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.