CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du...
-
Upload
gladys-watkins -
Category
Documents
-
view
216 -
download
0
Transcript of CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du...
![Page 1: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/1.jpg)
CO - The Silent Killer
Martin Laliberté MD FRCP ( C ) ABEM
McGill University
Centre Anti-Poison du Québec
![Page 2: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/2.jpg)
Case study - Mrs B.
40 year old female presenting after a syncopal episode at home
Headache, nausea, dizziness x 2 weeksLives in a condominium building downtownHeard the alarm of the CO detector installed in
her apartment ( 100 - 150 ppm )
![Page 3: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/3.jpg)
Incidence of CO poisoning
Leading cause of poisoning mortalityMost common cause of death in combustion
related inhalation injury1000 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
![Page 4: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/4.jpg)
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
![Page 5: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/5.jpg)
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
![Page 6: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/6.jpg)
Pathophysiology - Tissue hypoxia
Binding to Hb to form COHbHb affinity for CO 250 times affinity for O2Effect on oxyHb dissociation curve
left shift, distortion of shape
Impaired release of oxygen at tissue levelIncreased minute ventilation with subsequent
increased CO uptake
![Page 7: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/7.jpg)
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
![Page 8: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/8.jpg)
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 perfusionIschemic reperfusion injury
![Page 9: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/9.jpg)
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- )
![Page 10: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/10.jpg)
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
![Page 11: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/11.jpg)
Clinical manifestations
General headache, nausea, vomiting, weakness
Cardiovascular chest pain, tachypnea, tachycardia, hypotension pulmonary edema, arrythmias, cardiac arrest
Neurologic dizziness, ataxia, seizures, coma
Others retinal hemorrhages, metabolic acidosis
![Page 12: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/12.jpg)
Severity of CO intoxication
Inhaled CO concentrationDuration of exposureIndividual susceptibility
minute ventilation pregnancy
Presence of systemic illnesses cardiac and pulmonary diseases
Initial COHb not predictive
![Page 13: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/13.jpg)
Case study - Mrs B.
Neurologic examination reveals that the patient is confused and disoriented
COHb measured on admission is 15 %Patient is a non-smoker Head CT Scan and ECG is normal
![Page 14: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/14.jpg)
COHb elimination half-life
O2 20.9 % 1 atm 320 min ( 128-409 ) - Peterson
O2 100 % 1 atm 131 min ( 27-462 ) - Myers 72 min ( 26-146 ) - Weaver
O2 100 % HBO 3 atm : 23 min - Peterson 1.58 atm : 27 min - Jay 2.5 atm : 22 min - Pace
![Page 15: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/15.jpg)
Shimazu et al. ( 2000 )
CO elimination : two-compartment modelShort term exposure
initial phase - half life 5.7 minutes slower phase - half life 103 minutes
Long terme exposure initial phase - half life 21.5 minutes slower phase - half life 118 minutes
Two compartments intravascular and extravascular
![Page 16: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/16.jpg)
Delayed or persistent CO toxicity
Persistent : present from exposureDelayed : 2 to 40 days post-exposureDementia, psychosis, memory deficitParkinsonism, paralysis, choreaPersonnality changes, gait disturbanceCortical blindness, apraxia, agnosiaPeripheral neuropathy, urinary incontinence
![Page 17: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/17.jpg)
Delayed or persistent CO toxicity
Reported neurologic impairment varies widely between 3 % and 44 %
Reported at 10 % to 30 % at 1 yearNeuropsychologic deficits often subtleCan be identified by psychometric testing Spontaneous recovery
mild poisoning : 100 % resolve at 2 months severe poisoning : 75 % resolve at 1 year
![Page 18: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/18.jpg)
Delayed CO toxicity
Lesions of cerebral white matter globus pallidus, cerebellum, hippocampus perivascular injury with blood flow abnormalities
Often associated with LOC in acute phaseHypotension is essential to cause white matter
lesions in animal modelPatients > 30 year old more susceptible to
delayed CO toxicity
![Page 19: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/19.jpg)
Low dose / chronic CO exposure
CO 61 ppm and COHb 4 % - effect on memory and learning abilities
COHb 2 - 3.9 % - worsening ischemia in patients with pre-existing CAD
COHb 6 % - exercise-induced ventricular arythmias in patients with CAD
CO 38 ppm - 35 % cardiovascular mortality excess in workers
![Page 20: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/20.jpg)
Clinical evaluation
Maintain a high level of suspicionHistory of exposure can be absentCOHb
< 3 % non-smokers or < 10 % in smokers not predictive of outcome correlation with symptoms useless
ABG : metabolic acidosis ( lactate )ECG : ischemia, arrythmias
![Page 21: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/21.jpg)
Pulse oximetry in CO poisoning
Pulse oximetry : HbO2 and RHb at two wavelengths : 660 nm and 940 nm
Unreliable with significant amount of abnormal Hb : MetHb, COHb, SHb
Pulse oximetry overestimates true fractional arterial oxygen saturation
Elevation of COHb level falsely elevates the SaO2 by an amount less than the COHb level
![Page 22: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/22.jpg)
Neurologic evaluation
Neurologic examinationMental status examination
Folstein
Psychometric testing CO Neuropsychological Screening Battery
Neuroradiologic imaging : CT, MRI
![Page 23: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/23.jpg)
Psychometric testing
Lack of standardized methodsNormalisation of psychometric testing
practice effect when repeated decreasing effect of other toxins with time very subjective, tester can be biased
Abnormal testing : at risk of persistent or delayed neurologic sequelae
Predictive of need for HBO therapy in mild toxicity ?
![Page 24: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/24.jpg)
Severity of CO poisoning
COHb level does not correlate with severity or outcome
Severity of neurologic lesions correlate better with hypotension than with hypoxia
Duration of exposure as important as concentration
Total CO load = [ ] x ventilation x exposureSusceptibility of individual to CO
![Page 25: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/25.jpg)
Case study - Mrs B.
Patient is given O2 100 % on arrivalHBO facility is contacted for consultationBased on the history of LOC and persistent
confusion, transfer for admission is advisedPatient receives 4 treatments of HBO
![Page 26: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/26.jpg)
Management of CO poisoning
Identify the source to correct the problemDomestic exposition
verification of heating or cooking appliances
Occupational exposition CSST investigation
CO poisoning : mandatory reporting to public health services
Making the diagnosis can save lives !
![Page 27: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/27.jpg)
Case study - Mrs B.
Case reported to public healthHigh CO concentrations measured in buildingTwo other cases diagnosed in building
needing treatmentInvestigation identifies serious flaws in
ventilation system in the basement garage and inadequate CO dectors
![Page 28: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/28.jpg)
Management of CO poisoning
Oxygen 100 % ASAPABGCOHbECGCXRCardiac enzymesCardiac monitoring
![Page 29: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/29.jpg)
Hyperbaric oxygen therapy
Enhanced elimination of COHbImproved tissue oxygenationEnhanced dissociation of CO from
cytochrome oxidaseInhibition of B2 integrin adhesion to vascular
endothelium Prevention of CNS lipid peroxydation
![Page 30: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/30.jpg)
HBO vs NBO studies
Isolated case reportsUncontrolled clinical observationsStudies
small non-randomized unblinded assessment of outcome incomplete assessment of outcome
![Page 31: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/31.jpg)
Raphael et al. - 1989
Prospective randomised clinical trial of NBO ( n=170 ) vs HBO ( n=173 )
Patients without LOC admitted within 12 hours of CO exposure
NBO : 6 hrs of NBO O2HBO : 2 hrs of O2 at 2.0 atm, 4 hrs of NBOEvaluation at 1 month : interview, telephone
![Page 32: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/32.jpg)
Raphael - Results
Time to randomisation shorter in HBO groupLost to follow up : NBO 12.9 % HBO 8.0 %Recovering at 1 month
NBO 66 % HBO 68 % p=0.75
> 90 % patients functional at 1 monthHBO at a low pressure ( 2 vs 2.5-3 atm )HBO after > 6 hours in 50 % casesSoft outcome measures at 1 month
![Page 33: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/33.jpg)
Ducasse et al. - 1995
Prospective randomised clinical trial of NBO ( n=13 ) vs HBO ( n=13 )
Patients exposed to CO without LOCDiscovery to admission < 2 hrsNBO : O2 100 % x 6 hrs, 50 % x 6 hrsHBO : O2 100 % 2.5 atm x 2 hrs, 100 % x 4
hrs, 50 % x 6 hrs
![Page 34: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/34.jpg)
Ducasse - Results
Clinical abnormalities at 2 hrs reflex impairment, headache, asthenia NBO 9 HBO 2 p < 0.01
Clinical abnormalities at 12 hrs headache, moderate pulmonary edema NBO 5 HBO 0 p < 0.05
Patients treated with HBO at 3 weeks ( n=18 ) fewer EEG abnormalities abnormalities normal reactivity to CO2 on SPECT scans
![Page 35: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/35.jpg)
Thom et al. - 1995
Prospective randomized study NBO ( n=32 ) vs HBO ( n=33 )
Reffered patients with mild to moderate CO poisoning no history of LOC no cardiac instability
Outcome : delayed neurologic sequelaeNeither patients nor investigators blinded to
treatment
![Page 36: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/36.jpg)
Thom - Interventions
NBO : 100 % O2 until all symptoms resolvedHBO : 100 % O2 at 2.8 atm x 30 minutes and
at 2.0 atm x 90 minutesTreatment given within 6 hours in all cases
![Page 37: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/37.jpg)
Thom - Results
NBO : 7 / 30 patients ( 23 % ) with DNSHBO : 0 / 30 patients ( 0 % ) with DNSDNS persisted for a mean of 41 daysAll patients eventually recovered
![Page 38: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/38.jpg)
Scheinkestel et al. - 1999
Randomised controlled double-blind trialReferred patients, all severity of poisoningCluster randomisation to HBO ( n=104 ) vs
NBO ( n=87 )73 % with severe poisoningStratified in 4 groups : suicide, accidental,
ventilated, not ventilatedPsychometric testing : 0 and 1 month
![Page 39: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/39.jpg)
Scheinkestel - Interventions
All patients had daily txs x 3 days100 % O2 daily to everyone between txsHBO :100 % O2 x 100 min, 60 min at 2.8
atmNBO : 100 % O2 x 100 min at 1.0 atmPatients with abnormal clinical evaluation or
poor psychometric testing had 3 more txs
![Page 40: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/40.jpg)
Scheinkestel - Results
HBO patients required more txsHBO patients had worse outcome in learning
testGreater % of severely poisoned patients in HBO
group had a poor outcome at end of txDNS restricted to HBO patientsNo difference if tx < 4 hours or with accidental
poisoning
![Page 41: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/41.jpg)
Scheinkestel - Limitations
Mean delay to treatment 7.1 hours ( 95 % CI 1.9-26.5 )
Large number of severily poisoned patients46 % had 1 month follow up44 % with possibility of co-ingestantsHigh proportion of depressed patientsBaseline O2 100 % x 3 days different from other
studies
![Page 42: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/42.jpg)
Weaver et al. - Abstract - 1995
Undersea Hyperbar Med 1995 ; 22 : 14Reported - Dr K. Olson - October 1st 1999Prospective double-blind RCT with 152
patients ( last update May 1999 )No difference in outcome between HBO vs
NBO
![Page 43: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/43.jpg)
Mathieu et al. - 1996
Undersea Hyperbar Med 1996;23 (suppl) : 7-8Prospective unblinded RCT with 575 non-
comatose patientsRandomisation to HBO at 2.5 atm vs NBOTime to treatment < 12 hoursNo difference in outcome at 1 year between
HBO vs NBO
![Page 44: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/44.jpg)
Uncontrolled case series
Relation suggested between favorable outcome and HBO therapy in severe poisoning
Severely poisoned patients ( comatose ) can have a normal outcome without HBO
Poisoned patients can have a bad outcome despite HBO
Variability in severity, treatment modalities, psychometric testing, length of follow up with potential for selection bias
![Page 45: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/45.jpg)
Classic indications for HBO
Coma or loss of consciousnessNeurologic abnormalitiesCardiovascular dysfunctionSevere metabolic acidosisCOHb > 40 %COHb > 15 %
![Page 46: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/46.jpg)
Timing of HBO
Patients treated at > 6 hours tend to do worse delayed CO toxicity : 30 % vs 19 % mortality : 30 % vs 14 %
Benefit shown as late as 21 days in anecdotal, uncontrolled case reports
Natural history of delayed neurologic toxicity mild poisoning : 100 % resolve at 2 months severe poisoning : 75 % resolve at 1 year
![Page 47: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/47.jpg)
Adverse effects of HBO
Need for transfer to HBO facility with risk of deterioration
Otic barotrauma effusion, hemorrahge, TM rupture
CNS oxygen toxicity : seizuresEpistaxis
![Page 48: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/48.jpg)
CO poisoning in pregnancy
High incidence of neurologic abnormalities and stillbirth after CO poisoning
Fetal Hb binds CO more avidly that Hb ACO absorption and elimination slower in fetal
circulationHBO felt to be safe in pregnancyNo scientifically established role for HBO in
pregnancy : COHb > 15 % suggested
![Page 49: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/49.jpg)
Prevention of CO poisoning
Public education about CO poisoningIdentification of activities at riskTraining of workers for proper use of propane-
powered toolsAppropriate ventilation of confined placesIndustrial and domestic use of CO detectorsReporting to public health services
![Page 50: CO - The Silent Killer Martin Laliberté MD FRCP ( C ) ABEM McGill University Centre Anti-Poison du Québec.](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649da15503460f94a8cb70/html5/thumbnails/50.jpg)
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
Misleading information and myths are perpetuated in the literature
Making the diagnosis and preventing further exposure to CO is too often forgotten