Effect of infusion line connection and infusion line characteristics on start-up fluid delivery from syringe infusion pumps used for microinfusion.

Background: Connecting an infusion line to a closed stopcock results in pressurization of fluid within the syringe infusion pump assembly leading to flow irregularities when opening the stopcock and activating the pump.

Aims: It was the purpose of this study to assess the extent of pressurization under different conditions and its impact on start-up fluid delivery.

Methods: Intraluminal pressures and start-up fluid delivery at 1 mL/h flow rate were assessed with connection of the infusion line 1 min (delayed connection) or immediately after purging (immediate connection) using two different infusion lines made from polyvinylchloride (PVC) or polyethylene (PE).

Results: Delayed connection resulted in an increase of intraluminal pressures from zero to 5.1 [4.5 to 5.7] mmHg with the PVC line and from zero to 47.1 [44.8 to 49.3] mmHg with the PE line (mean difference 42.0 [95% CI 39.3-44.7] mmHg; p < .0001). Immediate connection resulted in an increase of intraluminal pressures from zero to 44.3 [41.8-46.8] mmHg with the PVC line and from zero to 61.3 [57.2-65.4] mmHg with the PE line (mean difference 17.0 [95% CI 11.8-22.2] mmHg; p < .0001). The increase in intraluminal pressures was significantly higher with PE lines for both delayed and immediate connection when compared to the PVC lines (mean difference 29.5 [95% CI 19.3-39.7] mmHg; p < .0001). Related fluid volumes delivered at 10 s and 360 s after starting the pump ranged from -252% to 1321% (10 s) of expected infusion volumes and from 59% to 129% (360 s), respectively.

Conclusions: Both, timing of infusion line connection after purging and infusion line characteristics considerably affect intraluminal pressures and start-up fluid delivery when connecting a new syringe infusion pump assembly to a closed stopcock. Consecutive alterations in drug administration can have considerable hemodynamic consequences when dealing with catecholamine infusions in critically ill patients.