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Arterial blood gas sampling


  • Wash hands; Introduce self; Patient’s name, DOB and wrist band; Explain procedure and obtain consent
  • Check for allergies (including chlorhexidine)
  • Ask preferred (or non-dominant) arm 
Arterial blood gas equipment


  • Wash hands 
  • Clean tray
  • Gather equipment around tray (think through what you need in order)
    • Gloves
    • Alcohol 70%/chlorhexidine 2% skin-cleansing wipe
    • Arterial blood gas kit
      • Heparinised 1-3ml syringe with 23G needle
      • Rubber cube or needle cover
      • Cap for syringe
    • Sterile gauze 
    • Tape
  • Wash hands
  • Open packets and place neatly in tray, keeping items in plastic parts of packets (without touching the instruments themselves)
  • Put needle on syringe if not already attached
  • Return to patient


Modified Allen’s test

  • Wash hands 
  • Expose wrist and place a pillow beneath it
  • Perform modified Allen’s test
    • With patient’s palm facing upwards, occlude both radial and ulnar arteries
    • Ask patient to open and close hand until the palm becomes pale, then ask them to hold it open
    • Release the ulnar artery and time how long the hand takes to reperfuse (i.e. become pink again)
    • If ≤10 seconds, continue with ABG


  • Firmly hyper-extend the patient’s wrist (ask them, or hold it down yourself)
  • Palpate radial artery with index and middle fingers
  • Wash hands
  • Put on gloves
  • Sterilise area using skin-cleansing wipe (clean for 30 seconds, then allow to air-dry for 30 seconds)
  • Expel air from the heparinised syringe (only necessary for some ABG kits)
  • With the index and middle fingers of your non-dominant hand, re-palpate the artery just proximal to the point of insertion
  • Holding the bevel of the needle as close to your non-dominant hand’s fingers as possible (without touching them), insert the needle (bevel up) into the site of pulsation, at 45˚ to the skin
  • When blood enters the syringe, hold it still while it self-fills (no need to aspirate)
  • Place gauze loosely over the puncture site while you remove the needle. Then apply pressure to the gauze once the needle is fully removed.
  • Secure needle with rubber block or needle cover
  • Maintain pressure over the gauze for 5 minutes. Check it has stopped bleeding before taping down the gauze.

To complete

  • Thank patient and restore clothing
  • Remove the needle from the syringe and dispose of it in the sharps bin
  • Put the cap on the end of the syringe and expel the air
  • Discard waste and clean tray; then discard gloves; wash hands
  • Label the sample and take it to the blood gas machine or call the porters to collect it on ice
  • Document procedure and results in patient’s notes with the patient’s FiO2 and temperature