The ultrasound-guided technique allows to insert not only short cannulas in the deep veins of the arm, but also other peripheral accesses, such as mini-midlines (6-15 cm) or traditional midlines (15-25 cm). The traditional midlines have little role in emergency, while the mini-midlines, although having an expectation of shorter duration compared to midlines (weeks) are appropriate in the emergencyurgency since they are quicker and easier to insert (simple Seldinger's technique) and are less expensive.
The opportunity to remove emergency mini-midlines within 24-48 hours is controversial: removal is mandatory if the standard precautions recommended for infection prevention have not been adopted. On the othe hand, a mini-midline inserted with appropriate technique (skin antisepsis with chlorhexidine 2% in alcohol, maximum barrier precautions, appropriate aseptic technique, sutureless securement, cover with transparent dressing) can be left even beyond 48 hours.
There are mini-midlines of different materials; in the case of long duration - polyurethane catheters should be preferred to polyethylene (the latter being associated with greater risk of thrombosis). The material obviously has little relevance if the mini-midline is to be removed within 48 hours.
Some mini-midlines are designed to be positioned with simple Seldinger technique (needle puncture - insertion of the metal guide into the needle - needle removal - catheter insertion above the guide) but others have more complex design (needle, cannula and metal guidewire assembled coaxially in an all-in-one device). At present there is no evidence to recommend the latter type of mini-midlines, since they are more expensive and more difficult to use.