Introduction Peripheral intravenous catheters (PIVCs) are essential for administration of intravenous fluids and medications. While patient need for PIVCs is high, up to 69% fail due to complications such as occlusion and infiltration. Midline catheters (MCs) are an alternative to PIVCs; they are 8–20cms in length and terminate at, or are distal to, the axillary vein, not in the central venous circulation. Midline catheters’ rising popularity is due to concerns that patients’ veins are depleted by multiple consecutive PIVCs. However, there have been no randomised controlled trials (RCTs) comparing these devices to guide practice.

Methods and analysis This single centre, parallel group, pilot RCT is designed to compare effectiveness of MCs with PIVCs for patients with difficult vascular access (≤2 visible and palpable veins) and/or receiving peripherally compatible intravenous therapy for ≥5 days. This trial will be conducted at the Royal Brisbane and Women’s Hospital, Australia. The recruitment target is 70 participants per group (n=140). There are three primary outcomes of interest to test: 1) Feasibility of an adequately powered RCT with pre-established criteria for eligibility, recruitment, protocol adherence and retention; 2) Insertion failure (number of PIVCs/MCs unable to be inserted); and 3) Post-insertion failure: all-cause failure. Secondary outcomes to be collected include: number of insertion attempts; time to insert; catheter dwell time; costs (staff time/equipment); patient-reported insertion pain; and individual causes of failure, e.g. phlebitis. Feasibility outcomes will be reported descriptively and analysed against pre-determined acceptability criteria. As a pilot study, statistical comparison methods will be tested. Cox regression will assess the effect of patient and treatment differences.