including breathing, heart rate, and consciousness. The most common test is the brainstem auditory evoked response test. In the UK, where brainstem death is considered an important criterion for determining whether a person is technically alive or dead, further tests must be performed before declaring a person dead.
The brain stem auditory evoked response test uses a series of sounds to evoke a response within the brain stem. During the procedure, the patient wears headphones through which sounds are transmitted. Electrodes attached to the scalp and earlobes measure the brain stem’s response to these sounds. The main purpose of the test is to determine the general functioning of the nervous system and to diagnose hearing problems.
Some countries, such as the UK, define death as an irreversible loss of consciousness as well as an irreversible loss of the ability to breathe. Because the brainstem plays an important role in both functions, if it is damaged beyond repair, patients often fall under the definition of death. Before a patient can be pronounced dead, a series of brainstem tests must be performed. These tests are performed by two different doctors several hours apart.
Before doctors can begin brainstem tests, a few criteria must be met. First, a patient’s presumed brain stem death must have a cause, such as an accident or disease affecting this region of the brain. Second, the coma cannot be the result of something potentially reversible, such as a drug overdose or metabolic disorder. After these two main criteria have been met, tests of brainstem function can begin.
The first of the brain stem tests involves shining a light, usually a pen light, into a patient’s eyes. When the brainstem stops functioning, the pupils appear fixed and dilated. Typically, this test is done without any special equipment aside from the light. In rare cases, however, patients still show signs of pupillary activity despite meeting all other criteria for brain stem death, and special imaging scans or brain wave testing equipment may be used to determine the cause of the abnormal reaction.
Testing the cornea’s reaction to irritation by rubbing it with some sort of coarse material, such as a piece of gauze, is typically the next step in the brainstem test series. In a patient with a functioning brainstem, this highly sensitive part of the eye would evoke a pain response when touched with gauze. Additional tests to measure pain response include firmly pinching the nose and pricking the forehead. The gag reflex, which is controlled by the brainstem, is also measured by inserting a tube down the patient’s throat.
The final test to determine brainstem death involves removing the patient from life support for a short period of time to see if the patient begins to breathe spontaneously without assistance. Several hours later, these tests must be done a second time by another senior doctor to confirm the results. If the patient fails the second time, the doctor can legally declare death.
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