Cyanide vs carbon monoxide toxicities

Present similarly:
Frequent complications after patient exposure to fire
Normal pulse oximetry
Cherry-red facies
Dizziness, headache, confusion, disorientation, weakness
Cyanide toxicity
Pathophys: binding of ferric ions on mitochondrial cytochrome complex → inhibits oxidative phosphorylation → functional hypoxia →
Severe lactic acidosis (lactate 8-10)
More hemodynamic instability
Arrhythmia
Tx: Na thiosulfate, hydroxocobalamin, or amyl nitrate = → converts CN into form that can be excreted
Carbon monoxide toxicity
Pathophys: CO binds to Hb → carboxy- hemoglobin → L shift in O2-Hb dissociation curve → difficult for O2 to offload in tissues → tissue hypoxia →
Milder lactic acidosis
CO also mitochondrial toxin → inhibits ox phos → reduces ATP prod (less than cyanide)
CO has 200x affinity to Hb compared to O2
Tx: 100% O2 → hyperbaric O2 if CO over 30%