A 16-year-old girl is brought to the emergency department from home due to altered mental status. Her parents note that she was in her usual state of health at lunch, which was about 6 hours ago. Temperature is 38.3 C (100.9 F), blood pressure is 120/70 mm Hg, pulse is 104/min, and respirations are 30/min. Pulse oximetry is 97% on room air. The girl is disoriented and drowsy. Physical examination shows normal-sized reactive pupils and clear lungs. There is tenderness over the epigastric area. Laboratory studies are as follows: Which of the following is the most likely cause of this patient's findings?

Question

A 16-year-old girl is brought to the emergency department from home due to altered mental status.  Her parents note that she was in her usual state of health at lunch, which was about 6 hours ago.  Temperature is 38.3 C (100.9 F), blood pressure is 120/70 mm Hg, pulse is 104/min, and respirations are 30/min.  Pulse oximetry is 97% on room air.  The girl is disoriented and drowsy.  Physical examination shows normal-sized reactive pupils and clear lungs.  There is tenderness over the epigastric area.  Laboratory studies are as follows:  Which of the following is the most likely cause of this patient's findings?

Quizplus · Accepted Answer

This patient with acutely altered mental status has an elevated anion gap and tachypnea, findings concerning for salicylate intoxication. Toxicity in children is usually due to accidental salicylate (eg, aspirin, wintergreen oil) ingestion but can be seen with intentional overdose in adolescents and adults. Symptoms of acute salicylate overdose begin within a couple hours of ingestion and include: Tinnitus (eg, ringing/buzzing sound) is an early sign that can occur even with normal serum salicylate concentrations. Hyperventilation (causing a primary respiratory alkalosis) due to stimulation of the medullary respiratory center. Nausea and vomiting due to activation of the chemoreceptor trigger zone in the medulla and from direct gastric irritation (epigastric tenderness) as a result of decreased prostaglandin synthesis. Uncoupling of oxidative phosphorylation leads to hyperthermia and increased anaerobic metabolism. The resulting increase in lactic acid production causes a primary metabolic acidosis with an elevated anion gap (22 = 140 - [104 + 14]). Altered mental status can occur due to the direct effect of salicylates on the CNS and as a result of neuroglycopenia (cerebral glycolysis increases due to the oxidative phosphorylation impairment). (Choice A) Ethanol intoxication causes slurred speech, nystagmus, decreased coordination, and CNS depression. It is associated with respiratory depression (not tachypnea). (Choice C) Carbon monoxide poisoning causes flu-like symptoms, headaches, and altered mental status. An anion gap metabolic acidosis can occur due to increased lactate production. However, hyperthermia and tachypnea would not be expected. In addition, symptoms in only one household member would be unusual. (Choice D) Insulin deficiency and hyperglycemia in type I diabetics can lead to diabetic ketoacidosis, which is characterized by lipolysis, ketoacid production, and an anion gap metabolic acidosis. Abdominal pain and mental status changes can be seen. However, this patient's normal glucose level is inconsistent with this diagnosis. (Choice E) Symptoms of pulmonary embolism include hypoxia, tachycardia, chest pain, and shortness of breath. However, this patient has no risk factors (eg, recent surgery, cancer), and an anion gap metabolic acidosis would not be seen. Educational objective: Acute salicylate toxicity causes a primary respiratory alkalosis and a primary metabolic acidosis with an anion gap due to increased lactate production. Symptoms include tinnitus, tachypnea, hyperthermia, vomiting, and altered mental status. __________ References: Salicylates toxicity. (http://www.ncbi.nlm.nih.gov/pubmed/29763054)

A 16-Year-Old Girl Is Brought to the Emergency Department from Home