SALICYLATE OVERDOSE
DEFINITION:
An acute or chronic toxic accumulation of salicylate.
EPIDEMIOLOGY:
- incidence: ?
- age of onset:
- risk factors:
PATHOGENESIS:
- oral: liquid, pills (+/- enteric-coated), methyl salicylate
(oil of wintergreen) is found in candy flavouring and numerous
liniments (Ben-Gay)
- topical: dermal applicates as a keratolytic agent (for
psoriasis)
2. Toxicitiy
- mild symptoms (gastrointestinal irritation & vomiting)
2. 150-300 mg/kg
3. >300 mg/kg
4. Done Nomogram
- developed in 1960 by Done (Peds 26:800)
- used to assist in predicting the degree of toxicity after
an acute, single ingestion of a non-enteric coated salicylate
- may over- or underestimate the severity of poisoning so it
is important to treat the patient and not the nomogram
3. Pathogenesis
- salicylate overdose will cause a metabolic acidosis by:
- uncoupling oxidative phosphorylation and thus, by a
complicated process, increases the hydrolysis of ATP to
produce H+
2. Ketoacidosis
- stimulating lipolysis resulting in the production of
ketones (acetoacetate, beta-hydroxybutyrate)
3. Organic Acidemia
- interfering with the TCA cycle
2. Respiratory Alkalosis
- salicylate directly stimulates the respiratory centre in
the brainstem resulting in tachypnea, hyperpnea, and
subsequent respiratory alkalosis
3. Hypokalemia
- due to gastrointestinal losses and increased urinary
excretion of K+
CLINICAL FEATURES:
- agitation, confusion, hallucinations, lethargy, tinnitis
- coma, malignant cerebral edema, death
2. Respiratory Manifestations
- tachypnea, hyperpnea, apnea
- noncardiogenic pulmonary edema
- adult respiratory distress syndrome (ARDS)
3. Cardiovascular Manifestations
- supraventricular and ventricular arrhythmias
- heart failure
4. Gastrointestinal Manifestations
- abdominal pain, vomiting, hematemesis
- peptic ulcer +/- bleeding or perforation
- oropharyngeal burns (from salicylate)
5. Hematologic Manifestations
- increased bleeding tendency (altered platelet function,
prolonged PT, DIC)
6. Other Manifestations
- hyperthermia
- rhabdomyolysis +/- acute renal failure
- SIADH
INVESTIGATIONS:
- blood gas - mixed metabolic acidosis with wide anion gap
with respiratory alkalosis
- electrolytes - hyponatremia (SIADH), hypo- or hyperkalemia,
hypo- or hypercalcemia
- glucose - hyperglycemia early followed by hypoglycemia
- CBC - leukocytosis
- prolonged PT, positive DIC screen
- drug screen
2. Urine
3. Imaging Studies
2. Endoscopy
- if salicylate levels continue to rise then must rule out a
concretion of salicylate in the stomach
- if evidence of corrosive injury to the gastrointestinal
tract
MANAGEMENT:
- D5W/0.45 NaCl with 40 mEqu/L KCl for a target urine output
of 2-3 cc/kg/hr
2. Alkalinize Urine
- to trap ionized salicylate in the urine and prevent its
absorption
- to prevent the production and tissue uptake of unionized
salicylate (which increase with acidemia)
- give 1-2 mmol/kg HCO3 over 1 hour and repeat on a prn
basis over the first 8 hours in order to keep the urine pH
about 7.5
- can bolus with more HCO3 if the serum pH falls but do not
administer if the serum pH >7.5
3. Moniter
- gas, electrolytes, glucose q1h x4 initially then q2-4h
- moniter CPK (rhabdomyolysis), CBC, liver function tests,
BUN, creatinine, calcium, salicylate q4h
- for arrhythmias
- Neurovitals
4. Complications
- indicated for continued neurological deterioration,
acute or chronic renal failure, or respiratory distress (ARDS,
pulmonary edema, aspiration)
3. Others
- blood transfusions for gastrointestinal bleed
- parenteral Vitamin K
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