Carbon monoxide binds haemoglobin to form carboxyhaemoglobin (COHb), reducing oxygen carrying capacity and causing severe tissue hypoxia. Carboxyhaemoglobin measurement is indicated when there is a clinical suspicion of carbon monoxide poisoning e.g. house fires, domestic boiler leaks. Signs and symptoms include headache, nausea and vomiting, irritability and weakness followed by dizziness, confusion, ataxia, seizures, impairment of consciousness and respiratory failure. Cerebral oedema and metabolic acidosis may develop in serious cases. Note that the correlation between carboxyhaemoglobin concentration and clinical outcome is weak.
|06 (HP) - Heparin No Gel
|Samples should be drawn as early as possible after suspected exposure (as normal breathing rapidly reduces the COHb level), and before oxygen administration. Samples analysed on co-oximeter on blood gas analyser. Whole blood is required with lithium heparin only, EDTA CANNOT be used. DO NOT SPIN OR SEPARATE. Sample will be analysed by acute lab staff, notify them on arrival. COHb is stable for up to 28 days (Hampson, 2008). Samples are accepted from GPs - they need to be tracked through reception and tested on the Core Lab gas machine - pass to a Chemistry BMS.
|Co-oximetry on blood gas analyser.
|Balanced (blood gas) heparin or non-gel heparin are the ONLY presevatives that should be used for these samples.
|COHB1L / COHB1J