Severe Toxicity with Guanidine Thiocyanate Ingestion

Objective: To describe the toxicity of deliberate guanidine thiocyanate ingestion and it's treatment including dialysis. Case report: A 52-year-old male presented to hospital with abdominal pain after giving a history of ingesting bottled water. His initial vital signs and examination were normal. Soon after the patient became confused and agitated, necessitating intubation and ventilation for presumed encephalitis. His chloride was unmeasurable and the ionised calcium was low at 0.59 mmol/L (reference range [RR] 1.15-1.32 mmol/L). His pH and osmolar gap were normal. Analysis of the ingested water on two chemistry analysers gave discrepant chloride readings (129 mmol/L and 49 mmol/L) suggesting interference from a cross reacting analyte, which subsequently was proven to be thiocyanate with a concentration of 1485mg/L and 538mg/L in the bottled water and admission serum respectively (RR 0.1-4 mg/L). Dialysis in the form of continuous veno-venous haemodiafiltration (CVVHDF) was instituted based on this high level. Serial thiocyanate levels demonstrated zero order elimination kinetics pre dialysis and first order kinetics with a half-life of 5.4 h during dialysis. The patient made a full recovery and admitted to the addition of guanidine thiocyanate to the bottled water. Discussion: Guanidine thiocyanate appears to cause an encephalopathic type presentation with discordant and/or error chloride readings and ionised hypocalcaemia. Dialysis could be considered in the management of its toxicity.