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If your child needs medicine administered over a period of time, your doctor may have talked to you about using a midline catheter. This factsheet describes how and why midlines are used.

What is a midline?

A midline is a type of catheter or small tube, usually 5-8 cm long that is inserted into a vein in the upper arm up to the armpit.

Why would my child need a midline?

Midlines are used for intravenous antibiotics, when treatment will go on for more than a week. Some antibiotics are not suitable to be given via a midline and your child may need to have a catheter inserted in a larger vein towards the heart (called a peripherally inserted central catheter or central venous access device) instead. This will be discussed with you if it’s recommended for your child.

How is the midline inserted?

A midline can be inserted while your child is awake as it is a short and simple procedure. Some children may need sedation or a general anaesthetic.

The procedure is done in an operating theatre to reduce the risk of infection.

The midline is inserted by a doctor who has been specially trained and is inserted using ultrasound.

Local anaesthetic may be given in the surrounding area to numb it and make the insertion more comfortable.

An X-ray is not needed after the procedure.

Potential challenges with insertion

It may be difficult to insert the midline if your child’s veins are small. If the procedure is not successful, alternative types of catheter choices will be discussed with you before you provide your consent for the midline insertion.

How is the midline kept in place?

The midline is kept in place with a clear dressing and a securement device. The dressing covers the midline and keeps it clean and dry to prevent infection. The securement device prevents the midline from being pulled back or pulled out.

How is the midline removed?

Removal of the midline is done as soon as it is no longer needed, such as on completion of treatment, unresolved complication or if there is an infection. All staff removing midlines are trained in this task. Removal of the line can be done in the ward and is not painful.

What is ‘flushing’ and ‘locking’?

‘Flushing’ of the midline occurs when normal saline (salt water) is injected in the line to prevent it from blocking. This is typically done after medications have been given.

‘Locking’ refers to when a solution made out of anti-blood clotting agent (heparin or citrate) is left in the line when it is not being used. This is usually done when the midline isn’t going to be used for a period of time.

Possible problems

Serious problems are very rare and most of the time, a midline is the best choice for your child. However, it’s important to know of the risks involved before you consent to the procedure.

Accidental removal

The midline may be pulled out by mistake.

If this happens, any fluid or medication running through the midline should be stopped and the midline clamped.

Apply pressure over the insertion site and inform medical staff immediately.


A common complication is blockage of the midline.

This happens if blood or medications get stuck in the line.

To try to prevent blockages, the midline will either have fluid running through it or be locked.

A blocked midline can sometimes be fixed by flushing. Sometimes the midline is too blocked and needs to be removed.


As with any procedure there is a risk of infection, although we do our best to avoid this by making sure everything is clean and sterile in the operating theatre.

Signs of infection to look for include:

  • Redness, pain, heat and swelling over the site where the line is inserted.
  • Your child might also have a fever or feel unwell. Your child needs to present to the Emergency Department if they have a temperature of 380C or more as the Midline is a possible portal for infection.
  • If the infection is thought to be caused by the midline, then the midline may need to be removed and your child given antibiotics.


Sometimes there is bleeding or oozing around the insertion site. This usually settles fairly quickly.

Damage to the midline

The part of the midline outside the body may become damaged with a split or crack.

You may notice some fluid ooze from the midline or under the dressing.

If this happens, the midline may need to be removed.

Air bubbles

There is a small risk of air bubbles entering the midline which can cause problems.

We make sure that there is no air in the syringes used to inject medication or fluid into the midline.

If there is a break or a leak in the midline it is important to clamp it immediately to prevent air from entering.

Very rarely, there may be serious problems. The line could damage or puncture the wall of blood vessels. A serious infection or blood clot could develop.

It is important to discuss these possible complications with your child’s doctor, as well as all the risks and benefits of the midline, before you consent to the procedure.

Please feel free to talk to your child’s team doctor or your anaesthetist about any concerns you have. Being informed will help you make the best choice for your child.


(Write down any questions or concerns you would like to discuss with your doctor/nurse)


The Sydney Children's Hospitals Network
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