Classically, methemoglobinemic blood is described as chocolate brown, without color change on exposure to air. In patients likely to have substantial amounts of cyanide bound to methemoglobin as cyanmethemoglobin, treatment of methemoglobinemia with methylene blue must be undertaken with extreme caution. When cyanide elimination is accelerated by the co-infusion of thiosulfate, thiocyanate production is increased. When prolonged infusions are more rapid than these, thiocyanate levels should be measured daily. Thiocyanate clearance rates during dialysis, on the other hand, can approach the blood wflow rate of the dialyzer.
Thiocyanate interferes with iodine uptake by the thyroid.
Abdominal pain, apprehension, diaphoresis, dizziness, headache, muscle twitching, nausea, palpitations, restlessness, retching, and retrosternal discomfort have been noted when the blood pressure was too rapidly reduced. The hypotensive effect of sodium nitroprusside is augmented by that of most other hypotensive drugs, including ganglionic blocking agents, negative inotropic agents, and inhaled anesthetics.