Eine Butterfly-Kanüle is a winged infusion set, a short cannula with two plastic wings and a length of flexible tubing that ends in a connector for the collection tubes. The wings allow the person drawing to hold the cannula flat against the skin at a shallow angle, and the tubing means the tube changes happen at the far end rather than at the puncture site. That combination is why it is reached for on small, fragile or rolling veins, on the back of the hand, and with people whose arms are difficult to work with.
The trade offs are practical rather than dramatic. A winged set costs more per draw than a straight holder and adds a step to the disposal routine, since the safety mechanism has to be activated before the set goes into the Abwurfbehälter. The tubing itself holds a small volume of air, and that dead volume is filled by the first blood entering the set. If a citrate tube for coagulation is drawn first, it takes that air instead of blood and ends up underfilled, which invalidates the ratio the method depends on. The usual answer is a discard tube drawn first, so the tubing is primed before the citrate tube is filled. This belongs in the written standard operating procedure rather than being decided at the chair.
It is also not automatically the gentler option. The lumen is narrow and the tubing long, so blood moves more slowly and under more shear, and combined with a vacuum tube on a thin vein that raises the risk of Hämolyse rather than lowering it. A slower draw also leaves the sample in contact with the additive for longer before it is mixed. Handled carefully the set is an excellent tool on a difficult vein. Used routinely because it feels safer, it simply moves the failure point from the puncture to the sample.
For a pharmacy the choice sits inside venöse Blutentnahme, which requires physician training before it may be offered at all, and for a small panel the alternative is often kapilläre Blutentnahme instead. Which sets and tubes are used is agreed with the laboratory in advance and documented as part of Präanalytik.
This glossary entry is general information about German pharmacy law and practice. It is not legal advice. For binding guidance on your own pharmacy, contact your Landesapothekerkammer.
