ABG Sampling Flashcards
What are the indications for ABG sampling?
Checking:
- Oxygenation
- Respiratory derangements
- Metabolic derangements
- Acid-base status
- CO poisoning/carboxyhaemoglobin
- Lactate Electrolytes and haemoglobin (preliminary)
- Response to treatment (with repeated measuring)
What are the contraindications for ABG sampling?
- Infection locally
- Anatomy distorted
- AV fistula
- PVD of distal limb
- Coagulopathy
What questions should you ask the patient/conditions to check for in the notes, before the procedure?
- Problems with circulation
- Taking antioagulants - “blood thiners”
- Coagulopathy - “problems with clotting”
- Allergies to e.g. latex
What is the main site for ABG sampling? What are the alternatives?
- Radial artery - found between the flexor carpi radialis and styloid process of the radius
Alternative sites:
- Brachial artery
- Femoral artery
What is Allen’s test?
Assesses whether there is adequate blood supply to the hand with the ulnar nerve
Steps:
- Ask patient to make a really tight fist
- Ask them to hold this for a few seconds
- Apply pressure on the ulnar and radial artery simultaenously
- Let go of the ulnar artery
- Check whether there is perfusion of the whole hand within 15 seconds.
What is the needle of choice for drawing up local anaesthetic and the needle of choice for its injection?
- Pink - drawing up
- Orange - injection
What are the arteries of the arm and forearm?
Axillary artery –> humeral circumflex artery –> deep brachial and brachial artery
Brachial artery –> radial artery (distal) and ulnar artery (medial)
Where does the axillary artery branch from?
Subclavian artery
What are the disadvantages of the alternative sites of ABG sampling?
- May be less superficial
- Poor collateral circulation
- Nearby structures (e.g. nerves) can be damaged by poor technique
What are the possible complications of ABG sampling?
- Arterial spasm - may be more likely if the site has been previously used for sampling
- Haematoma - pressure should be applied for 5-10 min due to high pressure within artery compared to vein
- Nerve damage - choose a good site
- Aneurysm
- Fainting and other vaso-vagal responses - patient should be lying down for the procedure
What equipment should you collect?
Aseptic kit - clean tray, alcogel wipes
Needles - AGB sampling kit, orange needle(~25G) and pink needle(~18G), needles bin
Local anaesthetic - 1% lignocaine, 2ml syringe.
Comfort - wrist prop, gauze, plaster
What is the local anaesthetic of choice for ABG sampling?
1% Lignocaine - injected locally
When is the onset of action of lignocaine? What is its duration of action when injected IV and IM?
Onset of action: 1.5 min
Duration IV: 10-20min
Duration IM: 0.5h - 3h
What should you do before inserting the ABG needle?(name all steps)
- Put on an apron
- Clean tray
- Collect kit
- Wash hands
- Identify patient and gain consent
- Identify appropriate site and clean it
- Apply gloves and unpack all equipment into tray
- Apply drawing up needle onto 2ml syringe
- Draw up 1ml of local anaesthetic
- Dispose of pink needle and apply orange needle
- Insert needle and aspirate - ensure no blood
- Inject a small amount of local anaesthetic at the site of injection (below where your fingers are feeling for the pulse)
- Wait for 1-2 min for anaesthetic to act
- Hold ABG needle like a pen
- Take lid off ABG needle and inject at 30-45 degrees until you draw up blood - some needles may self-fill
What are the steps after you have inserted the ABG sampling needle?
- Collect about 1-2ml of blood
- Remove the needle, applying pressure on the artery with gauze
- Apply pressure for 5-10min or ask the patient to do this
- Replace the ABG needle with the lid
- Invert the syringe to mix with the heparin in the tube
- Apply a plaster to the gauze
- Dispose of all equipment
- Document the procedure in patient’s notes
