Coma (Cohen) Flashcards
Coma, a medical emergency
A state of prolonged unconsciousness, from which the patient cannot be awakened, due to damage to either (1)both cerebral hemispheres, or (2)the reticular activating system of the brainstem….or both
It is a sleep like state, the lowest possible level of consciousness, from the Greek word, koma, meaning “deep sleep”
The term “unresponsive” is becoming popular, perhaps became it allow for error by the examining physician or nurse
Common causes of coma
In approximately decreasing order of frequency:
- Cardiac or pulmonary failure for over 5 minutes, causing hypoxic-ischemic damage throughout the brain
- Drug and alcohol overdose
- Cranial trauma, including subdural/epidural hematomas
- Severe derangements of organ function with abnormal serum chemistries of pH: hypoglycemia, renal failure, hepatic failure, dehydration, hypothermia, etc.
- Stroke or hemorrhage in the brain stem or large strokes or hemorrhage in the hemispheres, including subarachnoid hemorrhage
- Infections causing sepsis or encephalitis/meningitis
- Psychiatric pseudo-coma (rare)
Immediate steps to take
- Stabilize: patent airway, adequate breathing, circulation
- Blood pressure and perfusion check: there may be circulatory collapse from hemorrhage or dehydration
- Peripheral or central intravenous line; draw blood for labs first, if possible; if any chance of hypoglycemia, give dextrose and thiamine
- Intubation/ventilation in many cases, sometimes just a cannula or a face mask for oxygen delivery; arterial blood gases can be followed
- Look for evidence of trauma, especially head and cervical spine
- Complete history from witnesses or neighbors or family; keep them available or get telephone numbers for later inquiries
- Comprehensive laboratories: chemistry, blood count, toxicology
- If any chance of opiate overdose, give naloxone (Narcan)
The causes of coma: history
Learning the cause of coma is the best way to limit the damage, save the patient, and determine prognosis
Most clues are in the patient’s medical history:
Are there any chronic medical conditions, especially diabetes, pulmonary conditions, coronary artery disease or arrhythmias, seizure disorder, renal failure, bleeding tendency, alcohol or drug use, psychiatric disorders with a chance of suicide, new medications?
When was the past last seen conscious? The duration of coma is extremely important in diagnosis and prognosis
Any history or evidence of trauma, including relatively minor falls?
Neurologic examination
Observe the patient for a moment, if already stabilized:
- Spontaneous respiration, or ventilator-dependent?
- Spontaneous movement of the head and the extremities, or is there movement on only one side, or are there no movements at all?
- Abnormal movements, such as tremors, myoclonic jerks, or posturing?
- Is there any response of the patient to voice, or is there any response to physical stimulation, or is there simply no response at all?
- What is the general appearance of the patient: frail, elderly, or younger and in other wise good condition?
Brainstem functions and reflexes
Pupillary reaction to light, involving CNs II and III
Pupillary diameters or inequalities, also CNs II and III
Corneal reaction; unilateral or bilateral involving CNs V and VII
Eye movements and positions of eyes, involving CNs III, IV, VI
Oculocephalic reflex, or “Doll’s eyes” with eyes going opposite direction of head turn if there is NO inhibition by the cerebral hemispheres; rarely seen, because most coma patients have damage to brain AND both hemispheres, involving the pons and medulla oblongata
Oculovestibular reflex, or “cold calorics,”eyes deviate conjugately toward ear given ice water, involving the pons and medulla oblongata
Gag reflex; not easily done in intubated patients, also pons and medulla
Cranial Nerve III and Coma
The nuclei for CN III are at the top of the brain stem, in the midbrain
The nuclei and its oculomotor fibers can be compressed by uncal herniation of the ipsilateral, and occasionally contralateral hemisphere
A dilated unreactive pupil is seen, as well as inability to move the eye any direction except laterally (if preservation of CN VI)
Brain damage without herniation also tends to hit CN III hard, causing weakly reactive pupils and both eyes tend to deviate laterally (again, if preservation of CN VI)
Prognostic indicators for coma
Probably the two most important signs for a poor prognosis:
- No pupillary reactions to light
- No spontaneous movements
Any patient with coma for 72 hours, excluding those with reversible swelling from trauma or sedation from drug overdose, or hypothermia, with multiple missing brain stem reflexes, has less than a 5% chance of a meaningful recovery
Brain death
First considered in the 1950s and 1960s with the widespread use of intravenous lines and powerful ventilators; now seriously ill patients could be kept alive for a longer time
Patients would continue to have a pulse, and sometimes sustainable blood pressures with the use of drugs, but no spontaneous respiration and no evidence of brain function
In most cases, they would only have cardiac function for another week or less, before that was lost, too
Increasingly, this condition was seen as a universal precursor to conventional death, or cardiac death
Brain Death in the United States
In 1968, a committee led by a famous neurologist at Harvard Medical School, Dr. Raymond D. Adams, made recommendations for determining brain death
Recommendations have continued to be found useful, and are compulsory at all US hospitals:
The patient who is brain dead IS LEGALLY DEAD
If permission is obtained, brain dead patients may have some organs removed for transplantation
Other than transplantation, all medical care stops
Requirements for brain death
Exclude patients who may have a reversible condition: swelling from trauma, hypothermia, known drug overdose
No evidence of cerebral function: no response to stimulation, no movements, no vocalization
No evidence of brain stem function: all of the brain stem reflexes are absent, and no spontaneous respiration from centers in the medulla and pons
This is confirmed by an APNEA TEST, in which the patient’s ventilator is turned off, but 100% oxygen is still delivered, until the PC02 rises to approximately 60 mmHg; if brain dead, no respiratory effort is seen at a high PCO2
Hospitals may also require confirmatory tests, such as an isoelectric EEG, or a lack of any cerebral blood flow on cerebral arteriography or a radionuclide brain scan
The family and brain death
Family members need to be kept aware of the condition of the patient all along, especially when the patient becomes comatose
Prognosis should be given soon after coma occurs, and certainly by 72 hours
Families are often relieved to learn that comatose patients have no sense of pain or suffering
These updates make it somewhat easier to inform the family that a determination of brain death has been made, or to allow the family to terminate aggressive care before the patient becomes brain dead
Brain dead patients can be suitable candidates for organ donation, if patient had previously indicated this or if the family agrees
Continuing treatment of a brain dead patient in the United States is not an option
The Vegetative State
Replaces the old, somewhat derogatory term: patient is now a “vegetable,” for patients who SLIGHTLY awaken from coma
It suggests loss of both cerebral hemispheres, but maintenance of part or all of the brainstem
The brain stem can maintain sleep-wake cycles, respiration, heart beat, swallowing, some eye movements and facial contractions
Patients do not truly speak words but make some simple vocal sounds, such as grunts or event laughter
The arms and legs move but not in a directed manner
Gross vision is maintained, but no specific responses to what these patients seem to “see”
Criteria for Persistent Vegetative State (PVS)
DEFINED AS ONE MONTH OR MORE OF A VEGETATIVE STATE
- No awareness of self or surroundings, although eye opening and eye movements occur
- No meaningful communication between patient and others, including no comprehensible speech and no accurate mimicry
- Facial expressions not accurately related to stimulation, although patients may laugh or cry
- Sleep-wake cycles may be intact
- Arm or leg movements, but not under voluntary control or with a directed purpose
- Adequate control of cardiovascular functions
- Incontinent of bowel and bladder
Ending a vegetative state
Patients are usually hopeless after one month of PVS, and certainly are by three months; longer for head trauma
Most families will understand that this is “no life,” or a situation the patient would not want, and physicians stop care, including the feeding the patient and the giving of all medications
The deciding relative is normally the spouse of the patient
The physicians involve need to be honest with the family, and maintain clear communications with the patient’s family and with each other: send a consistent message from all physicians
There are usually “ethics committees” at hospitals with experts from multiple disciplines/professions (including attorneys)
