Infusion system carrier flow perturbations and dead-volume: large effects on drug delivery in vitro and hemodynamic responses in a swine model

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.

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.

Simultaneous infusion of two incompatible antibiotics: Impact of the choice of infusion device and concomitant simulated fluid volume support on the particulate load and the drug mass flow rates

Vancomycin and piperacillin/tazobactam are known to be incompatible. The objectives of the present study were to evaluate the impact of their simultaneous infusion on mass flow rates and particulate load and identify preventive strategies. We assessed both static conditions and a reproduction of an infusion line used in a hospital's critical care unit. A high-performance liquid chromatography/UV diode array system and static and dynamic laser diffraction particle counters were used. The mass flow rates were primarily influenced by the choice of the infusion device and the presence of simulated fluid volume support. Drug incompatibility also appeared to affect vancomycin's mass flow rate, and the dynamic particulate load increased during flow rate changes - especially in the infusion set with a large common volume line and no concomitant simulated fluid volume support. Only discontinuation of the piperacillin/tazobactam infusion was associated with a higher particulate load in the infusion set with a large common volume line and no concomitant simulated fluid volume support. A low common volume line and the use of simulated fluid volume support were associated with smaller fluctuations in the mass flow rate. The clinical risk associated with a higher particulate load must now be assessed.

Dose individualization of intravenous busulfan in pediatric patients undergoing bone marrow transplantation: impact and in vitro evaluation of infusion lag-time

OBJECTIVES

To apply therapeutic drug monitoring and dose-individualization of intravenous Busulfan to paediatric patients and evaluate the impact of syringe-pump induced Busulfan infusion lag-time after in vitro estimation.

METHODS

76 children and adolescents were administered 2 h intravenous Busulfan infusion every 6 h (16 doses). Busulfan plasma levels, withdrawn by an optimized sampling scheme and measured by a validated HPLC-PDA method, were used to estimate basic PK parameters, AUC, Cmax, kel, t1/2, applying Non-Compartmental Analysis. In vivo infusion lag-time was simulated in vitro and used to evaluate its impact on AUC estimation.

KEY FINDINGS

Mean (%CV) Busulfan AUC, Cmax, clearance and t1/2 for pediatric population were found 962.3 μm × min (33.1), 0.95 mg/L (41.4), 0.27 L/h/kg (33.3), 2.2 h (27.8), respectively. TDM applied to 76 children revealed 6 (7.9%) being above and 25 (32.9%) below therapeutic-range (AUC: 900-1350 μm × min). After dose correction, all patients were measured below toxic levels (AUC < 1500 μm × min), no patient below 900 μm × min. Incorporation of infusion lag-time revealed lower AUCs with 17.1% more patients and 23.1% more younger patients, with body weight <16 kg, being below the therapeutic-range.

CONCLUSIONS

TDM, applied successfully to 76 children, confirmed the need for Busulfan dose-individualization in paediatric patients. Infusion lag-time was proved clinically significant for younger, low body-weight patients and those close to the lower therapeutic-range limit.

Drug Flow Through Clinical Infusion Systems: How Modeling of the Common-volume Helps Explain Clinical Events

This review aims to describe analytic models of drug infusion that demonstrate the impact of the infusion system common-volume on drug delivery. The common-volume of a drug infusion system is defined as the volume residing between the point where drug and inert carrier streams meet and the patient’s blood. We describe 3 sets of models. The first is quantitative modeling which includes algebraic mathematical constructs and forward-difference computational simulation. The second set of models is with in vitro benchtop simulation of clinical infusion system architecture. This modeling employs devices including pumps, manifolds, tubing and catheters used in patient care. The final set of models confirms in vitro findings with pharmacodynamic endpoints in living large mammals. Such modeling reveals subtle but important issues inherent in drug infusion therapy that can potentially lead to patient instability and morbidity. The common-volume is an often overlooked reservoir of drugs, especially when infusions flows are slowed or stopped. Even with medications and carriers flowing, some mass of drug always resides within this common-volume. This reservoir of drug can be inadvertently delivered into patients. When infusions are initiated, or when dose rate or carrier flow is altered, there can be a significant lag between intended and actual drug delivery. In the case of vasoactive and inotropic drug infusions, these unappreciated time delays between intended and actual drug delivery can lead to iatrogenic hemodynamic instability. When a drug infusion is discontinued, drug delivery continues until the common-volume is fully cleared of residual drug by the carrier. The findings from all 3 sets of models described in this review indicate that minimizing the common-volume of drug infusion systems may enhance patient safety. The presented models may also be configured into teaching tools and possibly point to technological solutions that might mitigate sources of iatrogenic patient lability.

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.

Effect of insulin infusion line on glycaemic variability in a perioperative high dependency unit (HDU): a prospective randomised controlled trial

BACKGROUND

Glucose control is an important issue in post-operative patients. The objective here was to compare two insulin infusion lines by syringe pumps to assess the impact of medical devices on glycaemic variability in surgical patients under intensive insulin therapy. This open, prospective, single-centre randomised study was conducted in a fifteen-bed perioperative high dependency unit (HDU) in a university hospital. In total, 172 eligible patients receiving insulin therapy agreed to participate in the study. Subcutaneous continuous glucose monitoring was set up for all patients and an optimised system with a dedicated insulin infusion line for half of the patients.

RESULTS

Eighty-six patients were infused via the optimised infusion line and 86 patients via the standard infusion line. No significant difference was found according to the glycaemic lability index score [mean difference between groups (95% CI): -0.09 (-0.34; 0.16), p = 0.49 after multiple imputation]. A glucose control monitoring system indicated a trend towards differences in the duration of hypoglycaemia (blood glucose level below 70 mg dl^-1 (3.9 mmol l^-1) over 1000 h of insulin infusion (9.7 ± 25.0 h in the standard group versus 4.4 ± 14.8 h in the optimised group, p = 0.059) and in the number of patients experiencing at least one hypoglycaemia incident (25.7 vs. 12.9%, p = 0.052). Time in the target range was similar for both groups.

CONCLUSIONS

The use of optimised infusion line with a dedicated insulin infusion line did not reduce glycaemic variability but minimised the incidence of hypoglycaemia events. The choice of the medical devices used to infuse insulin seems important for improving the safety of insulin infusion in perioperative HDU.

Hypertensive Crisis During Norepinephrine Syringe Exchange: A Case Report

A 67-year critically ill patient suffered from a hypertensive crisis (200 mm Hg) because of a norepinephrine overdose. The overdose occurred when the clinician exchanged an almost-empty syringe and the syringe pump repeatedly reported an error. We hypothesized that an object between the plunger and the syringe driver may have caused the exertion of too much force on the syringe. Testing this hypothesis in vitro showed significant peak dosing errors (up to +572%) but moderate overdose (0.07 mL, +225%) if a clamp was used on the intravenous infusion line and a large overdose (0.8 mL, +2700%) if no clamp was used. Clamping and awareness are advised.

Infusion System Architecture Impacts the Ability of Intensive Care Nurses to Maintain Hemodynamic Stability in a Living Swine Simulator

BACKGROUND

The authors have previously shown that drug infusion systems with large common volumes exhibit long delays in reaching steady-state drug delivery and pharmacodynamic effects compared with smaller common-volume systems. The authors hypothesized that such delays can impede the pharmacologic restoration of hemodynamic stability.

METHODS

The authors created a living swine simulator of hemodynamic instability in which occlusion balloons in the aorta and inferior vena cava (IVC) were used to manipulate blood pressure. Experienced intensive care unit nurses blinded to the use of small or large common-volume infusion systems were instructed to maintain mean arterial blood pressure between 70 and 90 mmHg using only sodium nitroprusside and norepinephrine infusions. Four conditions (IVC or aortic occlusions and small or large common volume) were tested 12 times in eight animals.

RESULTS

After aortic occlusion, the time to restore mean arterial pressure to range (t1: 2.4 ± 1.4 vs. 5.0 ± 2.3 min, P = 0.003, average ± SD), time-out-of-range (tOR: 6.2 ± 3.5 vs. 9.5 ± 3.4 min, P = 0.028), and area-out-of-range (pressure-time integral: 84 ± 47 vs. 170 ± 100 mmHg · min, P = 0.018) were all lower with smaller common volumes. After IVC occlusion, t1 (3.7 ± 2.2 vs. 7.1 ± 2.6 min, P = 0.002), tOR (6.3 ± 3.5 vs. 11 ± 3.0 min, P = 0.007), and area-out-of-range (110 ± 93 vs. 270 ± 140 mmHg · min, P = 0.003) were all lower with smaller common volumes. Common-volume size did not impact the total amount infused of either drug.

CONCLUSIONS

Nurses did not respond as effectively to hemodynamic instability when drugs flowed through large common-volume infusion systems. These findings suggest that drug infusion system common volume may have clinical impact, should be minimized to the greatest extent possible, and warrants clinical investigations.

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.