A case of acute lithium poisoning and hypermagnesemia involving advanced colon cancer-induced colonic obstruction.

An 83-year-old woman presented with disturbance of consciousness and hand tremor. She had taken lithium carbonate 300 mg/day for bipolar disorder and magnesium oxide 660 mg/day for constipation. Blood tests revealed lithium poisoning, hypermagnesemia and acute kidney injury. Computed tomography showed colonic obstruction caused by cancer of the descending colon. In the outpatient section, her blood pressure decreased to 89/54 mmHg, and her heart rate dropped to 40 bpm. We considered that the obstructive ileus induced intravascular dehydration, which led to toxic serum concentrations of lithium and magnesium, triggering the emergence of severe arrythmia induced by sinus dysfunction. The patient was treated with fluid resuscitation and hemodialysis, followed by endoscopic stent replacement for the descending colon cancer obstruction. These treatments improved her general condition and alleviated the lithium poisoning, hypermagnesemia and colonic obstruction. Such a case is considered extremely rare.