Q: 58 year old male with CKD 3 (Chronic kidney Disease) is admitted to ICU with hypertensive crisis. Patient is started on Nitroprusside drip by an "Old fashioned ER Doc".  ICU fellow on call at night decided to "float swan" to determine volume status. After few hours of admission, patient went into undetermined lactic acidosis. Pulmonary artery catheter (PAC) progressively showed increase in SVO2. What is your concern?

A) Missed sepsis

B) Cyanide poisoning

C) Underlying Cirrhosis

D) Inadequate titration of drip

E) Artifact in PAC                            

Answer: Cyanide poisoning

High SvO2 accompanied by lactic acidosis indicates failure of the cells to extract. In nitroprusside toxicity, cyanide poisoning is well may be the cause, particularly in renal compromised patients. To make things complicated, possible early sign of cyanide toxicity is the acute resistance to the hypotensive effects of increasing doses of sodium nitroprusside.

Sepsis is a possibility but it usually presents with hypotensive shock. Similarly cirrhotic patients are usually hypotensive.