☝️ Midline Catheters: An Evidence-Based Review of the “Middle” Option Between PIV and PICC

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♦️ Introduction

Midline catheters first appeared in the 1950s as a relatively old vascular access device: a longer peripheral catheter inserted from a peripheral vein whose tip does not reach the central veins (SVC).
Initially inserted only by physicians, they largely disappeared from routine use for a while.
Recently, however, adoption of ultrasound guidance and reappraisal of complication risks versus PICC/central lines have brought midlines back into clinical attention.
From the late 2010s into the 2020s they have increasingly been used as a practical “middle” option for short–to–mid-term venous access, for example for about 5–14 days in many settings.

♦️ Overview of Midline Catheters

🔷 Definition

A midline catheter is a peripheral venous catheter inserted—typically from the upper arm (basilic, cephalic, or brachial territory)—with the tip positioned in axillary to proximal brachial veins.
The key point is that the catheter tip does not reach the intrathoracic central veins (SVC). Catheter lengths vary by product (a few cm up to around 20 cm are commonly used).
Clinically they are intended for short-to-mid-term dwell time; many facilities and guideline summaries cite an expected dwell range roughly between 5 and 14 days. This positioning and intended duration are described in standards such as the Infusion Nurses Society (INS) guidance and multiple review articles.

🔷 Indications and Contraindications

Clinical decision-making around use of a midline is commonly based on three main considerations:

Practically, midlines are suitable for medications that are safe peripherally (for example many common antibiotics) when infusion is expected to continue for a few days up to about two weeks.

Conversely, strong irritants/vesicants, high-osmolar solutions, and long-term parenteral nutrition (TPN) are best given via central access (PICC or central venous catheter).

Patients with prior deep vein thrombosis or very high thrombosis risk, and those who may require future dialysis access, require careful individualized assessment before choosing a midline.

🔷 Insertion Technique and Practical Management: Key Points

Insertion is recommended under sterile conditions with ultrasound guidance. A typical workflow is:

While learning the procedure, particular attention to vein assessment, securement/ fixation, and flush frequency reduces early mechanical complications (occlusion, dislodgement, leakage). Follow your facility’s protocol on flush volumes and whether heparin lock is used. Standardize documentation and daily site checks.

🔷 Advantages of Midline Catheters👍

Observational studies and systematic reviews report several practical benefits:

🔷 Disadvantages and Risks😫

Major midline complications include infection, thrombosis, occlusion, and extravasation.

Recent systematic reviews and larger trials show that while midlines may trend toward lower CRBSI, overall complication rates and thrombotic outcomes differ across studies; therefore midlines are not universally safer in every metric.

Preventing complications relies on sterile insertion, appropriate dressing care, adherence to flush protocols, and daily site monitoring. Remember also that because midlines do not reach the central circulation, they are not appropriate for TPN or certain vesicant/irritant agents.

🔷 What to Do If a Complication Is Suspected🚨

Suspected infection (erythema, warmth, fever):

Stop using the line, inspect dressing and catheter site, obtain peripheral and line blood cultures from the line and peripheral site. If clinical sepsis or lack of improvement is suspected, consider prompt catheter removal.

Suspected occlusion:

Follow your facility’s flush protocol (typically saline flush); if occlusion persists, evaluate for kinking, malposition, or securement problems. If mechanical issues are found, consider re-placement.

Suspected thrombosis (swelling, local pain):

Stop use immediately and assess with ultrasound. If deep venous thrombosis or high clinical risk is confirmed, involve vascular surgery or cardiology to consider anticoagulation and further management.

Because reported thrombosis rates vary across studies, follow your institutional guidelines for diagnosis and treatment.

♦️ Choosing Between PIV, Midline, and PICC

In clinical practice, decide based on three factors: drug irritability, planned duration of therapy, and thrombosis/vein risk.

♦️ Current Evidence

There has been growth in observational studies, randomized trials, and systematic reviews comparing midlines and PICCs. Differences in study design and outcome definitions lead to heterogeneous conclusions.

Many guideline summaries accept midlines as useful but rate the overall strength of evidence as low–moderate; final decisions are usually individualized to patient context and institutional practice.

📝 Summary：Take Home Points

📚 References & Further reading

Notes on evidence levels:

INS uses Levels I–V for evidence grading (Level I = meta-analyses/systematic reviews; Level II = RCTs; Level III = quasi-experimental; Level IV = cohort/observational; Level V = case reports/expert opinion). Many midline recommendations fall in Level II–IV, with some expert consensus (Level V) for specific procedural recommendations. For example, a 5–14 day suggested dwell time is generally based on Level IV evidence; contraindication for vesicants/TPN is Level III–IV; caution for prior thrombosis or vein preservation cases is often expert consensus (Level V).

Minor editorial note

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