A 65-year-old woman who fired a gun at figures she believed were 'dead people' was experiencing visual hallucinations that doctors attributed to aspirin poisoning, according to a published case report.

The woman, from Michigan, arrived at an emergency department by ambulance asking to see a psychiatrist because of vivid visual hallucinations. She told clinicians she had discharged a firearm at the hallucinations on one occasion, according to the report, which does not describe what she saw.

Blood tests showed raised salicylate levels, the group of compounds that includes aspirin. She had been taking more than 15 tablets a day of an over-the-counter painkiller containing 500mg of aspirin and 32.5mg of caffeine, amounting to at least 7.5 grams of aspirin daily for several weeks, or approximately 75mg per kilogram of body weight per day.

After 11 hours of intravenous sodium bicarbonate treatment, her blood salicylate level fell from 28.8 milligrams per decilitre to 18.3mg/dL. Her hallucinations stopped and her tinnitus improved within 48 hours of arrival, and she was discharged without seeing a psychiatrist.

The case was published in the journal Clinical Practice and Cases in Emergency Medicine by authors affiliated with Wayne State University in Detroit.

Calm Patient With No Psychiatric History

Despite her reaction to the hallucinations, the woman was calm and alert during her examination. Her vital signs were normal apart from a raised blood pressure reading of 148/84mmHg. Her history included high blood pressure, diabetes, heart failure and chronic back pain, but no prior psychiatric history.

When questioned further, she confirmed she had tinnitus, or ringing in the ears, a classic symptom of salicylate toxicity. She did not have other hallmark signs of overdose, such as nausea or fever. The authors described the case as an accidental, sub-chronic overdose.

Her daily intake was about half the typical dose associated with acute salicylate poisoning but was still a large amount to take every day for weeks. Older age is also a risk factor for severe outcomes of acute salicylate toxicity.

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Unusual Symptoms in Long-Term Aspirin Toxicity

The authors suggested that prolonged exposure to aspirin may contribute to neurological symptoms by increasing salicylate penetration into the brain. However, the mechanism behind hallucinations in chronic salicylate toxicity remains incompletely understood.

Salicylates also disrupt metabolism, causing a build-up of lactic acid that leads to metabolic acidosis, as the woman experienced. If this overwhelms the body's respiratory alkalosis and the blood becomes acidic, organ damage can occur. These metabolic effects may also help explain tinnitus.

Doctors consulted the Michigan Poison and Drug Information Center, which recommended intravenous sodium bicarbonate at 120 millilitres an hour. The treatment alkalinises the blood and urine, making them less acidic, so the kidneys can excrete more salicylate.

Cautionary Lesson for Emergency Doctors

The authors said the case should remind physicians to keep a 'high index of suspicion' for chronic toxicities, including salicylates, in patients who present with acute psychosis or altered mental status of unknown cause.

Previous case reports have described visual hallucinations in other patients with chronic salicylate toxicity, but the symptom is less well understood than more common ones such as tinnitus. Aspirin products are widely available over the counter, the report notes, but when taken inappropriately they can cause toxicity that may be difficult to diagnose.

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