Rosen & Barkin's 5-Minute Emergency Medicine Consult (93 page)

• Class of sedative–hypnotic agents
  
• Derivatives of barbituric acid
  
• Mechanism:
  
  • Enhances activity of γ-aminobutyric acid (GABA)
    
  • At high levels, directly opens GABA-A associated chloride channel
    
  • Leads to inhibition of vascular smooth muscle tone
    
  • May lead to direct myocardial depression
    

Overdose of barbiturates:

• Intentional or nonintentional
  

DIAGNOSIS

• CNS:
  
  • Lethargy
    
  • Slurred speech
    
  • Incoordination
    
  • Ataxia
    
  • Coma (can mimic brain death)
    
  • Loss of reflexes
    
• Cardiovascular:
  
  • Hypotension
    
  • Bradycardia
    
• Ophthalmologic:
  
  • Miosis (generally associated with deep coma)
    
  • Nystagmus
    
  • Dysconjugate gaze
    
• Other:
  
  • Respiratory depression
    
  • Hypothermia
    
  • Bullae or “barb blisters”
    

• Determine if there was an intentional overdose:
  
  • Pill bottles at the scene
    
  • History of depression or suicidal ideation
    
• Determine if there was a medication error:
  
  • What other medications was the patient taking?
    
  • Were there any recent changes in dose?
    
• Estimate how long the patient may have been unresponsive.
  

• CNS abnormalities:
  
  • Ataxia to coma
    
• Respiratory depression
  
• Cardiovascular:
  
  • Bradycardia and hypotension
    
• Ophthalmologic:
  
  • Miosis
    
  • Nystagmus
    
  • Dysconjugate gaze
    
• Hypothermia
  
• Bullae or “barb blisters”
  

• Fingerstick glucose
  
• Oxygen saturation monitor
  
• Monitor BP
  

• Electrolytes, BUN/creatinine, glucose:
  
  • Calculate anion gap
    
  • Assess for renal failure
    
• Urinalysis:
  
  • For myoglobin
    
  • For crystalluria (Primidone)
    
• Creatine phosphokinase for evidence of rhabdomyolysis
  
• Urine toxicology screen
  
• Obtain serum phenobarbital level (if suspected)
  
• Acetaminophen and salicylate levels if suspected suicide attempt
  
• Thyroid function tests
  

• CT scan of head for altered mental status
  
• CXR for evidence of aspiration
  

• Noncontrast head CT
  
• Lumbar puncture
  

• Sedative–hypnotic poisoning (including γ-hydroxybutyrate [GHB] and its precursors)
  
• Carbon monoxide poisoning
  
• CNS infections
  
• Space-occupying lesions of the head
  
• Hypoglycemia
  
• Uremia
  
• Electrolyte imbalance (i.e., hypermagnesemia)
  
• Postictal state following seizure
  
• Hypothyroidism
  
• Liver failure
  
• Psychiatric illness
  

TREATMENT

• Moderate to severe poisonings require paramedic transport.
  
• Intubation is often necessary because of respiratory depression or loss of gag reflex.
  
• IV access and supplemental oxygen:
  
  • IV fluid bolus for hypotension
    

• ABCs:
  
  • Administer supplemental oxygen.
    
  • Severe poisonings usually require endotracheal intubation.
    
• 0.9% NS:
  
  • Hypotensive patients require at least 1–2 L IV fluid resuscitation.
    
  • Pressor support may be necessary for refractory hypotension.
    
• Activated charcoal effectively binds barbiturates and may decrease systemic absorption.
  

• Administer 1 dose of activated charcoal:
  
  • Utility greatest if given within 1 hr of ingestion
    
  • Ensure patient is awake and alert (or airway protected) prior to administration.
    
  • Consider “gut dialysis” with repeated dose activated charcoal (without sorbitol) given q2–4h (as long as bowel sounds are present).
    
• Rewarm patient if hypothermic (see “Hypothermia” chapter).
  
• Treat hypotension resistant to IV fluid bolus with vasopressors (dopamine, norepinephrine, epinephrine).
  
• Treat hyperkalemia (from muscle breakdown) with calcium, sodium bicarbonate, insulin and glucose, and/or potassium-binding agents.
  
• Repeat phenobarbital level in 2–4 hr to determine whether level is increasing.
  
• Consider hemodialysis if patient has
  
  • decreased or no renal function
    
  • prolonged coma
    
  • serum phenobarbital level >100 mg/dL
    
  • refractory hypotension
    
• There is no role for urinary alkalinization
  

• Activated charcoal: 1 g/kg PO
  
• Dopamine: 5–10 μg/kg/min titrating to desired effect (to max. of 20 μg/kg/min)
  
• Norepinephrine: 2–4 μg/min titrating to desired effect (to max. of 10 μg/min)
  

Epinephrine: 0.1 μg/kg/min titrating to desired effect (to max. of 1 μg/kg/min)

FOLLOW-UP

ICU admission for:

• Coma
  
• Respiratory depression
  
• Hypotension
  
• Hypothermia
  
• Rhabdomyolysis
  

Asymptomatic after a minimum of 6 hr of observation with 2 consecutive subtoxic phenobarbital levels before discharge

• If intentional overdose, will require psychiatric evaluation
  
• For nonintentional overdose, referral for adjustment in medications
  

For nonintentional overdose, may need referral for adjustment in medications or change of medications to agents with a greater therapeutic window.

• Hypothermia may be pronounced:
  
  • Ensure accurate core temperature is measured.
    
• Check for rhabdomyolysis, since the patient may have been down for a while.
  
• Barbiturate poisoning can cause prolonged coma:
  
  • Ensure medication effects have resolved prior to making diagnosis of brain death.
    

• Lee DC, Ferguson KL. Sedative-hypnotic agents. In: Nelson LS, Lewin NA, Howland MA, et al., eds.
  Goldfrank’s Toxicologic Emergencies
  . 9th ed. New York, NY: McGraw-Hill; 2010.
  
• Pond SM, Olson KR, Osterloh JD, et al. Randomized study of the treatment of phenobarbital overdose with repeated doses of activated charcoal.
  JAMA
  . 1984;251:3104–3108.
  
• Roberts DM, Buckley NA. Enhanced elimination in acute barbiturate poisoning—a systematic review.
  Clin Toxicol (Phila).
  2011;49:2–12.
  

See Also (Topic, Algorithm, Electronic Media Element)

• Benzodiazepine, Poisoning
  
• Coma
  
• Hypothermia
  
• Rhabdomyolysis
  

CODES

967.0 Poisoning by barbiturates