[Toxicity and blood concentration of thiocyanate during sodium nitroprusside treatment]

In 25 patients receiving sodium nitroprusside (SNP) infusion for hypertension, the influence of SNP on renal function, thiocyanate (SCN) concentration, half-life of SCN and hemolytic actions or methemoglobinemia was measured. Creatinine clearance showed a slight increase while plasma creatinine was unchanged. There was no definite relationship between creatinine clearance and SCN clearance. For the individual patient there was no relationship between the SCN concentration at a constant dose of SNP and the degree of renal function. Independently of the grade of renal insufficiency, toxic concentrations of SCN were never seen if less than 100 gamma/min/SNP were infused for less than 5 days ( = less than 720 mg total dose). There was a linear relationship between half-life of SCN and the degree of renal function. Signs of hemolytic action could not be demonstrated. There was no methemoglobinemia. Although SCN concentration in relation to dose of SNP and renal function cannot be predicted, it is proposed that plasma SCN be checked only in patients receiving more than 100 gamma/min for more than 5 days.