Flow rate, syringe size and architecture are critical to start-up performance of syringe pumps

Significant start-up delays are inherent to syringe infusion pumps, particularly at low infusion rates, as routinely used in children's anaesthesia and intensive care. Such delays are mainly the result of engagement of gears in the mechanical drive or compliance of the syringe assembly. The purpose of the present study was to determine the effect of flow rate, syringe size and syringe architecture on fluid delivery during infusion start-up.

Elapsed time from infusion start to achievement of steady-state flow was gravimetrically determined for various infusion rates (0.1, 0.5, 1 mL h-1), different syringe sizes (10-, 20-, 30-, 50-mL) and syringes of two different brands (BD and Codan). Four measurements for each condition were performed with two identical Alaris Asena GH syringe infusion pumps (total of eight experiments). Statistical analysis was done by two-way ANOVA with Bonferroni's post-test; P < 0.05 was considered significant.

Start-up time was from 3.6 +/- 0.9 min (BD 10-mL syringe, 1.0 mL h-1) to 74.5 +/- 26.6 min (BD 50-mL syringe, 0.1 mL h-1). Overall, the start-up time markedly increased with lower flow rate (0.1 mL h-1 vs. 1 mL h-1; P < 0.0001), larger syringe size (50 mL vs. 10 mL; P < 0.01), and the BD brand in comparison with the Codan syringes (P < 0.01).

Highest possible flow rate, smaller sized syringes and syringe plungers with reduced compressibility should be preferred in order to avoid significant start-up delays in fluid delivery.