Syringe size and flow rate affect drug delivery from syringe pumps

Purpose: To evaluate the effect of syringe size and infusion rate on drug d elivery after vertical displacement of syringe pumps. Methods: Four syringes (10 ml, 20 ml, 30 ml, 50 ml) were studied at three i nfusion speeds (2 ml.hr(-1), 1 ml.hr(-1) and 0.5 ml.hr(-1)). Fluid delivery was measured gravimetrically using an electronic balance. Aspiration volum e (amount of fluid retracted into the syringe-infusion line assembly) and z ero-drug delivery time (time between the lowering of the syringe pump and r eattainment of the initial weight) were determined after lowering the syrin ge pump 130 cm or 50 cm. Then, infusion bolus was measured after elevating the pump to its initial position. Syringe compliance was calculated from th e occlusion release bolus at an occlusion pressure of 300 mmHg. Results: Zero-drug delivery time, aspiration volume and infusion bolus incr eased with syringe size (P < 0.000 1). At 0.5 ml.hr(-1), a zero-drug delive ry time of 29.7 +/- 0,6 min was recorded for the 50 ml syringe and 5.5 +/- 0.15 min for the 10 ml syringe. As infusion rates increased, zero-drug deli very times decreased following a I/x ratio. Zero-drug delivery time highly correlated with calculated syringe compliance (Pearson's r = 0.97, P < 0.00 1), which was closely related to syringe plunger area (R-2 = 0.93, P < 0.0 0 1). Conclusions: Vertical displacement of syringe pumps causes flow irregularit ies which correlate directly with syringe size and indirectly with infusion rate. Extreme vertical maneuvering of syringe pumps should be avoided. inf usion rates greater than or equal to 1 ml.hr(-1) and low-compliant, small s yringes are recommended when highly concentrated drugs are administered.