Rosen & Barkin's 5-Minute Emergency Medicine Consult (123 page)

Higher incidence of neurologic manifestations

• Overdose of carbamazepine or extended-release versions
  
• Time of ingestion
  
• Is the bottle available
  
• Accidental or intentional ingestion
  
• Coingestions
  

• May present with seizures or altered mental status
  
• May be combative or drowsy
  
• Sinus tachycardia (massive carbamazepine overdose)
  
• Bradydysrhythmia (often seen in elderly with mild increase in carbamazepine level)
  
• Anticholinergic manifestations:
  
  • Decreased bowel sounds
    
  • Mydriasis
    
  • Flushing
    
  • Urinary retention
    
• Neuromuscular changes:
  
  • Tremor
    
  • Slurred speech
    
  • Myoclonus
    
  • Choreiform and choreoathetoid movements
    

• Continuous cardiac monitor
  
• Serum carbamazepine level:
  
  • Therapeutic, 6–12 μg/L
    
  • Levels >25–40 μg/mL associated with serious toxicity:
    
    • Coma
      
    • Seizures
      
    • Respiratory failure
      
    • Conduction defects
      
  • Serum levels do not clearly predict clinical toxicity:
    
    • Active metabolite carbamazepine 10, 11 epoxide not measured
      
    • Neurologic manifestations depend on CNS (not serum) level
      
  • Serial levels may be needed owing to erratic absorption of carbamazepine.
    
• ECG:
  
  • Conduction delays:
    
    • Increased QRS interval
      
    • Increased PR interval
      
    • QTc prolongation
      
  • Dysrhythmias
    
• Serum acetaminophen level (to evaluate for coingestion in a suicide attempt)
  

• CBC:
  
  • Leukopenia or leukocytosis
    
• Electrolytes, BUN/creatinine, glucose:
  
  • Hyperglycemia
    
  • Hypokalemia
    
  • Hyponatremia
    
• Arterial blood gases (ABGs)
  
• Urinalysis:
  
  • Glucosuria
    
  • Ketonuria
    
• Pregnancy test
  
• ALT, AST, bilirubin, alkaline phosphatase:
  
  • May be mildly elevated
    
  • Usually not clinically significant
    

CXR:

• Aspiration pneumonia
  
• Pulmonary edema
  

• Drugs that cause decreased mental status:
  
  • Alcohol
    
  • Anticholinergics
    
  • Barbiturates
    
  • Benzodiazepines
    
  • Lithium
    
  • Opiates
    
  • Phenothiazines
    
• Drugs that cause seizures:
  
  • Alcohol withdrawal
    
  • Anticholinergics
    
  • Camphor
    
  • Isoniazid
    
  • Lithium
    
  • Phenothiazines
    
  • Sympathomimetics:
    
    • Amphetamine
      
    • Cocaine
      
  • TCAs
    
• Drugs that cause abnormal movement:
  
  • Antihistamines
    
  • Butyrophenones
    
  • Caffeine
    
  • Cocaine
    
  • Levodopa
    
  • Meperidine
    
  • Phencyclidine
    
  • Phenothiazines
    
  • Phenytoin
    
  • TCAs
    

TREATMENT

• Do
  not
  administer ipecac.
  
• Intubate if significant respiratory depression or airway compromise.
  
• Secure IV access.
  
• Get complete information about all products potentially ingested.
  

• ABCs
  
• IV access and fluid resuscitation if hypotensive
  
• Oxygen
  
• Cardiac monitor
  
• Naloxone, thiamine, D
  ₅₀
  W (or Accu-Chek) if altered mental status
  

• General management:
  
  • Activated charcoal:
    
    • Administer sorbitol with 1st dose (only) of activated charcoal.
      
    • Administer with caution if GI activity is decreased.
      
    • Contraindicated if bowel sounds are absent
      
  • Multidose activated charcoal:
    
    • Decreases mean half-life of carbamazepine
      
    • Binds unabsorbed drug in GI tract
      
    • Interrupts enterohepatic circulation
      
    • Do not give additional sorbitol
      
  • Charcoal hemoperfusion/hemodialysis:
    
    • Removes small to moderate amount of ingested dose
      
    • Patients usually do well with supportive care without hemoperfusion or dialysis
      
    • Indicated in cases of clinical deterioration or lack of improvement with good supportive care
      
• Respiratory depression:
  
  • Intubation
    
  • Ventilatory support
    
• Hypotension:
  
  • Bolus with IV isotonic crystalloid solution
    
  • Norepinephrine if unresponsive to IV fluids
    
• Seizures:
  
  • Diazepam (drug of choice)
    
  • Phenobarbital (if diazepam ineffective)
    
  • Phenytoin not effective in most toxic seizures
    
• Cardiac conduction delay:
  
  • QRS widening (>100 msec):
    
    • Sodium bicarbonate (to overcome sodium channel blockade)
      
• Psychiatric consultation if suicide attempt
  

• Activated charcoal (initial bolus): Slurry 1–2 g/kg up to 100 g PO
  
• Multidose activated charcoal: 25 g (peds: 0.25 g/kg) q2h PO after bolus dose (above); can also use 50 g q6h PO/NG
  

• Dextrose: D
  ₅₀
  W 1 ampule: 50 mL or 25 g (peds: D
  ₂₅
  W 2–4 mL/kg) IV
  
• Diazepam: 5–10 mg (peds: 0.2–0.5 mg/kg) IV
  
• Naloxone (Narcan): 2 mg (peds: 0.1 mg/kg) IV/IM initial dose
  
• Norepinephrine: 2–4 μg/min (peds: 0.05–0.1 μg/kg/min) IV titrated to effect
  
• Sodium bicarbonate: 1 or 2 amps IV push (peds: 1–2 mEq/kg)
  

FOLLOW-UP

• Decreased mental status at any time, even if resolving (tends to recur with fluctuating drug levels):
  
  • Observe at least 24 hr for late relapse.
    
• Seizures
  
• Cardiac dysrhythmias
  
• Lack of psychiatric clearance after suicidal ingestion
  

• Asymptomatic after 6 hr of observation
  
• Normal mental status
  
• Normal or baseline ECG
  
• GI motility present
  
• Psychiatric clearance (after suicidal ingestion)
  

Suicidal patients need psychiatric evaluation referral.

Supratherapeutic dosing will need ongoing monitoring by physician treating underlying disorder.

• Carbamazepine levels commonly rebound to higher levels during treatment. Obtain serial measurements for severe ingestions.
  
• Monitor closely for arrhythmias.
  
• Multidose charcoal may be needed for more serious ingestions.
  
• Paradoxical seizures may occur, use benzodiazepines to treat initially (diazepam is the drug of choice).
  

• Brahmi N, Kouraichi N, Thabet H, et al. Influence of activated charcoal on the pharmacokinetics and the clinical features of carbamazepine poisoning.
  Am J Emerg Med
  . 2006;24:440–443.
  
• Perez A, Wiley JF. Pediatric carbamazepine suspension overdose—Clinical manifestations and toxicokinetics.
  Pediatr Emerg Care
  . 2005;21(4):252–254.
  
• Pilapil M, Peterson J. Efficacy of hemodialysis and charcoal hemoperfusion in carbamazepine overdose.
  Clin Toxicol (Phila)
  . 2008;46(4):342–343.
  
• Schmidt S, Schmitz-Buhl M. Signs and symptoms of carbamazepine overdose.
  J Neurol
  . 1995;242:169–173.
  

CODES

966.3 Poisoning by other and unspecified anticonvulsants

BASICS

• Carbon monoxide (CO) is a colorless, odorless, nonirritating gas.
  
• Binds to hemoglobin to form carboxyhemoglobin:
  
  • Decreases O
    ₂
    -carrying capacity
    
• Direct cellular toxin
  
• Impairs cellular O
  ₂
  utilization