The moment of death- Brain and brain stem death

 

The Moment of Death

There is no difficulty in the diagnosis of somatic deaths. However, in some cases the heart sounds and breath sounds diminish greatly. Errors occur if proper clinical examination is not done or hurriedly done. The classical concept of so called tripod of life does not hold good now as lungs and heart could be maintained on artificial support system. The factor responsible for a fresh appraisal of moment of death is the growing practice of organ transplantation. A beating heart, which is the ideal specimen for trans­plan­tation cannot be taken out of an individual.

If we were to apply to classical cri­teria because the heart is beating in the pros­pective donor, he is obviously not dead.

On the contrary, if we wait for his heart to stop to resolve the ethical dilemma, the heart becomes useless for transplantation.

Therefore, the people all over the world were trying to find out the legal definition of death.

 

Brain Death

Philadelphia Protocol

(i) Lack of responsiveness to inter­nal and external environ­ment.

(ii) Absence of spon­taneous breathing move­ments for 3 minutes, in the absence of hypocarbia and while breathing room air.

(iii) No muscular movements with gene­ralized flaccidity and no evidence of postural activity or shivering.

(iv) Reflexes and responses: (a) Pupils fixed, dilated, and nonreactive to strong stimuli, (b) Absence of corneal reflexes, (c) Supra­orbital or other pressure response absent (both pain response and decerebrate posturing), (d) Absence of snouting and sucking responses, (e) No reflex response to upper and lower airway stimu­­lation, (f) No ocular response to ice water stimulation of inner ear, (g) No superficial and deep tendon reflexes, (h) No planter responses.

(v) Falling arterial pressure without support by drugs or other means.

(vi) Isoelectric EEG (in the absence of hypothermia, anesthetic deaths, and drug intoxi­cation) recorded spontaneously and during audi­tory and tactile stimulation.

Further, it was added that these criteria shall have been present for at least 2 hours and two physicians other than the physician of a potential organ recipient should certify that death.

   

Harvard criteria

1.Unreceptivity and unresponsivity

2.No spontaneous muscular movements in response to stimuli such as pain, touch, sound, or light for a period of at least one hour.

3.Absence of spontaneous breathing for at least one hour and when patient is on ventilator, the total absence of spontaneous breathing may be established by turning off the respirator for 3 minutes and observing whether there is any effort on the part of the subject to breath spontaneously.

4. Absence of elicitable reflexes: Irreversible coma with abolition of central nervous system activity is evidenced in part by the absence of elicitable reflexes. The pupils are fixed and dilated and does not respond to a direct source of bright light. Ocular movement and blinking are absent. There is no evidence of postural activity. Corneal and pharyngeal reflexes are also absent. Stretch tendon reflexes also cannot be elicited.

5. Isoelectric EEG: Has confirmatory value.

All these tests should be repeated after 24 hours with no change. Further it is stressed that the patient be declared dead before any effort is made to take him off the ventilator if he is then on a ventilator. This declaration should not be delayed until he has been taken off the respirator and all artificially stimulated signs have ceased.

 

Brainstem death

Since the brain contains fourteen billion neurons, how many neurons should be dead to declare a person dead and should one wait until the last neuron is dead? It was argued that even if one neuron is alive that shows electrical activity you cannot pronounce a person dead. However, the argument that remained was that how much human one remains after losing 90% of the brain’s tissue. In addition, it was argued that since we do not know where the seat of con­sciousness lies, it is only reason­able to assume that some consciousness does remain even if a single neuron is left.

Then a new school emerged known as Ameri­can school, led by Mohandas and Chou in 1971 that summarized the criteria of brain death at the University of Minnesota Health Services Center.

 

Minnesota Criteria

(i) Known but irreparable intracranial lesion

(ii) No spontaneous movement

(iii) Apnea when tested for a period of 4 minutes at a time.

(iv) Absence of brainstem reflexes: (a) dilated and fixed pupil (b) absent corneal reflexes (c) absent Doll’s head phenomenon (d) absent ciliospinal reflexes (e) absent gag reflex (f) absent vesti­bular response to caloric stimulation (g) absent tonic neck reflex.

(v) EEG not mandatory

(vi) Spinal reflex not important

(vii) All the findings above remain unchanged for at least 12 hours.

The basic teaching of the American school was not the brain, but the brainstem death, after which there is the point of no return that should be equa­ted as death.

There were several reasons for this equa­tion:

(i) Medullary neurons are most resis­tant to anoxia; if they are dead then higher centers are also dead.

(ii) Brainstem is responsible for the vital functions because it is the seat of respiratory and circulatory center.

(iii) Brainstem is nece­ssary for proper functioning of the cor­tex as all sensory and motor nerves pass through this gateway.

Immediately after an individual is put on respira­tor and other life support system, a systemic examination is done to exclude the possibility of brainstem death. If Minnesota criteria are fulfilled, life support systems should be withdrawn, and the person is to be declared dead.

 

Brainstem Death and Organ Transplantation

The diagnosis of death is traditionally made using the triad of Bichat that states that death is the failure of the body as an integrated system associated with the irreversible loss of circulation, respiration, and enervation. This is also known as somatic death or clinical death. Death is now accepted as synonymous with brainstem death. The brainstem is a small area of the brain that controls respiration and circulation. If this area is dead, the person will never be able to breathe spontaneously or regain consciousness.

Molecular death may be defined as the death of individual organs and tissues of the body consequent upon the cessation of circulation. Different tissues die at different rates depending on their oxygen requirement. Thus, within four min­u­tes ceasing of the blood supply to the brain, the central nervous system is irreversibly damaged.

   

Diagnosis of Brainstem Death

Exclusions: (i) Where the patient may be under the effects of drugs e.g., therapeutic drugs or overdoses, (ii) Where the core temperature of the body is below 35°C, (iii) Where the patient is suffering from severe metabolic or endocrine disturbances which may lead to severe but reversible coma. e.g., Diabetes.

Preconditions of diagnosis: (i) Patient must be deeply comatose, (ii) Patient must be kept on a ventilator, (iii) Cause of the coma must be known.

Personnel who should perform the tests:

(i) Brainstem death tests must be performed by two medical practitioners.

(ii) Doctors involved should be experts in this field. Under no circums­tances are brainstem death tests performed by transplant surgeons.

(iii) At least one of the doctors should be of consultant status. Junior doctors are not allowed to perform these tests.

(iv) Each doctor should perform the tests twice.

 

Tests to be performed: Before the tests are per­formed the core temperature of the body is taken to ensure that it is above 35°C. The diagnosis of brainstem death is established by testing the func­tion of the cranial nerves which pass through the brainstem. If there is no response to these tests the brainstem is irreversibly dead:

(i) Pupils are fixed in diameter and do not respond to changes in the intensity of light

(ii) There is no corneal reflex

(iii) Vestibulo-ocular reflexes are absent, i.e. No eye movement occurs after the instillation of cold water into the outer ears

(iv) No motor responses within the cranial nerve distri­bution can be elicited by painful or other sensory stimuli, which is the patient does not grimace in response to a painful stimulus

(v) There is no gag reflex to bron­chial stimulation by a suction catheter passed down the trachea

(vi) No respiratory movements occur when the patient is disconnec­ted from the ventilator for long enough to ensure that the carbon dioxide concentration in the blood rises above the threshold for stimulating respiration i.e., after giving the patient 100% oxygen for 5 minutes the ventilator is dis­connected for up to 10 minutes. If no spontaneous breathing of any sort occurs within those 10 minutes the brainstem is incapable of reacting to the presence of the carbon dioxide and is thus dead.

When two doctors have performed these tests twice with negative results, the patient is pronoun­ced dead and a death certificate can be issued.

It is at this stage that a decision concerning the use of organs for transplantation purposes may be raised and the decision made as to the whether the corpse should be kept on the ventilator until the organs may be harvested.

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