Coma

Definition and CausesTop

Coma is a prolonged loss of consciousness with reduced response to external stimuli. Causes: Table 1.

ManagementTop

1. Assess the patient (see Loss of Consciousness).

2. Assess consciousness (depth of coma): Check responsiveness (to voice, touch, and pain) using the Glasgow Coma Scale (GCS) (see Table 2 in Impaired Consciousness). Reevaluate the GCS score often to monitor for any fluctuation in the patient’s mental status.

3. Perform a complete head-to-toe assessment:

1) Vital signs: Tachycardia, bradycardia, hyperthermia, hypothermia, hyperventilation, hypoventilation, hypertension, hypotension.

2) Eyes: Pupil size and reactivity, nystagmus, gaze deviation, scleral icterus; fundoscopy for papilledema.

3) Head and neck: Meningismus, tongue biting (especially the lateral aspects of the tongue), Battle sign.

4) Neurologic examination: Ability to follow commands, tone, deep tendon reflexes, Babinski reflex, asterixis, posturing (decerebrate/extensor or decorticate/flexor), convulsions, myoclonus.

5) Cardiovascular examination: Murmurs, arrhythmias, volume status.

6) Respiratory examination: Pattern of breathing (Cheyne-Stokes, Kussmaul), decreased breath sounds, wheezes, crackles.

7) Abdominal examination: Distension, ascites, peritoneal signs, distended bladder.

8) Dermatologic examination: Cellulitis, sacral or heel ulceration, signs of IV drug use.

4. Initiate universal and specific antidotes (as applicable):

1) Thiamine 100 mg IM or IV (administer before glucose [dextrose]).

2) Glucose (1 ampoule of 50% dextrose in water).

3) Naloxone 0.4 mg IV (if opioid overdose is suspected).

4) Supplemental oxygen (100% fraction of inspired oxygen [FiO2] if carbon monoxide poisoning is suspected).

5. Order diagnostic tests:

1) Electrocardiography (ECG).

2) Laboratory tests:

a) Complete blood count (CBC): An elevated white blood cell count may indicate a central nervous system infection.

b) Serum biochemistry tests: Serum levels of glucose (low or elevated in hyperosmolar hyperglycemic nonketotic coma and diabetic ketoacidosis), sodium, potassium, ammonia (usually elevated in hepatic coma), urea/blood urea nitrogen (BUN) and creatinine (elevated in uremia), lactate (elevated in hypoxia and shock), calcium (elevated in hypercalcemic crisis), phosphate, magnesium.

c) Arterial blood gas analysis may reveal hypercapnia, hypoxemia, and acidosis.

d) Serum and urine osmolality (elevated in toxic alcohol ingestions).

e) Toxicology screen if ingestion suspected.

f) Levels of acetylsalicylic acid (ASA) and paracetamol (INN acetaminophen) (in all patients with suspected overdose, as ingestion is common).

g) Thyroid-stimulating hormone (TSH) levels (high in myxedema coma).

h) Urinalysis: Elevated ketone bodies (and sometimes glucose) in ketoacidosis.

i) Lumbar puncture and cerebrospinal fluid examination if meningitis or encephalitis are suspected.

3) Imaging studies: Computed tomography (CT) of the head with no contrast enhancement allows visualization of intracranial bleeding and cerebral edema. Chest radiographs are used to assess for atelectasis due to aspiration (perform a therapeutic bronchoscopy if necessary).

6. Perform a differential diagnosis of coma (Table 1), determine the cause, and treat the underlying condition, if possible.

TablesTop