Pressurized bag pump and syringe pump arterial flushing systems: an unrecognized hazard in neonates?

Objective: Hand-held flushing of radial arterial lines at 0.5 ml/s in neonates can result in retrograde embolization of flush solution into the central arterial circulation. We studied flush flow velocities during intermittent arterial line purging using a flow regulating device with an infusion bag pump and a syringe pump system. Measurements and interventions: In this in vitro experiment we simulated flushing of a 24- and a 22-G cannula against a mean arterial pressure of 45 mmHg. Fluid flow velocities were gravimetrically measured during flushing from an infusion bag system pressurized to 100, 200, and 300 mmHg and from a syringe pump flush system after initialization of boluses of 0.5, 1.0, 1.5, 2.0, and 2.5 ml. The flow regulating device was opened for 1, 2, and 5 s. Results: Both flush systems tested allowed delivery of flush flow velocities exceeding 0.5 ml/s (e.g., 22-G cannula; bag system, pressure 300 mmHg up to 0.64±0.08 ml/s; syringe pump, 2 ml bolus up to 0.74±0.05 ml/s). In syringe pump systems the main determinant of flow velocity was bolus size, in bag pump systems flushing time and bag pressure. Conclusions: Based on data about critical flow velocities through an radial arterial cannula in neonates, both tested flushing systems carry the risk of exceeding the critical value of 0.5 ml/s. They are likely to cause retrograde embolization of flushing solution into the central arterial circulation with the associated risk of clot and air embolization. In vivo studies should identify margins of safety to minimize the risk of retrograde flushing into the central arterial circulation.