Rosen & Barkin's 5-Minute Emergency Medicine Consult (689 page)

• 427.0 Paroxysmal supraventricular tachycardia
  
• 427.89 Other specified cardiac dysrhythmias
  

BASICS

• Direct or indirect stimulation of adrenergic receptors in sympathetic and central nervous systems
  
• Often no correlation between dosage and degree of toxicity
  
• Cocaine may also block sodium channels of cardiac myocytes, leading to “tricyclic” or class 1a–type dysrhythmias.
  

• Sympathomimetic poisoning in children may present similarly to meningitis or other systemic illness.
  
• Urinary toxicology screening may be only way to discover sympathomimetic poisoning in children presenting with altered mental status.
  
• Methylphenidate (Ritalin, Concerta) and other sympathomimetics used for ADHD may cross-react with altered mental status.
  

• Sympathomimetic toxicity can result from use of any sympathetically active drug, including:
  
  • All amphetamines, methamphetamines, and derivatives (ecstasy, MDMA)
    
  • Cocaine
    
  • Synthetic cathinones “Bath Salts”
    
  • Phencyclidine (PCP)
    
  • Lysergic acid diethylamide (LSD)
    
  • Decongestants (rare)
    
• Drug delivery routes: Inhalation, injection, snorting, or ingestion
  

DIAGNOSIS

• Vital signs:
  
  • Tachycardia:
    
    • Bradycardia possible for cocaine and some other decongestants
      
  • Increased BP:
    
    • Severely intoxicated patients may be hypotensive.
      
  • Tachypnea
    
  • Hyperthermia:
    
    • Often present, may be severe, and is often overlooked
      
• CNS:
  
  • Anxiety
    
  • Headache
    
  • Agitation
    
  • Altered mentation
    
  • Diaphoresis
    
  • Seizures
    
  • Stroke
    
  • Dystonia (rare)
    
• Cardiovascular:
  
  • Palpitations
    
  • Chest pain
    
  • Myocardial ischemia or infarction
    
  • Tachydysrhythmias
    
  • Cardiovascular collapse
    
  • Murmur (e.g., endocarditis)
    
• Other:
  
  • Dilated pupils
    
  • Dry mucous membranes
    
  • Urinary retention may cause enlarged bladder.
    
  • Needle track marks or abscesses on extremities should be sought.
    
  • Increased or decreased bowel sounds
    
  • The presence of diaphoresis and bowel sounds may help to differentiate sympathomimetic toxicity from anticholinergic poisoning.
    

• Assess history for possible sympathomimetic agents:
  
  • Cold preparations
    
  • Prescription amphetamines
    
  • Recreational drug use
    
• Assess for possible coingestions
  
• Evaluate for symptoms of end organ injury:
  
  • Chest pain
    
  • Shortness of breath
    
  • Headache, confusion, and vomiting
    

• Common findings include:
  
  • Agitation
    
  • Tachycardia
    
  • Diaphoresis
    
  • Mydriasis
    
• Severe intoxication characterized by:
  
  • Tachycardia
    
  • Hypertension
    
  • Hyperthermia
    
  • Agitated delirium
    
  • Seizures
    
  • Diaphoresis
    
• Hypotension and respiratory distress may precede cardiovascular collapse
  
• Evaluate for associated conditions:
  
  • Cellulitis and soft tissue infections
    
  • Diastolic cardiac murmurs or unequal pulses
    
  • Examine carefully for trauma
    
  • Pneumothorax from inhalation injury
    
  • Focal neurologic deficits
    

• Monitor vital signs:
  
  • Increased temperature (>40°C possible):
    
    • Core temperature recording essential
      
    • Peripheral temperature may be cool
      
    • Indication for urgent cooling
      
    • Ominous prognostic sign
      
  • BP:
    
    • Severe hypertension can lead to cardiac and neurologic abnormalities.
      
    • Late in course, hypotension may supervene.
      
• ECG:
  
  • Signs of cardiac ischemia
    
  • Ventricular tachydysrhythmias
    
  • Reflex bradycardia
    

• Urinalysis for:
  
  • Blood
    
  • Myoglobin
    
• Electrolytes, BUN/creatinine, glucose:
  
  • Hypoglycemia may contribute to altered mental status.
    
  • Acidosis may accompany severe toxicity.
    
  • Rhabdomyolysis may cause renal failure.
    
  • Hyperkalemia—life-threatening consequence of acute renal failure
    
• Coagulation profile to monitor for potential disseminated intravascular coagulation (DIC):
  
  • INR, PT, PTT, platelets
    
• Creatine phosphokinase (CPK):
  
  • Markedly elevated in rhabdomyolysis
    
• Urine toxicology screen:
  
  • For other toxins with similar effects (e.g., cocaine)
    
  • Some amphetamine-like substances (e.g., synthetic cathinones, MDMA) may not be detected.
    
• Salicylate and acetaminophen levels if suicide attempt a possibility or if OTC medications ingested (e.g., cough, cold)
  
• Venous blood gas, ABG
  

• CXR:
  
  • Adult respiratory distress syndrome
    
  • Noncardiogenic pulmonary edema
    
• Head CT for:
  
  • Significant headache
    
  • Altered mental status
    
  • Focal neurologic signs
    
  • Subarachnoid hemorrhage, intracerebral bleed
    

Lumbar puncture for:

• Suspected meningitis (headache, altered mental status, hyperpyrexia)
  
• Suspected subarachnoid hemorrhage and CT normal
  

• Sepsis
  
• Thyroid storm
  
• Serotonin syndrome
  
• Neuroleptic malignant syndrome
  
• Pheochromocytoma
  
• Subarachnoid hemorrhage
  
• Drugs that cause delirium:
  
  • Anticholinergics
    
  • Tricyclic antidepressants
    
  • Sympathomimetics
    
  • Ethanol withdrawal
    
  • Sedative/hypnotic withdrawal
    
  • Hallucinogens
    
  • PCP
    
• Drugs that cause hypertension and tachycardia:
  
  • Sympathomimetics
    
  • Anticholinergics
    
  • Ethanol withdrawal
    
  • PCP
    
  • Caffeine
    
  • Monoamine oxidase inhibitors
    
  • Theophylline
    
  • Nicotine
    
• Drugs that cause seizures:
  
  • Camphor
    
  • Carbamazepine
    
  • Carbon monoxide
    
  • Chlorinated hydrocarbons
    
  • Cholinergics
    
  • Cyanide
    
  • Ethanol withdrawal
    
  • Hypoglycemics
    
  • Isoniazid
    
  • Lead
    
  • Lithium
    
  • Local anesthetics
    
  • Phenothiazines
    
  • Propoxyphene
    
  • Salicylates
    
  • Sedative/hypnotic withdrawal
    
  • Strychnine
    
  • Sympathomimetics
    
  • Theophylline
    
  • Tricyclic antidepressants
    

TREATMENT

• Patient may be uncooperative or violent.
  
• Secure IV access.
  
• Protect from self-induced trauma.
  

• ABCs
  
• Establish IV 0.9% NS access
  
• Cardiac monitor
  
• Naloxone, dextrose (or Accu-Chek), and thiamine if altered mental status
  

• Decontamination:
  
  • Gastric lavage not routinely recommended:
    
    • May consider if recent (within 1 hr) of life-threatening ingestion.
      
    • Activated charcoal not routinely recommended.
      
    • Consider activated charcoal with sorbitol in 1st dose if administered.
      
    • Consider activated charcoal with body stuffer or body packer ingestions.
      
  • Whole-bowel irrigation with polyethylene glycol solution – electrolyte solution for body packers
    
• Hypertensive crisis:
  
  • Initially administer benzodiazepines if agitated.
    
  • α-blocker (phentolamine) as 2nd-line agent
    
  • Nicardipine or nitroglycerin IV for severe HTN unresponsive to benzodiazepines
    
  • Nitroprusside can also be used for severe, unresponsive HTN
    
  • Avoid β-blockers, which may exacerbate HTN due to unopposed α activity
    
• Agitation, acute psychosis:
  
  • Administer benzodiazepines.
    
  • Use butyrophenones (e.g., haloperidol)
    with caution
    to manage agitation:
    
    • May lower seizure thresholds and may prolong QT duration
      
• Dysrhythmias:
  
  • Sodium bicarbonate IV push is treatment of choice for ventricular dysrhythmias indicative of sodium channel blocking (i.e., widened QRS complex).
    
  • Lidocaine for ventricular dysrhythmias refractory to alkalinization, benzodiazepines, and supportive care
    
• Hyperthermia:
  
  • Benzodiazepines if agitated
    
  • Active cooling if temperature >40°C:
    
    • Tepid water mist
      
    • Evaporate with fan
      
• Paralysis:
  
  • Indicated if muscle rigidity and hyperactivity contributing to persistent hyperthermia
    
  • Nondepolarizing paralytic preferred
    
• Rhabdomyolysis:
  
  • Administer benzodiazepines.
    
  • Hydrate with 0.9% NS.
    
  • Maintain urine output at 1–2 mL/min
    
  • Hemodialysis (if acute renal failure and hyperkalemia occur)
    
• Seizures:
  
  • Maintain airway
    
  • Administer benzodiazepines
    
  • Phenobarbital if unresponsive to benzodiazepines