Cyanide toxicity: Difference between revisions

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==Background==
==Background==
*Sources
*Burning of nitrogen-containing polymers (plastics, wool, silk)
**Burning of nitrogen-containing polymers (plastics, wool, silk)
*Gaseous [[chemical weapon]] known as prussic acid, hydrogen cyanide, or hydrocyanic acid
**Prolonged use of nitroprusside
*Prolonged use of [[nitroprusside]]
*Pathophysiology
*Pits of peaches, pears, apricots, crab apples
**Binds to cytochrome oxidase in mitochondria; leads to cessation of electron transport
*Intentional poisoning
***Causes switch from aerobic to anaerobic metabolism despite adequate O2  
 
===Pathophysiology===
*Binds to cytochrome oxidase in mitochondria; leads to cessation of electron transport
**Causes switch from aerobic to anaerobic metabolism despite adequate O2
 
===Paris Fire Brigade Protocol===
{{Paris Fire Brigade Protocol}}


==Clinical Features==
==Clinical Features==
#CNS
===Acute Intoxication===
##Headache, anxiety, confusion, vertigo, coma, seizure
*Affected by dose, route, formulation and exposure pattern
#Cardiovascular
**Inhaled toxins more rapid than ingested
##Tachycardia and hypertension initially, then bradycardia and hypotension
***Inhalation exposure may cause [[syncope]] and death after only a few breaths
#Respiratory
*'''Early signs'''
##Tachypnea initially, then then bradypnea and pulmonary edema
**CNS stimulation ([[Headache]], anxiety, [[confusion]])
#GI
**[[Tachycardia]], [[palpitations]] and [[hypotension]]
##Vomiting, abdominal pain
**Tachypnea
#Skin
**Cherry-red color (rarely seen)
##Cherry-red color (rarely seen), cyanosis (late finding)
*'''Late signs'''
#Renal
**[[Nausea]], vomiting
##Renal failure
**[[Bradycardia]], hypotension, [[arrhythmias]], asystole
#Hepatic
**[[Coma]], [[seizures]] (rare), Mydriasis
##Hepatic necrosis
**Bradypnea and [[pulmonary edema]] (non-cardiogenic), apnea
#Miscellaneous
**[[Renal failure]]
##Rhabdo, bright red venules seen on fundoscopy
**Hepatic Necrosis
**Cyanosis
**[[Rhabdo]], bright red venules seen on fundoscopy
 
===Chronic===
*Retrobulbar Optic Atropy (proposed)
**Heavy smokers
*Ataxic peripheral neuropathy
*Konzo
**Spastic upper motor neuron paraparesis seen in chronic ingestion of inadequately cooked casava
 
==Differential Diagnosis==
{{Chemical weapon DDX}}
{{Toxic gas exposure DDX}}
{{Burn DDX}}
 
==Evaluation==
===Work-Up===
*[[Lactate]] (normal lactate highly suggests another diagnosis)
**Serum lactate >8 mmol/L has 94% sensitivity
*[[VBG]] and [[ABG]] (narrowing of the venous-arterial PO2 gradient, causes venous hyperoxemia/increased redness -- as does [[CO poisoning]])
*Co-oximetry
*Chemistry ([[anion gap acidosis]])
*RBC or serum cyanide levels (unlikely to return in time to be clinically useful)
 
===Diagnosis===
*Smell of bitter almonds (only 60-80% of population can detect this)
*Severe unexplained metabolic acidosis (lactic)
*PO2 of venous blood similar to arterial blood
*Normal SpO2 (same as CO poisoning)
*Cherry-red skin color is uncommon
 
==Management==
*Supportive care
**[[O2]] 100% NRB
**[[IVF]] and vasopressors for hypotension
**Bicarb for acidemia (enchances of effect of nitrite and thiosulfate)
*Antidote
 
===Cyanokit ([[Hydroxocobalamin]])<ref>Borron SW, Baud FJ, Mégarbane B, Bismuth C. Hydroxocobalamin for severe acute cyanide poisoning by ingestion or inhalation. Am J Emerg Med. Jun 2007;25(5):551-8.</ref><ref>Bebarta VS, Tanen DA, Lairet J, Dixon PS, Valtier S, Bush A. Hydroxocobalamin and sodium thiosulfate versus sodium nitrite and sodium thiosulfate in the treatment of acute cyanide toxicity in a swine (Sus scrofa) model. Ann Emerg Med. 2010;55(4):345-51. </ref>===
*1st line therapy
*Give empirically if cyanide poisoning is suspected
====Mechanism of action====
Directly binds cyanide forming cyanocobalamin which is readily excreted in the urine
 
====Administration====
*Give 70mg/kg IV over 15min (5g is standard adult dose); may repeat 5g once as needed
*Also give 25% [[sodium thiosulfate]] 1.65ml/kg IV (12.5g max dose) over 10min; may repeat at half original dose if needed


==Diagnosis==
====Adverse Effects====
#Smell of bitter almonds (only 60-80% of population can detect this)
*May cause temporary reddish discoloration of skin, plasma, urine, mucous membranes
#Severe unexplained metabolic acidosis (lactic)
*'''Interferes with colorimetric tests''' -- Pulse ox, Hemoglobin, Carboyxhemoglobin, methemeglobin, oxyhemoglobin, Serum Cr, AST/ALT, bilirubin, magnesium for 2-3 days<ref>Lee J, Mukai D, Kreuter K, et al. Potential interference by hydroxocobalamin on co-oximetry hemoglobin measurements during cyanide and smoke inhalation treatments. Ann Emerg Med. 2007;49(6):802-805.</ref>
#PO2 of venous blood similar to arterial blood
;OBTAIN Co-ox and labs prior to Hydroxocobalamin administration
#normal SpO2
#Cherry-red skin color is uncommon


==Work-Up==
===Cyanide Antidote Package (Lilly kit)===
#Lactate
Composed of two drugs(2 nitrites and a thiosulfate). The nitrites convert the iron in hemoglobin from the ferrous to the ferric form, creating methemoglobinemia. The thiosulfate is a sulfate donor, which allows the enzyme rhodanese to convert the cyanide to thiocyanate that can be renally excreted.
#VBG and ABG (narrowing of the venous-arterial PO2 gradient)
*2nd line therapy - use if Cyanokit unavailable<ref>Hall AH, Saiers J, Baud F. Which cyanide antidote?. Crit Rev Toxicol. 2009;39(7):541-52.</ref>
#Co-oximetry
*Consider using only Na thiosulfate (no nitrites) in cases where concern for CO poisoning since nitrate administration will severely decrease oxygen carrying capacity
#Chemistry (anion gap acidosis)


==Treatment==
====Mechanism of action====
#Supportive care
*Nitrites: form metHb which binds cyanide more avidly than cytochrome oxidase
##O2 100% NRB
**Thiosulfate: donates its sulfur group to cyanide to form thiocyanate (less toxic than CN)
##IVF and vasopressors for hypotension
##Bicarb for acidemia (enchances of effect of nitrite and thiosulfate)
#Antidote


===Cyanokit (Hydroxocobalamin)===
====Warnings====
#1st Line Therapy
*Nitrites are relatively contraindicated in patients with concomitant CO toxicity
#Mechanism of action
*Induction of metHb further decreases O2 delivery
##Directly binds CN forming cyanocobalamin which is readily excreted in the urine
*Avoid nitrites in presence of severe hypotension if diagnosis is unclear
#How to use:
##Give 70mg/kg IV over 15min (5g is standard adult dose); may repeat 5g once as needed
##Also give Na thiosulfate 12.5g over 10min; may repeat at 1/2 original dose if needed
#Side effects
##May cause temporary reddish discoloration of skin, plasma, urine, mucous membranes
##Interferes w/ co-oximetry measurements


===Cyanide Antidote Package===
====Administration====
#Use if Cyanokit unavailable
*[[Amyl nitrite]]
#Mechanism of action
**Inhaled by patient (only use if unavailable to obtain IV)
##Nitrites: form metHb which binds CN more avidly than cytochrome oxidase
**Hold under patient's nose for 30s of each minute, for 3 minutes
##Thiosulfate: donates its sulfur group to CN to form thiocyanate (less toxic than CN)
*[[Sodium nitrite]]
#Warnings
**10mg/kg IV over 5min (use instead of amyl nitrite if IV is available)
##Nitrites are relatively contraindicated in pts w/ concomitant CO toxicity
**Lack of measurable MetHb levels after administration confirms CN presence
###Induction of metHb further exacerbates O2 delivery
**Monitor MetHb and keep level <30%
##Avoid nitrites in presence of severe hypotension if diagnosis is unclear
*Pediatric dosing is based on Hemoblogin (see Peds dosing below)
#How to use:
*25% [[Sodium thiosulfate]]
##Amyl nitrite inhaled by pt (only use if unavailable to obtain IV)
**1.65ml/kg IV (12.5g max dose) over 10min
###Hold under pt's nose for 30s of each minute, for 3 minutes
**may repeat at 1/2 original dose if needed
##Sodium nitrite 10 mg/kg IV over 5min (use instead of amyl nitrite if IV is available)
###Lack of measurable MetHb levels after administration confirms CN presence
###Monitor MetHb and keep level <30%
###Peds requires dosing based on Hb (see Peds dosing below)
##Sodium thiosulfate 12.5g over 10min; may repeat at 1/2 original dose if needed


===Sodium Thiosulfate (Peds Dosing)===
{{Sodium Nitrite Peds Dosing}}
#Max dose should not exceed 10mL
#Do not give faster than 5mL/min (to avoid hypotension)
#Hb 7 g/dL, dose is 0.19 mL/kg of 3% sodium nitrite
#Hb 8 g/dL, dose is 0.22 mL/kg of 3% sodium nitrite
#Hb 9 g/dL, dose is 0.25 mL/kg of 3% sodium nitrite
#Hb 10 g/dL, dose is 0.27 mL/kg of 3% sodium nitrite
#Hb 11 g/dL, dose is 0.30 mL/kg of 3% sodium nitrite
#Hb 12 g/dL, dose is 0.33 mL/kg of 3% sodium nitrite
#Hb 13 g/dL, dose is 0.36 mL/kg of 3% sodium nitrite
#Hb 14 g/dL, dose is 0.39 mL/kg of 3% sodium nitrite


==Disposition==
*Admit all patients for observation


==See Also==
==See Also==
*[[Carbon Monoxide]]
*[[Carbon Monoxide (CO)]]
*[[Hydrogen Sulfide]]
*[[Hydrogen Sulfide]]
*[[Burns]]
*[[Burns]]
*[[Acrylonitrile]]


==Source==
==References==
*Tintinalli
<references/>
*UpToDate


[[Category:Tox]]
[[Category:Toxicology]]

Latest revision as of 20:10, 17 April 2024

Background

  • Burning of nitrogen-containing polymers (plastics, wool, silk)
  • Gaseous chemical weapon known as prussic acid, hydrogen cyanide, or hydrocyanic acid
  • Prolonged use of nitroprusside
  • Pits of peaches, pears, apricots, crab apples
  • Intentional poisoning

Pathophysiology

  • Binds to cytochrome oxidase in mitochondria; leads to cessation of electron transport
    • Causes switch from aerobic to anaerobic metabolism despite adequate O2

Paris Fire Brigade Protocol

Paris Fire Brigade protocol recommend hydroxocobalamin administration patients who have had known smoke inhalation in an enclosed space with any of the following:[1][2]

  1. Altered mental status
  2. Soot in the nares or mouth
  3. Full arrest without full body burns incompatible with life. They found 50% ROSC in fire victims in full arrest when hydroxycobalamin was administered.

Clinical Features

Acute Intoxication

Chronic

  • Retrobulbar Optic Atropy (proposed)
    • Heavy smokers
  • Ataxic peripheral neuropathy
  • Konzo
    • Spastic upper motor neuron paraparesis seen in chronic ingestion of inadequately cooked casava

Differential Diagnosis

Chemical weapons

Toxic gas exposure

Burns

Evaluation

Work-Up

  • Lactate (normal lactate highly suggests another diagnosis)
    • Serum lactate >8 mmol/L has 94% sensitivity
  • VBG and ABG (narrowing of the venous-arterial PO2 gradient, causes venous hyperoxemia/increased redness -- as does CO poisoning)
  • Co-oximetry
  • Chemistry (anion gap acidosis)
  • RBC or serum cyanide levels (unlikely to return in time to be clinically useful)

Diagnosis

  • Smell of bitter almonds (only 60-80% of population can detect this)
  • Severe unexplained metabolic acidosis (lactic)
  • PO2 of venous blood similar to arterial blood
  • Normal SpO2 (same as CO poisoning)
  • Cherry-red skin color is uncommon

Management

  • Supportive care
    • O2 100% NRB
    • IVF and vasopressors for hypotension
    • Bicarb for acidemia (enchances of effect of nitrite and thiosulfate)
  • Antidote

Cyanokit (Hydroxocobalamin)[3][4]

  • 1st line therapy
  • Give empirically if cyanide poisoning is suspected

Mechanism of action

Directly binds cyanide forming cyanocobalamin which is readily excreted in the urine

Administration

  • Give 70mg/kg IV over 15min (5g is standard adult dose); may repeat 5g once as needed
  • Also give 25% sodium thiosulfate 1.65ml/kg IV (12.5g max dose) over 10min; may repeat at half original dose if needed

Adverse Effects

  • May cause temporary reddish discoloration of skin, plasma, urine, mucous membranes
  • Interferes with colorimetric tests -- Pulse ox, Hemoglobin, Carboyxhemoglobin, methemeglobin, oxyhemoglobin, Serum Cr, AST/ALT, bilirubin, magnesium for 2-3 days[5]
OBTAIN Co-ox and labs prior to Hydroxocobalamin administration

Cyanide Antidote Package (Lilly kit)

Composed of two drugs(2 nitrites and a thiosulfate). The nitrites convert the iron in hemoglobin from the ferrous to the ferric form, creating methemoglobinemia. The thiosulfate is a sulfate donor, which allows the enzyme rhodanese to convert the cyanide to thiocyanate that can be renally excreted.

  • 2nd line therapy - use if Cyanokit unavailable[6]
  • Consider using only Na thiosulfate (no nitrites) in cases where concern for CO poisoning since nitrate administration will severely decrease oxygen carrying capacity

Mechanism of action

  • Nitrites: form metHb which binds cyanide more avidly than cytochrome oxidase
    • Thiosulfate: donates its sulfur group to cyanide to form thiocyanate (less toxic than CN)

Warnings

  • Nitrites are relatively contraindicated in patients with concomitant CO toxicity
  • Induction of metHb further decreases O2 delivery
  • Avoid nitrites in presence of severe hypotension if diagnosis is unclear

Administration

  • Amyl nitrite
    • Inhaled by patient (only use if unavailable to obtain IV)
    • Hold under patient's nose for 30s of each minute, for 3 minutes
  • Sodium nitrite
    • 10mg/kg IV over 5min (use instead of amyl nitrite if IV is available)
    • Lack of measurable MetHb levels after administration confirms CN presence
    • Monitor MetHb and keep level <30%
  • Pediatric dosing is based on Hemoblogin (see Peds dosing below)
  • 25% Sodium thiosulfate
    • 1.65ml/kg IV (12.5g max dose) over 10min
    • may repeat at 1/2 original dose if needed

Sodium nitrite (Pediatric Dosing)

Hb Level (g/dL) Dose of 3% sodium nitrite (mL/kg)
7 0.19
8 0.22
9 0.25
10 0.27
11 0.30
12 0.33
13 0.36
14 0.39
Max dose should not exceed 10mL
Do not give faster than 5mL/min (to avoid hypotension)

Disposition

  • Admit all patients for observation

See Also

References

  1. ↑ Fortin JL, et al. Prehospital administration of Hydroxoco- balamin for smoke inhalation-associated cyanide poisoning: 8 years of experience in the Paris Fire Brigade. Clin Toxicol. 2006;44 Suppl 1:37-44. PMID: 16990192.
  2. ↑ Borron SW, et al. Prospective study of hydroxocobalamin for acute cyanide poisoning in smoke inhalation. Ann Emerg Med. 2007 Jun;49(6):794-801, e1-2. PMID: 17481777.
  3. ↑ Borron SW, Baud FJ, Mégarbane B, Bismuth C. Hydroxocobalamin for severe acute cyanide poisoning by ingestion or inhalation. Am J Emerg Med. Jun 2007;25(5):551-8.
  4. ↑ Bebarta VS, Tanen DA, Lairet J, Dixon PS, Valtier S, Bush A. Hydroxocobalamin and sodium thiosulfate versus sodium nitrite and sodium thiosulfate in the treatment of acute cyanide toxicity in a swine (Sus scrofa) model. Ann Emerg Med. 2010;55(4):345-51.
  5. ↑ Lee J, Mukai D, Kreuter K, et al. Potential interference by hydroxocobalamin on co-oximetry hemoglobin measurements during cyanide and smoke inhalation treatments. Ann Emerg Med. 2007;49(6):802-805.
  6. ↑ Hall AH, Saiers J, Baud F. Which cyanide antidote?. Crit Rev Toxicol. 2009;39(7):541-52.
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