# Venous Blood Sampling

## Overview

This module describes how to obtain blood from a vein.

## Indications

1. To obtain blood for investigations

## Contraindications

1. Damaged skin, localised swelling, sclerosed veins, haematomas, or infection at the drawing site

2. An AV fistula, IV line or lymph node resection on the same limb

3. First four hours after blood transfusion

## Patient information and consent

Always verify your patient’s identity and obtain informed consent before proceeding.

### How do I explain this procedure?

“I need to draw blood from a vein to use it for tests. We use a new needle for every patient, and losing this amount of blood does not harm you.”

### What can my patient expect?

“You may feel a sharp scratch when I insert the needle. Test results can sometimes take several days to become available.”

### What is my patient’s role?

“Let me know if you have any allergies or a bleeding tendency, or use blood thinners. Fearing blood or needles is normal, but tell me if you have fainted from it. Keep as still as possible. If you feel strange sensations or pain, tell me immediately. Afterwards, press firmly on the area with cotton wool to prevent bleeding.”

## Preparation

### Documentation

1. Laboratory request forms

2. Patient labels

3. Patient notes

### Equipment

1. Non-sterile gloves

2. Alcohol-based hand rub

3. Sharps container
   Sharps container

   If a sharps container is not within arm's length, use a kidney dish or other hard container to temporarily hold used sharps and to carry them to the sharps container for disposal.

4. Alcohol swab

5. Tourniquet

6. Blood collection tubes (Vacutainers)

7. Collection tube rack
   Collection tube rack

   These are often not available in our setting. See Troubleshooting for how to safely fill blood tubes without a rack.

8. Vacutainer barrel (“bulldog”) and Vacutainer safety needle (OR a needle and syringe OR winged set “butterfly” and syringe)

9. Cotton wool and a plaster

10. Specimen bag

## Site and Positioning

Always position the patient seated, reclining or supine to avoid injury caused by possible fainting.

The most common site for venous blood sampling is from the antecubital fossa where veins are easy to see and palpate. The median cubital vein is the first choice. Avoid inserting the needle where two veins meet as there are often valves.

Other sites include the basilic and cephalic veins, the veins on the hands and wrists, and femoral veins. These sites pose increased risks, and should only be used if the median cubital vein is not an option.

## Procedure

Follow medical asepsis with sterile gloves for collecting samples that include blood culture.

Follow medical asepsis with non-sterile gloves for other samples.

1. Complete laboratory request forms and label with patient labels. Label collection tubes with patient labels and if using a syringe, place them in a tube rack.

2. Perform hand hygiene and don gloves.

3. Find a straight, visible, large vein and apply a tourniquet 7-10 cm above. Don’t leave the tourniquet on for more than a minute; if you need more time, loosen it and tighten it again just before you puncture.

4. Clean the site with an alcohol swab and allow to dry. Do not touch this area again.

5. If using a syringe: connect the needle to the syringe. If using a barrel: twist the cap to break the seal and reveal the shorter, rubber-covered needle. Attach the needle so the rubber-covered side is inside the barrel.

6. Anchor the vein by placing the thumb of your non-dominant hand below the puncture site and tensing the skin.

7. Insert the needle at a less than 30° angle with the bevel up. Advance until you enter the vein. When using a winged set or needle and syringe you should see blood in the needle chamber (flashback); then advance 1 mm more.

8. If using a syringe: Move your non-dominant hand to steady the syringe against the skin and slowly pull back on the plunger to draw blood. If using a barrel: Move your non-dominant hand to steady the barrel against the skin. Insert the first collection tube into the barrel firmly so the needle pierces the top of the tube and blood flows into it. Remove the filled tube, gently up-end a few times and repeat for further tubes in the correct

   order of filling.
   order of filling.

9. Release the tourniquet before exiting the skin.

10. Cover the injection site with the cotton bud. Withdraw the needle, and if using a barrel, immediately activate the safety mechanism if present.

11. Apply pressure with the cotton bud; ask the patient to take this over.

12. If using a syringe: puncture each collection tube’s cap and allow the blood to flow into the tube. Use the correct

    order of filling.
    order of filling.

    Do not push the plunger. Up-end each tube a few times gently. Activate the needle safety mechanism if present.

13. Secure the cotton bud with a plaster if the site is still bleeding.

14. Dispose of medical waste safely.

15. Record the completion of the procedure in patient notes.

16. Place tubes in a sealable bag with the form and send it to the laboratory.

## Troubleshooting

I can’t find a vein.

Check each antecubital fossa. Apply heat to the skin and tap on the site to help raise the vein. Ask the patient to make a fist. If not successful, try the backs of the hands. Inflating a manual sphygmomanometer between systolic and diastolic blood pressure can help to visualise the veins better. Other sites include the feet, the fine veins on the wrists, the femoral veins in the groin, or the neck. Alternatively, switch to arterial blood sampling procedure.

The blood flow stopped during aspiration.

Advance 1 mm and withdraw 1 mm. Attempt rotating the needle 90°.

Don’t poke around any further. Rather withdraw and restart the procedure at another site.

The puncture site continues bleeding.

Use continuous, direct pressure for 5 minutes. If unsuccessful, call your senior and consider investigation for bleeding tendency.

The patient is uncooperative/confused.

Don’t risk a needlestick injury. Call an assistant to hold the limb steady.

I see rapid, pulsatile bleeding at puncture site.

You accidentally entered an artery. Withdraw the needle and apply firm pressure until bleeding stops.

I don’t have a rack to position collection tubes for filling.

It is unsafe to fill tubes while holding them in your hand. To avoid sharps injuries, hold the back end of the tube between index finger and thumb and lay the tube flat on a surface. Pierce the top carefully with your needle at a downward angle, so that if you miss, you will strike the table and not your hand.

## Risks

1. Minor bleeding/pain/haematoma at puncture site

2. Infection at puncture site

3. Sharps injury to healthcare personnel

4. Vasovagal response (fainting)

## References

1. WHO Guidelines on Drawing Blood: Best Practices in Phlebotomy. Geneva: World Health Organization; 2010. Available from: https://www.ncbi.nlm.nih.gov/books/NBK138665/ .

2. Olivier N. Phlebotomy. In: Mulder M, Joubert A, Olivier N, eds. Practical Guide for General Nursing Sciences. 2nd ed. Pearson: Cape Town; 2020.