Downward movement of syringe pumps reduces syringe output.

We studied how lowering a syringe pump and changing the outflow pressure could affect syringe pump output. We experimentally reduced the height of three different syringe pump systems by 80 cm (adult setting) or 130 cm (neonatal setting), as can happen clinically, using five flow rates. We measured the time of backward flow, no flow and the total time without flow. An exponential negative correlation was present between infusion rate and time without flow (r2=0.809 to 0.972, P<0.01). Minimum flow rates of 4.4 and 2.6 ml h(-1) respectively were calculated to give 60 and 120 s without infusion. The compliance of the different syringe pumps and their infusion systems was linearly correlated with the effective time without infusion (r2=0.863, P<0.05). We conclude that the height of the syringe pumps should not be changed during transportation. If vertical movement of the syringe pump is necessary, the drugs should be diluted so that the flow rate is at least 5 ml h(-1).