Venepuncture - Amplified

Anatomy

The same veins used for cannulation apply to venepuncture. Start distal and work proximal to preserve sites.

Prep

Consent and explain procedure

Always explain what you're doing and why. Most patients are familiar with blood tests but appreciate knowing how many tubes you'll fill. Warn them about the tourniquet pressure.

Hand hygiene, non-sterile gloves

Standard infection control. Non-sterile gloves protect you from blood exposure - not a sterile procedure.

Select appropriate tubes for tests ordered

Check the request form. Each tube colour has a specific additive:

Tourniquet 10-15cm proximal

Apply tight enough to impede venous return but not arterial flow. If you can't feel a radial pulse, it's too tight. Don't leave on >1 minute or results (especially K+) may be affected.

Execute

Palpate vein, select site

Use your index finger to palpate, not look. A good vein feels bouncy and refills when compressed. Avoid veins that feel hard (thrombosed) or those near joints.

Clean with 2% chlorhexidine, allow to dry

The drying is essential - chlorhexidine works through contact time. 30 seconds minimum. Don't re-palpate after cleaning.

Anchor vein with non-dominant thumb

Pull the skin taut 2-3cm distal to your entry point. This stabilises the vein and prevents it rolling away.

Insert 15-30°, bevel up

Enter the skin with the bevel facing upward. A shallow angle reduces the chance of going through-and-through. You can lower the angle once in the vein.

Watch for flashback in hub

Modern butterfly needles and vacutainer holders have a flash chamber. When blood appears, you're in. Hold still and attach or advance the tube.

Order of Draw

The order matters to prevent additive carryover:

1. Blood cultures - always first if needed (sterile)
2. Light blue (citrate) - coagulation studies, must be accurate 1:9 ratio
3. Red/yellow (serum) - clot activator, no anticoagulant
4. Green (lithium heparin) - biochemistry
5. Purple (EDTA) - haematology
6. Grey (fluoride oxalate) - glucose/lactate

Fill to the black line. Under-filled citrate tubes give falsely prolonged clotting times.

Finish

Remove tourniquet, withdraw needle

Release tourniquet first to reduce haematoma risk. Withdraw smoothly.

Apply pressure 2-3 min

Direct pressure with cotton ball. Ask patient to press firmly (not rub). Anticoagulated patients need longer (5+ min).

Label tubes at bedside

Never pre-label. Wrong-blood-in-tube (WBIT) errors are serious. Label immediately at the bedside with patient watching.