Synonyms |
|
COHb |
Clinical
Indications |
|
Investigation
of possible carbon monoxide poisoning.
|
Request Form |
|
Combined Pathology Blood form
(Yellow/Black)
|
Availability |
|
On
request
|
Specific
Criteria |
|
None
|
Patient
Preparation |
|
Ideally,
blood should be collected as soon as possible after exposure;
in an emergency situation if a patient has received oxygen
before arrival the carboxyhaemoglobin levels may be
misleadingly low.
In patients being investigated for domestic poisoning samples
must be collected as soon as possible after exposure to the
combustion products; if there is a delay in leaving the house
and having the test done results may be misleadingly low.
|
Turnaround
Time |
|
Same
day
|
Specimen |
|
Whole
blood
|
Volume |
|
1 ml
|
Container |
|
Purple
top (EDTA) tube
|
Lab. Handling |
|
Sample stored at 4°C
|
Causes for
Rejection |
|
Unlabelled sample.
|
Reference
Range |
|
Carbon
monoxide is produced continuously in the body as a by-product
of haem breakdown. This leads to a normal baseline COHb
concentration of about 0.5%. In pregnancy and especially in
haemolytic anaemias this can rise towards 5%. Cigarette
smoking leads to COHb concentrations of up to about 13% in
heavy smokers
(Reference: Letter from the Chief Medical Officer and
Chief Nursing Officer dated 7th September 1998
(PL/CMO/98/5, PL/CNO/98/8)
|
Elimination
Half-life |
|
On
air: 250 minutes
On 100 % oxygen: 50 minutes
On Hyperbaric oxygen: 22 minutes
Samples should be collected as soon as possible after exposure
|