Counteraction of cyanide poisoning by thiosulphate when administering sodium nitroprusside as a hypotensive treatment.

A 42-year old patient received a continuous infusion of sodium nitroprusside (SNP) at a dosage rate of 600 microgram/min for approximately four days. On the third day of treatment a dangerous high level of cyanide was measured in the blood. When an additional continuous infusion of sodium thiosulphate at five times the molar concentration of the SNP was given, this cyanide level dropped over a period of 7h to one-seventh of its initial value. The thiosulphate did not reduce the effectiveness of the SNP in lowering the blood pressure.