Background: Research has identified high failure rates of peripheral intravenous catheter (PIVC) and varied flushing practices.

Methods: This is a single-centre, pilot, non-masked, factorial randomised controlled trial. Participants were adults, with a PIVC of expected use ≥24 hours (n = 160), admitted to general medical or surgical wards of a tertiary referral hospital in Queensland (Australia). Patients were randomly allocated to one of four flush groups using manually prepared syringes and 0.9 % sodium chloride: 10 mL or 3 mL flush, every 24 or 6 hours. The primary endpoint was PIVC failure, a composite measure of occlusion, infiltration, accidental dislodgement and phlebitis.

Results: PIVC average dwell was 3.1 days. PIVC failure rates per 1000 hours were not significantly different for the volume intervention (4.84 [3 mL] versus 7.44 [10 mL], p = 0.06, log-rank). PIVC failure rates per 1000 hours were also not significantly different for the frequency intervention (5.06 [24 hour] versus 7.34 [6 hour], p = 0.05, log-rank). Cox proportional hazard regression found neither the flushing nor frequency intervention, or their interaction (p = 0.21) to be significantly associated with PIVC failure. However, female gender (hazard ratio [HR] 2.2 [1.3–3.6], p < 0.01), insertion in hand/posterior wrist (HR 1.7 [1.0–2.7], p < 0.05) and the rate per day of PIVC access (combined flushes and medication pushes) (HR 1.2 [1.1–1.4], p < 0.01) significantly predicted PIVC failure.

Conclusion: Neither increased flushing volume nor frequency significantly altered the risk of PIVC failure. Female gender, hand/posterior wrist placement and episodes of access (flushes and medication) may be more important. Larger, definitive trials are feasible and required.