Generality
The irreversible coma is a state of profound unconsciousness, characterized by the definitive arrest of all the functions of the brain and the brainstem ( brain death ).
Unfortunately, the patient cannot be awakened, but can be kept "artificially" alive.
In fact, diagnostic investigations show that the blood no longer flows to the brain, although cardiac activity remains.
The most frequent causes of irreversible coma are:
- Prolonged cardiocirculatory arrest (due to lack of oxygen supply to the tissues, hemorrhagic shock, intoxication, etc.);
- Head trauma ;
- Severe stroke .
The irreversible coma involves the loss of the vegetative functions, which is evident due to the absence of response to strong external stresses, such as painful (nociceptive) or acoustic stimuli, the inability to breathe autonomously, the drop in blood pressure and the decrease of body temperature ( hypothermia ).
The definitive arrest of brain activity is evidenced by two flat electroencephalograms (EEGs), many hours apart. This condition corresponds in all respects to the death of the patient. For legal reasons, the diagnosis of irreversible coma involves careful observation of several hours by a commission of specialist doctors, who make use of all the clinical data and instrumental supports, to clarify any minimum and theoretical doubts.
Once the doctors have decreed this situation, therefore, there is no possibility of awakening the patient. In this case, organ donation can be considered.
What's this
The irreversible coma is a state of brain death (or brain death) with persistent cardiac activity. This condition coincides with the last stage (or degree), more severe and deeper than the coma; for this reason, the irreversible coma is also called " fourth degree coma " or " stage 4 coma ".
Did you know that…
Coma - understood as a generic condition of profound and lasting unconsciousness - is not an indication of brain death, that is, of the irreversible cessation of all the functions of the brain, but may evolve in this condition.
The irreversible coma corresponds to the deepest state of the coma and is characterized by the complete disappearance of signs of brain activity, lack of reflexes and non-autonomous breathing . The individual has no awareness of himself, of the surrounding environment and of the stimuli that come from it. However, in this pathological condition, the heartbeat continues to persist.
The irreversible coma is, therefore, a somewhat artificial situation: the patient needs mechanical respiration that, outside of an intensive therapy, could not last for more than a few minutes.
What are the degrees of depth of the coma?
Before delving into the characteristics of irreversible coma, it is necessary to summarize the various degrees of depth of the coma, to better understand the different alterations of the state of consciousness.
Depending on the brain regions involved in a lesion, the coma is classified into 4 stages of gravity ; to each of these, specific characteristics correspond that make it negotiable or not.
To these different degrees, corresponds the depth of the state of unconsciousness, that is:
- 1st grade coma (or first stage) : it is a mild coma. The subject appears in a dormant state: he cannot keep vigilant, but he is able to respond, even if with difficulty, to verbal and painful stimuli coming from the outside. The first-degree coma is reversible;
- 2nd grade (or second stage) coma : it is a deeper state than the previous one. The subject does not respond to verbal stimuli, but maintains the ability to respond to painful stimuli. Pupillary and corneal reflexes are lost, as well as the ability to retain the sphincters (therefore, there is a picture of incontinence). Also in this case, the coma is reversible, although the times of awakening are longer;
- 3rd grade coma (or third stage) : it is a deep coma, in which there is the total absence of response to external stimuli. The patient may experience: increased body temperature (hyperthermia), increased heart rate (tachycardia) and significant changes in respiratory rate. Third-degree coma may evolve into brain death or be reversible, although with significant consequences;
- 4th grade coma (or fourth stage) : it is the most serious and profound state of unconsciousness; corresponds to the condition of irreversible coma or brain death. No patient who satisfies the criteria of the latter degree of comatose status can recover.
Causes
The irreversible coma is the result of a dysfunction of both cerebral hemispheres or of damage to the ascending reticular formation (also known as "ascending activating reticular system", it is a complex of neurons specialized in the control of the waking state and the rhythm circadian, which is located in the brain stem). In other words, this condition depends on an alteration of those areas responsible for maintaining the state of consciousness : the patient in an irreversible coma is not alert and is not aware.
At the origin of the irreversible coma there can be different causes, structural (eg increased intracranial pressure and cerebral ischemia) and not (as in the case of toxic disorders or metabolic imbalances). This state can also depend on the primitive involvement of the brain (neurological diseases) or on a series of extracranial pathologies (eg metabolic problems, respiratory failure, etc.).
The most common causes of irreversible coma include:
- Prolonged cardiocirculatory arrest, regardless of its origin:
- Lack of oxygen supply to tissues;
- Intoxication (abuse of alcohol, barbiturates, opiates or narcoleptics);
- Cerebral, cerebellar or brain stem infarction;
- Hemorrhagic shock.
- Head trauma :
- Concussion;
- Intracranial haemorrhages due to impact;
- Formation of cerebral hematomas (extradural, subdural or intracerebral).
- Severe stroke :
- Cerebral hemorrhage;
- Cerebral ischemia.
Furthermore, irreversible coma can result from conditions that produce widespread effects (such as hypoglycemia, hypoxia, uremia and overdose) or focal conditions (a more rare occurrence; a unilateral focal hemispheric lesion can alter consciousness, if the contralateral hemisphere is already compromised).
Other causes of irreversible coma are:
- Infections and complications of the same (eg meningitis, encephalitis, brain abscess etc.);
- Vascular affections (eg subarachnoid hemorrhage, encephalopathy, venous thrombosis and vasculitis);
- Brain tumors;
- Severe alterations of thermoregulation (hypothermia or, on the contrary, hyperthermia);
- Epilepsy (epileptic coma);
- Neurodegenerative diseases (Alzheimer's, limbic encephalitis and Creutzfeldt-Jakob disease).
Irreversible coma can also depend on metabolic causes, such as:
- Hyperglycemia (glycemic coma);
- Brain hypoxia (secondary, for example, to carbon monoxide intoxication);
- Alterations of the acid-base balance;
- Renal or hepatic failure;
- Endocrine disorders (pancreas, thyroid, adrenal gland, hypophysis etc.).
Symptoms and Complications
The irreversible coma, also called dépassé, is a protracted loss of consciousness, from which the subject cannot be awakened. The death occurs due to the fact that the brain injury is so severe and extensive that it causes insufficiency and death of the brain.
The patient lies motionless with his eyes closed and is in a state of non-responsiveness to a command or to the strong external stresses, whatever stimulus is applied (painful, bright or acoustic).
In fact, irreversible coma manifests itself with the loss of vegetative functions ; this involves:
- The inability to breathe independently;
- The fall in blood pressure;
- The decrease in body temperature (hypothermia).
In irreversible coma, blood circulation is maintained in function only to preserve the vitality of the organ (or organs) destined for removal, with the consent of the family members.
Coma, brain death and vegetative state
- The vegetative state is the loss of the functions of the cerebral hemispheres, therefore of the conscience and of the life of relationship, but it is accompanied to an acceptable autonomy of the breath and of all the automatic functions of the organism. Unlike the chronic vegetative state, the fourth stage of the coma is irreversible and characterized by the cessation of all brain activity ( cerebral insufficiency ).
- Brain death does not represent an evolution of the coma, but is a different, irreversible state: it indicates that the person is no longer able to autonomously manage vital functions.
Diagnosis
Irreversible coma is a very complex condition, whose assessment involves several medical disciplines, namely: neurology, internal medicine, cardiology and forensic medicine.
The diagnosis of irreversible coma is based on the evidence of some clinical signs, such as:
- Absence of state of vigilance and conscience (state of coma);
- Absence of corneal reflex (pupillary areflexia);
- Absence of spontaneous breathing (apnea);
- Absence of reactions to stimuli (absence of trunk reflexes).
The doctor must ascertain the absence of factors capable of interfering with the general clinical picture, therefore he must verify that the subject in coma is not in hypothermia (lowering of the body temperature below the normal value of 37 ° C) or victim of intoxication with substances or drugs that depress the nervous system. Other conditions to be excluded, before declaring the irreversible coma, are the systemic hypotension and the presence of concomitant endocrine-metabolic pathologies that can alter the neurological picture (hypoglycemic coma, hepatic encephalopathy etc.).
Absence of cerebral blood flow
In the case of irreversible coma, imaging diagnostics, such as computerized axial tomography (CT) and magnetic resonance imaging (MRI), show that blood no longer flows to the brain.
Absence of cerebral electrical activity
In irreversible coma, the electroencephalogram remains flat, for a prolonged time, despite the interruption of sedative administration.
Irreversible coma: Glasgow scale
To define the level of consciousness, a specific scale called the Glasgow Scale of the coma is used, which is based on the evaluation of 3 parameters:
- Verbal response / ability to express oneself;
- Ability to open the eyes;
- Motor response.
For each of these parameters, a score from 1 to 5 is provided. The sum can therefore fall within an interval between 15 (value indicating the full state of consciousness and vigilance) and 3 (minimum score, deep coma index).
Iter to decree brain death
The diagnostic procedure to determine the state of irreversible coma is articulated and subject to very clear guidelines (Decree of the Ministry of Health of 11.04.2008, published in the Official Journal No. 136).
The Hospital Health Management, at the request of the ward doctor or emergency room that treats the patient, convenes a board composed of 3 doctors:
- A neurologist (or, alternatively, a professional figure expert in electroencephalography, such as neurophysiologist or neurosurgeon);
- A specialist in Anesthesia and Resuscitation ;
- A medical examiner (an anatomo-pathologist or a doctor of the Health Department), who is given the role of guarantor of the correct performance of the procedure.
These professionals have the task of viewing the patient for a total period of 6 hours (adults and children over the age of 5), in order to ascertain the presence of 3 parameters necessary to declare the state of irreversible coma, ie :
- Loss of consciousness and alertness that is accompanied by loss of brain stem reflexes and loss of autonomous respiration;
- Absence of brain activity, detected by electroencephalogram (EEG);
- Absence of cerebral blood flow, detected by performing angiography of the skull, cerebral angiography, cerebral scintigraphy or transcranial doppler.
The board of doctors convened has the obligation to carry out two surveys of the parameters described, one at the beginning of the 6 hours of observation and one at the end.
If these criteria are met, there is the doubly confirmed and legally valid validation of the brain death diagnosis.
Warning! The diagnosis of irreversible coma allows the interruption of health services to a person. Care must be taken not to confuse the procedural procedure aimed at decreeing the state of irreversible coma with euthanasia . In the fourth degree coma, there is no longer a way to restore brain functions, irreversibly compromised, a condition that decrees death itself.
Treatment
As the term "irreversible" suggests, from the last stage of the coma recovery is not possible and, unfortunately, there are no useful interventions to restore vital functions. In other words, the diagnosis of irreversible coma is equivalent to the death of the person .
What happens after the diagnosis of irreversible coma
- Irreversible coma: cardio-respiratory support suspension
After the diagnosis of irreversible coma has been confirmed, all cardio-respiratory support treatments are suspended.
During the apnea of the patient in an irreversible coma, spinal motor reflexes may occur (Lazarus phenomenon); these movements include opisthotonos (hyperextension and spasticity of the head and spine), rotation of the neck, stiffening of the legs and flexion of the upper extremities.
The cessation of ventilatory support results in terminal arrhythmias; the final cardiac arrest of the patient in an irreversible coma occurs after a few hours or a few days.
- Irreversible coma: organ donation
Once the procedural procedure aimed at decreeing the state of irreversible coma has been completed, the possibility of donating organs can be considered, subject to the consent of the family members and if the general conditions allow (ie if the subject is a good candidate for age or there are no serious concomitant diseases).
In this case, the patient in an irreversible coma can be kept "alive" artificially, with the resuscitation equipment, until the organ donation is removed, according to the Guidelines of the National Transplant Center.
