A literature review on flow-rate variability in neonatal IV therapy

Pump-driven clinical infusions: laboratory comparison of pump types, fluid composition and flow rates on model drug delivery applying a new quantitative tool, the pharmacokinetic coefficient of short-term variation (PK-CV)

Critically ill or anesthetized patients commonly receive pump-driven intravenous infusions of potent, fast-acting, short half-life medications for managing hemodynamics. Stepwise dosing, e.g. over 3-5 min, adjusts physiologic responses. Flow rates range from < 0.1 to > 30 ml/h, depending on pump type (large volume, syringe) and drug concentration. Most drugs are formulated in aqueous solutions. Hydrophobic drugs are formulated as lipid emulsions. Do the physical and chemical properties of emulsions impact delivery compared to aqueous solutions? Does stepwise dose titration by the pump correlate with predicted plasma concentrations? Precise, gravimetric, flow rate measurement compared delivery of a 20% lipid emulsion (LE) and 0.9% saline (NS) using different pump types and flow rates. We measured stepwise delivery and then computed predicted plasma concentrations following stepwise dose titration. We measured the pharmacokinetic coefficient of short-term variation, (PK-CV), to assess pump performance. LE and NS had similar mean flow rates in stepwise rate increments and decrements between 0.5 and 32 ml/h and continuous flows 0.5 and 5 ml/h. Pharmacokinetic computation predictions suggest delayed achievement of intended plasma levels following dose titrations. Syringe pumps exhibited smaller variations in PK-CV than large volume pumps. Pump-driven deliveries of lipid emulsion and aqueous solution behave similarly. At low flow rates we observed large flow rate variability differences between pump types showing they may not be interchangeable. PK-CV analysis provides a quantitative tool to assess infusion pump performance. Drug plasma concentrations may lag behind intent of pump dose titration.

Examining safety and efficacy of a fixed concentration heparin dosing strategy for anticoagulation in neonatal extracorporeal membrane oxygenation

OBJECTIVES

The paediatric intensive care unit changed heparin infusion dosing from a variable weight-based concentration to a fixed concentration strategy, when smart pump-based drug library was introduced. This change meant significantly lower rates of infusion were needed for the same dose of heparin in the neonatal population. We performed a safety and efficacy assessment of this change.

METHODS

We performed a retrospective single-centre evaluation based on data from respiratory VA-extracorporeal membrane oxygenation (ECMO) patients weighing ≤5 kg, pre and post the change to fixed strength heparin infusion. Efficacy was analysed by distribution of activated clotting times (ACT) and heparin dose requirements between the groups. Safety was analysed using thrombotic and haemorrhagic event rates. Continuous variables were reported as median, interquartile ranges, and non-parametric tests were used. Generalised estimating equations (GEE) were used to analyse associations of heparin dosing strategy with ACT and heparin dose requirements in the first 24 h of ECMO. Incidence rate ratios of circuit related thrombotic and haemorrhagic events between groups were analysed using Poisson regression with offset for run hours.

RESULTS

33 infants (20 variable weight-based, 13 fixed concentration) were analysed. Distribution of ACT ranges and heparin dose requirements were similar between the two groups during the ECMO run and this was confirmed by GEE. Incidence rate ratios of thrombotic (fixed v weight-based) (1.9 [0.5-8], p = .37), and haemorrhagic events (0.9 [0.1-4.9], p = .95) did not show statistically significant differences.

CONCLUSIONS

Fixed concentration dosing of heparin was at least equally effective and safe compared to a weight-based dosing.

Bedside visualisation tool for prediction of deviation from intended dosage in multi-infusion therapy

BACKGROUND

In multi-infusion therapy, multiple infusion pumps are connected to one single vascular access point. Interaction between pressure changes from different pumps may result in temporary dosing errors, which can be very harmful to the patient. It is known that these dosing errors occur. However, clinicians tend to find it hard to estimate the order of magnitude of these errors.

METHODS

This research uses an existing mathematical model to create a bedside prediction tool that is able to provide clinicians with the dosing errors that will occur after flow rate changes in multi-infusion therapy. A panel of clinicians, consisting of both nurses and doctors, was formed, and, in order to assess the level of knowledge about dosing errors in multi-infusion, the panel was presented with four medication schedules in which a syringe exchange or change in flow rate took place. The panel was asked to predict the resulting dosing errors.

RESULTS

A prediction tool was developed that describes a two pump multi-infusion system and predicts dosing errors resulting from changing the flow rate at one pump. 44% of the panel members wrongly predicted the impact of changing the set flow of liquid A on the flow of liquid B that reaches the patient. Nobody was able to correctly predict the dosing deviation if a very small catheter was used. After the prediction tool was shown, the clinicians indicated they had a improved understanding of what deviations to expect and that the tool would be useful in understanding multi-infusion dosing errors.

CONCLUSIONS

Using the predictive tool to visualise the deviations from the set flow rate is an effective method to allow clinicians to gain insight in dosing errors in multi-infusion therapy. This knowledge can be used to better anticipate future dosing errors in clinical situations.

Pressure-adjusted venting eliminates start-up delays and compensates for vertical position of syringe infusion pumps used for microinfusion

Microinfusions are commonly used for the administration of catecholamines, but start-up delays pose a problem for reliable and timely drug delivery. Recent findings show that venting of the syringe infusion pump with draining of fluid to ambient pressure before directing the flow towards the central venous catheter does not counteract start-up delays. With the aim to reduce start-up delays, this study compared fluid delivery during start-up of syringe infusion pumps without venting, with ambient pressure venting, and with central venous pressure (CVP)-adjusted venting. Start-up fluid delivery from syringe pumps using a microinfusion of 1 mL/h was assessed by means of liquid flow measurement at 10, 60, 180 and 360 s after opening the stopcock and starting the pump. Assessments were performed using no venting, ambient pressure venting or CVP-adjusted venting, with the pump placed either at zero, - 43 cm or + 43 cm level and exposed to a simulated CVP of 10 mmHg. Measured fluid delivery was closest to the calculated fluid delivery for CVP-adjusted venting (87% to 100% at the different timepoints). The largest deviations were found for ambient pressure venting (- 1151% to + 82%). At 360 s after start-up 72% to 92% of expected fluid volumes were delivered without venting, 46% to 82% with ambient pressure venting and 96% to 99% with CVP-adjusted venting. CVP-adjusted venting demonstrated consistent results across vertical pump placements (p = 0.485), whereas the other methods had significant variances (p < 0.001 for both). In conclusion, CVP-adjusted venting effectively eliminates imprecise drug delivery and start-up delays when using microinfusions.

Evaluation of the venting principle to reduce start-up delays in syringe infusion pumps used for microinfusions

Start-up delays of syringe pump assemblies can impede the timely commencement of an effective drug therapy when using microinfusions in hemodynamically unstable patients. The application of the venting principle has been proposed to eliminate start-up delays in syringe pump assemblies. However, effectively delivered infusion volumes using this strategy have so far not been measured. This invitro study used two experimental setups to measure the effect of the venting principle compared to a standard non-venting approach on delivered start-up infusion volumes at various timepoints, backflow volumes, flow inversion and zero drug delivery times by means of liquid flow measurements at flow rates of 0.5, 1.0 and 2.0 mL/h. Measured delivered initial start-up volumes were negative with all flow rates in the vented and non-vented setup. Maximum backflow volumes were 1.8 [95% CI 1.6 to 2.3] times larger in the vented setup compared to the non-vented setup (p < 0.0001). Conversely, times until flow inversion were 1.5 [95% CI 1.1 to 2.9] times shorter in the vented setup (p < 0.002). This led to comparable zero drug delivery times between the two setups (p = 0.294). Start-up times as defined by the achievement of at least 90% of steady state flow rate were achieved faster with the vented setup (p < 0.0001), but this was counteracted by the increased backflow volumes. The application of the venting principle to the start-up of microinfusions does not improve the timely delivery of drugs to the patient since the faster start-up times are counteracted by higher backflow volumes when opening the three-way stopcock.

Flow Rate Deviation in Infusion Pump: Infusion Set Defect Enables Pump Malfunction and Considerable Accuracy Deviation

Volumetric infusion pumps are used together with infusion sets to deliver medication to patients. Flow rate errors leading to overinfusion or underinfusion are known problems with these devices. Recently, numerous underinfusion flow rate errors were reported at a Swedish hospital. This experimental study reports on the investigation of these errors and specifically investigates the effect of operating the pump with a defective infusion set that has a visible elongation of the silicone segment of the set. Pump flow rate accuracy testing was performed using a gravimetric method. Experiments included a manipulated infusion set and a defective infusion set used in clinic. The use of a defective infusion set resulted in considerable accuracy deviations. The pump reported an infused amount greater than what was infused and did not provide any alarm or information indicating a reduced output. Using an elongated infusion set, the pump can be brought into an erroneous operating state where the infused amount delivered by the pump is considerably less than what has been programmed and what is shown on the pump display. This could put the patient at risk of not receiving the intended medication within the appropriate time.

Effect of vertical pump position on start-up fluid delivery of syringe pumps used for microinfusion

BACKGROUND

Connection and opening a syringe infusion pump to a central venous line can lead to acute anterograde or retrograde fluid shifts depending on the level of central venous pressure. This may lead to bolus events or to prolonged lag times of intravenous drug delivery, being particularly relevant when administering vasoactive or inotropic drugs in critically ill patients using microinfusion. The aim of this study was to assess the effect of syringe pump positioning at different vertical heights on start-up fluid delivery before versus after purging and connection the pump to the central venous catheter.

METHODS

This in vitro study measured ante- and retrograde infusion volumes delivered to the central venous line after starting the syringe pump at a set infusion rate of 1 mL/h. In setup one, the pump was first positioned to vertical levels of +43 cm or -43 cm and then purged and connected to a central venous catheter. In setup two, the pump was first purged and connected at zero level and secondarily positioned to a vertical level of +43 cm or -43 cm. Central venous pressure was adjusted to 10 mmHg in both setups.

RESULTS

Positioning of the pump prior to purging and connection to the central venous catheter resulted in a better start-up performance with delivered fluid closer to programmed and expected infusion volumes when compared to the pump first purged, connected, and then positioned. Significant backflow volumes were observed with the pump purged and connected first and then positioned below zero level. No backflow was measured with the pump positioned first below zero level and then purged and connected.

CONCLUSIONS

Syringe infusion pump assemblies should be positioned prior to purging and connection to a central venous catheter line when starting a new drug, particularly when administering highly concentrated vasoactive or inotropic drugs delivered at low flow rates.

Closed intravenous systems for central vascular access: A difference maker for CLABSI rates in neonates?

BACKGROUND

Infants in neonatal units are susceptible to numerous potential iatrogenic risks. One key concern is central line-associated blood stream infection (CLABSI). To ensure patient safety and reduce the incidence of CLABSI toward zero, numerous evidence-based clinical interventions and product innovations have been implemented. Nevertheless, sustaining zero CLABSI for sustained periods remains challenging.

AIM

The purpose of this study was to evaluate the impact on CLABSI rates of introducing a preassembled closed intravenous (IV) administration set in a neonatal intensive care unit (NICU).

METHODS

This was a retrospective observational analysis of routinely collected anonymized IV therapy infection data in a NICU. The study period was from January 2019 through June 2020.

RESULTS

Nine-hundred eighty five patients with a Epicutaneo-Caval Catheter (ECC) were included (456 legacy IV set, 529 closed IV set). Patient demographics were comparable between the two groups. ECC dwell time was the only IV characteristic associated (p = 0.04) with CLABSI. Mann-Whitney U-test demonstrated significant differences between the two sets for CLABSI complication events (p = 0.031). Prior to using the closed IV administration sets (January 2019-September 2019) the mean monthly CLABSI rate was 2.87 (/1000 device days). This figure declined to 0.22 (/1000 device days) afterwards (October 2019-June 2020). Zero CLABSIs were observed during January to June 2020.

CONCLUSIONS

Utilization of a pre-assembled closed IV administration set was associated with a reduction in CLABSI rates. The study results suggest that using a pre-assembled closed IV set concurrently with evidence-based central line infection control interventions can help attain extended periods of zero CLABSI.

Effect of central venous pressure on fluid delivery during start-up of syringe infusion pumps for microinfusion

BACKGROUND

Intravenous administration of highly concentrated and potent drugs at low flow rates is common practice, particularly in critically ill children. Drug delivery during infusion start-up can be considerably delayed by intrinsic factors of syringe infusion pump assemblies. The impact of central venous pressures on the course of start-up fluid delivery of such microinfusions remains unknown.

METHODS

Infusion volumes delivered after activation of the start button in a conventional 50 mL syringe infusion pump assembly equilibrated (representing classical in vitro testing) and not equilibrated (representing real clinical conditions) to central venous pressure levels of 0, 10 and 20 mmHg at a set infusion flow rate of 1 mL/h were measured using a fluidic flow sensor.

RESULTS

The experimental setup mimicking real life conditions demonstrated considerable differences in fluid delivery during pump start-up depending on central venous pressure. A central venous pressure of 0 mmHg resulted in massive fluid delivery at infusion start-up, while central venous pressure levels of 10 and 20 mmHg resulted in retrograde flows with related mean (95% CI) zero-drug delivery times of 3.22 (2.98-3.46) min and 4.51 (4.33-4.69) min, respectively (p < .0001).

CONCLUSION

Depending on central venous pressure level, connection and starting a new syringe pump can result in significant antegrade or retrograde fluid volumes. In clinical practice, this can lead to hemodynamic instability and hence requires clinical alertness. Further research and methods to improve start-up performance in syringe infusion pump systems are desirable.

Effects of infusion tubing line lengths and syringe sizes on infusion system compliance: an experimental study using a syringe-type infusion pump at low flow rate

Ideally, the flow delivery of an infusion system is proportional only to the rate of mechanical actuation of the syringe pump plunger. However, in the real world, overall infusion system compliance may be affected by components such as an extension of tubing lines, or different sizes of syringes. With higher compliance, there may be greater chances of flow irregularity. In this experimental study, we investigated the effects of lengths of infusion lines and syringe sizes on the compliance of syringe pumps with low flow rate (2 ml h-1). In the first experiment, infusion system compliance was measured in various settings by occlusion release. As the infusion tubing length and size of the syringe increased, the time to reach each pressure was delayed and the infusion system compliance increased. The contributions to system compliance from syringes were significantly greater compared to those of extended infusion lines. In the occlusion alarm experiment, the occlusion alarm could be delayed by 69.76 ± 3.98 min for the 50-ml syringe with a 560 cm infusion line set-up. In conclusion, the compliance of a syringe pump system increases as the loaded syringe size, or the length of the infusion tubing increases. The occlusion alarm may be much delayed and not useful in highly compliant systems with respect to the potential occlusion of the infusion system, so more attention is required when using a highly compliant infusion system.

Determinants of Intravenous Infusion Longevity and Infusion Failure via a Nonlinear Model Analysis of Smart Pump Event Logs: Retrospective Study

BACKGROUND

Infusion failure may have severe consequences for patients receiving critical, short-half-life infusions. Continued interruptions to infusions can lead to subtherapeutic therapy.

OBJECTIVE

This study aims to identify and rank determinants of the longevity of continuous infusions administered through syringe drivers, using nonlinear predictive models. Additionally, this study aims to evaluate key factors influencing infusion longevity and develop and test a model for predicting the likelihood of achieving successful infusion longevity.

METHODS

Data were extracted from the event logs of smart pumps containing information on care profiles, medication types and concentrations, occlusion alarm settings, and the final infusion cessation cause. These data were then used to fit 5 nonlinear models and evaluate the best explanatory model.

RESULTS

Random forest was the best-fit predictor, with an F1-score of 80.42, compared to 5 other models (mean F1-score 75.06; range 67.48-79.63). When applied to infusion data in an individual syringe driver data set, the predictor model found that the final medication concentration and medication type were of less significance to infusion longevity compared to the rate and care unit. For low-rate infusions, rates ranging from 2 to 2.8 mL/hr performed best for achieving a balance between infusion longevity and fluid load per infusion, with an occlusion versus no-occlusion ratio of 0.553. Rates between 0.8 and 1.2 mL/hr exhibited the poorest performance with a ratio of 1.604. Higher rates, up to 4 mL/hr, performed better in terms of occlusion versus no-occlusion ratios.

CONCLUSIONS

This study provides clinicians with insights into the specific types of infusion that warrant more intense observation or proactive management of intravenous access; additionally, it can offer valuable information regarding the average duration of uninterrupted infusions that can be expected in these care areas. Optimizing rate settings to improve infusion longevity for continuous infusions, achieved through compounding to create customized concentrations for individual patients, may be possible in light of the study's outcomes. The study also highlights the potential of machine learning nonlinear models in predicting outcomes and life spans of specific therapies delivered via medical devices.

Bio-Inspired Micromachined Volumetric Flow Sensor with a Big Dynamic Range for Intravenous Systems

Real-time monitoring of drug delivery in an intravenous infusion system can prevent injury caused by improper drug doses. As the medicine must be administered into the vein at different rates and doses in different people, an ideal intravenous infusion system requires both a low flow rate and large dynamic range monitoring. In this study, a bio-inspired and micromachined volumetric flow sensor is presented for the biomedical application of an intravenous system. This was realized by integrating two sensing units with different sensitivities on one silicon die to achieve a large dynamic range of the volumetric flow rate. The sensor was coated with a parylene layer for waterproofing and biocompatibility purposes. A new packaging scheme incorporating a silicon die into a flow channel was employed to demonstrate the working prototype. The test results indicate that the sensor can detect a volumetric flow rate as low as 2 mL/h, and its dynamic range is from 2 mL/h to 200 mL/h. The sensor performed better than the other two commercial sensors for low-flow detection. The high sensitivity, low cost, and small size of this flow sensor make it promising for intravenous applications.

Reliability of Marked Scales on Intravenous Fluid Plastic Bags

Precise fluid administration is important to prevent hypo- or hypervolemia. However, the accuracy of scales marked on intravenous (IV) fluid plastic bags had remained unknown. Ten 1 L sized IV crystalloids were prepared from each of three manufacturers (H, J, and D). At each scale, the actual volume of the IV fluid was measured. Differences with the measured volumes for each scale were investigated between the three manufacturers. All initial total volume was greater than 1 L. Except for the full-filled level, H overfilled, whereas J and D filled less. For J and D, the maximal differences between the scale and the measured volume were about 200 mL. Fluid volumes of each scale were significantly different among the three manufacturers (P < 0.001). It is inaccurate to measure the amount of fluid depending on the IV bag scales. Clinicians must use electronic infusion pumps for accurate fluid administration.

Flowmetering for microfluidics

Originally designed for chromatography, electrophoresis, and printing technologies, microfluidics has since found applications in a variety of domains such as engineering, chemistry, environmental, and life sciences. The fundamental reason for this expansion has been the development of miniature components, allowing the handling of liquids at the microscale. For the maturation of microfluidic technologies, the need for affordable, reliable, and quantitative techniques to measure flow rates from 1 nL min^-1 to 1 mL min^-1 appears as a strong challenge. We review herein the different technologies available and those under development, and discuss their sensing principles and industrial maturity. Given the need of traceability of these measurements, we then focus on the developments of primary standards to measure microfluidic flow rates by metrological institutes. We conclude this review with some perspectives and pending challenges for microfluidic flowmeters.

Start-up delay in syringe infusion pumps with different rates and priming techniques of intravenoust sets

OBJECTIVE

To investigate infusion pumps start-up delay according to different brands of infusion pumps, flow rates and intravenous sets priming techniques.

METHOD

The experimental study simulated clinical practice under controlled conditions, using a 50 mL syringe with NaCl 0.9% solution, two syringe infusion pumps (A and B), six rates (0.3, 0.5, 1.0, 5, 10 and 20 mL/h), two purging techniques (manually or infusion pump's electronic bolus). Data were analyzed according to mean, standard deviation, Student's t and ANOVA tests (p<0.05).

RESULTS

The start-up delay was greater in low rates regardless the priming technique. The electronic bolus increased the infusion pump A accuracy at 0.3mL/h (p=0.010), 0.5 mL/h (p=0.002) and 1.0mL/h (p=0.004). Pump's accuracy in all studied rates and manual IV sets filling was similar.

CONCLUSION

In low infusion rates the start-up delay was greater despite the infusion pump brand and electronic bolus improved pumps accuracy.

Atraso na inicialização em bombas de infusão por seringa com diferentes velocidades de infusão e técnicas de preenchimento do sistema de infusão

RESUMO Objetivo: Verificar o atraso de inicialização de bomba de infusão, segundo diferentes marcas de bombas de infusão, velocidades e técnicas de preenchimento do sistema de infusão intravenosa. Método: Estudo experimental que simulou a prática clínica, utilizando seringas de 50 mL com solução de NaCl 0,9%, duas marcas de bombas de infusão por seringa (A e B), seis velocidades (0,3; 0,5; 1,0; 5; 10 e 20 mL/h), dois modos de preenchimento do sistema (manual ou eletrônico pelo modo bolus do equipamento). Os dados foram analisados segundo média, desvio padrão e testes t de Student e ANOVA (p<0,05). Resultados: O atraso na inicialização foi maior em velocidades baixas, independentemente da marca e modo de preenchimento. O preenchimento eletrônico aumentou a acurácia na bomba A em 0,3 mL/h (p=0,010), 0,5 mL/h (p=0,002) e 1,0 mL/h (p=0,004). A acurácia em preenchimento manual foi semelhante. Conclusão: Em baixas velocidades de infusão o atraso de inicialização foi maior e o preenchimento do sistema de infusão pelo modo eletrônico melhorou a acurácia dos equipamentos.

Simulation study on flow rate accuracy of infusion pumps in vibration conditions during emergency patient transport

Infusion pumps are frequently used when transferring critically ill patients via patient transport cart, ambulance, or helicopter. However, the performance of various infusion pumps under these circumstances has not been explored. The aim of this study was to evaluate the flow rate accuracy of infusion pumps under various clinical vibration conditions. Experiments were conducted with four different types of pumps, including two conventional syringe pumps (Injectomat MC Agilia, Fresenius Kabi and TE-331, Terumo), one conventional peristaltic pump (Volumed μVP7000; Arcomed), and one new cylinder pump (H-100, Meinntech). The flow rate was measured using an infusion pump analyzer on a stable table (0 m/s²) for 1 h with 1 ml/h and 5 ml/h. Experiments were repeated in mild vibration (2 m/s²) (representing vibration of patients in a moving stretcher or ambulance), and in moderate vibration (6 m/s²) (representing vibration in helicopter transport). Any accidental bolus occurrence in extreme vibration situations (20 m/s²) was also analyzed. Simulated vibrations were reproduced by a custom-made vibration table. In the resting state without vibration and in mild vibration conditions, all pumps maintained good performance. However, in moderate vibration, flow rates in syringe pumps increased beyond their known error ranges, while flow rates in peristaltic pumps remained stable. In extreme vibration, accidental fluid bolus occurred in syringe pumps but not in peristaltic pumps. The newly developed cylinder pump maintained stable performance and was unaffected by external vibration environments.

Does carrier fluid reduce low flow drug infusion error from syringe size?

BACKGROUND

Critically ill neonates and pediatric patients commonly require multiple low flow infusions. Volume limitations are imposed by small body habitus and co-morbidities like cardiopulmonary disease, renal failure, or fluid overload. Vascular access is limited by diminutive veins. Maintenance fluids or parenteral nutrition in conjunction with actively titrated infusions such as insulin, fentanyl, prostaglandins, inotropes and vasopressors may necessitate simultaneous infusions using a single lumen to maintain vascular catheter patency. This requirement for multiple titratable infusions requires concentrated medications at low flows, rather than more dilute drugs at higher flows that in combination may volume overload small infants.

AIM

To determine whether carrier fluid reduces variability that variability of low flow drug infusions is proportional to syringe size in pediatric critical care.

METHODS

We assessed concentrations of orange “drug” in a 0.2 mL/h low flow clinical model with blue dyed carrier fluid at 5 mL/h, using 3-, 10-, or 60-mL syringes. A graduated volumetric pipette was used to measure total flow. Mean time to target concentration was 30, 21, and 46 min in 3-, 10-, and 60-mL syringes, respectively (P = 0.42). After achieving target concentration, more dilute drug was delivered by 60-mL (P < 0.001) and 10-mL syringes (P = 0.04) compared to 3-mL syringes. Drug overdoses were observed during the initial 45 min of infusion in 10-and 60-mL syringes. Total volumes infused after target concentration were less in the 60-mL condition compared to 3-mL (P < 0.01) and 10-mL (P < 0.001) syringes.

RESULTS

Linear mixed effects models demonstrated lesser delivered drug concentrations in the initial 30 min by 3-mL compared to 10-and 60-mL syringes (P = 0.005 and P < 0.001, respectively) but greater drug concentrations and total infused drug in the subsequent 30-60 and 60-90 min intervals with the 3- and 10-mL compared to 60-mL syringes.

CONCLUSION

With carrier fluid, larger syringes were associated with significantly less drug delivery, less total volume delivered, and other flow problems in our low flow drug model. Carrier fluid should not be used to compensate for inappropriately large syringes in critical low flow drug infusions.

Evaluation of Clinical Infusion Pump Performance Through Downstream Microdrop Monitoring: A Preliminary Study

As low-flow infusion is becoming more prevalent for clinical care, there is an increasing need for better evaluation of clinical infusion pump performance at low flow rates and in ways that are accessible to the clinical community. However, the current method in international standard require specialized facilities, costly equipment, long durations of testing, and the data produced is hard to interpret. We propose downstream microdrop monitoring (DMM) as a low-cost, easy-to-perform, and easy-to-interpret alternative. In particular, we show that the count and timing of microdrops are useful for evaluating flow accuracy and flow uniformity at low flow rates.

The Use of Cardiotonic Drugs in Neonates

There is a distinct lack of age-appropriate cardiotonic drugs, and adult derived formulations continue to be administered, without evidence-based knowledge on their dosing, safety, efficacy, and long-term effects. Dopamine remains the most commonly studied and prescribed cardiotonic drug in the neonatal intensive care unit (NICU), but evidence of its effect on endorgan perfusion still remains. Unlike adult and pediatric critical care, there are significant gaps in our knowledge on the use of various cardiotonic drugs in various forms of circulatory failure in the NICU.

Effect of multi-lumen perfusion line on catheter-related bacteremia in premature infants: study protocol for a cluster-randomized crossover trial

Background

Catheter-related bacteremia (CRB) is the most frequent nosocomial infection in neonatal intensive care unit (NICU) patients, especially in very low-birth-weight infants. Administration of injectable drugs in premature newborn infants has many particularities and several types of infusion incidents have been reported. The Edelvaiss® Multiline NEO device is a novel multi-lumen access infusion device adapted to the specificities of infusion in neonatology. This multicenter, randomized, controlled study was therefore designed to determine whether or not Edelvaiss® Multiline NEO reduces the risk of CRB in preterm newborn infants in an NICU.

Methods/design

This is a multicenter, randomized, controlled trial, using a cluster-randomized crossover design. Four investigator centers (four clusters) will participate in the study and will be randomized into two groups, corresponding to two different sequences (either the Edelvaiss® Multiline NEO or standard infusion system sequence, then vice versa). A total of 280 patients will be recruited. Infants will be enrolled in the study at the time of placing a single-lumen central venous catheter. Three visits recording specific data are planned in the study protocol. The primary outcome measure is the incidence density (ID) of CRB. For each patient, the total number of catheters and CRB incidents as well as the duration of stay in the NICU will be computed and considered for analysis.

Discussion

The study will provide high-quality evidence to determine whether the Multiline NEO device reduces the risk of CRB in preterm newborns in NICUs or not.

Trial registration

ClinicalTrials.gov, NCT02633124. Registered on 7 December 2015.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3218-6) contains supplementary material, which is available to authorized users.

Epinephrine syringe exchange events in a paediatric cardiovascular ICU: analysing the storm

Introduction Haemodynamically unstable patients can experience potentially hazardous changes in vital signs related to the exchange of depleted syringes of epinephrine to full syringes. The purpose was to determine the measured effects of epinephrine syringe exchanges on the magnitude, duration, and frequency of haemodynamic disturbances in the hour after an exchange event (study) relative to the hours before (control). Materials and methods Beat-to-beat vital signs recorded every 2 seconds from bedside monitors for patients admitted to the paediatric cardiovascular ICU of Texas Children's Hospital were collected between 1 January, 2013 and 30 June, 2015. Epinephrine syringe exchanges without dose/flow change were obtained from electronic records. Time, magnitude, and duration of changes in systolic blood pressure and heart rate were characterised using Matlab. Significant haemodynamic events were identified and compared with control data.

RESULTS

In all, 1042 syringe exchange events were found and 850 (81.6%) had uncorrupted data for analysis. A total of 744 (87.5%) exchanges had at least 1 associated haemodynamic perturbation including 2958 systolic blood pressure and 1747 heart-rate changes. Heart-rate perturbations occurred 37% before exchange and 63% after exchange, and 37% of systolic blood pressure perturbations happened before syringe exchange, whereas 63% occurred after syringe exchange with significant differences found in systolic blood pressure frequency (p<0.001), duration (p<0.001), and amplitude (p<0.001) compared with control data.

CONCLUSIONS

This novel data collection and signal processing analysis showed a significant increase in frequency, duration, and magnitude of systolic blood pressure perturbations surrounding epinephrine syringe exchange events.

Inotropes for Preterm Infants: 50 Years on Are We Any Wiser?

For almost half a century, inotropes have been administered to preterm infants with the ultimate goal of increasing their blood pressure. A number of trials, the majority of which focused on dopamine administration, have demonstrated increased blood pressure following inotrope administration in preterm infants and have led to continued use of inotropes in our neonatal units. We have also seen an increase in the number of potential agents available to the clinician. However, we now know that hypotension is a much broader concept than blood pressure alone, and our aim should instead be focused on improving end organ perfusion, specifically cerebral perfusion. Only a limited number of studies have incorporated the organ-relevant hemodynamic changes and long-term outcomes when assessing inotropic effects in neonates, the majority of which are observational studies or have a small sample size. In addition, important considerations, including the developing/maturing adrenergic receptors, polymorphisms of these receptors, and other differences in the pharmacokinetics and pharmacodynamics of preterm infants, are only recently being recognized. Certainly, there remains huge variation in practice. The lack of well-conducted randomized controlled trials addressing these relevant outcomes, along with the difficulty executing such RCTs, leaves us with more questions than answers. This review provides an overview of the various inotropic agents currently being used in the care of preterm infants, with a particular focus on their organ/cerebral hemodynamic effects both during and after transition.

Drug Infusion Systems: Technologies, Performance, and Pitfalls

This review aims to broadly describe drug infusion technologies and raise subtle but important issues arising from infusion therapy that can potentially lead to patient instability and morbidity. Advantages and disadvantages of gravity-dependent drug infusion are described and compared with electromechanical approaches for precise control of medication infusion, including large-volume peristaltic and syringe pumps. This review discusses how drugs and inert carriers interact within infusion systems and outlines several complexities and potential sources of drug error. Major topics are (1) the importance of the infusion system dead volume; (2) the quantities of coadministered fluid and the concept of microinfusion; and (3) future directions for drug infusion.The infusion system dead volume resides between the point where drug and inert carrier streams meet and the patient's blood. The dead volume is an often forgotten reservoir of drugs, especially when infusion flows slow or stop. Even with medications and carriers flowing, some mass of drug always resides within the dead volume. This reservoir of drug can be accidentally delivered into patients. When dose rate is changed, there can be a significant lag between intended and actual drug delivery. When a drug infusion is discontinued, drug delivery continues until the dead volume is fully cleared of residual drug by the carrier. When multiple drug infusions flow together, a change in any drug flow rate transiently affects the rate of delivery of all the others. For all of these reasons, the use of drug infusion systems with smaller dead volumes may be advantageous.For critically ill patients requiring multiple infusions, the obligate amount of administered fluid can contribute to volume overload. Recognition of the risk of overload has given rise to microinfusion strategies wherein drug solutions are highly concentrated and infused at low rates. However, potential risks associated with the dead volume may be magnified with microinfusion. All of these potential sources for adverse events relating to the infusion system dead volume illustrate the need for continuing education of clinical personnel in the complexities of drug delivery by infusion.This review concludes with an outline of future technologies for managing drug delivery by continuous infusion. Automated systems based on physiologic signals and smart systems based on physical principles and an understanding of dead volume may mitigate against adverse patient events and clinical errors in the complex process of drug delivery by infusion.

Novel Pump Control Technology Accelerates Drug Delivery Onset in a Model of Pediatric Drug Infusion

BACKGROUND

Laboratory data suggest that newly initiated drug infusions reach steady-state delivery after a significant time lag. Depending on drug and carrier flow rates and the infusion system's common volume, lag times may exceed 20 or more minutes, especially in the neonatal/pediatric critical care environment. This study tested the hypothesis that a computer-executed algorithm controlling infusion pumps in a coordinated fashion predictably hastens the achievement of the intended steady-state drug delivery in a model of neonatal/pediatric drug infusion.

METHODS

We constructed an in vitro model of neonatal/pediatric drug infusions through a pediatric 4-Fr central venous catheter at total system flows of 2 mL/h or 12 mL/h, representing a clinically relevant infusion range. Methylene blue served as the model infused drug for quantitative analysis. A novel algorithm, based on Taylor Dispersion Theory of fluid flow through tubes and executed by a computer, generated flow patterns that controlled and coordinated drug and carrier delivery by syringe pumps. We measured the time to achieve the intended steady-state drug delivery by conventional initiation of the drug infusion ("turning on the drug pump") and by algorithm-controlled infusion initiation.

RESULTS

At 2 mL/h total system flow, application of the algorithm reduced the time to achieve half of the intended drug delivery rate (T50) from 17 minutes [17, 18] to 3 minutes [3, 3] (median, interquartile range). At 12 mL/h total system flow, application of the algorithm reduced T50 from 6 minutes [6, 7] to 3 minutes [3, 3] The bootstrapped median difference is -14 (95% confidence interval [CI], -16 to -12, adjusted P=.00192) for 2 mL/h flow and -3 (95% CI, -4 to -3, adjusted P=.02061) for 12 mL/h flow. Compared with conventional initiation, the additional fluid required by the algorithm-directed infusion was 0.43 and 1.03 mL for the low- and high-infusion rates, respectively.

CONCLUSIONS

The output of infusion pumps can be predictably controlled and coordinated by a computer-executed algorithm in a model of neonatal/pediatric drug infusions. Application of an algorithm can reduce the time to achieve the intended rate of infused drug delivery with minimal incremental volume administration.

What Should We Do about Low Blood Pressure in Preterm Infants

The management of preterm infants with low blood pressure soon after birth remains unresolved. The definition of what constitutes low blood pressure is uncertain. At birth, mean blood pressure appears to be gestation specific and increases in the first few days of life. Antenatal steroids, delayed cord clamping, and the avoidance of mechanical ventilation are all associated with higher mean blood pressure and less hypotension after birth. Rates of hypotension of 15-50% have been reported in various studies of extremely preterm infants. However, only about 10% of all extremely preterm infants receive inotropes, suggesting that clinicians take into account other factors such as clinical, biochemical, and echocardiographic findings before deciding to intervene. The exact role of functional echocardiography in assessing the need for treatment of low blood pressure in extremely preterm infants remains to be determined. Near- infrared spectroscopy to assess cerebral perfusion may also have a role to play. Volume expansion (usually 10 mL/kg of saline) remains the most commonly used intervention for low blood pressure but evidence of benefit is lacking and there may be safety concerns. Whilst dopamine is the most commonly used inotropic drug, dobutamine, epinephrine, corticosteroids, milrinone, and vasopressin have also been utilised in preterm infants with low blood pressure. Clinical trials with long-term outcomes are needed to determine the most suitable inotrope and when to use it. Early hypotension differs from late hypotension with regard to cause, treatment, and outcome. A number of recent studies aimed at improving the evidence base for the treatment of early hypotension in extremely preterm infants have been terminated early because of poor recruitment. Currently, the answer to the question of what to do about low blood pressure in preterm infants remains unclear.

Standard concentration infusions in paediatric intensive care: the clinical approach

The use of standard concentrations of intravenous infusions has been advocated by international organisations to increase intravenous medication safety in paediatric and neonatal critical care. However, there is no guidance on how to identify and implement these infusions leading to great interunit variability.

OBJECTIVE

To identify the most appropriate clinical concentrations required by our paediatric intensive care unit (PICU) population with regard to accuracy of delivery and overall fluid allowance.

METHODS

Firstly a matrix was used to balance the concentration, dose and infusion volume (weight range 1.5-50 kg). Results were further refined considering: patient fluid allowance based on fluid volume targets, infusion pump accuracy and challenging each infusion against clinical scenarios requiring administration of multiple drug infusions found in PICU. Consideration was given to the standard concentrations routinely used in adults, in order to assess whether alignment with paediatrics was possible for some of the concentrations proposed. Finally a risk assessment of the infusions was conducted using the NPSA 20 tool.

KEY FINDINGS

Twenty-five drugs identified as the most commonly used intravenous infusions in the unit. For the majority of the medicines, three weight bands of standard concentrations were necessary to cover the children's weight ranges and kept within predefined fluid requirements and accuracy of delivery.

CONCLUSIONS

This work shows a patient focused systematic approach for defining and evaluating standardised concentrations in intensive care children.

Criteria for choosing an intravenous infusion line intended for multidrug infusion in anaesthesia and intensive care units

OBJECTIVE

The aims are to identify critical parameters influencing the drug mass flow rate of infusion delivery to patients during multidrug infusion and to discuss their clinical relevance.

DATA SOURCES

A review of literature was conducted in January 2016 using Medline, Google Scholar, ScienceDirect, Web of Science and Scopus online databases.

DATA EXTRACTION

References relating to the accuracy of fluid delivery via gravity-flow intravenous (IV) infusion systems and positive displacement pumps, components of IV administration sets, causes of flow rate variability, potential complications due to flow rate variability, IV therapies especially at low flow rates and drug compatibilities were considered relevant.

DATA SYNTHESIS

Several parameters impact the delivery of drugs and fluids by IV infusion. Among them are the components of infusion systems that particularly influence the flow rate of medications and fluids being delivered. By their conception, they may generate significant start-up delays and flow rate variability. Performing multidrug infusion requires taking into account two main points: the common dead volume of drugs delivered simultaneously with potential consequences on the accuracy and amount of drug delivery and the prevention of drug incompatibilities and their clinical effects.

CONCLUSION

To prevent the potentially serious effects of flow rate variability on patients, clinicians should receive instruction on the fluid dynamics of an IV administration set and so be able to take steps to minimise flow rate changes during IV therapy.

Flow variability and its physical causes in infusion technology: a systematic review of in vitro measurement and modeling studies

Infusion therapy is medically and technically challenging and frequently associated with medical errors. When administering pharmaceuticals by means of infusion, dosing errors can occur due to flow rate variability. These dosing errors may lead to adverse effects. We aimed to systematically review the available biomedical literature for in vitro measurement and modeling studies that investigated the physical causes of flow rate variability. Special focus was given to syringe pump setups, which are typically used if very accurate drug delivery is required. We aimed to extract from literature the component with the highest mechanical compliance in syringe pump setups. We included 53 studies, six of which were theoretical models, two articles were earlier reviews of infusion literature, and 45 were in vitro measurement studies. Mechanical compliance, flow resistance, and dead volume of infusion systems were stated as the most important and frequently identified physical causes of flow rate variability. The syringe was indicated as the most important source of mechanical compliance in syringe pump setups (9.0×10-9 to 2.1×10-8 l/Pa). Mechanical compliance caused longer flow rate start-up times (from several minutes up to approximately 70 min) and delayed occlusion alarm times (up to 117 min).

How physical infusion system parameters cause clinically relevant dose deviations after setpoint changes

Multi-infusion therapy, in which multiple pumps are connected to one access point, is frequently used in patient treatments. This practice is known to cause dosing errors following setpoint changes in the drug concentrations that actually enter the patients. Within the Metrology for Drug Delivery Project, we analyzed and quantified the two main physical phenomena leading to these errors: the "push-out" effect and the system mechanical compliance. We compared the dosing errors of a three-pump system with two infusion sets, both with and without anti-reflux valves, using in vitro spectrophotometric experiments. Additionally, computer simulations were used to study the compliance effect separately. We found a start-up time of more than 1 h, and a dosing error following a setpoint increase of another pump for the low flow rate pump, corresponding to 0.5 μg noradrenaline delivered in 8 min. We showed that the dead volume inside the tubes and syringe compliance produce opposite deviations from the setpoint values in the actual drug output concentrations, making the net result hard to predict and often counterintuitive. We conclude that metrology on compliance and push-out effects could be used by infusion device manufacturers to successfully improve drug delivery performance and relevant standards for high-risk multi-infusion applications.

Challenges in Treating Low Blood Pressure in Preterm Infants

Whilst the prevalence of low blood pressure in preterm infants seems to have fallen over the last number of years, the problem is still frequently encountered in the neonatal intensive care unit and many babies continue to receive intervention. Great variability in practice persists, with a significant number of extremely low gestational age newborns in some institutions receiving some form of intervention, and in other units substantially less. A great degree of this variability relates to the actual criteria used to define hypotension, with some using blood pressure values alone to direct therapy and others using a combination of clinical, biochemical and echocardiography findings. The choice of intervention remains unresolved with the majority of centres continuing to administer volume followed by dopamine as a first line inotrope/vasopressor agent. Despite over 40 years of use there is little evidence that dopamine is of benefit both in the short term and long-term. Long-term follow up is available in only two randomised trials, which included a total of 99 babies. An under recognized problem relates to the administration of inotrope infusions in very preterm infants. There are no pediatric specific inotrope formulations available and so risks of errors in preparation and administration remain. This manuscript outlines these challenges and proposes some potential solutions.

Measurement of compliance of infusion device consumable elements using an analytical weighing balance

The value of compliance of disposable elements such as infusion lines and syringes can significantly affect the performance characteristics of infusion devices. In a technique used to determine the compliance of infusion lines, the item under test is placed in a semi sealed water filled enclosure and the volume of fluid displaced is measured on an analytical weighing balance as set pressures are applied to the test item. Thermal drift of the measurement chamber was minimised by inclusion of discs of Invar alloy. Measurements were also made to determine the compliance of syringes used with syringe drivers where the volume of fluid displaced upon release of established pressure levels within a syringe was measured using a separate measurement configuration using again an analytical weighing balance. These techniques were used to determine the relative contributions to compliance of infusion lines and syringes to the dynamics of operation of syringe drivers. This indicated that contributions to compliance from syringes were significantly greater than that of connected infusion lines. Values of time to occlude, occlusion bolus and effects of height elevation for infusion devices with elements of varying compliance and line configuration are discussed.