Toxic compounds during nitroprusside infusions:
(1) thiocyanate (SCN) - anorexia, nausea, fatigue, disorientation, toxic psychosis, seizures, coma
(2) cyanide (CN) - headache, lactic acidosis, cardiac depression
Risk factors for toxicity:
(1) higher than recommended doses (> 4 µg/kg/min according to Ellenhorn; > 5 µg/kg/min according to Oates and Brown, with different values reported in other texts)
(2) prolonged infusions > 48 hours, especially if tachyphylaxis requires steadily increasing doses
(3) renal failure (accumulation from decreased excretion and rhodenase activity)
(4) hepatic failure (decrease in rhodenase activity)
(5) low body stores of thiosulfate and other sulfhydryl donors
A patient with one or more risk factors for toxicity should be considered for an alternative vasodilator. If nitroprusside is continued, then:
(1) use the lowest dose possible
(2) monitor serum thiocyanate levels
(3) administer sodium thiosulfate IV
