Here's some info on midlines:From Nursing 2000
"SUITABLE FOR many patients who need I.V. therapy for 2 to 4 weeks, midline catheters can remain in place longer than peripheral I.V. catheters-up to 4 weeks, compared with 48 to 72 hours for a short peripheral catheter. Besides lowering costs, midline catheters can reduce patient discomfort and save nursing time because they don't need to be replaced as often as peripheral catheters.
In this column, I'll discuss indications and catheter placement. In my next column, I'll cover potential complications and how to deal with them.
Midline catheters are typically inserted just above or below the antecubital area in the basilic, cephalic, or median cubital vein; the catheter is then advanced until the tip rests in the upper arm, just short of the axilla. The basilic vein is preferred because of its larger diameter and straight pathway up the inner aspect of the arm.
Whether your patient is a candidate for a midline catheter depends on the expected duration of IN. therapy and whether he has suitable veins available for the catheter. Other factors to consider are;
patient preference (use the nondominant arm, if possible)
type of therapy to be administered. Midline catheters shouldn't be used to administer chemotherapy, total parenteral nutrition, solutions with a pH below 5 or above 9, solutions with an osmolality greater than 500 mOsm/liter, or rapid high-volume infusions or high-pressure bolus injections.
the patient's physical condition. If he's dehydrated, administer fluids via a small-gauge IN. catheter for a few hours before attempting to place a midline catheter.
medical history. If the patient has experienced thrombosis from other invasive procedures, thrombosis is a risk with a midline catheter. Other contraindications include conditions that impede venous return from the extremity, such as paralysis or lymphedema; orthopedic or neurologic conditions affecting the extremities; dialysis grafts (anticipated or present); and hypercoagulopathy.
Most midline catheters are 7 to 8 inches (18 to 20 cm) long. If midline catheter insertion is a nursing responsibility at your facility, measure the patient's arm from the planned insertion site to about an inch below the patient's axilla to determine how much catheter to insert and the amount of catheter to be left externally.
You may need patient consent and a physician's order before you place the catheter. Follow your facility's protocol and the manufacturer's recommendations.
During I.V. therapy with a midline catheter, assess arm circumference regularly. When you insert the catheter, mark a small X in waterproof marker on the patient's arm about 6 inches (15 cm) above the insertion site and document the baseline arm circumference at the mark. All nurses caring for the patient should measure the arm circumferences at the X.
Document arm circumference at least once every 8 hours during a continuous infusion. If the patient is receiving an intermittent infusion, measure arm circumference before infusing each dose. A deviation of more than an inch in arm circumference from the measurement taken by the previous shift may indicate edema, infiltration, or phlebitis in the underlying deep tissue where the catheter tip dwells. Monitor the patient closely; the catheter might need to be removed. (For more on complications, see Recognizing Midline Catheter Complications.)
Also assess the insertion site every 1 to 2 hours during a continuous I.V. infusion. Document changes in the site, such as redness, drainage, fluid leakage, or cracks in the catheter, and check the external catheter length. Changes indicate that the catheter tip has moved; if most of the midline catheter is outside the I.V. site, the catheter must be removed. "
I'm not a big fan of midlines--they account for only 3-4% of my insertions--but agree that they have their use. As for insertion tips/techniques,the ones I know of do not have a tapered end,so you have to make a 4.5Fr hole in the vein with the introducer but you're only plugging things with a 4 FR line. So the insertion site can ooze more than a tapered PICC will. They rarely are reliable for blood draws,so the patients get stuck by lab anyhow.
They can also end up poorly positioned--funny curls can happen in arm veins so if we ever have a doubt we get an Xray.
2 UK references for you,'cannulation'--First,the Royal College of Nursing's Standards for Infusion Therapy,last update I believe was Nov 2005. Next,do a google on "Doncaster and Bassetlaw hospitals" and "PICC" for a very nice didactic course on PICC's (and 99% of it apllies to midlines,too).