Carbon_Monoxide - CO The Silent Killer Martin Laliberté MD...

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Unformatted text preview: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec Case study - Mrs B. ❚ 40 year old female presenting after a syncopal episode at home ❚ Headache, nausea, dizziness x 2 weeks ❚ Lives in a condominium building downtown ❚ Heard the alarm of the CO detector installed in her apartment ( 100 - 150 ppm ) 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 ❙ ED visit rate 16.5 / 100 000 population Sources of CO ❚ Motor vehicle exhaust ❙ running engine in closed space ❙ faulty exhaust systems ❚ Propane-powered equipement ❙ lift, water heater, concrete saw, polishers ❚ Combustion for heating or cooking ❙ camping equipment, heating systems ❚ Smoke inhalation in fires Xenobiotics metabolism ❚ Methylene chloride ❙ peak of 50 % in humans ❚ Dibromomethane ❙ peak of 27 % in rodents ❚ Diiodomethane ❙ peak of 14.2 % in humans ❚ Bromochloromethane ❙ peak of 11 % in rodents Pathophysiology - Tissue hypoxia ❚ Binding to Hb to form COHb ❚ Hb affinity for CO 250 times affinity for O2 ❚ Effect on oxyHb dissociation curve ❙ left shift, distortion of shape ❚ Impaired release of oxygen at tissue level ❚ Increased minute ventilation with subsequent increased CO uptake Pathophysiology - Cellular level ❚ 15 % of CO bound to extravascular heme- containing proteins ❚ Cytochrome oxidase ( aa3 ) ❙ alteration in ATP production ❙ intracellular acidosis ❙ persists after exposure ❚ Cardiac and skeletal myoglobin ❙ occuring at COHb 2 % ❙ alteration in tissue O2 uptake Pathophysiology - Cardiovascular ❚ Myocardial depression consequence of ❙ hypoxic stress ❙ cytochrome a3 dysfunction ❙ CO binding to cardiac myoglobin ❚ Arterial hypotension ❙ myocardial depression ❙ NO-related peripheral vasodilatation ❚ LOC with reduction of cerebral perfusion ❚ Ischemic reperfusion injury 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- ) Pathophysiology - Neurovascular ❚ Peroxynitrite binds to perivascular tissue proteins causing injury ❚ Increased capillary permeability in CNS and pulmonary vascular beds ❚ Endothelial injury causing expression of adherence molecules - beta 2 integrins ❚ Leucocytes bind to injured endothelium reducing cerebral perfusion ❚ Initiation of CNS lipid peroxidation Clinical manifestations ❚ General ❙ headache, nausea, vomiting, weakness ❚ Cardiovascular ❙ chest pain, tachypnea, tachycardia, hypotension ❙ pulmonary edema, arrythmias, cardiac arrest...
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This note was uploaded on 01/11/2012 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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Carbon_Monoxide - CO The Silent Killer Martin Laliberté MD...

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