Many times the primary disorder underlying coma is perfectly obvious, as with severe cranial trauma or a known drug overdose. All too often, however, the comatose patient is brought to the hospital and little pertinent medical information is available. The need for efficiency in reaching a diagnosis and providing appropriate acute care demands that the physician have a methodical approach that first addresses the common and treatable causes of coma. When the comatose patient is first seen, the patient’s airway is cleared and blood pressure is restored; if trauma has occurred, one must check for bleeding from a wound or ruptured organ (e.g., spleen or liver). With hypotension, placement of a central venous line and administration of fluids and pressor agents, oxygen, blood, or glucose solutions (preferably after blood is drawn for glucose determinations and thiamine is administered) take precedence over diagnostic procedures. If respirations are shallow or labored, or if there is emesis with a threat of aspiration, tracheal intubation and mechanical ventilation are instituted. An oropharyngeal airway is otherwise adequate in a comatose patient who is breathing normally. Deeply comatose patients with shallow respirations require endotracheal intubation. The patient with a head injury may also have suffered a fracture of the cervical vertebrae, in which case caution must be exercised in moving the head and neck as well as in intubation lest the spinal cord be inadvertently damaged. These matters are discussed in detail further on, under “Management of the Acutely Comatose Patient.”
An inquiry is then made as to the circumstances in which the person was found and their previous health, whether there was a history of diabetes, a head injury, a convulsion, alcohol or drug use, or a prior episode of coma or attempted suicide. Persons who accompany the comatose patient to the hospital should be encouraged to remain until they have been questioned. In addition to the basic laboratory tests that apply to coma, a toxicology screen is usually appropriate.
In assessing confusion, stupor, or coma in an already hospitalized patient, it is usually instructive to review the patient’s medications carefully. A large number of compounds may reduce alertness to the point of profound somnolence or stupor, particularly if there are underlying medical problems (e.g., a liver failure). Prominent in lists of iatrogenic drug intoxications are sedatives, antiepileptic drugs, opiates, certain antibiotics, antidepressants, and antipsychosis compounds. From an initial survey, many of the common causes of coma, such as severe head injury, alcoholism or other forms of drug intoxication, and hypertensive brain hemorrhage, are readily recognized. Following this, the basic electrolyte, glucose and renal function tests are established as a derangement of any of these may lead to stupor or coma. In certain circumstances a toxicology screen may be added, as if the patient is being seen the first time in an emergency setting.
Alterations in vital signs (temperature, heart rate, respiratory rate, and blood pressure) are important aids in diagnosis. Fever is most often the result of a systemic infection such as pneumonia or bacterial meningitis or viral encephalitis. An excessively high body temperature (42°C [107.6°F] or 43°C [109.4°F]) associated with dry skin should arouse suspicion of heat stroke or intoxication by a drug with anticholinergic activity. Fever should not be too easily ascribed to a brain lesion that has disturbed the temperature-regulating center, so-called central fever, which is a rare occurrence. Hypothermia is observed in patients with alcohol or barbiturate intoxication, drowning, exposure to cold, peripheral circulatory failure, advanced tuberculous meningitis, and myxedema.