Rosen & Barkin's 5-Minute Emergency Medicine Consult (629 page)

BASICS

• Respiratory alkalosis and metabolic acidosis:
  
  • Secondary to inhibition of Krebs cycle and uncoupling of oxidative phosphorylation
    
• Dehydration, hyponatremia or hypernatremia, hypokalemia, hypocalcemia:
  
  • Owing to increased sweating, vomiting, tachypnea
    
• Noncardiogenic pulmonary edema:
  
  • Because of toxic effect of salicylate on pulmonary endothelium resulting in extravasation of fluids
    
• Salicylate pharmacokinetics change from first order to zero order in overdose setting; i.e., a small dosage increment results in a large increase in salicylate concentration.
  

• Greater morbidity
  
• Respiratory distress/altered mental status indicative of severe toxicity
  
• Diagnosis of salicylate intoxication delayed because underlying disease states mask signs and symptoms; e.g., CHF
  

• Children exhibit faster onset and more severe signs and symptoms than adults:
  
  • Results from salicylate being distributed more quickly into target organs such as brain, kidney, and liver
    
• Respiratory alkalosis (hallmark of salicylate poisoning in adults) may not occur in children.
  
• Metabolic acidosis occurs more quickly in children than in adults.
  
• Hypoglycemia more common than hyperglycemia
  
• Ingestion of more than “a taste” of oil of wintergreen (98% methyl salicylate) by children <6 yr or >4 mL of oil of wintergreen by patients >6 yr warrants ED assessment.
  

Sources of salicylate:

• Aspirin:
  
  • Ingestion of >150 mg/kg can cause serious toxicity
    
• Oil of wintergreen:
  
  • Any exposure should be considered dangerous.
    
• Bismuth subsalicylate
  
• Salicylsalicylic acid (salsalate)
  

DIAGNOSIS

• GI:
  
  • Nausea
    
  • Vomiting
    
  • Epigastric pain
    
  • Hematemesis
    
• Pulmonary:
  
  • Tachypnea
    
  • Noncardiogenic pulmonary edema
    
• CNS:
  
  • Tinnitus
    
  • Deafness
    
  • Delirium
    
  • Seizures
    
  • Coma
    

• Ask if taking aspirin or aspirin products:
  
  • Many patients do not list aspirin among their regular medications, may not consider aspirin a medication.
    
• Patients may not know the difference between aspirin, acetaminophen, and the OTC NSAIDs
  

• Salicylate level:
  
  • At presentation and then q2h until level begins to decline
    
  • Verify that units are correct, generally mg/dL.
    
• Watch for recurrence of signs of salicylate toxicity and increasing levels even after levels have declined due to intestinal absorption of enteric-coated products and salsalate
  

Guidelines for Assessing Severity of Salicylate Poisoning

• Acute ingestion of:
  
  • <150 mg/kg or <6.5 g of aspirin equivalent—considered nontoxic
    
  • 150–300 mg/kg—mild to moderately toxic
    
  • >300 mg/kg—potentially lethal
    
• In the chronic overdose setting:
  
  • Manage patient on clinical findings and not solely on levels
    
  • Clinical findings are better indication of severity than plasma salicylate levels
    
  • No valid nomogram exists for salicylate level interpretation
    
  • Salicylate levels needed to achieve anti-inflammatory effect (20–25 mg/dL) approach toxic levels
    
  • Enteric-coated aspirin absorbed in intestine; peak level delayed
    

• Arterial blood gas (ABG):
  
  • Respiratory alkalosis
    
  • Metabolic acidosis
    
• CBC
  
• Electrolytes, BUN/creatinine, glucose:
  
  • Anion-gap metabolic acidosis
    
  • Hypokalemia
    
  • Baseline renal function
    
• Urinalysis:
  
  • Urine pH
    
• PT/PTT with significant ingestions
  
• Ferric chloride test:
  
  • Purple if salicylate present
    
  • Positive 30 min postingestion
    
• In the presence of salicylate, Phenistix turn brown-purple; may detect concentrations as low as 20 mg/dL
  

• Abdominal flat-plate radiograph for concretions
  
• Chest radiograph for pulmonary edema
  

• Acute salicylate poisoning:
  
  • Consider with change in mental status, unexplained noncardiogenic pulmonary edema, mixed acid–base disorder.
    
  • Methanol
    
  • Ethylene glycol
    
  • Conditions causing noncardiogenic pulmonary edema
    
• Chronic salicylate poisoning:
  
  • Impending myocardial infarction
    
  • Alcohol withdrawal
    
  • Organic psychoses
    
  • Sepsis
    
  • Dementia
    

TREATMENT

In suspected overdose settings, medication bottles must be brought in for review

• Management of airway, breathing, and circulation (ABCs)
  
• Naloxone, thiamine, glucose (or Accu-Chek) for altered mental status
  
• IV rehydration with 0.9% normal saline (NS) for hypotension
  

• Morbidity from chronic salicylate poisoning may be greater than from acute poisoning.
  
• Aggressively manage all salicylate intoxication.
  

• Administer activated charcoal in alert patients.
  
• Whole-bowel irrigation of theoretical benefit:
  
  • For concretions visible on abdominal radiograph
    
  • For ingestion of sustained-release preparation
    
  • If salicylate levels continue to increase despite appropriate management
    
  • Do not use in patients who may develop altered mental status
    

• Alkalinization:
  
  • Enhances elimination of ionized salicylate
    
  • Indications:
    
    • Acidosis
      
    • Presence of symptoms
      
    • Elevated salicylate levels
      
  • 1 or 2 ampules of sodium bicarbonate followed by
    IV D
    ₅
    W 1L with 3 ampules of sodium
    bicarbonate:
    
    • Goal: Urine pH of 7.5–8 at the rate of 3–6 mL/kg/h
      
    • Add 20–40 mEq KCl per liter to avoid hypokalemia
      
    • Avoid fluid overload with CHF or CAD
      
    • Closely monitor serum potassium
      
• Indications for hemodialysis include:
  
  • CHF
    
  • Noncardiogenic pulmonary edema
    
  • CNS depression
    
  • Seizures
    
  • Unstable vital signs
    
  • Severe acid–base disorder
    
  • Hepatic compromise
    
  • Coagulopathy
    
  • Underlying disease state compromising elimination of salicylate
    
  • Absolute salicylate level should not be used as sole criterion for deciding to dialyze without considering patient’s clinical status unless level is >80–100 mg/dL in acute ingestion.
    
• Threshold to dialyze is lower in patients with chronic overdose.
  

• Activated charcoal slurry: 1–2 g/kg up to 90 g PO
  
• Dextrose: D
  ₅₀
  W 1 amp (50 mL or 25 g) (peds: D
  ₂₅
  W 2–4 mL/kg) IV
  
• Naloxone (Narcan): 2 mg (peds: 0.1 mg/kg) IV or IM initial dose
  
• Thiamine (vitamin B
  ₁
  ): 100 mg (peds: 50 mg) IV or IM
  

FOLLOW-UP

• Monitor patients with salicylate levels >25 mg/dL until level drops <25 mg/dL and symptoms abate.
  
• Salicylate levels increasing after having trended downward to nontoxic levels:
  
  • In patients who ingest sustained-release aspirin, enteric-coated aspirin, and any aspirin product with delayed absorption
    
• ICU admission for altered mental status, metabolic acidosis, pulmonary edema
  

Repetitive salicylate levels <25 mg/dL and resolution of symptoms

• Psychiatric referral for intentional ingestions
  
• Close primary care follow-up for chronic ingestions