Cyanide toxicity

Background

Older cyanide kit with potential to cause metHgb which potentially problem as patient may have CO as well

Newer CyanoKit safer (but very expensive) without significant adverse rxn

Pathophysiology

-glucose metabolized to pyruvate yields 2 ATP by anaerobic glycolysis. No O2 needed.

- pyruvate then enters Kreb cycle and with O2, yields 36 more ATP. Requires function of mitochondrial electron xport system, the last step of which transfers electrons to oxygen to form water.

- cyanide, hydrogen sulfide and carbon monoxide bind to and inhibit cytochrome part of electron xport chain.

- if pyruvate blocked from entering Krebs cycle, pyruvate metabolized to lactic acid- leads to lactic acidosis.

Diagnosis

-cn and h2s pts can’t extract o2 from blood. Po2 of venous blood similar to arterial blood. May diagnose cn poisoning by similar mixed venous o2 and arterial o2- get arterial and venous blood gases ana compare O2

- Venous PO2 = Arterial PO2

- lactic acidosis

- nl SaO2

Treatment

1. Amyl nitrite inhaler
2. then, iv sodium nitrite
   1. 10cc of 3% over 2- 4 min (0.2cc/kg in peds)
      1. may cause hypotension if given too fast
      2. will generate methb level of 8%
         1. lack of measurable methb levels after administration confirms Cyanide presence
3. then sodium thiosulfate 12.5 gm (50 cc of 25% soln of 5X vol of na nitrite)
   1. Sulfur will bind with CN to make thiocyanate which is nontoxic and renally excreted
4. follow methemoglobn levels
5. If incomplete response, consider
   1. retreatment
   2. ongoing absorption (e.g. oral Cyanide poisoning)
6. using vit b12 hydroxycobalamin (to make cyanocobalamine)

CO/CN Combined Poisoning

1. if pt has co poisoning already and is given cn antidote and methb make, two dyshemoglobins cohb and methb will further inhibit o2 carriage.
2. cn poisoning correlated with lactate level > 10mmol/L
3. sodium thiosulfate given alone is safe without alteration of o2 carrying capacity of nitrites. Consider emperic tx c 12.5 mg to all smoke inhalation victims with hypotension, acidosis, or CV collapse.

CO/CN COMBINED POISONING

1. sodium thiosulfate given alone (no alteration O2 carrying capacity)
   1. consider emperic tx (12.5 mg) for smoke inhalation victims with
2. hypotension, acidosis, or CV collapse
   1. See also Burns

See Also

Hydrogen Sulfide

Burns

Source

Pani

8/07 DONLDSON (adapted from Sandness, Mistry)