Analgesic

Salicylate Overdose

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Salicylate Overdose, Salicylate Toxicity, Aspirin Overdose, Aspirin Toxicity, Salicylism, Salicylate Poisoning, Chronic Salicylate Poisoning

  1. Aspirin
  2. Pepto Bismol
  3. Topical Salicylates
    1. Ben Gay
    2. Salicylic Acid
    3. Methyl Salicylate (oil of wintergreen)
      1. One teaspoon contains 7000 mg of Salicylate
  • Precautions
  1. Salicylate Poisoning (especially chronic Poisoning) has a high mortality and is easily mis-diagnosed
  2. Consider intentional Overdose (Suicidality) in the elderly
  • Pathophysiology
  1. Salicylates directly act at the cerebral Medulla, increasing Respiratory Rate (with a Respiratory Alkalosis)
  2. Salicylate Toxicity uncouples oxidative phosphorylation (ATP generation in mitochondria from NADH and FADH2)
    1. Results in shift to anaerobic metabolism, resulting in a Lactic Acidosis (and Metabolic Acidosis with Anion Gap)
    2. Compensatory Hyperventilation (triggered by Metabolic Acidosis) further increases Tachypnea
  1. Comprehensive metabolic panel findings
    1. Alkalosis or acidosis
      1. Metabolic Acidosis with increased Anion Gap is most typical
    2. Hyponatremia
    3. Hypokalemia
    4. Hyperglycemia or Hypoglycemia
    5. Acute Renal Failure
  1. Precautions
    1. Interpret Salicylate level based on Salicylate nomogram in the context of time since ingestion
      1. Done Nomogram (formulated in 1961) is only valid in a single acute Salicylate ingestion
      2. Done Nomogram is not typically used clinically
        1. Not predictive of serious Salicylate Toxicity
        2. Contrast with Rumack-Matthew Nomogram used in Acetaminophen Overdose
    2. Manage Salicylate level based on local lab protocols and poison control
    3. Be aware of Units of Measure (local lab may use a measurement other than mg/dl)
  2. Serious toxicity occurs with ingestion >150 mg/kg
  3. Therapeutic Levels
    1. Plasma Salicylate level <10 mg/dl: Analgesic effect
    2. Plasma Salicylate level 10-20 mg/dl: Anti-inflammatory
  4. Overdosage levels (based on 6 hour Salicylate levels in acute toxicity)
    1. Plasma Salicylate level 20-45 mg/dl: Asymptomatic mild toxicity
    2. Plasma Salicylate level 45-65 mg/dl: Mild symptomatic toxicity
      1. Tinnitus (especially children) or Decreased Hearing (especially adults)
      2. Hyperventilation
    3. Plasma Salicylate level 65-90 mg/dl: Moderate toxicity
      1. Fever
      2. Metabolic Acidosis
    4. Plasma Salicylate level 90-110 mg/dl: Severe toxicity
      1. Coma
      2. Cardiovascular instability
    5. Plasma Salicylate level >110 mg/dl: Lethal toxicity
      1. Renal Failure
      2. Respiratory Failure
  • Management
  • Salicylate Overdose
  1. General measures
    1. Start management prior to serum level available if high level of suspicion and symptomatic patient
    2. Consider Gastric Decontamination (e.g. Activated Charcoal, Gastric Lavage) in early presentation or large ingestion
    3. Consult poison control
    4. Supplemental Oxygen
    5. Protect airway
  2. Load crystalloid to maintain Urine Output (critical to maximize urine Salicylate excretion)
    1. Adult: Start with NS 1-2 Liter bolus
    2. Child: Start with NS 10-20 cc/kg bolus
  3. Alkalinizing urine increases Salicylate excretion
    1. Solution: 3 Sodium Bicarbonate ampules in 850 ml D5W
      1. Add 40 meq KCl (if not hyperkalemic)
      2. Maintain pH 7.4 to 7.5 (by VBG)
      3. Goal Urine Output 1 to 1.5 ml/kg/h
    2. Adult: Infuse above solution at 150-200 ml/hour or 2-3 ml/kg/hour
      1. Consider preceding infusion with 1-2 amps of Sodium Bicarbonate
    3. Child: Infuse above solution at 1.5 to 2 times maintenance
      1. Consider preceding infusion with 1-2 meq/kg of Sodium Bicarbonate
  4. Monitoring
    1. Urine pH
      1. Confirm Urine pH 7.5 to 8.0 at 1-2 hours after starting Sodium Bicarbonate infusion
      2. Adjust alkalinization protocol if urine not adequately alkalinized
    2. Serum Potassium
      1. Correct Hypokalemia
    3. Mental Status
      1. Salicylates cross the blood brain barrier in Metabolic Acidosis
      2. Mental status may paradoxically worsen despite a decreasing serum Salicylate level
  5. Hemodialysis indications
    1. Acute toxicity: Salicylate level >100 mg/dl in adults (>80 mg/dl in children)
    2. Chronic toxicity: Salicylate level >60 mg/dl in adults
    3. Worsening mental status
    4. Patient requiring intubation
  6. Intubated patients
    1. Match Ventilatory rate to respiratory prior to intubation
    2. Risk of rapidly progressive, catastrophic Metabolic Acidosis if hypoventilated
  • References