Coma

Abstract

The spectrum of depressed consciousness includes lethargy, stupor, and coma. Coma is characterized by the total absence of awareness of self and relationship to the environment without any localizing or discrete defensive responses to external painful stimuli. Coma may be due to structural, infectious, seizure-related, toxic, metabolic, and systemic causes among other etiologies. It is imperative to identify patients with a sufficiently depressed level of consciousness that may place them at risk for aspiration and respiratory compromise. Obtaining supplemental sources of history from witnesses, relatives, and emergency medical services is key. These patients require expeditious and systematic evaluation and stabilization of airway, breathing, and circulation. Beyond routine labs, early investigations should include finger-stick glucose, arterial blood gases, toxicology screens, and an emergent head CT scan to rule out intracranial lesions. More detailed neurological examination should be done when sedation is sufficiently held. Deficits in mental status, cranial nerve function, and motor and sensory examination findings indicate the extent of neurological injury and have prognostic value. Further investigations may include lumbar puncture, EEG, and brain MRI/MRA. Depending on the underlying cause, treatment may involve that for raised intracranial pressure, specific therapy for cytotoxic and vasogenic edema as well as meningitis/encephalitis. Usually coma from metabolic causes and drug intoxication has the most favorable prognosis followed by coma secondary to trauma, whereas coma from hypoxic ischemic encephalopathy carries the least favorable prognosis.