Importance of Arterial Line
To measure central venous pressure. Placement of an arterial line is indicated for continuous monitoring of arterial pressure and direct arterial blood sampling. The radial pulse is palpated between the distal radius and the flexor carpi radialis tendon.
For accurate assessment of acid-base status and for assessing degree of oxygenation of blood and adequacy of alveolar ventilation.
- Blood gas analysis
- Biochemical/and haematological investigations
- Infusions of glucose solution preclude sampling for blood glucose estimation
- Blood drawn from an arterial line may not be suitable for clotting studies
Definition- Blood Collection from Arterial Line
Arterial Blood – Collection of blood sample from any artery by performing any arterial puncture.
Requirements / Equipments
- Disinfectant for Hand Hygiene.
- Sterile Gloves.
- Sterile Syringes – Size according to amount of blood to be collected.
- Sterile Gauze Pieces.
- Blood Collection tube appropriate for required investigation.
- Kidney Tray.
How to do Blood Collection from Arterial Line
- Approach the patient, introduce yourself and ask the patient to state their full name.
- Place the patient on their back, lying flat. Ask the nurse for assistance if the patient’s position needs to be altered to make them more comfortable. If the patient is clenching their fist, holding their breath or crying, this can change breathing and thus alter the test result.
- Locate the radial artery by performing an Allen test for collateral circulation. If the initial test fails to locate the radial artery, repeat the test on the other hand. Once a site is identified, note anatomic landmarks to be able to find the site again. If it will be necessary to palpate the site again, put on sterile gloves.
- Perform hand hygiene, clear off a bedside work area and prepare supplies. Put on an impervious gown or apron, and face protection, if exposure to blood is anticipated.
- Disinfect the sampling site on the patient with 70% alcohol and allow it to dry.
- If the needle and syringe are not pre-assembled, assemble the needle and heparinized syringe and pull the syringe plunger to the required fill level recommended by the local laboratory.
- Holding the syringe and needle like a dart, use the index finger to locate the pulse again, inform the patient that the skin is about to be pierced then insert the needle at a 45 degree angle, approximately 1 cm distal to (i.e. away from) the index finger, to avoid contaminating the area where the needle enters the skin.
- Advance the needle into the radial artery until a blood flashback appears, then allow the syringe to fill to the appropriate level. DO NOT pull back the syringe plunger.
- Withdraw the needle and syringe; place a clean, dry piece of gauze or cotton wool over the site and have the patient or an assistant apply firm pressure for sufficient time to stop the bleeding. Check whether bleeding has stopped after 2–3 minutes. Five minutes or more may be needed for patients who have high blood pressure or a bleeding disorder, or are taking anticoagulants.
- Activate the mechanisms of a safety needle to cover the needle before placing it in the ice cup. In the absence of a safety-engineered device, use a one-hand scoop technique to recap the needle after removal.
- Expel air bubbles, cap the syringe and roll the specimen between the hands to gently mix it. Cap the syringe to prevent contact between the arterial blood sample and the air, and to prevent leaking during transport to the laboratory.
- Label the sample syringe.
- Dispose appropriately of all used material and personal protective equipment.
- Remove gloves and wash hands thoroughly with soap and water, then dry using single-use towels; alternatively, use alcohol rub solution.
- Check the patient site for bleeding (if necessary, apply additional pressure) and thank the patient.
- Label all samples accurately and record in the computer and pathology register
- Transport the sample immediately to the laboratory, following laboratory handling procedures.
Inappropriate collection and handling of arterial blood specimens can produce incorrect results. Reasons for an inaccurate blood result include…
presence of air in the sample;
collection of venous rather than arterial blood;
an improper quantity of heparin in the syringe, or improper mixing after blood is drawn;
a delay in specimen transportation.
Complications Related to Arterial Blood Collection
There are several potential complications related to arterial blood sampling. The points below list some of the complications related to the procedure, and how they can be prevented.
Arteriospasm or involuntary contraction of the artery may be prevented simply by helping the patient relax; this can be achieved, for example, by explaining the procedure and positioning the person comfortably.
Haematoma or excessive bleeding can be prevented by inserting the needle without puncturing the far side of the vessel and by applying pressure immediately after blood is drawn. Due to the higher pressure present in arteries, pressure should be applied for a longer time than when sampling from a vein, and should be supervised more closely, to check for cessation of bleeding.
Nerve damage can be prevented by choosing an appropriate sampling site and avoiding redirection of the needle.
Fainting or a vasovagal response can be prevented by ensuring that the patient is supine (lying down on their back) with feet elevated before beginning the blood draw. Patients requiring arterial blood sampling are usually inpatients or in the emergency ward, so will generally already be lying in a hospital bed. Children may feel a loss of control and fight more if placed in a supine position; in such cases, it may be preferable to have the child sitting on the parent’s lap, so that the parent can gently restrain the child.
Other problems can include a drop in blood pressure, complaints of feeling faint, sweating or pallor that may precede a loss of consciousness.