Acute confusional state or delirium in the elderly frequently requires a lengthy differential diagnosis in the emergency room (ER) to determine the factors of its multiple causes. Iatrogeny can be one of the causes, especially in elderly people with polypharmacy. We present a case of a 77-year-old female, independent in activities of daily living, with no cognitive impairment and a history of hypertension, dyslipidemia, and manic-depressive disorder. She arrived at the ER with diarrhea, vomiting, and myalgias. A blood test revealed an acute kidney injury. The patient was discharged with the diagnosis of acute gastroenteritis and prerenal acute kidney injury. The patient returned to the ER two days later due to worsening symptoms, including spatial and temporary disorientation and a marked prostration. The attending physician recommended a lithium blood level test due to the patient's history and the outpatient's psychiatric medication. The tests revealed a value of 2.18 mmol/L (toxic levels: >2.0 mmol/L). Support measures were initiated with diuresis control and vigorous hydration, with subsequent clinical and biochemical improvement (lithium blood levels reduced to 0.97 mmol/L). Lithium toxicity causes acute nausea, vomiting, diarrhea, and neurological symptoms that have a slower onset and correlate with chronic toxicity. A declining renal function and reduced volume of distribution (due to increased body fat mass and decreased total body water) contribute to more significant pharmacological toxicity in the elderly. In this case, dehydration triggered by diarrhea and vomiting may have been a cause or a consequence. Reviewing chronic medication and a detailed investigation of all etiological causes was essential for the patient's rehabilitation, avoiding possible irreversible neurological damage.
Keywords: acute confusional state; acute kidney injury; delirium; lithium intoxication; lithium toxicity.
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