Carbon Monoxide Poisoning

Last updated 02.01.13

 

Index

 

Definition

-  Toxic levels of carbon monoxide (CO) typically from inhalation

 

Features

-  Carbon monoxide (CO) is a colorless, odourless, tasteless & non-irritating gas

-  Produced from hydrocarbon combustion

-  Binds Hb w x250 affinity of O2 to form Carboxy Hb

-  Causes left shift of O2-Hb dissociation curve

-  T/2 CO

-  Room air 3-4hrs

-  High flow O2 (non-rebreather) 30-90min

-  100% hyperbaric O2 at 2.5atm 15-23min

-  CO removed from Hb by O2 by competetitive binding

-  Sometimes associated with cyanide poisoning if from smoke inhalation (Burns)

-  Must determine duration & mechanism of exposure

 

Associated S/S

-  Young children manifest S/S earlier than adults

-  Altered conscious state: confusion, coma

-  Headache

-  Dizziness

-  Malaise, nausea

-  +/- Burns

-  +/- LOC

-  Severe: seizures, syncope

-  Lactic acidosis (metabolic)

-  APO

-  Myocardial ischaemia (Angina, AMI), ventricular arythmias

-  Delayed neurological sequelae

-  3-240 days post recovery

-  Lasts up to 1yr

-  Cognitive defect

-  Movement disorders

-  Personality changes

-  Focal defecits

-  Possibly associated with LOC during poisoning

-  Rhabdomyolysis

 

Causes

-  Suicide

-  Engine fumes: boat, car..

-  Fires: smoke inhalation

-  Heating systems

 

Ix

-  GCS

-  O2Sat

-  Unreliable as also detects COHb

-  ABG/VBG

-  Lactic (metabolic) acidosis

-  PO2 usually normal as detects O2 dossolved in blood not bound to Hb

-  Carboxy Haemoglobin (COHb) levels

-  Normal = 0 (up to 3%)

-  Smokers baseline 10-15%+/-

-  +/- ECG &/or Cardiac biomarkers

-  Ischaemia secondary to hypoxaemia: AMI

-  +/- CK: rhabdomyolysis

 

Mx

-  Identify & remove from source

-  High flow O2

-  Via non-rebreather face mask

-  Intubate if comatose or impaired GCS

-  +/- Hyperbaric chamber if

-  COHb >25-40% (controversial)

-  COHb >20% if pregnant

-  +/- LOC

-  pH <7.1

-  Ichaemia: chest pain, ECG changes

-  +/- Psych evaluation (suicide attempt)

-  Observation 6-8hrs or until COHb <10%

 

 

 

References

 

Upto Date – Carbon Monoxide Poisoning 2010

eMedicine: Carbon Monoxide Toxicity in Emergency Medicine, emedicine.medscape.com/article/819987-overview