Psychiatry · Substance-Related Disorders
The facts most likely to be tested
Alcohol intoxication presents with slurred speech, ataxia, nystagmus, and disinhibition due to GABA-A receptor agonism and NMDA receptor antagonism.
The osmolar gap is elevated in alcohol intoxication because ethanol is an osmotically active substance that contributes to serum osmolality.
Patients with alcohol intoxication are at high risk for hypoglycemia because ethanol metabolism inhibits gluconeogenesis by increasing the NADH/NAD+ ratio.
Wernicke encephalopathy is a critical complication of chronic alcohol use, characterized by the classic triad of confusion, ophthalmoplegia, and ataxia.
Thiamine (Vitamin B1) must be administered before glucose in patients with suspected alcohol use disorder to prevent the precipitation of Wernicke-Korsakoff syndrome.
The anion gap metabolic acidosis seen in alcohol-related presentations is often due to alcoholic ketoacidosis resulting from increased beta-hydroxybutyrate production.
Respiratory depression and aspiration pneumonia are the most common life-threatening complications of severe acute alcohol intoxication.
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A 42-year-old male is brought to the emergency department by police after being found unconscious on the street. On examination, he has slurred speech, horizontal nystagmus, and gait ataxia. His blood glucose is 45 mg/dL, and his serum osmolality is 320 mOsm/kg. He appears confused and has bilateral ophthalmoplegia on extraocular movement testing.
What is the most appropriate initial step in the management of this patient's neurological findings?
Intravenous thiamine administration
The patient exhibits signs of Wernicke encephalopathy; thiamine must be administered before glucose to prevent the depletion of remaining thiamine stores during glucose metabolism.
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Etiology / Epidemiology
Caused by ethanol ingestion; common in binge drinkers and those with alcohol use disorder.
Clinical Manifestations
Presents with slurred speech, ataxia, and disinhibition; respiratory depression is the primary emergency.
Diagnosis
Diagnosis is clinical; serum ethanol level is the gold standard for quantification.
Treatment
Management is supportive care; do not induce emesis due to aspiration risk.
Prognosis
Most recover with metabolism; aspiration pneumonia and hypoglycemia are major mortality risks.
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Epidemiology & Etiology
Prevalence is highest in young adults and those with comorbid psychiatric conditions. Acute intoxication occurs when the rate of ingestion exceeds the liver's zero-order kinetics metabolism. Risk factors include low body mass, empty stomach, and lack of tolerance.
Pertinent Anatomy
The cerebellum is highly sensitive to ethanol, explaining the classic ataxia and impaired coordination. The medulla is the final target during severe overdose, leading to the life-threatening respiratory depression.
Pathophysiology
Ethanol acts as a potent GABA-A receptor agonist (inhibitory) and an NMDA receptor antagonist (excitatory). This dual action causes global CNS depression. Chronic exposure leads to receptor downregulation, explaining the tolerance seen in heavy users.
Clinical Manifestations
Patients exhibit slurred speech, nystagmus, and impaired judgment. Severe cases present with stupor or coma. Respiratory depression and aspiration are the most critical red flags requiring immediate airway protection.
Diagnosis
Diagnosis is primarily clinical based on history and physical exam. The serum ethanol level is the gold standard for objective measurement. A level of >0.08% is the legal threshold for impairment, while >0.40% is often associated with coma.
Treatment
Treatment is supportive care focusing on airway, breathing, and circulation. Do not induce emesis due to the high risk of aspiration. Administer thiamine and glucose if Wernicke encephalopathy or hypoglycemia is suspected.
Prognosis
Most patients recover as the liver metabolizes the ethanol. Aspiration pneumonia and hypoglycemia are the most common complications. Patients must be monitored until they are sober and clinically stable.
Differential Diagnosis
Hypoglycemia: check fingerstick glucose immediately
Opioid overdose: look for pinpoint pupils and respiratory depression
Sedative-hypnotic overdose: similar presentation but often longer duration
Head trauma: always consider in intoxicated patients with altered mental status
Diabetic ketoacidosis: check anion gap and ketones