1. Arterial Blood Gas Sampling Flashcards
Who are Arterial Blood samples drawn from?
- Critically Ill Patients
2. Deteriorating Patients
How often are Arterial Blood samples taken from Patients?
Daily
What do Arterial Blood samples assess?
- Adequacy of the Patients Oxygenation (PaO2)
- Adequacy of the Patients Ventilation (PaCO2)
- The Patients Acid - Base Status
- Determine Electrolyte Levels
What is the name of the Machine which analyses the Arterial Blood samples?
Blood Gas Analyser
What can Blood Gas Analysers (commonly) also measure?
- Electrolytes
- Glucose
- Lactate
When is an Indwelling Arterial Cannula placed?
- When it is Anticipated that the Patient will require frequent Arterial Blood Samples
- Continuous Monitoring of Arterial Blood Pressure is Required
What is the Initial Tests required to determine the Site for the Procedure?
- Both Left and Right Radial Arteries are Palpable
- “Allen’s Test” - required in some hospitals
- Infection or Haematoma at the Site, on each side
Which hand is normally used for this procedure?
Non-Dominant Hand is normally chosen
What should always be prepared before the blood is drawn?
The Disposal of the Needle - Use an Equipment Trap with a Sharps Attached and immediately dispose of the needle in the Sharps Bin
- What Size of Gauge Needle is used?
2. Why?
- A Small Gauge Needle - most commonly (in adults) are 22G, 23G, or 25G
- a) Minimise damage to the Vessel
- b) Minimise Haematoma formation afterwards
- Is there a special “Arterial Blood Sampling Kit” available?
- What is special about them?
- Yes
- The syringe is pre-filled with the required amount of Heparin - to prevent clotting
Note - The Heparin is not normally seen but is there
If an “Arterial Blood Sampling Kit” is not available, what is the procedure?
- 1mL of 1000 micrograms/mL of Heparin is Drawn into a Syringe
- The Heparin is completely expelled, leaving a very small amount of Heparin in the Hub
- The Needle is Changed to a fresh 25 Gauge Needle
How much Heparin is required for the 2-3mL Blood Sample taken?
0.2mL - This is what will remain in the Hub of the Syringe
Are Tourniquets used in the Arterial Blood Sampling procedure?
No
What information needs to be put into the Blood Gas Analyser before it will work?
The Patients Details
In Clinical Practice, do all Arterial Punctures occur in the Radial Artery?
No, e.g. during resuscitation the Brachial / Femoral Artery might be used
What is important to bear in mind if the Arterial Puncture is taking place on the Radial Artery?
It is a Superficial Artery (if you go more than 0.5cm deep then you are probably too deep)
What are the general contraindications to performing an Arterial Puncture?
- The Patient is on Anticoagulation Medication
- The Patient has a Coagulopathy
- History of Vascular Disease in the Area being used (e.g. Reynaud’s Disease)
What are the Site - Specific Contraindications for a Raidal Arterial Puncture?
- Presence of an AV Fistula in that Arm
- Cellulitis, Broken Skin or Other Signs of Infection
- No Palpable Raidal Pulse
- Negative Allen’s Test
- Fractured Limb
How is an “Allen’s Test” performed?
- Occlude both the Radial and Ulnar Arteries of the Patient
- Ask the Patient to Clench their Fist several times
- Ask the Patient to Extend their Fingers
Note - Blanching should be seen - Release the Ulnar Artery
Note - If colour returns in 10-15 seconds, the Test is positive
What does a Positive “Allen’s Test” indicate?
Good Collateral Arterial Blood Flow
What does a Negative “Allen’s Test” mean?
That the Arterial Puncture should not (ideally) be attempted at that site
What needs to be considered to minimize the discomfort of the patient?
The Depth of the Raidal Artery
Note - If you go to far it is very painful as you will hit the Periosteum of the Radius
What may be given to reduce the pain of the needle insertion?
Local Anesthetic:
- Anesthetic Transdermal Cream
- Anesthetic Spray
- Intradermal Injection of Lidocaine
What is needed in order to interpret results?
Inspired Oxygen Concentration (FiO2) at the time of the sampling
What needs to happen if the Arterial Blood Gas Sample will not be Analysed, by the Blood Gas Analyser, for 30 minutes or more?
- The Cap is Securely Fitted
- The Sample is Labelled with:
a) Patient’s Details
b) Time and Date of the Sample
c) FiO2 at the time of Sampling - The Syringe is placed in a Biohazard Bag and sealed
- The Biohazard Bag is placed in Ice
Why is the Sample placed in Ice if it will not be analysed for 30+ minutes?
To limit ongoing metabolism in the Blood Cells. Otherwise may result in:
- Increased CO2
- Decreased pH
- Decreased PaO2
What may affect the sample in the Syringe?
Air Bubbles present
Why does there need to be Heparin in the Syringe?
To Prevent the Sample from Clotting