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
- Causes:
- 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
- Very difficult to achieve adequate minute ventilation on vent
- 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
- Give fluids if no cerebral edema, no pulmonary edema
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