American Family Physician - Management of salicylate toxicity
Management of Salicylate Toxicity Salicylate intoxication remains a commonly encountered problem. Early measures to prevent drug absorption, along with alkaline diuresis of the drug, are essential to successful management. If initial therapy fails to produce a response or if the clinical condition rapidly deteriorates, the patient should be treated aggressively with prompt hemodialysis. Because of their widespread availability and use, salicylates have been an important cause of poisoning in adults and children for many years. During the 1960s, controls limiting the number of pills per package and the introduction of childproof caps led to a dramatic decline in accidental poisonings among children.(1) However, salicylate toxicity remains a common problem and is associated with a surprisingly large number of deaths.
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In children, salicylate toxicity is most often due to accidental ingestion or unintentional overdose. Chronic toxicity may result from overzealous administration of medication by parents. The problem is compounded when the parents attribute the fever, diaphoresis and tachycardia that occur with salicylate intoxication to the underlying illness and continue to increase the salicylate dose.
In adults, acute intoxication from salicylate ingestion is often associated with a suicide attempt. Chronic toxicity in adults may occur in those using high-dose salicylates to control pain. Medications that contain salicylates are a less obvious source of toxicity.
The following cases illustrate the spectrum of severity in salicylate toxicity.
Illustrative Cases
CASE 1
A 44-year-old woman came to the emergency department in moderate respiratory distress. For two days, she had experienced mild respiratory difficulty and shortness of breath. Intermittent vertigo and tinnitus had been present for three days, and her children had complained to her that “she was getting deaf.” Her past medical history included sciatica and bipolar disorder, which was treated with lithium. For her sciatica, the patient had been taking up to 16 aspirin tablets (325 mg each) per day, along with ibuprofen, 400 mg three times daily, and indomethacin (Indocin), 25 mg three times daily.
On admission, the patient was awake and alert. She was in moderate respiratory distress and appeared restless and diaphoretic. Her temperature was 37C (98.6F); blood pressure, 110/60 mm Hg; pulse, 80, and respirations, 30. Diffuse rales were heard bilaterally. Heart rhythm was regular; there were no murmurs or gallops. Abdominal and neurologic findings were normal.
The electrocardiogram revealed sinus tachycardia with nonspecific ST-T changes. A chest radiograph confirmed the presence or gastric lavage.(3) Obviously, inducing emesis is contraindicated in a patient who has a reduced level of consciousness or in whom such a state may be anticipated.
There is debate regarding the maximum time interval after ingestion in which gastric emptying should be performed. Because salicylates delay gastric emptying, emesis or lavage may be of value up to 12 hours after ingestion.(6) Emesis is induced with syrup of ipecac (15 mL in children and 30 mL in adults, taken with water or soft drinks).(8) Gastric lavage is performed through a large-bore orogastric tube using normal saline.(1) Lavage is continued until the returning contents are clear. It may be necessary to perform lavage with warm water to dissolve concretions of salicylate in the stomach.
ACTIVATED CHARCOAL
Activated charcoal acts by adsorbing to particles of salicylate in the gastrointestinal tract, thus preventing their absorption.(9) The efficacy of charcoal depends on how soon after ingestion it is given. Charcoal is of questionable value when it is given later than one to two hours after ingestion.(6) In general, the amount of activated charcoal given depends on the amount of salicylate ingested; a ratio of 10:1 (charcoal to salicylate) produces the best results.(4) Charcoal is administered as a slurry, preferably through a gastric tube (30 g of charcoal in 125 mL of water for a child; 55 g of charcoal in 250 mL of water for an adult). This should be followed by catharsis with magnesium sulfate (generally 250 mg per kg, given as a 20 percent solution) to facilitate propulsion through the gastrointestinal tract.(5)
ALKALINE DIURESIS
Alkaline diuresis, using fluids containing sodium bicarbonate, is the key component in the treatment of salicylate toxicity. It should be considered for all patients whose salicylate levels exceed 35 mg per dL (2.50 mmol per L).(4) The effects of sodium bicarbonate therapy include correcting metabolic acidosis, alkalinizing the urine to promote salicylate excretion and preventing passage of salicylate into the central nervous system and other tissues by increasing the ionized (nonreabsorbable) fraction.(10)
Alkalinization should be done parenterally, rather than orally, using sodium bicarbonate. (Although acetazolamide (Diamox) increases urinary pH, it should not be used in this situation, because it produces systemic acidosis.(4)) It is important to add potassium chloride, which is needed by the kidney to excrete acid. During this process, urinary pH should be monitored hourly and maintained between 7.5 and 8.0.(5) Arterial blood gas determinations should also be performed frequently to ensure that the arterial pH does not exceed 7.5.
