Rosen & Barkin's 5-Minute Emergency Medicine Consult (542 page)

• CBC
  
• Electrolytes, BUN/creatinine, glucose
  
• Urinalysis:
  
  • Dip for myoglobin (rhabdomyolysis)
    
• Creatine phosphokinase:
  
  • If urine dip for blood is positive
    
• Ethanol level
  

• Chest radiograph for aspiration pneumonia
  
• Extremity/spine radiographs when there is associated trauma
  
• CT of the head when there is head trauma/altered mental status
  

• Drugs of abuse:
  
  • Cocaine
    
  • Amphetamines
    
  • Designer drugs:
    
    • Methcathinone (“Cat”)
      
    • “Ecstasy”
      
    • “Ice” (methamphetamine)
      
  • Alcohols
    
  • Ketamine
    
  • Sympathomimetics
    
• Drugs that cause nystagmus:
  
  • Lithium
    
  • Carbamazepine
    
  • Sedative–hypnotics
    
  • Alcohols
    
  • Phenothiazines
    
  • Dextromethorphan
    

TREATMENT

• ABCs
  
• IV
  
• Cardiac monitor
  
• Naloxone, thiamine, glucose (or Accu-Chek) if altered mental status
  
• Protect patient and staff from injury.
  

• Maintain patient in a quiet place; avoid stimulation.
  
• Physical restraints for violent patient
  
• Sedation:
  
  • Benzodiazepines
    
  • Butyrophenones (haloperidol) theoretically can lower the seizure threshold.
    
• Activated charcoal if oral coingestants
  
• IV 0.9% normal saline for hydration, sodium bicarbonate/mannitol for rhabdomyolysis
  

• Ativan (lorazepam): 2 mg IV increments
  
• Diazepam: 5 mg IV increments
  

• Activated charcoal slurry: 1–2 g/kg up to 90 g PO
  
• Dextrose: D50W 1 amp: 50 mL or 25 g (peds: D25W 2–4 mL/kg) IV
  
• Mannitol: 25–50 g IV
  
• Naloxone (Narcan): 2 mg (peds: 0.1 mg/kg) IV or IM initial dose
  
• Sodium bicarbonate: 2 amps (50 mEq per amp) diluted in 1 L of D5W, given at 125–250 mL/h (for rhabdomyolysis) to urine pH of 7
  
• Thiamine (vitamin B
  ₁
  ): 100 mg (peds: 50 mg) IV or IM
  

FOLLOW-UP

• Prolonged altered mental status
  
• Significant traumatic injuries
  
• Rhabdomyolysis
  
• Hyperthermia
  

Becomes lucid after a period of observation (6 hr)

Psychiatry or social work referral for suicidal ideation or chronic drug use

• PCP poisoning can lead to traumatic injuries that can become life threatening.
  
• Adequate chemical restraints with benzodiazepines are needed to prevent excessive muscular activity leading to rhabdomyolysis.
  
• Dextromethorphan is a common cause for a false-positive PCP urine toxicology screen.
  
• Tramadol has been reported to cause a false-positive screen for PCP
  
• Ketamine abuse presents with similar signs and symptoms of PCP abuse.
  

• Hahn I-H. Phencyclidine and ketamine. In: Erickson TB, Ahrens W, Aks SE, et al., eds.
  Pediatric Toxicology
  . New York, NY: McGraw-Hill; 2004:297–302.
  
• Ly BT, Thornton SL, Buono C, et al. False-positive urine phencyclidine immunoassay screen result caused by interference by tramadol and its metabolites.
  Ann Emerg Med
  . 2012;59:545–547.
  
• Pugach S, Pugach IZ. Overdose in infant caused by over-the-counter cough medicine.
  South Med J
  . 2009;102:440–442.
  
• Wills B, Erickson T. Drug- and toxin-associated seizures.
  Med Clin North Am
  . 2005;89:1297–1321.
  

CODES

968.3 Poisoning by intravenous anesthetics

BASICS

• Phenytoin follows zero-order pharmacokinetics:
  
  • Small incremental increase in dose can result in a large increase in plasma concentration.
    
• Half-life in overdose prolonged; may be up to 70 hr
  
• Cardiovascular toxicity from IV administration likely due to the diluent propylene glycol
  
• Fosphenytoin, a prodrug for parenteral administration, is metabolized to phenytoin, its active moiety.
  

• Phenytoin intoxication results from acute, chronic, or acute-on-chronic administration.
  
• If the cause of the intoxication is unclear in a patient receiving chronic phenytoin therapy, consider that there may have been a:
  
  • Change in the brand of phenytoin
    
  • Change in dosage form
    
  • Drug interaction
    
  • Change in serum albumin
    

DIAGNOSIS

• Level 20–40 μg/mL (or mg/L):
  
  • Nystagmus
    
  • Dizziness
    
  • Ataxia
    
  • Drowsiness
    
  • Nausea/vomiting
    
  • Diplopia
    
  • Slurred speech
    
• Level 40–90 μg/mL:
  
  • Confusion
    
  • Disorientation
    
• Level >90 mg/mL:
  
  • Coma
    
  • Respiratory depression
    
  • Paradoxical seizures
    
• Hypotension/bradycardia with rapid IV administration:
  
  • Fosphenytoin injection does not contain propylene glycol
    
  • Hypotension/dysrhythmia unlikely with fosphenytoin
    
• Hypersensitivity reaction following chronic use:
  
  • Rash
    
  • Fever
    
  • Neutropenia
    
  • Agranulocytosis
    
  • Hepatitis
    
  • Cholangitis
    

• Determine the time, route, and amount of ingestion.
  
• Phenytoin level:
  
  • After oral overdose, the peak plasma concentration may not be reached until 24 hr or more post acute ingestion.
    
  • Absorption differs with various oral preparations and manufacturers
    
  • Repeat levels every 4 hr until levels have peaked and continue to steadily decline.
    
  • Once levels begin declining, check every 24 hr until <30
    µ
    g/mL.
    
  • Free phenytoin level may be required in patients who are hypoalbuminemic or patients who are poor metabolizers.
    

• Fosphenytoin level:
  
  • Measured as phenytoin
    
  • Measure fosphenytoin after conversion to phenytoin is complete (2 hr post IV infusion or 4 hr post IM injection).
    
  • Prior to complete conversion to phenytoin, immunoanalytic techniques may overestimate plasma phenytoin concentrations due to cross-reactivity with fosphenytoin.
    
• Electrolytes, BUN, creatinine, glucose:
  
  • Check for anion gap metabolic acidosis due to coingestant, seizure activity, from propylene glycol in the IV formulation
    
  • Determine glucose with altered mental status.
    

• Intoxication with other CNS depressants
  
• Guillain–Barré syndrome
  
• Botulism
  
• Posterior fossa tumor
  
• Acute cerebellitis
  

TREATMENT