Ultrasound-guided long peripheral and midline catheters: indications, safety, reliability and proposal for clinical research

In patients requiring a peripheral venous access for a difficult intravenous access condition (DIVA) or for medium-term intravenous therapies, long peripheral catheters (LPCs) or midline catheters (MCs) are recommended. Unfortunately, these devices are indiscriminately labelled with different names, leading to misclassifications both in primary and secondary studies. Additionally, several studies have used different methods of diagnosis and reporting outcomes, reducing the ability to perform accurate comparative research. The aims of this doctoral program were: 1) to explore the complications related to MCs and LPCs in adults, after reclassifying the devices and the reported outcomes according to the standardized recommendation; 2) to compare the risk of catheter failure in polyurethane MCs and LPCs in daily clinical practice, considering in particular the effect of the catheter-to-vein ratio at the catheter tip level; 3) to explore the differences in terms of safety and reliability between MCs and LPCs in daily clinical practice by comparing catheters used in different populations of hospitalized patients. To achieve the first objective, a systematic review of the literature was conducted. The second objective was pursued through a retrospective observational cohort study, while for the third objective a prospective observational cohort study was used. Fourteen studies were included in the systematic literature review, which were categorized according to their methodological quality. A large catheters’ misclassification was documented, particularly affecting LPCs who were often labeled as MCs. A lack of homogeneity in diagnosing, collecting and reporting catheter-related outcomes was found. Overall, a low rate of major complications (catheter-related bloodstream infection and 10 symptomatic thrombosis) was documented for both catheters. Minor complications and catheter failure were higher for LPCs. The clinical studies enrolled 240 and 269 patients, respectively, and found consistent results. MCs were associated with an adjusted lower risk of catheter failure (HR; 0.147; p=0.004), being the risk decreasing after nine days from positioning; a catheter-to vein ratio >45% at the catheter tip location was found as an independent predictor of a catheter failure (HR: 6.762; p = 0.023); a greater average number of drugs infused per day was associated to a higher of catheter failure (p=0.021). The incidence of CR-BSI and symptomatic CRT were low and similar in both catheters, while, overall, the incidence of minor complications was higher for LPC catheters. A misclassification in labelling MCs and LPCs and a widespread heterogeneity of diagnostic criteria adopted to classify the catheters’ outcomes has been clearly documented, exposing to the risk of misestimating the incidence of catheter-related complications and undermining the possibility of effectively comparing results of the published research. A list of definitions and relevant variables was proposed as a first step toward the development of standardized criteria to be adopted for research purposes. After considering the proposed, standardized criteria to classify the devices and the outcomes, MCs were found associated with a longer uncomplicated indwelling time despite a more intensive drug administration, probably because the more favorable final position of the catheter tip, characterized by greater blood flow and lower catheter-to-vein ratio (greater dilution and transport of drugs) than LPCs. We concluded that MCs should be preferred for more complex and longer therapies, reserving LPCs for DIVA patients needing a short-term use.