Coma

Chapter: Coma
McMaster Section Editor(s): Akbar A. Panju
Section Editor(s) in Interna Szczeklika: Miłosz Jankowski
McMaster Author(s): Hassan Masoom, Serena Gundy, Jason Cheung, Mohamed Panju, Ameen Patel
Author(s) in Interna Szczeklika: Miłosz Jankowski, Grażyna Zwolińska
Additional Information

Definition and CausesTop

Coma is a prolonged loss of consciousness with reduced response to external stimuli. Causes: Table 10.4-1.

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 10.3-2). 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: 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 studiesComputed 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 10.4-1), determine the cause, and treat the underlying condition, if possible.

TablesTop

Table 10.4-1. Typical manifestations of coma based on etiology

Etiology

Causes

Typical manifestations

Vascular

Subarachnoid or intracranial hemorrhage

Sudden onset, headache, vomiting, focal neurologic signs, signs suggestive of meningitis

Extensive stroke affecting bilateral cerebral hemispheres or brainstem

Sudden onset, focal neurologic signs, progressive clinical deterioration

Trauma

Direct brain injury or accumulating subdural hematoma

History of trauma, lacerations or other signs of head trauma, bleeding from ears or CSF leakage from nose or ears

Increased intracranial pressure

Brain tumor or abscess, subdural hematoma

History of escalating headache, progressive impairment of mental status, papilledema, focal neurologic signs

Inflammatory

Meningitis

History of headache and fever, subacute course, signs suggestive of meningitis

Encephalitis

As above plus signs of disseminated encephalopathy, seizures, involuntary movements

Metabolic

Hypoglycemia

Hyperhidrosis, dilated pupils, seizures, hyporeflexia, Babinski sign, sometimes focal neurologic signs

Hyperglycemia

Hyperventilation, Kussmaul breathing

Uremia

Progressive apathy, progressive obtundation, tremor, seizures

Liver disease

Coma preceded by memory impairment, confusion, and somnolence with subsequent development of pyramidal, extrapyramidal, and cerebellar signs and low frequency tremor

Hypercalcemia

Signs of hypercalcemia

Hyponatremia

Cerebral edema caused by changes in CSF and cell tonicity, can also be provoked by overly rapid correction in patient with chronic derangement

Hypernatremia

Signs of hypernatremia

Myxedema

History of hypothyroidism, gradual deterioration over weeks, common hypercapnia

Epilepsy

Epilepsy

Sudden abnormalities in behavior or mental status, seizures, sometimes extremity paresis

Hypoxia

Cardiac and respiratory arrest

Sudden onset, decortication or decerebration, myoclonus, epileptic seizures

Hypercapnia

Carbon dioxide retention in patients with respiratory insufficiency

Gradual deterioration of mental status, prior headache, shallow respiration, conjunctival injection

Extreme body temperatures

Hypothermia

Signs of hypothermia

Hyperthermia

Signs of hyperthermia

Toxins

Toxic alcohols, ethanol

Signs of alcohol intoxication

Anticholinergics, sedative hypnotics, antipsychotics, opioids, carbon monoxide poisoning

Signs of poisoning and intoxication

Psychiatric

Catatonia, pseudocoma

History of psychiatric diagnosis and deterioration, normal cold caloric testing

CSF, cerebrospinal fluid.

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