Salicylate toxicity: Difference between revisions

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Revision as of 21:10, 11 April 2011

Background

  • Fatal dose:
    • ~10-30g by adult
    • ~3g by child
  • Levels:
    • Therapeutic: 10-30mg/dL
    • Intoxication: >40-50 mg/dL
    • Peak occurs ~6hr after absorption
      • Up to 24hr if enteric-coated or extended release

Pathophysiology

  • As level rises, hepatic detox is saturated, switches to renal clearance (slower)
  • As pH drops more ASA is uncharged > crosses BBB
  • Altered mental status
    • Causes:
      • 1. Direct toxicity of salicylate species in the CNS
      • 2. Cerebral edema
      • 3. Neuroglycopenia
        • May occur despite normal serum glucose levels
  • Pulmonary Edema
    • Usually occurs in elderly
  • Anion gap metabolic acidosis (interferes w/ cellular metabolism)
  • Nausea/vomiting (stimulates chemoreceptor trigger zone)
  • Respiratory alkalosis (activates respiratory center of medulla)
    • If have resp acidosis consider pulm edema, resp depressing co-ingestant, or fatigue

Signs/Symptoms

  • Tinnitus
    • May occur within therapeutic range
  • Fever
  • Vertigo
  • N/V
  • Diarrhea
  • AMS
  • Coma
  • Noncardiac pulmonary edema
  • Death
    • Correlated with CNS salicylate levels

Vital signs

  • Tachypnea
  • Increase body temperature
    • Lack of hyperthermia does not rule out toxicity!
  • Tachycardia (due to hypovolemia, agitation, or general distress)

Work-Up

  • ASA level
    • Check q2hr until two consec levels show a decrease
  • Tylenol level
  • ETOH level
  • Utox
  • UA
  • VBG
  • CBC
  • Chem
    • If renal failure unable to clear ASA
    • Hypokalemia requires aggressive repletion
      • K+/H+ pump in distal tubule > decr ur. alkalinization
  • LFT
  • Coags
    • Rarely may cause hepatotoxicity
  • hCG
  • ekg
    • level >30mg/dL s/s of tox or >35 at any time

Treatment

Airway

  • Avoid intubation unless absolutely necessary!
    • Very difficult to achieve adequate minute ventilation on vent
      • Leads to resp acidosis > incr ASA crossing BBB
    • Sedation/paralysis > incr ASA crossing BBB
  • Indications = Hypoxemia or hypoventilation
  • If intubate maintain pH 7.50 - 7.59, hyperventilate

Breathing

  • Acute lung injury may lead to high O2 requirements

Circulation

  • Hypotension is common due to systemic vasodilation
    • Give fluids if no cerebral edema, no pulmonary edema
      • If these are present consider pressors

Decontamination

  • Charcoal 1g/kg up to 50g PO
    • Effectively absorbs ASA
    • Give multiple doses if tolerated
      • 25g PO q2hr x 3 doses OR 50g q4hr x 2 doses after initial dose

Glucose

  • Give D50 to altered pts regardless of serum glucose concentration
    • ASA toxicity impairs glucose metabolism


Alkalinization of plasma and urine

  • Traps ASA in blood and in rental tubules
    • Increases elimination, prevents diffusion across BBB
  • Alkalemia from resp alkalosis is NOT a contraindication to NaHCO3 tx
    • Blood pH goal = >7.5, <7.6
    • Urine pH goal = 7.5-8
  • Consider bicarb if ASA>35 or suspect serious toxicity
    • NaHCO3 1-2mEq/kg IV bolus then D5W w/ 3amps bicarb/L @ 2x maintenance for goal ur pH>7.5

Dialysis

Indicated for:

  • AMS
  • Coma
  • Seizure
  • Refractory acidosis
  • Pulmonary edema
  • Acute/chronic renal failure
    • Will not be able to clear ASA
  • 6hr level > 100


Source

UpToDate