Midline Catheters in Paediatrics – The Long and Short of it.

What are midline catheters?

There are three types of peripheral venous catheters:

1. Midline Catheter
2. PICC line
3. Long peripheral catheters.

Midline catheters (MCs) are peripheral intravenous lines that are longer (usually 6-20 cm) than routine peripheral IV cannulas. However, the tip of the catheter does not extend into a central vein. The final position of the tip should be in the axillary vein, ideally in the infraclavicular segment. MCs usually allow blood reflux. They are also sometimes called “short long line,” which is pretty much the definition mentioned above.

MCs are different from Peripherally inserted central lines (PICC). These extend into a central vein.

What about long peripheral catheters? The tip should be in the vein of the cannulated extremity but doesn’t pass the axillary fossa. Sampling (blood reflux) is impossible unless it’s in a big vein.

What are the best veins for midline cannulation?

We normally use the basilic vein or cephalic vein in the upper limbs and the saphenous vein in the lower limbs for midlines. But you can use any vein, provided they don’t branch too soon and are away from the arteries and joints. Select the most distal vein first and then progress proximally to avoid clotting off the venous system early.

What are the methods for cannulation?

Ultrasound-guided insertion is by far the ideal method of venous catheterisation, especially in Paediatrics. However, any cannula in the above-mentioned veins can be converted into a midline, provided it is done in a sterile way and following the recommendations of the insertion bundle (gown, gloves, sterile field, mask, sterile ultrasound probe cover).

What types of Midline are there?

There are many different midlines in the market. The catheters we use in paediatrics are usually 22G catheters, available in 6cm, 8cm, and 20 cm lengths.

They usually come with guidewires for insertion using the Modified Seldinger technique. The right length depends on the measurement from the insertion site to a point just distal to the shoulder joint (or knee joint in case of saphenous vein).

Take a look at this YouTube video for more on the Modified Seldinger techniques.

Always follow WHO checklist/LocSSIP for the procedure.

Ensure the guide wire is removed before the line is fixed and sharps are disposed of appropriately.

Why do we use midlines in paediatrics?

Midlines are preferred over routine peripheral cannulas for IV drug administration lasting more than four days.

Regular IV cannulas last 1-3 days and often must be replaced. The dwell time for the MCs is 2-4 weeks, making them preferable over the regular IV cannulas for long-term use. This reduces the repeated stress and trauma of multiple cannulations for children, parents and clinicians, improving patient care.

Some potential indications in Paediatric wards are:-

1. A longer course of IV antibiotics for conditions like meningitis, osteomyelitis, orbital cellulitis, cystic fibrosis
2. Prolonged administration of drugs with a high risk of thrombophlebitis, e.g. acyclovir, calcium gluconate, macrolides
3. Difficult vascular access like eczema herpeticum, burns, Staphylococcal Scalded Skin Syndrome, widespread dermatological conditions
4. Continuous drug infusions like prostaglandins (for duct-dependent cardiac lesions), N-Acetyl Cysteine (NAC)

How should you maintain the long-term patency of the catheter?

Midline catheters are at risk of developing occlusion due to blood, fibrin deposits, medication microcrystals, or incompletely dissolved medications creating microparticles. The risk of occlusion can be reduced by doing one of. the following:

1. Infusing normal saline 0.5 ml/hr through the line when not in use
2. A start-stop flushing technique with normal saline after every use

What are the possible complications of midlines?

1. Infection: A vascular access care bundle reduces the risk of infection.
2. Thrombophlebitis: Regular monitoring of thrombophlebitis scores is essential. The entry site should be visible through a transparent dressing.
3. Catheter migration outside the vein: though rare, this is a serious complication 
4. Clots in the vein: Thrombotic risk is high if the catheter occludes more than 30-45% of the lumen.
5. Bleeding

* It is important to respect the manufacturer’s recommendation regarding the pressure applied when flushing catheters—standard catheters should be flushed with a 10ml syringe only. They are not suitable for CT contrast administration. There are specific power lines made of highly resistant polyurethane compatible with the pressure necessary to administer contrast.

Midline catheters can improve the patient experience and deliver safe, effective care to the little ones.

References

Villalba-Nicolau M, Chover-Sierra E, Saus-Ortega C, Ballestar-Tarín ML, Chover-Sierra P, Martínez-Sabater A. Usefulness of Midline Catheters versus Peripheral Venous Catheters in an Inpatient Unit: A Pilot Randomized Clinical Trial. Nurs Rep. 2022 Oct 31;12(4):814-823. doi: 10.3390/nursrep12040079. PMID: 36412798; PMCID: PMC9680301.

Kleidon TM, Gibson V, Cattanach P, et al. Midline Compared With Peripheral Intravenous Catheters for Therapy of 4 Days or Longer in Pediatric Patients: A Randomized Clinical Trial. JAMA Pediatr. 2023;177(11):1132–1140. doi:10.1001/jamapediatrics.2023.3526

Kleidon TM, Gibson V, Cattanach P, Schults J, Royle RH, Ware RS, Marsh N, Pitt C, Dean A, Byrnes J, Rickard CM, Ullman AJ. Midline Compared With Peripheral Intravenous Catheters for Therapy of 4 Days or Longer in Pediatric Patients: A Randomized Clinical Trial. JAMA Pediatr. 2023 Nov 1;177(11):1132-1140. doi: 10.1001/jamapediatrics.2023.3526. PMID: 37695594; PMCID: PMC10495929.

Clinical practice guidelines Midline Catheters, Dr Liz Prentice, Anaesthetic Department, The Royal Children’s Hospital, Melbourne, September 2011