Alcoholic coma: signs and treatment

Alcohol coma is a depression of consciousness to the level of sopor/coma due to high blood ethanol concentrations, often combined with hypoglycemia, hypothermia, trauma, and/or cointoxication (opioids, benzodiazepines, sedatives). Ethanol potentiates GABA-A and inhibits glutamate via NMDA receptors, leading to CNS depression, respiratory depression, bronchial hyporeflexia, and the risk of aspiration. The primary immediate threat to life is respiratory failure and aspiration of gastric contents. [1]

As the dose increases, systemic effects are added: vasodilation and hypothermia, osmotic diuresis and dehydration, hypoglycemia, electrolyte shifts, and QTc prolongation. In chronic alcohol consumers, the risk of thiamine deficiency and Wernicke's encephalopathy is particularly high; this is important during the first hours of treatment. [2]

The "coma threshold" depends on tolerance, but most people develop severe depression of consciousness at levels ≥300 mg/dL (0.30%), and coma/fatality is more common at ≥400 mg/dL (0.40%). However, paradoxical observations of survival at very high concentrations have been reported, so clinical assessment is more important than the level. [3]

The key to survival is early airway and oxygenation, correction of hypoglycemia and electrolytes, prevention of aspiration, monitoring for delayed deterioration, and searching for other/concomitant causes of coma: head injury, “toxic alcohols,” opioids, stroke, infection. [4]

Epidemiology

Alcohol intoxication is a common cause of emergency room visits; recent reviews highlight its widespread prevalence and the resource burden it places on healthcare systems. Young men are most vulnerable, but severe cases and coma are more common in those with mixed intoxication and in the elderly. [5]

Trauma center studies show that a significant proportion of patients are admitted with alcohol levels ≥150 mg/dL, with the association of high BAC → low GCS being strong but not absolute due to tolerance and associated factors. Retrospective series have noted survival even with BAC ≥400-500 mg/dL, emphasizing the need for clinical assessment and monitoring rather than "managing the numbers." [6]

In countries with a 0.05% driving threshold, the risk of accidents is significantly reduced—this is an important public marker, although it is not directly related to clinical coma. Nevertheless, these thresholds are useful for educational purposes. [7]

Comorbid conditions (infections, injuries, metabolic disorders) and cointoxication (especially opioids) dramatically increase the risk of respiratory depression, requiring a low threshold for naloxone administration in the prehospital/admission stages when opioid involvement is suspected. [8]

Reasons

The main cause is acute consumption of large doses of ethanol over a short period of time ("binge drinking"), especially on an empty stomach or with dehydration. The risk increases sharply when combined with sedatives (benzodiazepines, Z-drugs, barbiturates), opioids, and other CNS depressants. [9]

Less commonly, alcoholic coma develops against the background of chronic alcoholism at comparatively lower concentrations due to concomitant hypoglycemia, electrolyte imbalances, infection, head injury, and liver failure. In a cold environment, hypothermia is added. [10]

"Toxic alcohols" (methanol, ethylene glycol, isopropanol) should be considered separately: they also cause depression of consciousness, but have different metabolic profiles and require specific therapy (fomepizole/ethanol as antidotes, hemodialysis). They should be excluded in cases of anion-osmotic dissociation and clinical inconsistency with ethanol levels. [11]

In the context of trauma, the combination of traumatic brain injury and alcohol masks neurological deficits. Any somatic cause of coma (hypoxemia, hypercapnia, hypo/hyperglycemia, stroke, sepsis) can coexist with alcohol intoxication, and therefore a diagnosis of exclusion is impossible without a basic examination. [12]

Risk factors

Event factors: high rate of consumption ("games," "shots"), strength of drinks, lack of food, warm room (vasodilation). Environmental factors: cold street/water → hypothermia, loneliness (late presentation). [13]

Medical factors: liver failure, low thiamine stores, diabetes mellitus (risk of severe hypoglycemia), electrolyte disturbances, old age, pregnancy. In chronic consumers, risk of Wernicke/Korsakoff encephalopathy. [14]

Pharmacological factors: opioid/benzodiazepine co-administration. In the fentanyl era, any "questionable" collapse requires naloxone availability. [15]

Social factors: availability of alcohol, lack of supervision, trauma, mood disorders, substance use, history of falls/TBI.

Pathogenesis

Ethanol enhances GABAergic inhibitory transmission and reduces glutamatergic activity (NMDA), leading to diffuse CNS inhibition. At the brainstem level, respiratory drive is suppressed; simultaneously, upper respiratory tract tone and the cough reflex are reduced → aspiration. [16]

Metabolically, ethanol shifts the NADH/NAD⁺ ratio, impairing gluconeogenesis → hypoglycemia, especially in patients with depleted glycogen stores. Vasodilation and peripheral heat loss → hypothermia. Dehydration and diuresis (inhibition of antidiuretic hormone) lead to hypovolemia. [17]

Thiamine deficiency impairs the function of thiamine-dependent enzymes (pyruvate dehydrogenase) → energy deficit in vulnerable areas of the brain (mamillary bodies, thalamus) and Wernicke's encephalopathy. Maintaining glycemia without delays, but with early thiamine, is the modern standard. [18]

In opioid cointoxication, central respiratory depression is added; rapid administration of naloxone may prevent respiratory/cardiac arrest.[19]

Symptoms

Mild to moderate intoxication: dysarthria, ataxia, confusion, nausea/vomiting, skin flushing, tachycardia. With increasing doses, deep sleep, stupor, miosis or normal pupil size, hypothermia, and hypotension may occur.

Severe intoxication/coma: GCS ≤8, shallow breathing, depressed reflexes, possible episodes of apnea, decreased saturation, smell of alcohol from the mouth (does not exclude another cause!), wet wheezing on aspiration, vomiting of “coffee grounds” due to mucosal injury.

Neurological red flags: pupillary asymmetry, anisocoria, hemiparesis, seizures – suggest traumatic brain injury/stroke and prompt further diagnostic testing. Metabolic: hypoglycemia, hyponatremia, prolongation of QTc.

After withdrawal - headache, severe weakness, amnesia of the episode, signs of withdrawal are possible (after 6-24 hours).

Forms and stages

In practice, a distinction is made between: (1) acute alcoholic coma (ethanol ± cointoxicants), (2) coma of mixed genesis (ethanol + traumatic brain injury/stroke/sepsis), (3) prolonged coma (with hypoxic-ischemic brain injury/aspiration/ARDS). The GCS classification helps standardize severity.

Clinical staging: depression phase (minutes to hours after ingestion), complication phase (aspiration, hypoxemia, metabolic breakdowns), recovery/observation phase (6-24 hours and longer in case of cointoxication). Each phase has its own priorities.

Chronic users have a special "latent" stage - thiamine deficiency and Wernicke's risk: ophthalmoplegia/nystagmus, ataxia, confusion; if suspected - immediate thiamine.

If toxic alcohols (methanol/ethylene glycol) are suspected, the staging is different (latent period, then metabolic acidosis/visual disturbances/renal failure) - this is a different protocol.

Complications and consequences

Early: aspiration pneumonia, hypoxemia, respiratory arrest, hypoglycemia and seizures, hypothermia, rhabdomyolysis, trauma (including traumatic brain injury). Without observation, death may occur "in the sleep." [20]

Delayed: pneumonia/ARDS after aspiration, delirium, withdrawal syndrome, rhabdomyolysis with acute renal failure, pressure ulcers. As patients recover, behavioral disorders, staff injuries, and patient loss from observation may occur.

Neurological: with hypoxia/prolonged hypoglycemia - diffuse brain damage, cognitive consequences. With thiamine deficiency - Wernicke-Korsakoff syndrome.

Rarely, in the case of extremely high levels and severe clinical symptoms, hemodialysis is considered to accelerate the elimination of ethanol if support resources have been exhausted/there is a threat of organ failure (the decision is individual, with a toxicologist/nephrologist). [21]

Diagnostics

The primary rule is ABC: assess the airway, breathing, and circulation, then quickly check glucose (capillary/blood) and saturation. For all severe cases, ECG, core temperature, pulse oximetry, and, if indicated, blood gas analysis. [22]

Laboratory: blood ethanol (better than urine), electrolytes, creatinine, ALT/AST, lactate, osmolality (calculated "osmolar gap"), anion gap - to exclude toxic alcohols and other metabolic causes. If in doubt - toxicology screening. [23]

Imaging: If there is any suspicion of injury/focal deficit, perform a CT scan of the head; if aspiration is present, perform a chest X-ray/CT scan. Evaluation of limb and spine injuries is clinical. A diagnosis of "alcohol-only" is made after excluding other pathologies. [24]

In chronic users and/or post-withdrawal confusion, Wernicke assessment and low threshold for parenteral thiamine. [25]

Differential diagnosis

Toxic alcohols (methanol, ethylene glycol, isopropanol): clinical signs out of proportion to ethanol levels, marked anion/osmolar gap, visual symptoms (methanol), oxaluria and renal failure (ethylene glycol). Require fomepizole/hemodialysis. [26]

Opioids: marked bradyrespiration/apnea, miosis, cyanosis. Naloxone (IV, IM, intranasal) with repeated doses is indicated; this may “unmask” the contribution of opioids in the presence of ethanol. [27]

Head injury/stroke/meningitis: focal deficit, meningeal signs, seizures, persistent loss of consciousness not consistent with an “alcohol-induced” scenario → neuroimaging and specialist consultations. [28]

Metabolic: hypoglycemia, hyper/hyponatremia, hypercapnia, hypothermia - checked in each patient with impaired consciousness (*see Table 4). [29]

Treatment

1) The first minutes - life support.

• Airway management: lateral position/endotracheal intubation if indicated, suction, and oxygen. The primary goal is to prevent aspiration and correct hypoxemia/hypoventilation.
• Glucose: If hypoglycemia occurs, give dextrose immediately; do not withhold glucose due to lack of thiamine, but give thiamine as early as possible (usually 100 mg IV; in high-risk groups, higher and/or multiple doses according to a local regimen). [30]
• Naloxone: if opioid use is suspected or respirations <12/min - empirically; if response - continue monitoring and repeat/infusion doses. Flumazenil is not used routinely. [31]

2) Support and prevention of complications.

• Infusions as indicated (there is no evidence that “IVs speed up sobriety”; the goal is correction of hypovolemia/electrolytes).
• Correction of hypothermia (active warming), control of electrolytes (especially Mg, K, P - important for the prevention of arrhythmias and withdrawal syndrome).
• Prevention and treatment of aspiration: positioning, early sanitation, antibiotics according to clinical indications, not “prophylactically”. [32]

3) Monitoring and surveillance.

• Continuous pulse oximetry, frequent respiratory/level of consciousness monitoring, repeat gases/laboratory as indicated.
• In patients with severe depression, observe for at least 6-24 hours as delayed aspiration/worsening may occur. [33]

4) When to consider hemodialysis?

• Rarely, in cases of extremely severe ethanol intoxication with refractory instability/organ dysfunction, if standard measures have been exhausted and toxicology support is available. Data are limited (cases/series), and the decision is individualized (toxicologist + nephrologist). This is not a standard, unlike for toxic alcohols. [34]

5) After stabilization – secondary prevention.

• Withdrawal risk assessment (with chronic use), thiamine supplementation, correction of deficiencies (Mg/P), referral to alcohol use disorder (AUD) services, motivational counseling, safety plan. [35]

Table 1. Blood alcohol levels (BAC) and estimated effects

BAC (mg/dL)	Clinical picture (average; variable)
50-100 (0.05-0.10%)	Euphoria, decreased coordination, reactions
150-250	Severe ataxia, vomiting, drowsiness
≥300 (0.30%)	Deep CNS depression, risk of coma
≥400 (0.40%)	Coma/respiratory arrest/fatality is more common

Table 2. Red flags for suspected mixed poisoning

Sign	What to suspect	Actions
Respiration <12/min, miosis	Opioids	Naloxone with repeat/infusion, observation
Anisocoria, focal deficit	Head injury/stroke	Urgent CT scan, neuroconsultation
Severe acidosis, osmolar gap	Methanol/ethylene glycol	Fomepizole, hemodialysis, toxicologist
Prolonged QTc, arrhythmia	Electrolytes/hypothermia, medications	Correction of K/Mg, warming, monitoring

Table 3. "Coma cocktail" - what is relevant and what is outdated

Component	Today's approach
Glucose	In case of hypoglycemia - immediately, do not wait for thiamine
Thiamine	IV before/together with glucose and then the course for the risk group
Naloxone	Clinically/suspected opioid use, low threshold
Flumazenil	Not routinely (risk of seizures), only according to strict indications

Table 4. Minimum diagnostic package for alcoholic coma

Study	For what
Capillary glucose	Rapidly identify/treat hypoglycemia
SpO₂ / blood gases	Assess respiratory failure
ECG, core temperature	Arrhythmias, hypothermia
Electrolytes, lactate, creatinine	Metabolic disorders/kidneys
Ethanol in the blood	Confirmation, dynamics
Osmolality/anion gap	Eliminate toxic alcohols
CT scan of the head (as indicated)	Rule out traumatic brain injury/stroke

Table 5. Airway and ventilation support

Situation	Tactics
Decreased level of consciousness, lack of protective reflexes	Positioning on the side, ready for intubation
Hypoxemia/hypoventilation	O₂, if necessary - NIV/ALV
Suspected opioids	Naloxone, monitoring, repeat doses
Aspiration	Suction, ventilation, antibiotics according to the clinic

Table 6. Thiamine and glucose: how to combine

Scenario	Recommendation
Hypoglycemia	Give glucose immediately
Wernicke's risk (alcoholism, exhaustion, vomiting)	Thiamine 100 mg IV before/together with glucose, then a course
Long-term carbohydrate infusion	Be sure to add thiamine.
No access to vein	IM/oral forms depending on the situation, but try to administer IV

Table 7. When to consider hemodialysis (not toxic alcohols)

Indicators	Comment
Extremely high ethanol levels + refractory instability/pulmonary edema/liver failure	Rarely and individually, after consultation with a toxicologist/nephrologist
Unavailability/inefficiency of standard support	Consider extracorporeal purification as an exception
NB: For methanol/ethylene glycol	Hemodialysis - standard according to indications

Prevention

Personal and family prevention. Avoid binge drinking and combining alcohol with sedatives/opioids. Do not leave a drinking person alone – if they are very drowsy, place them on their side, monitor their breathing, and call for help if breathing is slow or noisy. Training in the use of naloxone in families at risk of opioid cointoxication is a separate safety measure. [36]

Systemic measures. Promote safe behavior (avoid driving with a BAC ≥0.05%), access to AUD support programs, reduce the stigma of seeking help, and train bar/club staff to recognize danger signs. For services, provide clear "alcohol coma/unclear impaired consciousness" pathways with an emphasis on ABC, glucose, thiamine, and selective naloxone. [37]

Forecast

With prompt airway support, correction of hypoglycemia/hypothermia, and observation for 6-24 hours, most patients with isolated alcoholic coma recover consciousness without neurological sequelae. Risks are higher with aspiration, trauma, and opioid/sedative cointoxication.[38]

An unfavorable prognosis is associated with missed hypoxemia/aspiration, late presentation, severe hypoglycemia and lack of follow-up, as well as significant comorbidities (liver failure). In rare cases of extremely severe intoxication, hemodialysis is considered; however, for toxic alcohols, this is the standard, and for ethanol, the exception. [39]

FAQ

• In case of alcoholic coma, should glucose be given only after thiamine?

No. In case of hypoglycemia, glucose is administered immediately, and thiamine is administered before/along with glucose, and then as a course in the risk group. Retaining glucose is dangerous. [40]

• Does everyone need sobering-up IVs?

There is no evidence that infusions accelerate ethanol elimination; fluids are prescribed as indicated (hypovolemia, electrolytes). The main factors are airway management, oxygen, blood sugar, and observation. [41]

• When to give naloxone?

If there are signs of opioid contribution (bradyrespiration, miosis, apnea) or the situation is unclear, there is a low threshold for administering naloxone; if there is a response, observe and repeat doses/infusion. [42]

• At what BAC numbers do people go into a coma?

More common at ≥0.30% (300 mg/dL) and especially at ≥0.40% (400 mg/dL); however, tolerance varies, so follow your doctor's advice and do not delay treatment while waiting for testing. [43]

• When should you think not about “regular” alcohol, but about methanol/ethylene glycol?

If clinical signs are inconsistent with the ethanol level, severe acidosis/osmolar gap, visual disturbances (methanol), or renal dysfunction (ethylene glycol), these poisonings require fomepizole and often hemodialysis. [44]