Clinical signs and symptoms depend on age, serum concentration, and acuity of ingestion. The early manifestations of salicylate toxicity include hyperventilation, nausea, vomiting, diaphoresis and tinnitus. Hyperpyrexia may be seen in children as well as hypotension, noncardiogenic pulmonary edema, academia, cerebral edema, delirium, seizures, and coma. Acid base abnormalities may include an anion gap metabolic acidosis. In children less than 4 years of age, metabolic acidosis predominates. Acidemia is a hallmark of worsening toxicity as this means CNS salicylate is increasing. Dehydration and hypokalemia is usually present.
The Donne nomogram is of little value. Donne made the assumption that salicylates follow first order kinetics (rate of metabolism increases as serum concentration increases). However, it was subsequently revealed that salicylates follow zero order kinetics (constant rate of metabolism) when the serum concentration is above 30 mg/dL.
Be very careful of patients with chronic salicylate ingestion. A relatively low serum concentration does not reflect the potentially high tissue concentration. These patients can be very sick with seemingly unimpressive serum concentrations.
As always, if there are any questions, call the MTPC.
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