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How to Draw Umbilical Cord Blood Gases TUTORIAL

Taking an arterial blood gas (ABG) involves using a needle and syringe to directly sample blood from an artery (typically the radial artery). Beneath is a stride-by-step guide to taking an arterial blood gas sample in an OSCE setting, with an included video demonstration.

Download the ABG sampling PDF OSCE checklist, or use our interactive OSCE checklist. If you'd similar to learn more nearly interpreting an ABG then cheque out our ABG interpretation guide or put yourself to the examination with our ABG quiz or ABG interpretation flashcards. You might besides be interested in our guide to documenting ABG results.

Gather equipment

Gather the appropriate equipment:

  • Gloves
  • Frock
  • Pre-heparinised arterial blood gas syringe and bung or cap
  • Arterial claret gas needle (23 One thousand)
  • Alcohol wipe (70% isopropyl)
  • Gauze or cotton fiber
  • Tape
  • Lidocaine 1% (one mL)
  • Subcutaneous needle (25-27 Thousand)
  • Small syringe for lidocaine (1-2 ml)
  • Sharps container

Introduction

Wash your hands and don PPE if appropriate.

Introduce yourself to the patient including your name and office.

Ostend the patient's name and date of birth.

Briefly explain what the procedure will involve using patient-friendly language: "I need to take a sample of claret from an artery in your wrist to accurately assess your oxygen levels. The procedure will be a little painful, however, information technology should only have a short amount of time. If you want me to stop at whatever point, but permit me know. The procedure does involve some risks which include bleeding, bruising, infection and very rarely permanent damage to the artery being sampled from. "

Check for any contraindications to arterial blood gas sampling:

  • Absolute contraindications: peripheral vascular affliction in the limb, cellulitis surrounding the site or arteriovenous fistula.
  • Relative contraindications: impaired coagulation (due east.one thousand. anticoagulation therapy, liver disease, low platelets <50).

Bank check if the patient has an allergy to local anaesthetic (e.g. lidocaine).

Gain consent to go along with arterial claret gas sampling.

Adequately betrayal the patient's wrist for the procedure.

Position the patient so that they are sitting comfortably, ideally with their wrist supported by a pillow. If a bed is bachelor, the patient can lay down for the process (this is sometimes preferable, particularly if the patient is prone to vasovagal syncope).

Ask the patient if they have any pain before continuing with the clinical procedure.

How oxygen therapy impacts ABG results
  • PaO2  should be greater than x kPa when oxygenating on room air in a healthy patient.
  • If the patient is receivingoxygen therapy theirPaO2  should be approximately10kPa less than the% inspired concentration FiOii  (and then a patient on 40% oxygen would exist expected to accept a PaO2 of approximately 30kPa).

Yous might besides be interested in our OSCE Flashcard Collection which contains over 2000 flashcards that cover clinical examination, procedures, advice skills and data interpretation.

Modified Allen'due south test

Before taking a sample from the radial artery, a modified Allen's test should be performed to assess the collateral arterial supply of the paw from the ulnar artery. The thought behind this cess is to make certain the patient's paw isn't exclusively reliant on the radial artery for its claret supply, in which case sampling should exist avoided.

To perform a modified Allen'southward test:

ane.Ask the patient to clench their fist.

ii. Apply pressure over the radial and ulnar artery to occlude both vessels.

3. Ask the patient to open their hand, which should at present announced fair-skinned. If the hand does not announced it suggests yous are not completely occluding the arteries with your fingers.

4. Remove the pressure from the ulnar avenue whilst maintaining force per unit area over the radial avenue.

five.If there is adequate blood supply from the ulnar artery, the normal colour should return to the entire manus within 5-fifteen seconds. If the return of colour takes longer, this suggests poor collateral circulation Do not perform arterial blood gas sampling on a hand that does not appear to take an adequate collateral blood supply.

It should be noted that there is no evidence performing this test reduces the rate of ischaemic complications of arterial sampling.

Preparation

Oxygen and body temperature

Notation the patient's body temperature and if the patient is currently receiving oxygen therapy, note the oxygen delivery device and flow rate.

These factors tin significantly affect results and are taken into account by the arterial blood gas analyser.

Equipment

Remove all equipment from its packaging so that it is easily attainable during the procedure.

Attach the needle, with its protective cover intact, to the pre-heparinised ABG syringe.

Positioning

Position the patient's hand preferably on a pillow for comfort with the wrist extended by approximately 20-30°.

Procedure

Palpation

Assess the course of the radial avenue to determine where you plan to perform arterial sampling:

1. Palpate the radial artery over the wrist of the patient'southward non-dominant hand to identify an ideal puncture site. You should use the tips of your fingers to clearly map out the course of the radial artery and so identify a distal site where the avenue is nearly pulsatile. The radial avenue is typically most superficial over the lateral anterior aspect of the wrist.

2. Once you have identified your planned puncture site, make clean it with an alcohol wipe for 30 seconds and permit it to dry out before proceeding.

three. Wash your hands once again.

4. Don a pair of gloves and an frock.

Local anaesthetic

Hurting associated with arterial blood gas sampling tin exist markedly reduced by the employ of subcutaneous local anaesthetic. The British Thoracic Club recommends the routine use of local anaesthetic for obtaining ABG samples except in the context of an emergency or if the patient is unconscious.

Set up and administrate lidocaine subcutaneously over the planned puncture site (aspirate to ensure yous are not in a blood vessel before injecting the local anaesthetic). See our guide to subcutaneous injection for more details.

Let at least lx seconds for the local anaesthetic to work.

Arterial puncture

ane.Remove the protective comprehend from the ABG needle and so flush through the heparin from the syringe.

ii. Hold the patient's wrist extended by approximately twenty-thirty°.

three. Palpate the radial artery with your non-dominant hand'south index finger around 1cm proximal to the planned puncture site (fugitive contaminating the planned puncture site that you previously cleaned).

four. Warn the patient y'all are going to insert the needle.

5. Holding the ABG syringe like a dart, insert the needle through the skin at the insertion site at an bending of thirty-45°.

6. Continue to advance the needle slowly towards the pulsation until you lot feel a sudden reduction in resistance and run across a rush of blood back into the ABG syringe (this is known as "flashback").

7. The ABG syringe should then brainstorm to self-fill in a pulsatile manner. If this doesn't happen, it may indicate you accept gone through or missed the avenue and therefore need to re-accommodate your position based on your understanding of the form of the radial artery (due east.g. change in angulation or slight withdrawal of the needle).

8. Once the required amount of claret has been collected, remove the needle and apply firsthand business firm pressure over the puncture site with some gauze. Secure the gauze with some tape and proceed to use pressure.

9. Engage the needle safety device (ofttimes a clip that covers the needle or a bung that the needle is inserted into).

10. Remove the ABG needle from the syringe and discard it immediately into a sharps bin.

11. Carefully expel any air from the sample if present, place a cap onto the ABG syringe and invert it gently.

12. Attach a sticker containing the patient's details to the ABG sample.

13. Continue to use house pressure level to the puncture site for iii-5 minutes to reduce the take a chance of haematoma formation.

ABG reference ranges
  • pH: 7.35 – seven.45
  • PaCO2 : iv.vii – six.0 kPa || 35.2 – 45 mmHg
  • PaO2 : 11 – 13 kPa || 82.five – 97.five mmHg
  • HCO3–: 22 – 26 mEq/L
  • Base backlog (Exist): -2 to +two mmol/L

To complete the procedure…

Explain to the patient that the process is now complete.

Give thanks the patient for their time.

Dispose of your PPE and equipment into an advisable clinical waste matter bin.

Wash your easily.

Take the ABG sample to exist analysed every bit shortly as possible later being taken as delays longer than 10 minutes can affect the accurateness of results.

Document the ABG results in the patient'south notes (run into our guide to ABG documentation).

References

  1. WHO guidelines on cartoon blood: best practices in phlebotomy. Published in 2010. Available from: [LINK].

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How to Draw Umbilical Cord Blood Gases TUTORIAL

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