The goal of this observational study spanning over three years is to evaluate the effectiveness of implementing a co-designed, care bundle on intravascular access device (IVAD) quality and nurses and anaesthesiologist knowledge of IVADs best practices, at an intervention hospital compare to care as usual the a control hospital. Additional aims are to:

1. translate and validate a tool for identifying patients with difficult vein access within the Swedish healthcare context,
2. to evaluate the implementation related to its feasibility, acceptability, fidelity, and cost-effectiveness.

The main questions it aims to answer are:

• Does the implementation of evidence-based practices improve the quality of IVADs care, e.g. thrombophlebitis/phlebitis, extravasation, infiltration, dislodgement and increase register nurses and anaesthesiologists' knowledge of IVADs best practices?
• Does the intervention bridge barriers to successful implementation and support routinization of evidence-based practices.
• Which factors influence the implementation in terms of feasibility, acceptability, cost-effectiveness and compatibility with professionals' existing values and clinical workflows?

The study adopts a longitudinal implementation design with an embedded process evaluation,guided by Medical Research Council guidance (MRC) framework: developing, feasibility, refinement, implementation and evaluation. The design integrates mixed methods to assess the effectiveness, implementation process, and contextual factors influencing the prevention of IVAD-related complications across an intervention and a control hospital.

Data on IVAD care quality and healthcare professionals' knowledge will be collected at both sites once a month over a three-year period . Multiple data sources will be used, including repeated bedside audits of IVADs and electronic knowledge questionnaires, to capture changes over time and between study sites.

Quality of IVADs, power calculation: A conservative sample size calculation was based on a simple before-after comparison of independent PIVCs (PIVC-miniQ, SD = 1.55), assuming 80% power, a two-sided α = 0.05, and a detectable mean difference of 0.5 points, which requires approximately 150 PIVCs before and 150 after (≈300 total), inflated by 10 30% to account for clustering. Although the study includes all types of IVADs, this calculation provides a conservative estimate of the required sample size.

Data will be analyzed using linear mixed-effects models that explicitly account for clustering and repeated measures over time, which is expected to yield at least comparable, and likely higher, statistical power. Audit tool: Data on IVAD care quality will be collected by trained nurses, using a modified and validated audit tool (IVAD-miniQ). The tool has been piloted at both sites and adapted to fit all IVAD commonly used at the study sites, IVAD-miniQ-Sweden. The final version is in electronic format.

Knowledge assessment: Registered nurses and anaesthesiologists involved in IVADs management at the study sites. Electronic knowledge questionnaire distributed before, during and after the care bundle implementation, based on the Swedish Handbook for Healthcare IVAD best-practice recommendations.

Translation and cross-cultural adaptation of an adult difficult vein access scale (A-DIVA) to Swedish context - Face validity (performed by the expert committee members through qualitative analysis of the participant's comments), reliability (test-retest intra class correlation coefficient, one week interval), construct validity (exploratory factor analysis (EFA)) will be performed. Factors will be extracted using the maximum likelihood method (MLE)

Process evaluation Quantitative process data: Attendance rate in meetings, completed IVAD certificates and staff turnover. Qualitative process data: Implementation logbook (notebook on processes, meetings, and reflections). Semi-structured interviews, with a strategic selection of participants on micro- and meso-level within the organization (variation from the involved units, type of profession, age, working years, and gender). The interviews will be performed by a researcher who is not involved in the intervention.

The questions will investigate the participants' experiences of:

• participating in the intervention, what worked? How and why?
• how the intervention interacted with different contextual features?
• how the intervention affected other care giving activities?
• how competing priorities affected the intervention and its activities?
• how different goals and prioritization such as limited resources in healthcare, affected the intervention? Data analysis The process data will be analyzed using a thematic analysis.

Cost-effectiveness analysis will be used to compare incremental costs from a health system perspective (implementation, intervention, and downstream) to the incremental health outcomes; the IVADs complications. The economic evaluation will include scenario analyses and sensitivity analyses according to state of the art, to account for uncertainty of parameters and underlying model uncertainty.

Data management plan A data management plan will be developed following the Swedish national data service checklist, ensuring compliance with Swedish regulations, FAIR principles, and Horizon Europe guidelines throughout data collection, storage, sharing, and preservation

Inclusion Criteria:

• Register nurses and anesthesiologist

Exclusion Criteria:

-

Sahlgrenska university hospital/Mölndal

Not ethical approved. Only data on group level.