Coma
Background
- Coma is a state of unresponsiveness from which the patient cannot be aroused, even with vigorous stimuli[1]
- Defined as GCS ≤8 or inability to follow commands, speak, or open eyes[2]
- Requires dysfunction of both cerebral hemispheres or the reticular activating system (brainstem)
- Coma is a medical emergency — rapid assessment and stabilization take priority while pursuing diagnosis
- The mnemonic AEIOU-TIPS helps recall the differential:
- A — Alcohol, Acidosis
- E — Endocrine, Electrolytes, Encephalopathy
- I — Insulin (hypoglycemia, DKA, HHS)
- O — Opiates, Overdose, Oxygen (hypoxia)
- U — Uremia
- T — Trauma, Temperature
- I — Infection (meningitis, encephalitis, sepsis)
- P — Psychiatric (rare, diagnosis of exclusion), Poisoning
- S — Stroke, Seizure (nonconvulsive status), Shock
Clinical Features
- No eye opening, verbal response, or motor response to command
- Key exam components:
- Pupils: Bilateral fixed/dilated (anoxic brain injury, sympathomimetic), bilateral pinpoint (opioids, pontine lesion), unilateral fixed/dilated (uncal herniation, CN III compression)
- Eye movements: Oculocephalic reflex (doll's eyes), oculovestibular reflex (cold calorics); absent = brainstem dysfunction
- Motor response: Purposeful withdrawal, flexion posturing (decorticate), extension posturing (decerebrate), flaccid
- Breathing pattern: Cheyne-Stokes (bilateral hemispheric or early transtentorial), central hyperventilation (midbrain), ataxic/apneustic (medulla/pons)
- Signs of trauma: Battle sign, raccoon eyes, hemotympanum, scalp lacerations
Differential Diagnosis
Structural Causes
- Stroke (ischemic or hemorrhagic)
- Intracranial hemorrhage (subdural hematoma, epidural hemorrhage, subarachnoid hemorrhage)
- Elevated intracranial pressure / herniation syndromes
- Brain tumor with mass effect
- Cerebral venous sinus thrombosis
- Brain abscess
- Hydrocephalus
- Traumatic brain injury
Diffuse/Metabolic Causes
- Hypoglycemia — most important to rule out immediately
- Drug overdose / poisoning (opioids, benzodiazepines, barbiturates, alcohols)
- Hepatic encephalopathy
- Uremia
- Sepsis / systemic infection
- Meningitis / Encephalitis
- Nonconvulsive status epilepticus
- DKA / HHS
- Hypothermia / hyperthermia
- Hyponatremia / hypernatremia
- Carbon monoxide toxicity
- Hypertensive encephalopathy
- Anoxic brain injury (post-cardiac arrest)
- Wernicke encephalopathy
- Myxedema coma / thyroid storm
Evaluation
- Immediate:
- ABCs — secure airway if GCS ≤8 (intubate)
- Finger stick glucose — treat hypoglycemia immediately
- Rapid vitals including temperature
- Focused workup:
- CBC, BMP, LFTs, ammonia, lactate, VBG/ABG
- Toxicology screen (urine drug screen, serum ethanol, salicylate, acetaminophen levels)
- Serum osmolality and osmolar gap
- Blood cultures if infection suspected
- Coagulation studies (PT/INR) if bleeding or liver disease suspected
- Thyroid function (TSH) if no clear cause identified
- Imaging:
- CT head without contrast — first-line; rules out hemorrhage, mass, hydrocephalus, herniation
- Consider CTA head/neck if large vessel occlusion or vascular dissection suspected
- MRI if CT negative and structural cause still suspected
- Other:
- Lumbar puncture if meningitis/encephalitis suspected (after CT, if safe)
- EEG for suspected nonconvulsive status epilepticus
- ECG — arrhythmia or toxicologic cause
Management
- Stabilize first:
- Airway protection — intubate if GCS ≤8 or unable to protect airway
- IV access, continuous monitoring
- Treat hypoglycemia immediately with dextrose
- Empiric interventions ("coma cocktail"):
- Dextrose (D50) if glucose unknown or low
- Thiamine 100 mg IV (give before or with glucose to prevent Wernicke encephalopathy)
- Naloxone 0.4-2 mg IV if opioid overdose suspected (pinpoint pupils, respiratory depression)
- Flumazenil — generally avoided in undifferentiated coma (risk of seizures in benzodiazepine-dependent patients)
- Treat underlying cause once identified
- Herniation management if signs present (unilateral dilated pupil, posturing):
- Head of bed 30°
- Mannitol or hypertonic saline
- Emergent neurosurgical consultation
- See Elevated intracranial pressure
Disposition
- All comatose patients require ICU admission
- Emergent neurosurgical consultation for surgical lesions (EDH, SDH with mass effect, hydrocephalus)
- Neurology consultation for suspected nonconvulsive status epilepticus or unexplained coma
See Also
- Altered mental status
- Altered mental status (peds)
- Elevated intracranial pressure
- Herniation syndromes
- Glasgow Coma Scale
- Nonconvulsive status epilepticus
- Hypoglycemia