Barbiturates Poisoning, Emergency Medicine

Basics

Description

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

Etiology

Overdose of barbiturates: �

Intentional or nonintentional

Diagnosis

Signs and Symptoms

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"�

History

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.

Physical Exam

CNS abnormalities:
- Ataxia to coma
Respiratory depression
Cardiovascular:
- Bradycardia and hypotension
Ophthalmologic:
- Miosis
- Nystagmus
- Dysconjugate gaze
Hypothermia
Bullae or "barb blisters"�

Essential Workup

Fingerstick glucose
Oxygen saturation monitor
Monitor BP

Barbiturate poisoning can mimic brain death: �

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

Diagnosis Tests & Interpretation

Lab

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

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 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

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 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

Medication

First Line

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)

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

Follow-Up

Disposition

Admission Criteria
ICU admission for: �

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 �
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. �

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 �DC, Ferguson �KL. Sedative-hypnotic agents. In: Nelson �LS, Lewin �NA, Howland �MA, et al., eds. Goldfranks 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.

Codes

ICD9

967.0 Poisoning by barbiturates �

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)

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