Ultrasound-guided midline catheters in the neonatal intensive care unit: a single-center pilot study

To assess the feasibility and performance of ultrasound-guided midline catheters in term and preterm neonates requiring prolonged intravenous therapy without an indication for central access, and to generate hypotheses on factors influencing catheter outcomes. Single-center prospective observational cohort: 70 consecutive neonates received 2-Fr polyurethane midline catheters in a level IV NICU (March 2024-November 2025). Data were analyzed descriptively; complication-free survival was estimated by Kaplan-Meier, and exploratory subgroup comparisons used Fisher's exact test. Mean weight at insertion was 2582 g (range 700-4920), including very low-birth-weight infants. Median dwell time was 9 days (range 0-176), corresponding to 1144 catheter-days. The primary composite outcome (complication-free dwell ≥ 7 days or elective removal before day 7) was met in 94.3% of devices. Kaplan-Meier complication-free survival was 98.6% at 3 days and 81.2% at 14 days. Device-related complications occurred in 21.4%, predominantly minor and resolving after removal. Bloodstream infection and thrombosis rates were 2.62 and 0.87 per 1000 catheter-days; no thrombophlebitis occurred. Complication rates did not differ by vein diameter < 2 mm or weight < 1500 g, although the study was underpowered for these comparisons. CONCLUSION: In this pilot study, ultrasound-guided midline catheters were feasible in neonates, including very low-birth-weight infants and those with small-caliber veins, with predominantly minor complications. These hypothesis-generating findings require confirmation in adequately powered; comparative studies before midlines can be recommended as an alternative to central access or repeated peripheral cannulation. WHAT IS KNOWN: • Midline catheters may offer an intermediate option between peripheral and central venous access, but neonatal experience, particularly in preterm infants, is limited. • Data on the feasibility and performance of midline catheters in the NICU are scarce. WHAT IS NEW: • In this single-center pilot cohort of 70 neonates, ultrasound-guided midline catheters achieved a high rate of complication-free dwell time, with predominantly minor, self-limiting complications. • Complication rates did not appear to increase in infants < 1500 g or with veins < 2 mm; these hypothesis-generating observations require confirmation in adequately powered studies.