Methylene blue for treating toxic encephalopathy due to acute nickel poisoning: A case report

Acute nickel poisoning is a rare clinical entity with no established management guidelines. Diagnosis is often delayed by non-specific clinical presentations that can mimic other common toxidromes, such as organophosphate poisoning.

A female in her late twenties presented with a Glasgow Coma Scale of 3, profound hypotension, miosis, and hypersalivation following intentional ingestion of an unlabeled toilet cleaner. Initial management for suspected cholinergic toxidrome and corrosive ingestion failed to achieve clinical stability. The patient developed refractory vasoplegic shock and went into a deep coma. Magnetic resonance imaging revealed cytotoxic lesions of the corpus callosum, suggesting toxic encephalopathy. Comprehensive toxicological screening by inductively coupled plasma mass spectrometry confirmed severe nickel toxicity with significantly elevated levels in the blood, urine, and cerebrospinal fluid (55.5 μg/L). Methylene blue, initially administered as a rescue therapy for vasoplegic shock, was associated with a paradoxical spike in urinary nickel excretion (from 8.8 μg/L to 51.9 μg/L) and a rapid decline in serum levels. This biochemical "washout" coincided with dramatic neurological recovery from Glasgow Coma Scale of 3 to 15 within 72 hours.

Early comprehensive toxicological screening is essential in patients with suspected poisoning by unknown substances. In this case, nickel toxicity was confirmed by prompt screening. In the absence of standard treatment protocols in rare poisoning cases, treatment is largely supportive. The apparent clinical benefit of methylene blue-mediated nickel clearance in this case remains speculative.