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CO – “The Silent Killer”

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CO – “The Silent Killer”. Carbon Monoxide (CO) vs. Carbon Dioxide (CO 2 ). Incidence of CO poisoning. Leading cause of poisoning mortality. Most common cause of death in combustion related inhalation injury. 1000 to 2000 deaths / year ( USA ) Difficult diagnosis :

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incidence of co poisoning
Incidence of CO poisoning
  • Leading cause of poisoning mortality.
  • Most common cause of death in combustion related inhalation injury.
  • 1000 to 2000 deaths / year ( USA )
  • Difficult diagnosis :
    • incidence of unrecognized cases higher
    • estimated > 42 000 visits / year
sources of co
Sources of CO
  • Motor vehicle exhaust
    • running engine in closed space
    • faulty exhaust systems
  • Propane gas -powered equipment
    • lift, water heater
  • Combustion for heating or cooking
    • camping equipment, heating systems
  • Smoke inhalation in fires
pathophysiology
Pathophysiology
  • Hemoglobin’s affinity for CO is 200 to 250 times its affinity for oxygen
  • CO binding to hemoglobin causes allosteric modifications increasing its affinity for oxygen
  • Shift of O2 dissociation curve to the left
  • Decreased tension at which O2 is released from hemoglobin
  • Less O2 delivery to the cells
pathophysiology cellular level
Pathophysiology - Cellular level
  • 15 % of CO bound to extravascular heme-containing proteins
  • Cytochrome oxidase
    • alteration in ATP production
    • intracellular acidosis
    • persists after exposure
  • Cardiac and skeletal myoglobin
    • occuring at COHb 2 %
    • alteration in tissue O2 uptake
pathophysiology cardiovascular
Pathophysiology - Cardiovascular
  • Myocardial depression consequence of
    • hypoxic stress
    • CO binding to cardiac myoglobin
  • Arterial hypotension
    • myocardial depression
    • NO-related peripheral vasodilatation
  • LOC with reduction of cerebral perfusion
pathophysiology neurovascular
Pathophysiology - Neurovascular
  • CO in circulation associated with massive increase in NO in perivascular tissues
  • NO released from vascular endothelial cells and platelets
  • Production of oxygen radicals from impaired mitochondrial function
  • Reaction NO with oxygen radicals to form peroxynitrite ( ONOO- )
  • Peroxynitrite binds to perivascular tissue proteins causing injury
  • Increased capillary permeability in CNS and pulmonary vascular beds
diagnosis symptoms
Diagnosis - Symptoms
  • Most common symptoms :

headache 91%

dizziness 77%

weakness 53%

nausea 47%

confusion 43%

shortness of breath 40%

slide12
Cont…

visual changes 25%

chest pain 9%

loss of consciousness 6%

abdominal pain 5%

muscle cramping 5%

slide13
Cont…
  • The Delayed Neuropsychiatric Syndrome
    • Subacute manifestation (days to months)
    • Occurs in spite of normal HbCO levels
    • symptoms including : cognitive defects, personality changes, parkinsonism, amnesia, incontinence, gait disturbances, etc.
diagnosis signs
Diagnosis - Signs
  • Physical exam signs
  • tachypnea, tachycardia, vestibular signs (Ataxia, motion sickness, Nystagmus, circling, head tilt, fall to one side) common
  • retinal hemorrhages uncommon but more specific
slide15
Cont…
  • Signs of smoke inhalation such as burn nasal hairs, injured mucous membranes, carbonaceous mucus discharge
  • “Classic” findings of cherry-red lips, skin, and mucus membranes are very rare.

Note : - Young children (breath faster), elderly and household pets are usually effected first.

diagnosis
Diagnosis
  • High level of clinical suspicion
  • Serum COHb level
  • Exhaled breath COHb level
  • Pulse oximetry cannot distinguish between HbO2 and COHb
  • Comprehensive neurological and neuropsychological assessment
  • CT brain to exclude other conditions
severity of co intoxication
Severity of CO intoxication
  • Inhaled CO concentration
  • Duration of exposure
  • Presence of systemic illnesses
    • cardiac and pulmonary diseases
clinical evaluation
Clinical evaluation
  • Maintain a high level of suspicion
  • History of exposure can be absent
  • COHb
    • < 3 % non-smokers or < 10 % in smokers
  • ABG : metabolic acidosis ( lactate )
  • ECG : ischemia, arrythmias
pulse oximetry in co poisoning
Pulse oximetry in CO poisoning
  • Unreliable with significant amount of abnormal Hb : MetHb, COHb
  • Pulse oximetry overestimates true fractional arterial oxygen saturation
neurologic evaluation
Neurologic evaluation
  • Neurologic examination
  • Neuroradiologic imaging : CT, MRI
carbon monoxide alarm your best protection
Carbon Monoxide AlarmYour best protection!
  • Install a carbon monoxide alarm close to sleeping areas. For more protection:
    • Install one in every bedroom
    • Install one on every level of your home
  • Never ignore a carbon monoxide alarm, IT COULD SAVE YOUR LIFE!
emergency alarm sounds
EmergencyAlarm Sounds!
  • Get fresh air right away
  • Call local fire department
  • Do not re-enter an affected home until CO is gone
    • Fire department can determine when it is safe to re-enter a building
management of co poisoning
Management of CO poisoning
  • Identify the source to correct the problem
  • Domestic exposition
    • verification of heating or cooking appliances
  • Occupational exposition
  • CO poisoning : mandatory reporting to public health services
  • Making the diagnosis can save lives !
slide24
Cont…
  • Oxygen 100 %
  • ABG
  • COHb
  • ECG
  • CXR
  • Cardiac enzymes
  • Cardiac monitoring
hyperbaric oxygen therapy
Hyperbaric oxygen therapy
  • Enhanced elimination of COHb
  • Improved tissue oxygenation
  • Enhanced dissociation of CO from cytochrome oxidase
classic indications for hbo
Classic indications for HBO
  • Coma or loss of consciousness
  • Neurologic abnormalities
  • Cardiovascular dysfunction
  • Severe metabolic acidosis
  • COHb > 40 %
  • COHb > 15 %
co poisoning in pregnancy
CO poisoning in pregnancy
  • High incidence of neurologic abnormalities and stillbirth after CO poisoning
  • Fetal Hb binds CO more avidly than Hb A
  • CO absorption and elimination slower in fetal circulation
  • HBO felt to be safe in pregnancy
prevention of co poisoning
Prevention of CO poisoning
  • Public education about CO poisoning
  • Identification of activities at risk
  • Training of workers for proper use of propane-powered tools
  • Appropriate ventilation of confined places
  • Industrial and domestic use of CO detectors
problems in co poisoning
Problems in CO poisoning
  • Absence of reliable method to estimate prospectively the severity of CO poisoning
  • Difficulty in comparing results of studies because no staging in severity of disease
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