Coma

Background

• Coma is a state of unresponsiveness from which the patient cannot be aroused, even with vigorous stimuli
• Defined as GCS ≤8 or inability to follow commands, speak, or open eyes
• 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