Syringe pumps for infusion of vasoactive drugs: mechanical idiosyncrasies and recommended operating procedures

Syringe pumps for vasoactive infusions have the advantages of small size and weight, portability, and low cost of the disposable components. However, limited syringe capacity necessitates the use of high drug concentrations, and the accidental delivery of even a small volume of infusate could seriously alter the patient's hemodynamics. To determine the circumstances under which drug delivery might be delayed, or inadvertent boluses could be delivered into the manifold, two brands of commercially available clinical syringe pumps were connected to a stopcock manifold via small-bore tubing and a series of tests were performed. When the syringe pumps were operated at 3 mL/h against a closed stopcock, the pumps' occlusion alarms did not sound for 18-22 min, and when the stopcock subsequently was opened, 0.6-0.9 mL of infusate was delivered as a bolus. Elevating the syringe pump by 120 cm resulted in the delivery of up to 0.5 mL of infusate with the pump turned off. When a syringe pump operating at 6 mL/h was turned off, typically an additional 0.05 mL was delivered during the ensuing 2-3 min. Depending upon the method used to flush the tubing prior to use, delays in drug delivery of 2-3 min occurred at an infusion rate of 3 mL/h. These observations emphasize the need for careful equipment setup and proper use of the manifold stopcocks to avoid unintended drug administration or delay in drug administration.