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[Gr. kōma, a deep sleep]
A state of unconsciousness from which one cannot be aroused. Coma is the most severe of the alterations of consciousness. It differs from sleep in that comatose patients will not awaken with stimulation. It differs from lethargy, drowsiness, or stupor (states in which patients are slow to respond) in that comatose patients are completely unresponsive. Finally, it differs from delirium, confusion, or hallucinosis (states in which patients' sense of reality is distorted and expressions are bizarre) in that comatose patients cannot express themselves at all.
SEE: Glasgow Coma Scale
Two thirds of the time, coma results from diffuse brain injury or intoxication, such as may be caused by drug overdose, poisoning, hypoglycemia, uremia, liver failure, infection, or closed-head trauma. In about one third of cases, coma results from intracranial lesions, such as massive strokes, brain tumors, or abscesses. For these focal injuries to depress consciousness, the lesion must result in compression or injury to the brain's reticular activating system (the network of cells responsible for arousal). Rarely, coma is feigned by patients with psychiatric illnesses.
The airway, breathing, and circulation are supported. The cervical spine is protected if there is any question of traumatic injury to the head and neck. A rapid physical examination is performed to determine whether the patient has focal neurological deficits. Simultaneously, intravenous dextrose, naloxone, and thiamine are given (to try to reverse narcotic overdose or diabetic coma). If the examination reveals focal findings, an intracranial lesion may be present and should be quickly diagnosed (with brain scans) and treated, e.g., with neurosurgery, if appropriate. If the patient is neurologically nonfocal, treatment focuses on metabolic support, the administration of antidotes for any proven intoxications, and treatment for infections. Seizures, if present, should be promptly controlled with anticonvulsants. Blood sugar levels should be tightly controlled (between 80 and 110 mg/dL). Fevers should be suppressed with antipyretics. Acid-base disturbances should be corrected.
If there is a question whether the coma is due to an overdose of insulin or to hypoglycemia, it is crucial to give glucose intravenously. Administration of naloxone is also standard care.
A patent airway is maintained. If neck trauma is suspected, e.g., if the patient was found on the floor, the patient should not be moved, except after protecting the cervical spine. Neurological status is monitored with the Glasgow Coma Scale. Frequency of assessment depends on protocol and the patient's stability. Findings are documented, and evidence of clinical deterioration is reported.
Fluid and electrolyte balance is monitored and maintained; gastrointestinal and urinary functions are assessed; care for the indwelling urinary catheter, intravenous line, and nasogastric or percutaneous endoscopic gastrostomy feeding tube is provided, as well as adequate enteral or parenteral nutrition; and bowel elimination is maintained with stool softeners, suppositories, or enemas. Ventilatory status is assessed by auscultating for abnormal lung sounds, and adequate ventilation and oxygenation are determined by arterial blood gases or oxygen saturation values. The nurse or respiratory therapist assists with intubation and provides mechanical ventilation as required. The patient is repositioned to improve aeration of lung bases, and drainage of secretions is encouraged. The oropharynx (and endotracheal tube) is suctioned gently but briefly as necessary, considering concerns for increased intracranial pressure. The corneas are protected from ulceration by applying artificial tears to moisturize the eyes and by patching the eyes closed if the patient is unable to close them. Skin status is assessed and a plan instituted to prevent or manage pressure areas; passive range-of-motion exercises are provided; the patient is repositioned frequently; distal extremities are supported and elevated to prevent dependent edema; and appropriate supportive devices are used to prevent external hip rotation, flexion and extension contractures, and footdrop. Therapy to prevent deep venous thrombosis should be given, e.g., heparin, warfarin, or compression stockings. Early enteral feeding of the patient prevents malnutrition.
Verbal and tactile stimulation is provided; the patient is assessed per orders (or hospital protocol) to person, time, place, and activities; nothing is said in the patient's presence that the patient should not hear, because the unresponsive patient may occasionally be somewhat aware of his or her surroundings. Emotional and educational support is offered to family members.