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Barbiturates Poisoning, Emergency Medicine

Basics

Description

- Class of sedative-hypnotic agents - Derivatives of barbituric acid - Mechanism: - Enhances activity of Оі-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

- Cardiovascular: - Ophthalmologic: - Miosis (generally associated with deep coma) - Nystagmus - Dysconjugate gaze

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

Etiology

Overdose of barbiturates: пїЅ

  • Intentional or nonintentional

Diagnosis

Signs and Symptoms

  • CNS:LethargySlurred speechIncoordinationAtaxiaComa (can mimic brain death)Loss of reflexes
  • Cardiovascular:
  • Ophthalmologic:Miosis (generally associated with deep coma)NystagmusDysconjugate gaze
  • Other:Respiratory depressionHypothermiaBullae or "barb blisters"пїЅ

History

  • Determine if there was an intentional overdose:Pill bottles at the sceneHistory 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.

Physical Exam

  • CNS abnormalities:
  • Respiratory depression
  • Cardiovascular:Bradycardia and hypotension
  • Ophthalmologic:MiosisNystagmusDysconjugate gaze
  • Hypothermia
  • Bullae or "barb blisters"пїЅ

Essential Workup

  • Fingerstick glucose
  • Oxygen saturation monitor
  • Monitor BP

Barbiturate poisoning can mimic brain death: пїЅ

  • Cannot pronounce a patient brain dead until barbiturate poisoning has been ruled out

Diagnosis Tests & Interpretation

Lab

  • Electrolytes, BUN/creatinine, glucose:Calculate anion gapAssess for renal failure
  • Urinalysis:For myoglobinFor 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

Imaging

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

Diagnostic Procedures/Surgery

  • Noncontrast head CT
  • Lumbar puncture

Differential Diagnosis

  • Sedative-hypnotic poisoning (including Оі-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

Pre-Hospital

  • 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

Initial Stabilization/Therapy

  • 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.

Ed Treatment/Procedures

  • Administer 1 dose of activated charcoal:Utility greatest if given within 1 hr of ingestionEnsure patient is awake and alert (or airway protected) prior to administration.Consider "gut dialysis"пїЅ with repeated dose activated charcoal (without sorbitol) given q2-4h (as long as bowel sounds are present).
  • Rewarm patient if hypothermic (see "Hypothermia"пїЅ 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 hasdecreased or no renal functionprolonged comaserum phenobarbital level >100 mg/dLrefractory hypotension
  • There is no role for urinary alkalinization

Medication

First Line

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

Second Line

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

Follow-Up

Disposition

Admission Criteria

ICU admission for: пїЅ

  • Coma
  • Respiratory depression
  • Hypotension
  • Hypothermia
  • Rhabdomyolysis

Discharge Criteria

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

Issues for Referral

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

Followup Recommendations

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

Pearls and Pitfalls

  • 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.

Additional Reading

  • Lee пїЅDC, Ferguson пїЅKL. Sedative-hypnotic agents. In: Nelson пїЅLS, Lewin пїЅNA, Howland пїЅMA, et al., eds. Goldfranks Toxicologic Emergencies. 9th ed. New York, NY: McGraw-Hill; 2010.
  • Pond пїЅSM, Olson пїЅKR, Osterloh пїЅJD, et al. Randomized study of the treatment of phenobarbital overdose with repeated doses of activated charcoal. JAMA. 1984;251:3104-3108.
  • Roberts пїЅDM, Buckley пїЅNA. 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

ICD9

967.0 Poisoning by barbiturates пїЅ

ICD10

  • T42.3X1A Poisoning by barbiturates, accidental (unintentional), init
  • T42.3X2A Poisoning by barbiturates, intentional self-harm, init
  • T42.3X4A Poisoning by barbiturates, undetermined, initial encounter

SNOMED

  • 44003006 Poisoning by barbiturate (disorder)
  • 216497003 Accidental poisoning by barbiturates (event)
  • 418108003 Barbiturate poisoning of undetermined intent (disorder)
  • 296036006 Barbiturate overdose (disorder)