- special syringes are used for blood gas analysis
- collection of a blood sample for accurate analysis by a blood gas machine
- usually pre-packaged and disposable
- contain a small amount of lyophilised heparin (e.g. Li heparin)
- usually plastic (previously glass and required heparin to be added)
- have a cap to prevent contact with gases in the air
- should be left at room temperature and analysed within 30 minutes (previously glass syringes were kept chilled on ice to prevent metabolism and allow delays in analysis)
- usually 1 or 3 mL sizes
- needles of different length and gauge built into the syringe or are needle-less
- safety covers for needles when they retract or a foam pad to inject the sharp into before removing the syringe
- Luer lock tips
- ‘self filling’ plungers that move when arterial pulsation is detected or plungers that are retractable to a desired sample volume creating a chamber for blood to enter
- gradations showing volumes on the side
METHOD OF USE
- Blood is drawn into the syringe, using a needle that enters a vessel or from an intravascular cannula (e.g. arterial sampling line)
- analysis is performed as soon as possible by a blood gas machine
Sources of inaccuracy associated with sample collection:
- Excessive delay to processing (allows continued metabolism by the erythrocytes and reduces pH and pO2 and increases pCO2)
- Air bubbles (cause a fall in pCO2 and an increase in pO2)
- Severe anaemia (the capacity for buffering oxygen may be reduced)
- Leucocyte larceny (severe leucocytosis causes metabolic decrease in pO2 and increase in pCO2 and cell lysis with increase K+)
- Failure to interpret that a sample is venous rather than arterial and vice versa
- Excess haemolysis causing artefactually increased potassium
- Inadequate mixing of syringe before analysis (falsely low Hb due to RBCs settling out)
- Sample take from a crushed or ischemic limb
- Not all syringes are compatible with all blood gas machines and point of care devices
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.