Arterial Blood Gas Sample

Last Updated on by frcemuser


  • Evaluate the adequacy of ventilation, acid–base status, and oxygenation.
  • Evaluate the patient’s response to therapy and/or diagnostic evaluation (e.g. oxygen delivery).
  • Monitor severity and progression of a known disease process.

Test Before ABG

  • The Allen test is a good and valid screening test for the circulation of the hand.


  • Absent ulnar circulation – as demonstrated by Modified Allen’s Test.
  • Impaired circulation e.g. Raynaud’s Disease
  • Arteriovenous fistula
  • Distorted anatomy/ trauma/burns to the limb – at or proximal to the
    attempted arterial puncture site.
  • Severe coagulopathy
  • Abnormal or infectious skin processes at/or near the puncture site


  • Failure and/or pain
  • Haematoma or haemorrhage
  • Arteriospasm
  • Trauma to the vessel
  • Arterial occlusion
  • Vasovagal response
  • Air or distal clotted-blood emboli
  • Pseudoaneurysm

Source of error in blood gas collection and handling

  • Sample contaminated with venous blood
  • Sample clotted
  • Air bubles will falsely elevate the PO2
  • Sample contains too much heparin (liquid heparin dilutes the sample, and causes pH changes)
  • Haemolysis en route to the ABG analyser
  • Inappropriate type of syringe used (gas-tight syringes are needed, rather than evacuated tubes)
  • The sample contains an excessive number of leukocytes, and they have consumed all the oxygen (eg. leukaemia blasts)
  • The sample took too long to transport, and blood cell metabolism has changed the gas concentration
  • Sample was chilled with ice (and then analysed at body temperature values)-Low temperatures also make the ABG syringe polymer more gas-permeable, allowing gases to exchange with the atmosphere.

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