Evaluation of midline vascular access: a descriptive study.

Background and significance: Vascular access is a mainstay of therapy in acute and chronic care. The use of midline catheters has been controversial, but little researchbased evidence shows its benefits and risks. The nursing vascular access team (VAT) in a 400-bed community hospital was asked to provide this service. To ensure the best care for patients, the development of the midline service was approached carefully by designing a study to track the outcomes. Research questions: What’s the incidence of complications for midline catheters? What’s the average dwell time for midline catheters? What are the relationships between infusates and complications? What are the relationships between dwell times and complications? Methods: This was a prospective descriptive study. The sample was a convenience sample of patients who had midline catheters inserted by the VAT nurses. Findings: Data on 345 midlines were collected. The average dwell time for the midlines was 6.9 days (SD, 6.1). The rate of phlebitis among 345 patients was 2% (7 cases), infiltration rate, 1.7% (6 cases), and thrombosis, 1.7% (6 cases). Two bloodstream infections occurred in 2,304 line days, or a rate of 0.9 per 1,000 line days. No relationships were identified between infusates or length of dwell and complications. Conclusions: In this study, the midline catheter was determined to provide stable and safe vascular access. The complication rate wasn’t greater than that of other vascular access devices. This descriptive study adds to the evidence for midline catheter use and provides an impetus for randomized controlled trials on midline catheters and infusates. We’ll continue to monitor this practice for safety and efficacy. Background The nursing vascular access team (VAT) in a tertiary care regional referral hospital was asked to perform midline catheter insertions at the bedside for adult patients in 2010. This request came from physicians who thought that the midline catheter would provide another choice of peripheral venous access for patients who didn’t need a central venous access device (CVAD) but who had poor vascular status, might benefit from a more stable venous access device, or required I.V. therapy with a nonirritant/nonvesicant solution for more than a week. This would be a new procedure for the VAT and for the hospital. A midline catheter has been considered a bridge or a compromise between a CVAD and a short peripheral catheter.1,2 Although the VAT nurses were dedicated to being team players and providing the best service to their patients, they’d heard from colleagues and others that using the midline was a potentially dangerous practice. For example, they’d heard reports of infiltration from midlines that wasn’t detected until patients suffered severe tissue injury. They recognized that all I.V. therapy options have some associated risks and had seen serious damage to extremities from short peripheral catheter infiltration as well as serious complications from CVAD therapy. The physicians in the organization didn’t agree that midline catheters presented a higher risk of complications than other venous access devices. Agreement on which infusates were safe for midlines was lacking. At this point, the VAT nurses had only anecdotal evidence and hearsay to support their reservations about the use of midline catheters. To gather evidence, their first step was to search the literature for data on complications and results of midline catheter therapy. Review of the literature The literature was searched using the search engine EBSCO and the databases CINAHL, Medline, Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews. No date limit was applied. Neonatal literature was excluded. The keywords “midline catheter” produced 52 results. Of the 52 publications, only nine were original research on children or adult patients. Eight studies were descriptive and prospective; one was retrospective. One used randomization of two types of midline catheters using a small sample size.3 Only one author included a large enough sample to analyze the multiple variables contributing to complications from vascular access, but this author didn’t include an analysis of these relationships.1 Determining adequate sample sizes Evaluation of midline vascular access: A descriptive study By Cheryl Dumont, PhD, RN, CRNI; Ozlem Getz, RN; and Sheri Miller, RN, CRNI, VA-BC Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. www.Nursing2014.com October l Nursing2014 l 61 for sufficient inferential power in research is complicated, but a useful general guideline is that about 20 to 40 patients are needed for every variable or patient factor that can impact the outcome.4 The researchers described complication rates in their own settings. Only Lawson attempted to compare complications to specific infusates.5 The authors differentiated vesicant and irritant infusates that by policy were to be infused only into the central circulation and not into midline catheters. These studies don’t represent head-to-head comparisons of peripherally inserted central catheters (PICCs) and midline catheters for thrombosis or phlebitis. The literature search was continued by reviewing the secondary sources and reference lists found in review articles. In a 2011 review, Alexandrou and colleagues also reported that they found only a few outcome-based studies showing the effectiveness of midline catheters and that most of these were descriptive and quasi-experimental.6 An older manuscript by Ryder references the original work conducted in animal labs in the 1970s and 1980s supporting a theory on the effects of osmolality and pH on the venous endothelium.7 One study by Sketch et al., cited by Ryder as a secondary source, compared the effects of an 8-in (20.3 cm) polyvinylchloride percutaneous peripheral catheter (a midline catheter) with a 21-in (53.3 cm) PICC in coronary care patients.8 The study included 484 catheter placements. Complications were reported to be higher with midline catheters than with PICCs. When antibiotics, potassium chloride, and lidocaine were added to the infusate, the incidence of phlebitis increased and dwell times were shorter with the midline catheters.7 No data support a recommendation for maximal dwell time for midlines, but the general consensus is 4 weeks. The Infusion Nurses Society (INS) and the CDC recommendation for short peripheral I.V. (PIV) catheter dwell time had been 72 to 96 hours. In 2011, evaluation of this practice prompted the INS and the CDC to change the recommendations for dwell time for PIVs to “replacement...when clinically indicated (such as when the patient develops signs of phlebitis, infection or a malfunctioning catheter....” Clinical data in 2011 at this study institution demonstrated an average PIV catheter dwell time for a sample of 393 patients was 2 days (SD, 1). In general, PIV catheters will have less than a week dwell time while PICCs, implanted ports, and tunneled CVADs can dwell for months to years.9,10 In the 1990s, the midline catheter fell out of favor because of reports of systemic adverse reactions to the hydrogel material used to make them.11 But recent research studies don’t demonstrate that today’s midlines are any more prone to complications than other types of venous access. Since that time, catheter materials have changed. In fact, researchers have demonstrated that midline catheters aren’t associated with phlebitis or infection any more often than PICCs or other CVADs and are associated with a lower rate of phlebitis and infiltration than PIVs.1,12 PIV therapy is also associated with phlebitis, infiltration, extravasation, hematomas, thrombosis, venous sclerosis, nerve injury, and bloodstream infection.13-15 In 2011, the National Healthcare Safety Network reported pooled mean rates for central line-associated bloodstream infections (BSIs) ranging from 0.9/1,000 catheter days in adult inpatient medical/surgical units to 3.7/1,000 catheter days in burn ICUs.16 PIV therapy is a less frequent source of BSI, but it does occur. The BSI rate for PIVs has been reported as 0.5/1,000 catheter days.17,18 Historically the BSI rate for midline catheters is hard to compare because it hasn’t always been reported as a rate (number of BSI/1,000 line days), but has been reported as a percent of infections per catheter at 0.3% to 1%.1,12 One important difference between a midline catheter and a CVAD is that the midline’s tip terminates in the cephalic, brachial, or basilic vein distal to the shoulder (the tip doesn’t enter the central vasculature), which flows into the distal axillary vein. The blood flow rate in the axillary vein (about 150 mL/min), although higher than that of a peripheral vein in the lower arm (40 mL/min), is much less than the blood flow in the superior vena cava (2,000 mL/min).7 Ideally, the tip of a CVAD is positioned in the lower third of the superior vena cava at the caval-atrial junction to allow maximal hemodilution of infusates classified as irritants and vesicants. INS Standard 32 states that it’s not recommended to administer infusates with a pH of less than 5 or greater than 9 or osmolality of greater than 600 mOsm/L in peripheral veins.9 Midline catheters are considered to be peripheral infusion catheters. These criteria virtually eliminate parental nutrition (PN) solutions and some antibiotics such as vancomycin (pH 2.4). Yet in 2009, Pittiruti and colleagues published a study demonstrating that the infusion of PN (osmolality not exceeding 800 mOsm/L) via midline catheters Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.