Catheters designed for superficial vessels that can be identified by palpation or direct visualization are not effective in accessing the deeper veins of the upper extremity. We have discussed the follies of ultrasound (US) guided peripheral venous catheters in a previous post, but in brief their length and intent hinder their reliability, so much so that the 24-hour failure rate has been cited as high as 46% (1).
Midline catheters have been proposed as a viable method of accessing deep vessels without introducing the mechanical and infectious complications associated with central venous access (1,2). Fabiani et al recently studied the effectiveness of midline catheters inserted under US-guidance in cardiac surgical patients (3).
The authors prospectively enrolled 71 consecutive patients admitted to the cardiac surgery unit with difficult venous access (defined as lack of easily visible veins with at least 3 failed attempts at traditional cannulation), and were expected to require venous access for at least 7-10 days. The authors utilized 18-20 gauge polyethylene catheters designed for both venous or arterial use. The length of the catheter (8, 10, or 18 cm), was left to the individual practitioner’s discretion. Catheters were inserted using a Selidger technique with a straight-tipped, soft wire, and semi-sterile precautions (sterile drape, gloves and US probe-cover). Success was defined as cannulation with blood return and visualization of the catheter in the vessel on US.
The overall success rate of midline insertion was 100%, with 91.5% successfully inserted on the first attempt. The median dwell time was 11-days. 59.2% of the catheters were removed because they were no longer needed, 12.7% were accidently dislodged by the patients, and 9.9% were discontinued after a clot at the distal tip. Only one patient had a catheter related blood stream infection (CR-BSI), and even this was of questionable clinical relevance. This translates to an infection rate of 1.9 per 1000 catheter days, which is consistent with previous data (4).
Obviously a sample of 71 patients will never adequately demonstrate safety, but at times common sense should outweigh methodological rigor. Unlike central access the insertion of midlines rarely traverses anatomical structures that react poorly to cannulation with a sharp tipped needle (lung and carotid artery for example). The increased length, when compared to traditional peripheral catheters, places midlines catheters in deeper, larger vessels leading to far more reliable access. And while data is limited, the use of midline catheters in place of central venous cannulation has been associated with decreased rates of mechanical and infectious complications (5).
- Elia F, Ferrari G, Molino P, et al. Standard-length catheters vs long catheters in ultrasound-guided peripheral vein cannulation. Am J Emerg Med. 2012;30(5):712-6.
- Eid Mohamed El-Shafey, Tarek F. Tammam. Ultrasonography-Guided Peripheral Intravenous Access: Regular Technique Versus Seldinger Technique in Patients with Difficult Vascular. European Journal of General Medicine. 2012; Vol. 9, No. 4 .
- Fabiani A, Dreas L, Sanson G. Ultrasound-guided deep-arm veins insertion of long peripheral catheters in patients with difficult venous access after cardiac surgery. Heart Lung. 2016;
- Adams DZ, Little A, Vinsant C, Khandelwal S. The Midline Catheter: A Clinical Review. J Emerg Med. 2016;
- Pathak R, Patel A, Enuh H, Adekunle O, Shrisgantharajah V, Diaz K. The Incidence of Central Line-Associated Bacteremia After the Introduction of Midline Catheters in a Ventilator Unit Population. Infect Dis Clin Pract (Baltim Md). 2015;23(3):131-134.
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But can they infuse this as quickly as a central line? I submit that a short, large bore catheter in a central vein can give rapid fluid resuscitation better than a long skinny arm catheter can. It’s simple fluid mechanics.
Yes you cannot infuse fluid quite as quickly but I would argue that this is hardly clinically relevant. In the patient crashing from hemorrhagic shock, yes I would agree a midline catheter is not optimal but in almost any other type of shock I find the flow rates I get from a midline catheter (I use a 10 cm, 5F catheter) adequate for resuscitation.
Great stuff Rory. I think this is an example of how we need to de-silo critical care. In most hospitals, midline catheters are owned by specifically trained IV nurses (who often aren’t available at night or on weekends). Physicians could easily learn how to do this, but the logistics of sharing this procedure from nursing teams to physicians may be tricky.
Agreed! Part of that hurdle is overcome with our now ubiquitous and competent use of US. These really are the same vessels we are accessing with the “long” peripheral catheters. The administrative hurdles seem to be more of a problem. Getting access to the kits is difficult. Currently I do not have a “formal” midline kit and instead use a 5F, 10 cm micropuncture sheath. Additionally how nursing documents and uses these lines always seems to be problematic and has been handled differently at every center I have worked. At my former shop we trained our Emergency Physicians and Intensivists… Read more »
Enjoyed the post. One issue at my hospital is that per policy, medications with a “very” high or low pH are not allowed to run through the midline. The most common medication as you may imagine that this becomes a problem because of is vanco. Small but numerous studies have demonstrated vanco is safe via midline and as we all know via PIV. Yet our hospital policy still will not allow it. Unfortunately this leads to patients who lose their PIV d/t being a “hard stick” winding up with a PICC or CL even though a midline would have otherwise… Read more »
Rory, I’ll make an argument for midline catheters in patients with seemingly ‘good’ veins too! In fact, why are we not placing midline catheters in ED patients that are likely to be admitted to the hospital with IV therapy extending beyond 72 hours? Under optimum conditions, peripheral IVs might last 72-96 hours or so, but many hospital policies require site rotation at that point anyway. In the ED, we can intuit length of stay sometimes before we even ask the patient their first name, so why can’t our first stick be one that counts? There is no contraindication to putting… Read more »
Great points Gavin!!
Can I ask a dumb Q…
Why are they called “midlines”
I find this term ambiguous, suggestive of multiple meanings.
Can we come up with a better term?
We actually called them WASPs (Wire Assisted sonographically placed) lines. If you want to start a revolution…