Today I was called to conduct a brain death evaluation on a patient in the medical intensive care unit. As I spoke with the family I again realised how alien this concept of death is. How very hard it is for the family to comprehend what brain death means.
” Doctor Sethi his heart is beating, the machine (ventilator) is moving his chest, how can he be dead?”
So what exactly is brain death? The old dictionary defination of death is relatively simple to understand and comprehend by the lay person. Death is the cessation of cardiorespiratory function. When your heart stops you die. Everyone understands this. But as medicine advanced in the 1960’s we reached the stage when we were able to sustain and keep patients alive with advanced cardiorespiratory support. We had ventilators now which did the work of breathing and good medicines to sustain the blood pressure. It was at this time that the need was felt to have an alternative defination of death. The reason was that there were many patients who were on ventilators and their heart was strong, but who had suffered so much damage to the brain that their chance of a meaningful neurological recovery was zero.
Also at this time transplant medicine was kicking off and there was need for organs for transplantation. A brain dead patient usually is a good candidate for organ harvesting because the heart is still perfusing organs like kidneys etc. That is when a new defination of death was born: brain death.
So what exactly is brain death? Well like I said earlier a brain dead patient is one whose brain has suffered irreversible damage and there is zero chance of a neurological recovery. The heart may be beating on its own and the respiration may be aided by a ventilator but the brain is no more. Usually these are patients who have suffered head trauma or a major bleed or stroke in the brain such as a massive subarachnoid hemorrhage.
So how is the diagnosis of brain death made? Well first and foremost the diagnosis of brain death is a clinical diagnosis and you do not need any confirmatory tests unless there is doubt or because the clinical examination is hampered by something. The doctor who usually does the clinical examination testing is one trained in neurosciences either a neurologist or a neurosurgeon. What we usually test for is the integrity of the brain stem (the lower part of the brain which controls the vital functions of the heart and respiration). We do this by checking the brain stem reflexes, are they intact or not?
Do the pupils react to light or they fixed and dilated?
Does the patient have a corneal reflex?
Do they have spontaneous respiration when we disconnect them from the ventilator? This is an important test called apnea test.
Do they gag when we try to suction them?
Do they have an oculocephalic reflex?
Do their eyes move when we put cold water into their ears (this is a test called cold caloric testing)?
We go over the entire chart to make sure that the patient is not on any medication (sedatives) or has any other condition that might explain his current examination. We make sure that the patient is not hypothermic.
If all the above conditions are met then the patient meets the criteria for brain death. I want to add the criteria for brain death vary from country to country and the protocol may vary from one hospital to another. In some countries four doctor are needed to make a diagnosis or brain death. One of them has to be a neurologist or neurosurgeon, the other a doctor who is not involved in the active care of the patient, the third is the doctor involved in the care of the patient and the fourth is usually the medical superintendent of the hospital (like I said the criteria vary from country to country).
The criteria also vary with regards to the time of observation between two examinations of brain death. In some countries the examination has to repeated to confirm there is no change in the findings after 6 hours and in others this time is 12 to 24 hours.
Need for confirmatory testing: as I stated at the onset, brain death is a clinical diagnosis and no confirmatory testing is required. In situations where we cannot do some of the tests like the apnea test or the diagnosis is in doubt or the family requests it, confirmatory testing may be done. The most common test done is an EEG (this EEG is done under specific criteria and should show no activity above 2 microvolts). Other confirmatory tests include angiogram, transcranial doppler or a radioisotope scan.
Once the diagnosis of brain death is confimed the patient can be disconnected from the ventilator legally (the law gives the doctor permission to do that). Of course we try to make the family understand and be part of the final decision of removing from the ventilator.
IF YOU ARE BRAIN DEAD, YOU ARE DEAD. YOU CANNOT DIE TWICE, ONCE WHEN YOUR HEART STOPS AND ONCE WHEN YOUR BRAIN STOPS.
I hope I have made some sense of this technical topic for my readers
Nitin Sethi, MD