Common Questions and Answers
I can't get flashbacks when using butterfly needles or IV cannulas, do you have advice for me?
Certainly! When using a butterfly needle or IV cannula, blood flashback should be seen when the vein/fake vein is successfully accessed.
- Successful flashback depends on the following factors:
- Venous pressure within the simulated vein.
- The gauge diameter of the needle being used.
- The viscosity of the simulated blood.
- Ensuring proper insertion technique to enter the vein with the needle.
Let's discuss each of these topics in turn:
1. Venous pressure within the artificial vein:
Increasing the pressure in the prosthetic vein can result in better flashback. This is done by raising the reservoir bag about 6 inches (15 cm) at a time.
2. Needle Diameter:
Smaller diameter needles, such as 22 G or higher, produce slow/weak flashback. Wider diameter needles, such as 21 G or smaller, produce better flashback. However, the disadvantage is that larger diameter needles are more damaging to the prosthetic vein, limiting the length of time the arm can be used.
Therefore, better flashback can be obtained with larger diameter needles.
3. Viscosity of fake blood:
The higher the viscosity, the lower the chance of getting a good flashback effect. This can be problematic if fake blood is used, as many fake blood formulas contain corn syrup, which can make the blood quite viscous. Real unclotted blood is fairly non-sticky. We recommend using tap water and a few drops of red food coloring as fake blood. Clean thoroughly after each use.
4. Opening the deflector rollers and clamps (if applicable):
If any of the inflow clamps are closed, the venous pressure will remain close to zero and no blood return will occur.
5. Successful needle entry into the vein:
Regardless of how high the venous pressure is and what caliber needle is used, if the needle is not successfully punctured into the vein, there will be no flashback! Suggestion - keep practicing with Ultrassist Venipuncture IV and Phlebotomy Training Kit. Additionally, if you do not successfully enter a dummy vein, then your vacuum sampler will lose its vacuum and deteriorate.