A model for technology assessment as applied to closed loop infusion systems. Technology Assessment Task Force of the Society of Critical Care Medicine

Early assessment of innovation in a healthcare setting

OBJECTIVES

Early assessment can assist in allocating resources for innovation effectively and produce the most beneficial technology for an institution. The aim of the present study was to identify methods and discuss the analytical approaches applied for the early assessment of innovation in a healthcare setting.

METHODS

Knowledge synthesis based on a structured search (using the MEDLINE, Embase, and Cochrane databases) and thematic analysis was conducted. An analytical framework based on the stage of innovation (developmental, introduction, or early diffusion) was applied to assess whether methods vary according to stage. Themes (type of innovation, study, analysis, study design, method, and main target audience) were then decided among the authors. Identified methods and analysis were discussed according to the innovation stage.

RESULTS

A total of 1,064 articles matched the search strategy. Overall, thirty-nine articles matched the inclusion criteria. The use of methods has a tendency to change according to the stage of innovation. Stakeholder analysis was a prominent method in the innovation stages and particularly in the developmental stage, as the introduction and early diffusion stage has more availability of data and may apply more complex methods. Barriers to the identified methods were also discussed as all of the innovation stages suffered from lack of data and substantial uncertainty.

CONCLUSIONS

Although this review has identified applicable approaches for early assessment in different innovation stages, research is required regarding the value of the available data and methods and tools to enhance interactions between different parties at different stages of innovation.

Design and implementation of a closed-loop control system for infusion of propofol guided by bispectral index (BIS)

BACKGROUND

This study describes the design of a hypnosis closed-loop control system with propofol. The controller used a proportional-integral (PI) algorithm with the bispectral index (BIS) as the feedback signal. Our hypothesis was that a PI closed-loop control could be applied in clinical practice safely keeping the BIS within a pre-determined target range.

METHODS

The adjustment of the PI parameters was based on simulation. The procedure had three steps: obtaining a patient model using data from 12 patients, designing and adjusting the controller in simulation, and fine tuning the PI parameters in a pilot study (10 patients). The resulting controller was tested in 24 American Society of Anesthesiology (ASA) I-II patients. The controller directly decides the infusion rate of propofol, and no model is necessary in its online operation. The BIS target was set to 50. Remifentanil was used for analgesia.

RESULTS

We evaluated the efficiency and safety of the automatic feedback system. It worked properly in all the patients. The median performance error was -1.62, and the median absolute performance error was 11.03. Average propofol-normalized consumption was 5.3 ± 1.8 mg/kg/h. Mean percentage of BIS in the range 40-60 was 83%. Mean time to open eyes was 8 ± 4 min. Time to extubation was 9 ± 5 min. Hemodynamic adverse event or intraoperative awareness were not recorded.

CONCLUSIONS

The closed-loop system was able to maintain the BIS within an acceptable range of levels. The control of a propofol infusion guided by the BIS is feasible without hemodynamic instability in ASA I/II patients.

Physiologic insulin delivery with insulin feedback: a control systems perspective

Individuals with type 1 diabetes mellitus must effectively manage glycemia to avoid acute and chronic complications related to aberrations of glucose levels. Because optimal diabetes management can be difficult to achieve and burdensome, research into a closed-loop insulin delivery system has been of interest for several decades. This paper provides an overview, from a control systems perspective, of the research and development effort of a particular algorithm--the external physiologic insulin delivery system. In particular the introduction of insulin feedback, based on β-cell physiology, is covered in detail. A summary of human clinical trials is provided in the context of the evolution of this algorithm, and this paper outlines some of the research avenues that show particular promise.

Adaptive multi-infusion decision support for the multivariable circulatory management of critically ill patients

We have developed a novel adaptive multi-infusion advisory system for circulatory management of critically ill patients which co-ordinates infusion adjustments to ensure safe trajectories. This system should reduce patient hospital stay and improve patient outcome by enhancing the quality of patient circulatory control; alleviating the clinical cognitive load, giving staff more time for direct patient care, while also reducing infusion adjustment errors. We have applied three derived circulatory variables which relate to the three main types of cardiovascular infusions (inotropic, vasoactive and fluid). A lumped parameter steady flow model of the human circulatory system and the effects of cardiovascular infusions was constructed for algorithm development, clinical experts providing feedback on a representative test set of simulated patients in circulatory shock. Independent self-learning fuzzy logic controllers (SLFLC) were found to give good adaptation to variable patient infusion sensitivities. A supervisory, rule-based module co-ordinates infusion adjustments to ensure safe circulatory trajectories. Monitoring of manual infusion adjustments allows timely advice and also a critiquing capability which can train junior staff and reduce infusion adjustment errors. A physical mock circulatory loop was used to construct and test our physical advisory system. Preliminary clinical results show good clinical utility of our adaptive multi-infusion advisory system.

A tool predicting future mean arterial blood pressure values improves the titration of vasoactive drugs

BACKGROUND

Vasoactive drug infusion rates are titrated to achieve a desired effect, e.g., mean arterial blood pressure (MAP), rather than using infusion rates based on body weight. The purpose of this study is to evaluate a method to automatically identify a patient's sensitivity to sodium-nitroprusside, dobutamine or dopamine and to evaluate, whether an advisory system that predicts MAP 5 min in the future enhances a clinician's ability to titrate sodium-nitroprusside infusions.

METHODS

We used published models implemented in MATLAB to simulate the response of 100 individual patients to infusions of sodium-nitroprusside, dopamine and dobutamine. The simulated patient's sensitivity to the three drugs was identified using an adaptive filter approach, where MAP was altered in a binary stepwise fashion. Next, 9 nurses were asked to control the MAP of 6 of the simulated patients. For half of the patients, we used the identified sensitivity to predict and display MAP 5 min into the future.

RESULTS

Identifying each individual patient's sensitivity improved the accuracy of the MAP prediction by 75% for sodium-nitroprusside, 82% for dopamine and 52% for dobutamine over the MAP prediction based on an "average" patient's sensitivity. The advisory system shortened the median time to reach the desired MAP from 10.2 to 4.1 min, decreased the median number of infusion rate changes from 6 to 4, and resulted in a significant reduction of mental workload and effort.

DISCUSSION

Patient-specific drug sensitivity identifi- cation significantly improved the prediction of future MAP. By predicting and displaying the expected MAP 5 min in the future, the advisory system helped nurses titrate faster, reduced their perceived workload and might improve patient safety.

The ethics of rationing of critical care services: should technology assessment play a role?

The costs of health care continue to increase rapidly and steeply in the United States. One area of great expense is that of intensive care units (ICUs). The causes of inflation have not been addressed effectively. ICU resources could become stretched such that they may no longer be available. This paper discusses some of the ethics and concerns behind decision making when providing ICU services in the United States. In particular, the use of electronic records with decision making tools, risk-analysis methods, and documentation of patient wishes for extraordinary care may help with better utilization of resources in the future.

Sedation in the critically ill patient

The goal of critical care medicine is to support organ function and maintain homeostasis until healing can occur. Sedation and analgesia may blunt the physiologic and psychologic sequelae of intensive care unit stress, and support homeostasis. Although a wide variety of agents have been used empirically, the recognition of analgesia, amnesia, and hypnosis as discrete elements comprising the sedated state has facilitated an individualized approach to therapy. Because intensive care unit patients are a highly heterogeneous population with varying levels of end-organ compromise, the development of specific, easily titratable, parenteral agents has made intensive care unit sedation safer. A trend toward refining dosage regimens in order to minimize the total dose of drug administered and to reduce the occurrence of residual sedation is driven by utilization and cost concerns. The capability for simple bedside electrophysiologic monitoring of the level of sedation is expected to improve the ability to provide optimal therapy.

Acquisition strategies for critical care technology

Technological advances in critical care will undoubtedly find their way into the ICU of the 21st century. The challenge for critical care practitioners is to meticulously assess these innovations and adopt the most appropriate and efficient technologies that will improve unit function and staff efficiencies, support educational programs, and most importantly, enhance patient outcome at a reasonable cost. Hospital-based intensivists have excellent opportunities to establish leadership roles in the technology evaluation process by cultivating relationships with administrators, and through active participation in the hospital-based Technology Committee and the ICU-based multidisciplinary committee. The authors' experience has left them with the lasting impression that the evaluation and introduction of new technology is time consuming and requires perseverance and patience. Ultimately, it is hoped that technological breakthroughs coupled with a standardized approach to delivery of ICU services in the coming decades will ensure better and more efficient care to critically ill patients.

Local perfusion of diazepam attenuates interictal and ictal events in the bicuculline model of epilepsy in rats

PURPOSE

We evaluated the efficacy of local perfusion of diazepam (DZP) in suppression of EEG spikes and behavioral seizures produced by bicuculline methiodide (BMI) applied to rat sensory motor cortex and hippocampus.

METHODS

Data were obtained from 37 rats implanted with EEG head plugs and perfusion cannulas. BMI 4 mM, 5 microliters was infused on neocortex through the epidural space in 23 rats. BMI 0.1 mM, 2 microliters was infused into the left hippocampus in 14 rats.

RESULTS

DZP 0.75-1.0 mg markedly reduced the spiking to a level of 9.9 +/- 15.8% of baseline for DZP as compared with 90.2 +/- 57.9% of baseline for vehicle-treated rats. DZP reduced spiking in a hippocampal BMI focus to 1.9 +/- 2.4% of baseline spiking, as compared with 98.0 +/- 95.6% of that in vehicle-treated animals. The amount of spread of solution was estimated with methylene blue (MB) injections. Ictal events also were attenuated. In most of the animals, systemic levels of DZP were unmeasurable and injection on the contralateral side did not reduce spiking.

CONCLUSIONS

These findings suggest that focal application of antiepileptic drugs (AEDs) in brain may be a useful new avenue for therapy of intractable partial seizures.