DESIGN FLAW CAN CONVERT COMMERCIALLY AVAILABLE CONTINUOUS SYRINGE PUMPS TO INTERMITTENT BOLUS INJECTORS

Objective:To investigate if unexpected behaviour of neonatal and paedi atric patients connected to syringe pumps could be explained by transi ent elevation of these devices. Design: Five different commercially av ailable syringe pumps were set at an infusion rate of 1 ml/h and then subjected to a vertical displacement manoeuvre (height 1 m). The actua l delivered infusion volumes in association with the displacement mano euvre were measured by a high precision weight scale connected to a co mputer. Setting: A medical technology laboratory in a university hospi tal. Measurements and results: Elevation of the devices resulted in a rapid bolus injection of 0.19-2.28 ml. Returning the devices to their original positions resulted in an aspiration into the system of 0.06-0 .34 ml. The times both for bolus injection and for aspiration into the system were less than 1 min in all cases. The up-down manoeuvre was f ollowed by a period with zero infusion ranging from 8 to 105 min. Conc lusions: Design flaws in the construction of syringe pumps can expose patients to substantial danger following vertical displacement if pote nt drugs are being infused. If potent drugs are infused, care should b e taken not to change the vertical position of the syringe pump even f or short periods of time. Before buying new equipment, the authors rec ommend that the delivery characteristics of these devices should not o nly be tested during ordinary bench testing but should also include th e reaction to a vertical displacement manoeuvre.