62 Obtaining blood samples

62
Obtaining blood samples

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Obtaining blood samples overview


Venepuncture requires the introduction of a needle into a vein for the purposes of obtaining a blood sample for haematological, biochemical or bacteriological analysis. It can be traumatic for the child and family so careful preparation and planning are required.


This is one of the most common invasive procedures that is performed in clinical practice and is an essential component of clinical care that informs clinical decision-making. For the nurse who is performing venepuncture, it is their responsibility to be familiar with blood tests commonly undertaken, the requirements for each test (fasting, pre-drug administration), and know the normal blood component values.


Preparation of the child and family is key and needs to include the following elements:



  • Explanation and rationale of the procedure and need to take blood.
  • Previous history of venepuncture is useful to know.
  • Informed consent.
  • Involvement of play and distraction techniques.
  • Analgesia, both local and systemic.

Principles



  • The smallest gauge needle should be used in order to minimize damage to the vein. The vacuum system is likely to cause small veins to collapse so is not recommended for small children.
  • If the child is receiving intravenous fluids, ideally another limb should be used but if this is not possible, then a vein below the level of the cannula should be chosen with the intravenous infusion stopped for 5–10 minutes prior to venepuncture.
  • Avoid areas where a pulse is present as it is not desirable to accidently puncture an artery.
  • Avoid areas where the skin is broken or where rashes are present.
  • Good infection control practice is essential.
  • The age of the child will determine how the sample is drawn and the needle device used.
  • On the blood sample tubes, identify the child by checking the name band and complete the information required on the blood sample tubes: name, hospital identification number, date of birth, sex, date and time sample taken.

Selection of a vein


Selecting the right vein is a very important aspect of venepuncture:



  • The superficial veins of the arm are usually the site of choice in the child, namely, branches of the basilic, cephalic, median cephalic and median cubital vein.
  • Care must always be taken to avoid the brachial artery and this should be done by palpation and then avoiding it.
  • The vein should feel soft and bouncy, be straight and free from valves.
  • In the infant, it may be difficult to palpate a vein so transillumination, i.e. the transmission of light through a sample, may be used.
  • In the infant, the superficial veins in the dorsum of the hand, the dorsal venous arch or the metacarpal veins may be more accessible.
  • Listen to the child, children who have blood taken on a regular basis will usually instruct you on which vein to use.
  • The veins in the lower limbs should be avoided if at all possible, as the risk of thromboembolism has been identified.

Equipment



  • Butterfly needle or needle-appropriate gauge: 25 or 23 gauge.
  • Syringes.
  • Vacuum system may be used in an older child.
  • Disposable tourniquet.
  • Alcohol swab.
  • Appropriate collection tubes.
  • Specimen request form.
  • Low linting swab.
  • Hypoallergenic plaster.
  • Apron.
  • Non-sterile gloves.
  • Sharps bin.
  • Light.

Procedure



  • Wash and dry hands thoroughly.
  • Apply non-sterile gloves and apron.
  • Remove local anaesthetic cream.
  • Bring the prepared equipment to the child.
  • Assess veins and identify suitable vein/veins by palpation.
  • Support limb with a pillow and ask parent/carer to hold child securely, ensuring that they are comfortable doing this and that child will be safe during the procedure. The child may wish to lie down.
  • Apply tourniquet or ask staff to squeeze the limb being used gently. The older child could be asked to make a fist. The vein may be gently tapped or stroked in order to increase its prominence.
  • Release the tourniquet.
  • Wash and dry hands thoroughly.
  • Apply non-sterile gloves and apron.
  • Reapply the tourniquet.
  • Clean skin with an alcohol-based solution for 30–60 seconds and allow to dry.
  • Apply ethyl chloride spray if indicated as per manufacturer’s instructions if topical anaesthetic cream has not been used.
  • Remove the protective cover from the needle and inspect.
  • Stabilize the skin with the thumb, stretching the skin downwards, or the vein can be stretched using the forefinger and thumb of the non-dominant hand. This will apply traction to the vein, thus anchoring it and preventing it rolling.
  • Insert the needle at a 30° angle.
  • Reduce the angle of descent when a flashback is seen. This will be in the tubing if using a butterfly device or in the hub of the needle if using a syringe. If using a syringe, pull back on the plunger of the syringe before commencing so that blood will flow into the syringe once the vein has been punctured.
  • Slightly advance the needle into vein.
  • Using very gentle pressure, withdraw the required amount of blood into the syringe. If using a needle, allow the blood to drip into the appropriate sample bottles without exerting any pressure on the needle.
  • Loosen and remove tourniquet or relax pressure on limb.
  • Remove needle from vein.
  • Apply gentle digital pressure with the low lint swab over the puncture site for approximately one minute.
  • Transfer the blood to the appropriate sample tubes in the correct order as soon as possible. Gently invert the tubes at least six times.
  • Label all samples immediately.
  • Inspect puncture site and apply sterile hypoallergenic plaster, checking their allergic status to plasters first.
  • Ascertain comfort status of child.
  • Dispose of all waste appropriately.
  • Wash and dry hands.
  • Document venepuncture in child’s care records.

Heel or finger prick


Heel or finger pricking is not considered venepuncture as direct entry to a vein is not required.


It is important that when either of these sites are used, the correct area is identified and cleaned prior to piercing of the skin. Piercing of the skin is either with a barrelled needle or a lancing device. Blood flows freely through the needle into a specimen bottle, tube or directly onto collection paper (newborn blood spot screening). The same procedure as above should be followed once the appropriate sample has been obtained.

Oct 25, 2018 | Posted by in NURSING | Comments Off on 62 Obtaining blood samples
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