Barbiturate Poisoning

Clinical assessment

Based on history of ingestion (if known or suspected). Clinical picture dominated by CNS depression, respiratory depression, hypotension, and hypothermia. Consider barbiturate overdose in any patient presenting with coma of unknown origin.

Investigations

• Serum Barbiturate Levels: Can confirm exposure and help guide management, especially for phenobarbital (quantitative levels useful).
• Arterial Blood Gas (ABG): Essential to assess severity of respiratory depression (hypercapnia, hypoxia) and presence of metabolic acidosis (from hypoxia/hypoperfusion).
• Point-of-care Blood Glucose: Rule out hypoglycemia.
• Electrocardiogram (ECG): Monitor heart rate and rhythm, assess for conduction abnormalities.
• Chest X-ray: Evaluate for aspiration pneumonia or pulmonary edema.
• Consider: Electrolytes, Renal function tests, Creatine Kinase (CK) for rhabdomyolysis (due to prolonged immobility/coma).
• Rule out other causes of coma/CNS depression.

Diagnostic criteria

Clinical syndrome consistent with barbiturate toxicity + History of exposure +/- Confirmatory serum drug levels.

Non-pharmacological management

• Stabilization: ABCDE approach is paramount.
• Airway Management: High priority. Intubation and mechanical ventilation are frequently required for patients with coma (GCS <8), inability to protect airway, or severe respiratory depression.
• Breathing Support: Provide supplemental oxygen. Ensure adequate ventilation (mechanical if intubated).
• Circulation Support: Establish IV access. Administer IV fluids (Normal Saline or Ringer's Lactate) for hypotension. If hypotension persists despite fluids, vasopressors (e.g., norepinephrine) may be needed (Hospital level).
• Temperature Management: Gradual rewarming for hypothermia (passive measures like blankets, warm IV fluids; active rewarming if severe).
• GI Decontamination:
• - Activated Charcoal (Single dose): Consider 50g oral/NGT if patient presents within 1-2 hours of ingestion AND the airway is protected (e.g., patient is intubated).
• - Multiple-Dose Activated Charcoal (MDAC): Particularly effective for enhancing elimination of phenobarbital (long-acting). Give 25-50g every 4-6 hours via NGT. Requires protected airway and presence of bowel sounds. Contraindicated in ileus.
• - Gastric Lavage: Generally NOT recommended due to risk of aspiration and limited efficacy.
• Skin Care: Prevent pressure sores in comatose patients.
• Enhanced Elimination (Hospital/RR):
• - Haemodialysis or Haemoperfusion: Effective for removing long-acting barbiturates like phenobarbital in cases of severe poisoning (e.g., very high levels, refractory shock, renal failure, failure to improve with supportive care).

Pharmacological treatment

• Supportive Care is the Mainstay: There is no specific antidote for barbiturate poisoning.
• Urinary Alkalinization: For phenobarbital poisoning specifically. IV Sodium Bicarbonate infusion to maintain urine pH 7.5-8.5 enhances renal excretion. Requires careful monitoring of fluid balance, electrolytes (esp. K+), urine pH, and serum pH (Hospital/RR).
• Treat complications: e.g., antibiotics for aspiration pneumonia.

Monitoring

Continuous monitoring of: Vital signs (HR, BP, RR, SpO2, Temp), Neurological status (GCS), Respiratory status (ventilator parameters if intubated), Cardiovascular status (ECG, need for vasopressors), Urine output, Fluid balance. Monitor electrolytes, acid-base status (ABG), renal function. Monitor phenobarbital levels if MDAC or enhanced elimination used.