Balanced heparin syringe
(*Please note that different brands of syringe with different size and heparin content are used in NTEC hospitals.)
Minimum blood volume: 0.6 mL (using 1 mL syringe containing 30 IU balanced lithium heparin)
Minimum blood volume: 1.6 mL (using 3 mL syringe containing 80 IU balanced lithium heparin)
Authorisation code required
No
24 Hr available service
Yes
Precaution
Blood Taking Procedure
- Appropriate volume of blood should be collected anaerobically in a special balanced heparin syringe. (Collect 0.6 mL blood for 1 mL syringe and 1.6 mL for 3 mL syringe so that the final concentration of the balanced heparin in sample is 50 IU/mL.)
- Dispose the needle, tap syringe to move air bubble to the top and slowly advance plunger to expel air from sample, and then re-cap the syringe with a cap.
- To ensure thorough mixing of blood with heparin, hold syringe in hand and rotate back and forth for 20 to 30 sec.
- Send the blood sample in ice bath to the laboratory immediately for analysis.
At the dosage given as an antidote for cyanide poisoning, hydroxocobalamin may cause falsely low results in total haemoglobin, carboxyhaemoglobin and methaemoglobin measurement and falsely high results in oxyhaemoglobin measurement.
Method
Co-oximetry
Reference interval
| Oxyhaemoglobin fraction (FO2Hb) | Normal 90 - 95% |
| Carboxyhaemoglobin fraction (FCOHb) | Non-smoker < 1.5% |
| Moderate smoker = 4 - 5% | |
| Heavy smoker = 8 - 9% | |
| Toxic > 20% | |
| Lethal > 50% |
(Source: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics 4th Edition, USA Elsevier Saunders, 2006: 2259, 2286, 2289)
Clinical indication
Investigation of possible carbon monoxide exposure and poisoning
Result interpretation
| Between 10 - 20% | headache and dyspnoea on exertion |
| Above 20% | confusion and irritability |
| Above 50% | unconsciousness, with death likely if exposure is prolonged |
| Above 70% | death is rapid |
Measurement of uncertainty
Frequency of measurement
Daily