Taking Blood from PIVC - Amplified

Quick Reference

Why Take Blood from a New Cannula?

Taking blood at the time of cannula insertion saves the patient a separate venepuncture. It's efficient and minimises needle sticks. However, this only works at insertion - once the cannula is flushed with saline, any blood drawn will be diluted.

Limitations

• Only valid at time of insertion (before any flush)
• Some tests may be affected (lactate can be falsely elevated from tourniquet time)
• Some hospitals don't allow blood cultures from PIVC (risk of contamination)
• If the cannula doesn't flush well afterward, you've lost both the bloods AND the access

Common Tests by Tube

Prep

Label tubes with patient details

Label all tubes at the bedside before or immediately after collection. Never pre-label tubes before seeing the patient - this is a major source of wrong-blood-in-tube errors. Include patient name, DOB, UR number, date/time of collection.

Know order of draw

The order matters to prevent additive carryover between tubes:

1. Blood cultures (if needed) - must be first to prevent contamination
2. Light blue (citrate) - coagulation, ratio-sensitive
3. Red/yellow (serum) - clot activator
4. Green (lithium heparin) - biochemistry
5. Purple (EDTA) - haematology
6. Grey (fluoride oxalate) - glucose

The main concern is EDTA contaminating citrate tubes (falsely prolongs clotting times) or lithium heparin affecting potassium results.

Have vacutainer ready

You need the vacutainer adaptor that screws onto the cannula hub. Have this open and ready - once you have flashback, you don't want to be fumbling for equipment. Also have all your tubes lined up in order of draw.

Execute

Insert cannula, get flashback

Standard cannula insertion technique. Once you see flashback in the chamber, you know you're in the vein. Don't advance further yet.

Remove needle to sharps

Withdraw the needle from the cannula and dispose immediately in sharps. Keep pressure on the vein proximal to the cannula tip to prevent blood spilling. The cannula stays in the vein.

Attach vacutainer to cannula hub

Screw the vacutainer adaptor onto the cannula hub. Hold the cannula steady - this is when it can easily dislodge. The adaptor has a rubber diaphragm that the tube will pierce.

Insert tubes in order

Push each tube onto the vacutainer needle, piercing the rubber stopper. The vacuum draws blood automatically. Fill in the correct order (see Prep section). Gently invert each tube as you remove it to mix with the additive.

Fill to black line

Each tube has a black fill line. Under-filling is a problem, especially for citrate tubes where the ratio of blood to anticoagulant is critical (1:9). Under-filled citrate = falsely prolonged clotting times. Over-filling is less common but can also affect results.

Finish

Remove vacutainer to sharps

Once all tubes are filled, remove the vacutainer adaptor. Dispose of it in sharps (it has a needle inside). Apply pressure proximal to cannula tip.

Flush cannula with saline

Attach a saline flush and flush briskly. This confirms the cannula is working and clears any blood. If it doesn't flush well, you may need to remove and resite - but at least you have the bloods.

Secure with dressing

Apply a transparent dressing so the site remains visible. Ensure the cannula is stable and won't catch on clothing or bedding.

Date the cannula

Write the date (and time if your hospital requires it) on the dressing. Cannulas should be reviewed daily and replaced at 72-96 hours or sooner if there are signs of phlebitis.

Document: date, time, site, gauge, bloods taken, tubes filled, cannula flushes well.