Carbon monoxide toxicity: Difference between revisions

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==Background==
== Background ==
#Colorless, odorless gas
 
#Most toxic component in smoke inhalation and major contributor to fire-related deaths
#Colorless, odorless gas  
##Can co-occur with [[Cyanide]] toxicity in industrial fires
#Most toxic component in smoke inhalation and major contributor to fire-related deaths  
#Sources
##Can co-occur with [[Cyanide]] toxicity in industrial fires  
##Automotive exhaust
#Sources  
##Propane-fueled heaters
##Automotive exhaust  
##Wood or coal-burning heaters
##Propane-fueled heaters  
##Structure fires
##Wood or coal-burning heaters  
##Gasoline-powered motors
##Structure fires  
##Natural gas-powered heaters
##Gasoline-powered motors  
##Natural gas-powered heaters  
#Peak incidence in winter months
#Peak incidence in winter months


==Pathophysiology==
== Pathophysiology ==
#Hypoxia
 
##Binding affinity of Hb for CO (carboxyhemoglobin) is 200x that of O2
#Hypoxia  
##Half-Life
##Binding affinity of Hb for CO (carboxyhemoglobin) is 200x that of O2  
###Room air: ~5hrs
##Half-Life  
###100% O2: ~1hr
###Room air: ~5hrs  
###HBO 2.5atm: 24min
###100% O2: ~1hr  
#Lactic acidosis
###HBO 2.5atm: 24min  
##CO inhibits oxidative phosphorylation
#Lactic acidosis  
#Hypotension
##CO inhibits oxidative phosphorylation  
##CO induces NO2 and guanylate cyclase release --> vasodilation release
#Hypotension  
##CO induces NO2 and guanylate cyclase release --> vasodilation release
 
== Workup ==


==Workup==
#VBG  
#VBG
##Co-oximetry analysis will provide carboxyhemoglobin level  
##Co-oximetry analysis will provide carboxyhemoglobin level
#Lactate  
#Lactate
#Chemistry  
#Chemistry
#Troponin  
#Troponin
#Total CK (rhabdo)  
#Total CK (rhabdo)
#ECG  
#ECG
##May range from normal to STEMI (most common ST, then prolonged QT)
##May range from normal to STEMI
###Few of the pts w/ AMI from CO have occlusive lesions in their arteries  
###Few of the pts w/ AMI from CO have occlusive lesions in their arteries
#?Head CT  
#?Head CT
##May show b/l globus pallidus lesions in severe cases
##May show b/l globus pallidus lesions in severe cases


==Clinical Features==
== Clinical Features ==
#May range from "flu-like" symptoms to coma
 
#CNS
#May range from "flu-like" symptoms to coma  
##Headache
#CNS  
##Visual disturbances
##Headache  
##Confusion
##Visual disturbances  
##Ataxia
##Confusion  
##Seizure
##Ataxia  
##Syncope
##Seizure  
##Retinal hemorrhage
##Syncope  
##Focal neurologic deficit
##Retinal hemorrhage  
#GI
##Focal neurologic deficit  
##Vomiting
#GI  
#Pulm
##Vomiting  
##Dyspnea/tachypnea
#Pulm  
#Cardio
##Dyspnea/tachypnea  
##Chest pain
#Cardio  
##ECG changes/dysrhythmias
##Chest pain  
#Derm
##ECG changes/dysrhythmias  
##Bullous skin lesions
#Derm  
##Bullous skin lesions  
##Classic finding of cherry red oral mucosa is rarely seen in living pts
##Classic finding of cherry red oral mucosa is rarely seen in living pts


==Diagnosis==
== Diagnosis ==
#Must have high clinical suspicion (esp in pts w/ coma, AMS, or anion gap acidosis)
 
##Comatose pt removed from fire should be assumed to have CO poisoning
#Must have high clinical suspicion (esp in pts w/ coma, AMS, or anion gap acidosis)  
#Carboxyhemoglobin Level
##Comatose pt removed from fire should be assumed to have CO poisoning  
##Interpretation must take into account time since exposure and O2 tx
#Carboxyhemoglobin Level  
##Normal value in non-smokers is ~1%, normal value in smokers may be up to 10%
##Interpretation must take into account time since exposure and O2 tx  
##Symptoms and COHb levels do not always correlate well
##Normal value in non-smokers is ~1%, normal value in smokers may be up to 10%  
##Symptoms and COHb levels do not always correlate well  
#Pulse oximetry is unreliable  
#Pulse oximetry is unreliable  
##CoHb registers the same as O2Hb so will have artificially high SpO2
##CoHb registers the same as O2Hb so will have artificially high SpO2  
##O2 saturation gap reflects discordance of SpO2 by pulse oximeter vs by VBG
##O2 saturation gap reflects discordance of SpO2 by pulse oximeter vs by VBG


==Treatment==
== Treatment ==
#O2 100% by NRB or ETT
 
##Provide O2 until COHb value <10%
#O2 100% by NRB or ETT  
#Hyperbaric Therapy (HBO)
##Provide O2 until COHb value &lt;10%  
##Decision to initiate HBO should be made in consultation w/ hyperbaric specialist
#Hyperbaric Therapy (HBO)  
##Controversial who exactly benefits from tx
##Decision to initiate HBO should be made in consultation w/ hyperbaric specialist  
##Pt must be stable prior to transport
##Controversial who exactly benefits from tx  
##Indications (generally accepted guidelines):
##Pt must be stable prior to transport  
###Syncope
##Indications (generally accepted guidelines):  
###Confusion/AMS
###Syncope  
###Seizure
###Confusion/AMS  
###Coma
###Seizure  
###Focal neuro deficit
###Coma  
###Pregnancy w/ CoHb level >15%
###Focal neuro deficit  
###Blood level >25%
###Pregnancy w/ CoHb level &gt;15%  
###Blood level &gt;25%  
###Acute myocardial ischemia
###Acute myocardial ischemia


==Disposition==
== Disposition ==
#Minimal or no symptoms
 
##Discharge
#Minimal or no symptoms  
#Mildly symptomatic
##Discharge  
##Headache, vomiting, elevated COHb level
#Mildly symptomatic  
##Discharge after 4hr obs and symptom resolution
##Headache, vomiting, elevated COHb level  
#Severely symptomatic
##Discharge after 4hr obs and symptom resolution  
##Ataxia, syncope, chest pain, neuro deficit, dyspnea, ECG changes, pregnant w/ COHb >15%
#Severely symptomatic  
##Ataxia, syncope, chest pain, neuro deficit, dyspnea, ECG changes, pregnant w/ COHb &gt;15%  
##Admit; discuss with hyperbaric specialist
##Admit; discuss with hyperbaric specialist


==Source==
== Source ==
Tintinalli
 
Tintinalli  


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

Revision as of 23:35, 21 April 2012

Background

  1. Colorless, odorless gas
  2. Most toxic component in smoke inhalation and major contributor to fire-related deaths
    1. Can co-occur with Cyanide toxicity in industrial fires
  3. Sources
    1. Automotive exhaust
    2. Propane-fueled heaters
    3. Wood or coal-burning heaters
    4. Structure fires
    5. Gasoline-powered motors
    6. Natural gas-powered heaters
  4. Peak incidence in winter months

Pathophysiology

  1. Hypoxia
    1. Binding affinity of Hb for CO (carboxyhemoglobin) is 200x that of O2
    2. Half-Life
      1. Room air: ~5hrs
      2. 100% O2: ~1hr
      3. HBO 2.5atm: 24min
  2. Lactic acidosis
    1. CO inhibits oxidative phosphorylation
  3. Hypotension
    1. CO induces NO2 and guanylate cyclase release --> vasodilation release

Workup

  1. VBG
    1. Co-oximetry analysis will provide carboxyhemoglobin level
  2. Lactate
  3. Chemistry
  4. Troponin
  5. Total CK (rhabdo)
  6. ECG
    1. May range from normal to STEMI (most common ST, then prolonged QT)
      1. Few of the pts w/ AMI from CO have occlusive lesions in their arteries
  7. ?Head CT
    1. May show b/l globus pallidus lesions in severe cases

Clinical Features

  1. May range from "flu-like" symptoms to coma
  2. CNS
    1. Headache
    2. Visual disturbances
    3. Confusion
    4. Ataxia
    5. Seizure
    6. Syncope
    7. Retinal hemorrhage
    8. Focal neurologic deficit
  3. GI
    1. Vomiting
  4. Pulm
    1. Dyspnea/tachypnea
  5. Cardio
    1. Chest pain
    2. ECG changes/dysrhythmias
  6. Derm
    1. Bullous skin lesions
    2. Classic finding of cherry red oral mucosa is rarely seen in living pts

Diagnosis

  1. Must have high clinical suspicion (esp in pts w/ coma, AMS, or anion gap acidosis)
    1. Comatose pt removed from fire should be assumed to have CO poisoning
  2. Carboxyhemoglobin Level
    1. Interpretation must take into account time since exposure and O2 tx
    2. Normal value in non-smokers is ~1%, normal value in smokers may be up to 10%
    3. Symptoms and COHb levels do not always correlate well
  3. Pulse oximetry is unreliable
    1. CoHb registers the same as O2Hb so will have artificially high SpO2
    2. O2 saturation gap reflects discordance of SpO2 by pulse oximeter vs by VBG

Treatment

  1. O2 100% by NRB or ETT
    1. Provide O2 until COHb value <10%
  2. Hyperbaric Therapy (HBO)
    1. Decision to initiate HBO should be made in consultation w/ hyperbaric specialist
    2. Controversial who exactly benefits from tx
    3. Pt must be stable prior to transport
    4. Indications (generally accepted guidelines):
      1. Syncope
      2. Confusion/AMS
      3. Seizure
      4. Coma
      5. Focal neuro deficit
      6. Pregnancy w/ CoHb level >15%
      7. Blood level >25%
      8. Acute myocardial ischemia

Disposition

  1. Minimal or no symptoms
    1. Discharge
  2. Mildly symptomatic
    1. Headache, vomiting, elevated COHb level
    2. Discharge after 4hr obs and symptom resolution
  3. Severely symptomatic
    1. Ataxia, syncope, chest pain, neuro deficit, dyspnea, ECG changes, pregnant w/ COHb >15%
    2. Admit; discuss with hyperbaric specialist

Source

Tintinalli

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