NHA Certified Phlebotomy Technician (CPT)Collection RoutineHard
A phlebotomy technician is performing a venipuncture and notices that the blood flow stops abruptly after collecting only a small amount. The needle is correctly positioned in the vein. Which of the following is the most likely cause?
- AThe vacuum in the evacuated tube has been lost.
- BThe patient's vein has collapsed.
- CThe needle bevel is resting against the vein wall.
- DThe tourniquet was applied too tightly.
Show answer & explanationAnswer & explanation
Correct answer: C. The needle bevel is resting against the vein wall.
If the needle is correctly in the vein and blood flow stops, the bevel resting against the vein wall is a common cause. This blocks the opening, preventing further blood flow. Gently rotating the needle slightly can often resolve this.
Why the other options are wrong
- A. Loss of vacuum in the tube would prevent blood from flowing at all, or only very little, but if blood initially flowed then stopped, the tube's vacuum was likely intact at first.
- B. Vein collapse is possible, especially in patients with small or fragile veins, but a bevel against the vein wall is a more immediate and common cause of abrupt cessation with correct initial placement.
- D. A tourniquet applied too tightly might impede arterial flow, but typically doesn't cause abrupt cessation of venous flow once established, unless it completely obstructs the vein.
Abrupt Blood Flow Cessation
When blood flow stops suddenly during venipuncture despite correct needle placement, it often indicates the needle bevel is obstructed by the vein wall, a valve, or the vein has collapsed.
- Bevel against vein wall is common.
- Vein collapse can also occur.
- Gently adjusting needle can resolve.
Memory trick: Flow stops? Check the 'B' for 'Bevel' or 'C' for 'Collapse'!