These mild symptoms can rapidly progress to seizures, coma and death. Usually a progression of clinical signs begin to appear as the salicylate level in the serum and central nervous system increases. These signs include nausea and vomiting, hematemesis, hyperventilation, vertigo, agitation or lethargy, respiratory alkalosis, metabolic acidosis, and refractory seizures. Chronic salicylism manifests similar symptoms, although at much lower serum levels, and is often occult. The metabolic derangements seen with salicylate overdose deserve special mention.
Salicylates directly stimulate the medulla and cause hyperventilation and respiratory alkalosis.
Concurrent direct effects on intracellular metabolism cause the formation of lactate, pyruvate, and other organic acids producing an anion gap metabolic acidosis. Fluid and electrolyte disorders are common and therapy with intravenous bicarbonate can worsen hypolkalemia, cause volume overload, and cause hypernatremia. A paradoxic aciduria is also common as hydrogen ions are excreted in order to retain potassium ions. Since blood levels aren't that helpful, monitor the patient's clinical symptoms closely. The central nervous system is the site of the lethal effects of salicylates.