Case Study:


A 68-year-old female in a hypertensive (high blood pressure) crisis is being treated in the intensive care unit (ICU) with intravenous nitroprusside (blood pressure lowering drug)* for 48 hours. The patient’s blood pressure was brought back down to normal levels, however, she was complaining of a burning sensation in her throat and mouth followed by nausea, vomiting, diaphoresis ("sweaty"), agitation and dyspnea (difficulty breathing). The nurse noticed a sweet almond smell in her breath. An arterial blood gas revealed a significant metabolic acidosis. A serum test suggests a metabolite of nitroprusside, thiocyanate, is at toxic levels.


1. What is the likely cause of her symptoms??


Cyanide poisoning

“Almond” smell…..





2. What is the biochemical mechanism of this problem??


Cyanide inhibits Complex IV in the respiratory chain

Result: No ATP synthesis

Review “Electron Transport”





*Sodium nitroprusside breaks down in the blood and releases a chemical call nitric oxide (NO). Nitric oxide enters the muscle cells in the walls of the blood vessels and causes them to relax. When the muscles relax, the blood vessels become wider and the blood pressure decreases.



© Sturm 2019

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