Performance of modern syringe infusion pump assemblies at low infusion rates in the perioperative setting.

BACKGROUND: Syringe infusion pumps are used for the precise continuous administration of intravenous drugs. Their compliance and mechanical deficiencies have been found to cause considerable start-up delays, flow irregularities during vertical displacement, as well extensive delays of occlusion alarms at low infusion rates. The aim of this study was to evaluate the performance of several modern syringe infusion pumps at low infusion rates and the impact on drug concentration. METHODS: Seven currently marketed syringe infusion pump assemblies were assessed in an in vitro study during start-up, vertical displacement manoeuvres, and infusion line occlusion at a set flow rate of 1 ml h-1. The measured data were used as input for a pharmacokinetic simulation modelling plasma concentration during a standard neonatal continuous epinephrine infusion. RESULTS: The mean time from starting the infusion pump to steady-state flow varied from 89 to 1622 s. The zero-drug delivery time after lowering the pump ranged from 145 to 335 s. In all assemblies tested, occlusion alarm delays and measured flow irregularities during vertical displacement manoeuvres resulted in relevant deviations in plasma epinephrine concentration (>25%) as calculated by the pharmacokinetic simulation model. CONCLUSION: Problems with the performance of syringe infusion pump assemblies can have considerable impact on plasma drug concentration when highly concentrated short-acting cardiovascular drugs are administered at low flow rates. The problems, which affected all assemblies tested, are mainly related to the functional principle of syringe infusion pumps and will only partially be solved by incremental improvements of existing equipment.

Flow irregularities from syringe infusion pumps caused by syringe stiction.

OBJECTIVE: The current study aimed to evaluate the extent of the slide-stick phenomenon in differently designed infusion syringes at various infusion rates and filling positions. METHODS: Fluid delivery from three 50-mL infusion syringe brands (BD; Codan; Fresenius) was investigated using a flow sensor at flow rates of 0.5, 1.0, or 5.0 mL h-1 , with the syringes filled with either 10, 30, or 50 mL of distilled water. Two identical models (A/B) of the same infusion pump model were used. The effect of flow rate variations on the plasma concentration of a continuous epinephrine infusion in a 3 kg neonate receiving a continuous infusion of 0.1 µg kg min-1 epinephrine was studied using a pharmacokinetic simulation model. RESULTS: Considerable variations in calculated plasma epinephrine concentration were detected between flow rates of 5 and 0.5 or 1 mL h-1 for all syringe types and filling volumes. The median deviation of plasma concentration for the 5 mL h-1 flow rate varied depending on assembly from 1.3% (Codan) to 1.8% (Fresenius). This was more pronounced for lower flow rates, where at 1 mL h-1 the deviation varied from 3.3% (BD) to 4.8% (Fresenius) and at 0.5 mL h-1 from 4.9% (BD) to 5.4% (Fresenius). Differences between filling volumes (within syringe type and flow rate) did not appear to have relevant influence on variations in calculated plasma epinephrine concentration. CONCLUSION: Infusion set rate rather than syringe brand or filling volume was a major predictor for syringe stiction-related amount of variation in the calculated plasma epinephrine concentration.

Short-term physiological response to high-frequency-actuated pVAD support.

Ventricular assist devices (VADs) are an established treatment option for heart failure (HF). However, the devices are often plagued by material-related hemocompatibility issues. In contrast to continuous flow VADs with high shear stresses, pulsatile VADs (pVADs) offer the potential for an endothelial cell coating that promises to prevent many adverse events caused by an insufficient hemocompatibility. However, their size and weight often precludes their intracorporeal implantation. A reduction of the pump body size and weight of the pump could be achieved by an increase in the stroke frequency while maintaining a similar cardiac output. We present a new pVAD system consisting of a pump and an actuator specifically designed for actuation frequencies of up to 240 bpm. In vitro and in vivo results of the short-term reaction of the cardiovascular system show no significant changes in left ventricular and aortic pressure between actuation frequencies from 60 to 240 bpm. The aortic pulsatility increases when the actuation frequency is raised while the heart rate remains unaffected in vivo. These results lead us to the conclusion that the cardiovascular system tolerates short-term increases of the pVAD stroke frequencies.