Accuracy and reliability of continuous blood glucose monitor in post-surgical patients

Accuracy of continuous glucose monitoring systems in intensive care unit patients: a scoping review

PURPOSE

Glycemic control poses a challenge in intensive care unit (ICU) patients and dysglycemia is associated with poor outcomes. Continuous glucose monitoring (CGM) has been successfully implemented in the type 1 diabetes out-patient setting and renewed interest has been directed into the transition of CGM into the ICU. This scoping review aimed to provide an overview of CGM accuracy in ICU patients to inform future research and CGM implementation.

METHODS

We systematically searched PubMed and EMBASE between 5th of December 2023 and 21st of May 2024 and reported findings in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline for scoping reviews (PRISMA-ScR). We assessed studies reporting the accuracy of CGM in the ICU and report study characteristics and accuracy outcomes.

RESULTS

We identified 2133 studies, of which 96 were included. Most studies were observational (91.7%), conducted in adult patients (74%), in mixed ICUs (47.9%), from 2014 and onward, and assessed subcutaneous CGM systems (80%) using arterial blood samples as reference test (40.6%). Half of the studies (56.3%) mention the use of a prespecified reference test protocol. The mean absolute relative difference (MARD) ranged from 6.6 to 30.5% for all subcutaneous CGM studies. For newer factory calibrated CGM, MARD ranged from 9.7 to 20.6%. MARD for intravenous CGM was 5-14.2% and 6.4-13% for intraarterial CGM.

CONCLUSIONS

In this scoping review of CGM accuracy in the ICU, we found great diversity in accuracy reporting. Accuracy varied depending on CGM and comparator, and may be better for intravascular CGM and potentially lower during hypoglycemia.

Continuous ex vivo glucose sensing in human physiological fluids using an enzymatic sensor in a vein replica

Managing blood glucose can affect important clinical outcomes during the intraoperative phase of surgery. However, currently available instruments for glucose monitoring during surgery are few and not optimized for the specific application. Here we report an attempt to exploit an enzymatic sensor in a vein replica that could continuously monitor glucose level in an authentic human bloodstream. First, detailed investigations of the superficial venous systems of volunteers were carried out using ocular and palpating examinations, as well as advanced ultrasound measurements. Second, a tubular glucose-sensitive biosensor mimicking a venous system was designed and tested. Almost ideal linear dependence of current output on glucose concentration in phosphate buffer saline was obtained in the range 2.2-22.0 mM, whereas the dependence in human plasma was less linear. Finally, the developed biosensor was investigated in whole blood under homeostatic conditions. A specific correlation was found between the current output and glucose concentration at the initial stage of the biodevice operation. However, with time, blood coagulation during measurements negatively affected the performance of the biodevice. When the experimental results were remodeled to predict the response without the influence of blood coagulation, the sensor output closely followed the blood glucose level.

Continuous Glucose Monitoring in the Hospital

Continuous glucose monitors (CGMs) have suddenly become part of routine care in many hospitals. The coronavirus disease 2019 (COVID-19) pandemic has necessitated the use of new technologies and new processes to care for hospitalized patients, including diabetes patients. The use of CGMs to automatically and remotely supplement or replace assisted monitoring of blood glucose by bedside nurses can decrease: the amount of necessary nursing exposure to COVID-19 patients with diabetes; the amount of time required for obtaining blood glucose measurements, and the amount of personal protective equipment necessary for interacting with patients during the blood glucose testing. The United States Food and Drug Administration (FDA) is now exercising enforcement discretion and not objecting to certain factory-calibrated CGMs being used in a hospital setting, both to facilitate patient care and to obtain performance data that can be used for future regulatory submissions. CGMs can be used in the hospital to decrease the frequency of fingerstick point of care capillary blood glucose testing, decrease hyperglycemic episodes, and decrease hypoglycemic episodes. Most of the research on CGMs in the hospital has focused on their accuracy and only recently outcomes data has been reported. A hospital CGM program requires cooperation of physicians, bedside nurses, diabetes educators, and hospital administrators to appropriately select and manage patients. Processes for collecting, reviewing, storing, and responding to CGM data must be established for such a program to be successful. CGM technology is advancing and we expect that CGMs will be increasingly used in the hospital for patients with diabetes.

Continuous Glucose Monitors and Automated Insulin Dosing Systems in the Hospital Consensus Guideline

This article is the work product of the Continuous Glucose Monitor and Automated Insulin Dosing Systems in the Hospital Consensus Guideline Panel, which was organized by Diabetes Technology Society and met virtually on April 23, 2020. The guideline panel consisted of 24 international experts in the use of continuous glucose monitors (CGMs) and automated insulin dosing (AID) systems representing adult endocrinology, pediatric endocrinology, obstetrics and gynecology, advanced practice nursing, diabetes care and education, clinical chemistry, bioengineering, and product liability law. The panelists reviewed the medical literature pertaining to five topics: (1) continuation of home CGMs after hospitalization, (2) initiation of CGMs in the hospital, (3) continuation of AID systems in the hospital, (4) logistics and hands-on care of hospitalized patients using CGMs and AID systems, and (5) data management of CGMs and AID systems in the hospital. The panelists then developed three types of recommendations for each topic, including clinical practice (to use the technology optimally), research (to improve the safety and effectiveness of the technology), and hospital policies (to build an environment for facilitating use of these devices) for each of the five topics. The panelists voted on 78 proposed recommendations. Based on the panel vote, 77 recommendations were classified as either strong or mild. One recommendation failed to reach consensus. Additional research is needed on CGMs and AID systems in the hospital setting regarding device accuracy, practices for deployment, data management, and achievable outcomes. This guideline is intended to support these technologies for the management of hospitalized patients with diabetes.

Point-of-care testing in diabetes management

The prevalence of diabetes mellitus (DM) has rapidly increased over the last decades, reaching epidemic magnitudes, particularly in lowand middle-income countries. Point-of-care (POC) technology enables decision making near or at the site of patient care. Portable blood glucose meters and HbA1c testing are used by the healthcare provider and millions of patients with diabetes to monitor the safety and effectiveness of the diabetes treatment. However, POC capillary blood glucose and POC HbA1c testing are not recommended for diabetes diagnosis. Rather, they have been used for screening diabetes in lowand middle-income countries to decrease the disease burden.

Diabetes Technology Update: Use of Insulin Pumps and Continuous Glucose Monitoring in the Hospital

The use of continuous subcutaneous insulin infusion (CSII) and continuous glucose monitoring (CGM) systems has gained wide acceptance in diabetes care. These devices have been demonstrated to be clinically valuable, improving glycemic control and reducing risks of hypoglycemia in ambulatory patients with type 1 diabetes and type 2 diabetes. Approximately 30-40% of patients with type 1 diabetes and an increasing number of insulin-requiring patients with type 2 diabetes are using pump and sensor technology. As the popularity of these devices increases, it becomes very likely that hospital health care providers will face the need to manage the inpatient care of patients under insulin pump therapy and CGM. The American Diabetes Association advocates allowing patients who are physically and mentally able to continue to use their pumps when hospitalized. Health care institutions must have clear policies and procedures to allow the patient to continue to receive CSII treatment to maximize safety and to comply with existing regulations related to self-management of medication. Randomized controlled trials are needed to determine whether CSII therapy and CGM systems in the hospital are associated with improved clinical outcomes compared with intermittent monitoring and conventional insulin treatment or with a favorable cost-benefit ratio.

Impact of newly developed, next-generation artificial endocrine pancreas

BACKGROUND

Recent studies have shown that strict perioperative blood glucose management may reduce mortality and morbidity in critically ill adult patients. The purpose of this study was to assess the accuracy and efficacy of the intraoperative application of a newly developed, next-generation artificial endocrine pancreas (STG-55, Nikkiso Co., Ltd., Tokyo, Japan).

METHODS

Twenty patients scheduled to undergo surgery were enrolled in this study. The STG-55 is designed to be more user-friendly than its conventional counterpart (STG-22) while maintaining the latter's fundamental functions, such as a closed-loop system using algorithms for insulin and glucose infusion. After anesthetic induction, a 20G intravenous catheter was inserted into a peripheral forearm vein and connected to a continuous blood glucose monitor. The resultant 105 scores for paired blood glucose values were compared by Bland-Altman analysis.

RESULTS

Stable blood glucose values were maintained automatically, and there were no complications related to use of the STG-55. A close correlation (r=0.96) was observed between continuous glucose measurements using the STG-55 and conventional intermittent glucose measurements. The difficulty of manipulation using this system was decreased by improved preparation procedures.

CONCLUSION

The glycemic control system using the STG-55 could provide an alternative way to achieve effective and safe perioperative glycemic control.

Comparison between a novel and conventional artificial pancreas for perioperative glycemic control using a closed-loop system

This clinical study aimed to compare a novel and conventional artificial pancreas (AP) used in surgical patients for perioperative glycemic control, with respect to usability, blood glucose measurements, and glycemic control characteristics. From July in 2010 to March in 2015, 177 patients underwent perioperative glycemic control using a novel AP. Among them, 166 patients were eligible for inclusion in this study. Intensive insulin therapy (IIT) targeting a blood glucose range of 80-110 mg/dL was implemented in 82 patients (49 %), and the remaining 84 patients (51 %) received a less-intensive regime of insulin therapy. Data were collected prospectively and were reviewed or analyzed retrospectively. A comparison study of 324 patients undergoing IIT for glycemic control using a novel (n = 82) or conventional AP (n = 242) was conducted retrospectively. All patients had no hypoglycemia. The comparison study revealed no significant differences in perioperative mean blood glucose level, achievement rates for target blood glucose range, and variability in blood glucose level achieved with IIT between the novel AP and conventional AP groups. The usability, performance with respect to blood glucose measurement, and glycemic control characteristics of IIT were comparable between novel and conventional AP systems. However, the novel AP was easier to manipulate than the conventional AP due to its smaller size, lower weight, and shorter time for preparation. In the near future, this novel AP system might be accepted worldwide as a safe and useful device for use in perioperative glycemic control.

Comparison of subcutaneous and intravenous continuous glucose monitoring accuracy in an operating room and an intensive care unit

Although we have used an intravenous continuous glucose monitor for blood glucose management, a previous study reported that a subcutaneous continuous glucose monitor was also reliable for use in critically ill patients. The aim of this study was to compare the subcutaneous and intravenous continuous glucose monitors. This was an observational trial (UMIN-CTR, ID:000013338). We included patients who were admitted to our intensive care units (ICU) after hepato-biliary pancreatic surgery. Continuous blood glucose measurement was performed from the beginning of the operation to ICU discharge using the intravenous continuous monitor STG-55 (Nikkiso, Tokyo, Japan) and the subcutaneous continuous monitor iPro2 (Medtronic Japan, Tokyo, Japan). The STG-55 measured the glucose level in real time, and the iPro2 measured this every 5 min. We compared glucose levels obtained using the two devices every 5 min using a Bland-Altman plot and a regression analyses. A total of 3592 comparative samples in 15 cases were analyzed. The mean glucose level measured using the STG-55 was 139 ± 21 mg/dl, and that measured using the iPro2 was 144 ± 31 mg/dl. A linear regression line had the equation of the form y = 0.225x + 106. The coefficient of determination was 0.11, and the F-test significance level was set as p < 0.01. The mean of the differences was -5.2 mg/dl, with a 95 % agreement limit of -67 to + 57 mg/dL. The percent error was 44 %. In conclusion, the current study suggests that subcutaneous and intravenous continuous glucose monitoring was not highly correlated during either surgery or ICU stay.

Vascular Glucose Sensor Symposium: Continuous Glucose Monitoring Systems (CGMS) for Hospitalized and Ambulatory Patients at Risk for Hyperglycemia, Hypoglycemia, and Glycemic Variability

Hyperglycemia, hypoglycemia, and glycemic variability have been associated with increased morbidity, mortality, length of stay, and cost in a variety of critical care and non-critical care patient populations in the hospital. The results from prospective randomized clinical trials designed to determine the risks and benefits of intensive insulin therapy and tight glycemic control have been confusing; and at times conflicting. The limitations of point-of-care blood glucose (BG) monitoring in the hospital highlight the great clinical need for an automated real-time continuous glucose monitoring system (CGMS) that can accurately measure the concentration of glucose every few minutes. Automation and standardization of the glucose measurement process have the potential to significantly improve BG control, clinical outcome, safety and cost.

Continuous glucose monitoring in insulin-treated patients in non-ICU settings

Inpatient hyperglycemia, in patients with and without a history of diabetes, is associated with increased risk of complications, mortality, and longer hospital stay in medicine and surgical patients. Bedside capillary point of care testing is widely recommended as the preferred method for glucose monitoring and for guiding glycemic management of individual patients; however, the accuracy of most handheld glucose meters is far from optimal. Recent studies in the hospital setting have reported that the use of continuous glucose monitoring (CGM) can provide real-time information about glucose concentration, direction, and rate of change over a period of several days. Because it provides glucose values every 5-10 minutes 24 hours a day, CGM may have an advantage over point of care testing with respect to reducing the incidence of severe hypoglycemia in acute care. Real-time CGM technology may facilitate glycemic control and to reduce hypoglycemia in insulin-treated patients. Recent guidelines, however, have recommended deferring the use of CGM in the adult hospital setting until further data on accuracy and safety become available. In this study, we review the advantages and disadvantages of the use of real-time CGM in the management of dysglycemia in the hospital setting.

Intensive versus intermediate glucose control in surgical intensive care unit patients

OBJECTIVE

The optimal perioperative blood glucose range to improve surgical site infection (SSI) in surgical intensive care unit (ICU) patients remains unclear. We sought to determine whether the incidence of SSI is reduced by perioperative intensive insulin therapy (IT).

RESEARCH DESIGN AND METHODS

Patients were randomly assigned to receive perioperative intensive IT, with a target blood glucose range of 4.4-6.1 mmol/L, or intermediate IT, with a target blood glucose range of 7.7-10.0 mmol/L in the surgical ICU. We defined the primary end point as the incidence of SSI.

RESULTS

Study participants were randomly assigned to glucose control with one of two target ranges: for 225 patients in the intermediate IT group or for 222 patients in the intensive IT group, respectively. No patients in either group became hypoglycemic (<4.4 mmol/L) during their stay in the surgical ICU. In our series, the rate of SSI after hepato-biliary-pancreatic surgery was 6.7%. Patients in the intensive IT group, compared with the intermediate IT group, had fewer postoperative SSIs (9.8% vs. 4.1%, P = 0.028) and a lower incidence of postoperative pancreatic fistula after pancreatic resection (P = 0.040). The length of hospitalization required for patients in the intensive IT group was significantly shorter than that in the intermediate IT group (P = 0.017).

CONCLUSIONS

We found that intensive IT decreased the incidence of SSI among patients who underwent hepato-biliary-pancreatic surgery: a blood glucose target of 4.4 to 6.1 mmol/L resulted in lower rate of SSI than did a target of 7.7-10.0 mmol/L.

Are closed-loop systems for intensive insulin therapy ready for prime time in the ICU?

PURPOSE OF REVIEW

Recent findings suggest that the effects of tight glycemic control (TGC) performing intensive insulin therapy (IIT) in medical and surgical ICU have had conflicting results. The purpose of this review is to summarize the current evidence in humans how closed-loop systems for IIT are ready for prime time in the ICU.

RECENT FINDINGS

Current evidence suggests that maintaining normoglycemia postoperatively can improve the outcome and reduce the mortality and morbidity of critically ill patients by TGC performing IIT according to the large randomized trials. However, trials examining the effects of TGC have had conflicting results. Systematic reviews and meta-analyses have also led to differing conclusions. The main reason these clinical trials and meta-analyses were negative results for TGC was because of the high incidence of hypoglycemia. This could not be prevented as there is no reliable technique currently able to avoid this condition during IIT. The development of accurate, continuous blood glucose monitoring devices, and closed-loop systems for computer-assisted blood glucose control in the ICU, will probably help avoid hypoglycemia in these situations.

SUMMARY

The challenge in the hospital setting demonstrated that a closed-loop glycemic control system is expected to the achievement of TGC with no occurrence of hypoglycemia induced by IIT after surgery. Closed-loop glycemic control systems for IIT are now ready for prime time in the ICU.

Treatment of endocrine disorders in the neuroscience intensive care unit

OPINION STATEMENT

This review discusses concepts and treatments associated with the most clinically relevant areas of acute endocrine dysfunction amongst patients with common diseases in neuroscience intensive care units (Neuro ICUs). We highlight the following points:• While a thorough work-up for hyponatremia when it is present is always warranted, subarachnoid hemorrhage (SAH) patients who are in a time window concerning for cerebral vasospasm and who are hyponatremic with high urine output are generally thought to have cerebral salt wasting. These patients are typically treated with a combination of continuous hypertonic saline infusion and fludrocortisone.• Diabetes insipidus (DI) is often seen in patients fulfilling death by neurological criteria, as well as in patients with recent pituitary surgery and less often in SAH and traumatic brain injury patients who are not brain dead. Patients with DI in the Neuro ICU often cannot drink to thirst and may require a combination of desmopression/vasopressin administration, aggressive fluid repletion, and serum sodium monitoring.• Diagnosing adrenal insufficiency immediately following pituitary injury is complicated by the fact that the expected atrophy of the adrenal glands, due to lack of a stimulus from pituitary adrenocorticotropic hormone, may take up to 6 weeks to develop. Cosyntropin testing can be falsely normal during this period.• Both hyperglycemia (glucose >200 mg/dL) and hypoglycemia (glucose <50 mg/dL) are strongly associated with neurological morbidity and mortality in ICUs and should be avoided. Glucose concentrations between 120-160 mg/dL can serve as a reasonable target for insulin infusion protocols.• There is no data to suggest that treatment of abnormal thyroid function tests in nonthyroidal illness syndrome/sick euthyroid leads to benefits in either mortality or morbidity. True myxedema coma is a rare clinical diagnosis that is treated with intravenous levothyroxine accompanied by stress-dose steroids.

Perioperative intensive insulin therapy using an artificial endocrine pancreas with closed-loop glycemic control system: the effects of no hypoglycemia

BACKGROUND

We examined whether perioperative intensive insulin therapy (IIT) using an artificial pancreas (AP) with a closed-loop glycemic control system can be used to prevent hypoglycemia in surgical patients.

METHODS

Between 2006 and 2012, perioperative glycemic control using an AP was performed in 427 patients undergoing general surgery. A total of 305 patients undergoing IIT using an AP in the target blood glucose range of 80 to 110 mg/dL were enrolled in the study. Data were collected prospectively and were reviewed or analyzed retrospectively.

RESULTS

No patients had hypoglycemia. Perioperative mean blood glucose level and achievement rates in target blood glucose range of 80 to 110 mg/dL were 100.5 ± 11.9 mg/dL and 88.1% ± 16.0%, respectively. For the 3 primary operative methods, including hepatic, pancreatic, and esophageal resections, there were no significant differences in glycemic control stability between the types of surgery.

CONCLUSION

Perioperative IIT using an AP with a closed-loop glycemic control system can be used to prevent hypoglycemia and maintain stable glycemic control with less variability of blood glucose concentration.

Diagnosis and management of insulinoma

Insulinomas, the most common cause of hypoglycemia related to endogenous hyperinsulinism, occur in 1-4 people per million of the general population. Common autonomic symptoms of insulinoma include diaphroresis, tremor, and palpitations, whereas neuroglycopenenic symptoms include confusion, behavioural changes, personality changes, visual disturbances, seizure, and coma. Diagnosis of suspected cases is based on standard endocrine tests, especially the prolonged fasting test. Non-invasive imaging procedures, such as computed tomography and magnetic resonance imaging, are used when a diagnosis of insulinoma has been made to localize the source of pathological insulin secretion. Invasive modalities, such as endoscopic ultrasonography and arterial stimulation venous sampling, are highly accurate in the preoperative localization of insulinomas and have frequently been shown to be superior to non-invasive localization techniques. The range of techniques available for the localization of insulinomas means that blind resection can be avoided. Intraoperative manual palpation of the pancreas by an experienced surgeon and intraoperative ultrasonography are both sensitive methods with which to finalize the location of insulinomas. A high proportion of patients with insulinomas can be cured with surgery. In patients with malignant insulinomas, an aggressive medical approach, including extended pancreatic resection, liver resection, liver transplantation, chemoembolization, or radiofrequency ablation, is recommended to improve both survival and quality of life. In patients with unresectable or uncontrollable insulinomas, such as malignant insulinoma of the pancreas, several techniques should be considered, including administration of ocreotide and/or continuous glucose monitoring, to prevent hypoglycemic episodes and to improve quality of life.

Technical challenges and clinical outcomes of using a closed-loop glycemic control system in the hospital

According to large randomized trials, results suggest that maintaining normoglycemia postoperatively through tight glycemic control (TGC) and intensive insulin therapy (IIT) can improve surgical outcomes as well as reduce mortality and morbidity in critically ill patients. However, trials examining the effects of TGC have had conflicting results. Systematic reviews and meta-analyses have also led to differing conclusions. The main reason these clinical trials and meta-analyses show negative results for TGC is the high incidence of hypoglycemia induced by IIT. This could not be prevented because there is no reliable technique that can avoid this condition during IIT. The development of accurate, continuous blood glucose monitoring devices and closed-loop systems for computer-assisted blood glucose control in the intensive care unit (ICU) will probably help avoid hypoglycemia in these situations. The STG closed-loop glycemic control system was introduced to our department to be used and evaluated for strict serum glucose control with no hypoglycemic episodes during IIT in the surgical ICU, to reduce the workload of ICU nurses, and to decrease incidents related to the management of blood glucose levels according to manual conventional venous infusion insulin therapy. The goal of our team was to use the STG closed-loop glycemic control system for perioperative TGC in surgical patients to solve the complications of IIT and reduce risk of hypoglycemia. The challenge at our hospital demonstrated that the STG closed-loop glycemic control system can be expected to achieve TGC with no occurrence of hypoglycemia induced by IIT after surgery.

Evaluation of a continuous blood glucose monitoring system using a central venous catheter with an integrated microdialysis function

INTRODUCTION

Glycemic control in critically ill patients has been the topic of an interesting debate during the last decade. An accurate continuous glucose monitoring system is essential to better understand this field. This prospective study thus evaluates the accuracy and technical feasibility of a continuous glucose monitoring system using intravascular microdialysis.

PATIENTS AND METHODS

Thirty patients undergoing cardiac surgery were monitored using a triple-lumen central venous catheter (Eirus TLC; Eirus Medical AB, Solna, Sweden) with an integrated microdialysis function. The catheter functions as a central venous catheter, enabling blood sampling and administration of infusions and medication while simultaneously providing continuous glucose monitoring. The patients were monitored for up to 48 h postoperatively. As reference, arterial blood gas samples were taken every hour and analyzed in a blood gas analyzer.

RESULTS

Six hundred seven paired samples were obtained for analysis. Using Clarke Error Grid analysis, 100% of the paired samples were in Zones A+B, and 97% were in Zone A. Mean difference (bias) was -0.12 mmol/L, and mean absolute relative difference was 5.6%. Of the paired samples, 97.5% were correct according to International Organization for Standardization criteria. Bland-Altman analysis showed bias ± limits of agreement were -0.12 ± 0.7 mmol/L. No hypoglycemic episodes were observed.

CONCLUSIONS

Central venous microdialysis is an accurate and reliable method for continuous blood glucose monitoring up to 48 h in patients undergoing cardiac surgery. With the microdialysis function integrated in a central venous catheter, no extra device for the continuous glucose monitoring is required. The system may be useful in critically ill patients.

Evaluation of a continuous blood glucose monitoring system using central venous microdialysis

BACKGROUND

Glycemic control in critically ill patients has been shown to be beneficial. In this prospective study, we evaluated the accuracy and technical feasibility of a continuous glucose monitoring system using intravascular microdialysis.

METHOD

Fifty patients undergoing cardiac surgery were monitored using a 4 Fr intravenous microdialysis catheter (Eirus SLC™, Dipylon Medical AB, Solna, Sweden) percutaneously placed with the tip of the catheter positioned in the superior vena cava. The catheter was connected to the Eirus™ monitoring system, and the patients were monitored for up to 48 h postoperatively in the intensive care unit (ICU). As reference, arterial blood samples were taken every hour and analyzed in a blood gas analyzer.

RESULTS

Data were available from 48 patients. A total of 994 paired (arterial blood gas microdialysis) samples were obtained. Glucose correlation coefficient (R2) was 0.85. Using Clarke error grid analysis, 100% of the paired samples were in region AB, and 99% were in region A. Mean glucose level was 8.3 mmol/liter (149 mg/dl), mean relative difference was 0.2%, and mean absolute relative difference was 5%. A total of 99.2% of the paired samples were correct according to International Organization for Standardization (ISO) criteria. Bland-Altman analysis showed that bias ± limits of agreement were 0.02 ± 1.1 mmol/liter (0.36 ± 20 mg/dl).

CONCLUSIONS

Central venous microdialysis using the Eirus monitoring system is a highly accurate and reliable method for continuous blood glucose monitoring up to 48 h in ICU patients undergoing cardiac surgery. The system may thus be useful in critically ill ICU patients.

Progressive artificial endocrine pancreas: The era of novel perioperative blood glucose control for surgery

Strict glycemic control needs to be maintained in critically ill surgical patients to reduce the mortality and morbidity due to hyperglycemia and associated infection. However, conventional intensive insulin therapy (IIT), which consists of intermittent blood glucose measurement and manually controlled infusions of insulin, tends to induce hypoglycemia and glucose variability. Many randomized clinical trials have been conducted to improve the efficacy of IIT, although some of these were stopped owing to frequent hypoglycemia. In pursuing safe and strict glycemic control for critically ill surgical patients, we found that a closed-loop glycemic control system was able to maintain appropriate blood glucose levels without hypoglycemia in more than 400 clinical cases. Considering the need for the perioperative and intensive care environment, a well-established artificial pancreas was modified into a new closed-loop glycemic control system, called the progressive artificial pancreas. The new device is slim in shape and shows clinical compatibility with the conventional artificial pancreas. We herein review this new closed-loop glycemic control system and the expectations for its future application in critically ill surgical patients.

Hospital Strategies for Insulin Therapy with Rapid-Acting Insulin Analogs

This article presents strategies on how to meet the challenges presented by the use of insulin in the hospital setting and describes trends seen in current hospital practice. Insulin provides the greatest flexibility in the hospital setting to achieve optimal blood glycemic control in patients with known type 2 diabetes, thereby reducing complications and death. Important challenges include implementing protocols for use of subcutaneous insulin injection (including optimal use of insulin pens), conversion from continuous subcutaneous insulin infusion or intravenous infusion to subcutaneous administration by multiple injections, and dosing of insulin in patients receiving corticosteroids. One important trend is a move away from the use of sliding-scale insulin to the use of correction-dose insulin as an adjunct to basal/bolus insulin. In this approach, insulin treatment is closely tailored to changing levels of glycemia, and a protocol is put in place for administration of a correction dose of rapid-acting insulin in response to a glycemic excursion. Insulin analogs can more closely mimic physiological insulin profiles than regular insulin, and rapid-acting analogs are invaluable agents as correction insulin administered by pump or in transition to multiple daily injections and as part of basal/bolus therapy. Good glycemic control can improve outcomes of hospital patients in several ways, including facilitating more rapid recovery from infections, shortening intensive care stays, and minimizing costs. Strategies employed to meet the challenges of insulin use in the hospital setting include the increasing use of continuous glucose monitoring systems and the development of insulin dosing algorithms.

Intensive insulin therapy during cardiovascular surgery

Recent evidence in the fields of surgery, emergency and critical care medicine indicates that strict glycemic control results in lower mortality. Hyperglycemia occurs frequently in patients with and without diabetes during cardiovascular surgery, especially during cardiopulmonary bypass. However, strict glucose control is difficult to achieve during cardiovascular procedures. To establish effective intensive insulin therapy during cardiovascular surgery, we conduct continuous blood glucose monitoring and employ automatic control by using an artificial endocrine pancreas (the STG-22, Nikkiso, Tokyo, Japan). In this review, we will outline the present status and problems of conventional glycemic control for perioperative cardiovascular surgery and introduce the new perioperative blood glucose management method that we are testing now. We will also discuss the importance of perioperative glycemic control for cardiovascular surgery as well as future prospects.

Year in review 2009: Critical Care--metabolism

Novel insights into the metabolic alterations of critical illness were published in Critical Care in 2009. The association between early hypoglycaemia/high glycemic variability and poor outcome was confirmed. Improvements in the understanding of the pathophysiological mechanisms of stress hyperglycemia and potential progress in the bedside management of glucose control were presented. With regard to enteral nutrition, some alterations of gastrointestinal physiology were better delineated. The relationship between the achievement of nutritional goals and outcomes was further investigated. Finally, understanding of some critical-illness-related endocrine and neuromuscular disorders improved through new experimental and clinical findings.

Effects of blood glucose transcription mismatches on a computer-based intensive insulin therapy protocol

PURPOSE

Computerized clinical decision support systems (CDSS) for intensive insulin therapy (IIT) generate recommendations using blood glucose (BG) values manually transcribed from testing devices to computers, a potential source of error. We quantified the frequency and effect of blood glucose transcription mismatches on IIT protocol performance.

METHODS

We examined 38 months of retrospective data for patients treated with CDSS IIT in two intensive care units at one teaching hospital. A manually transcribed BG value not equal to a corresponding device value was deemed mismatched. For mismatches we recalculated CDSS recommendations using device BG values. We compared matched and mismatched data in terms of CDSS alerts, blood glucose variability, and dosing.

RESULTS

Of 189,499 CDSS IIT instances, 5.3% contained mismatched BG values. Mismatched data triggered 93 false alerts and failed to issue 170 alerts for nurses to notify physicians. Four of six BG variability measures differed between matched and mismatched data. Overall insulin dose was greater for matched than mismatched [matched 3.8 (1.6-6.0), median (interquartile range, IQR), versus 3.6 (1.6-5.7); p < 0.001], but recalculated and actual dose were similar. In mismatches preceding hypoglycemia, recalculated insulin dose was significantly lower than actual dose [recalculated 2.7 (0.4-5.0), median (IQR), versus 3.5 (1.4-5.6)]. In mismatches preceding hyperglycemia, recalculated insulin dose was significantly greater than actual dose [recalculated 4.7 (3.3-6.2), median (IQR), versus 3.3 (2.4-4.3); p < 0.001]. Administration of recalculated doses might have prevented blood glucose excursions.

CONCLUSIONS

Mismatched blood glucose values can influence CDSS IIT protocol performance.

Pilot evaluation of a prototype critical care blood glucose monitor in normal volunteers

BACKGROUND

Availability of a highly accurate in-hospital automated blood glucose (BG) monitor could facilitate implementation of intensive insulin therapy protocols through effective titration of insulin therapy, improved BG control, and avoidance of hypoglycemia. We evaluated a functional prototype BG monitor designed to perform frequent automated blood sampling for glucose monitoring.

METHODS

Sixteen healthy adult volunteer subjects had intravenous catheter insertions in a forearm or hand vein and were studied for 8 hours. The prototype monitor consisted of an autosampling unit with a precise computer-controlled reversible syringe pump and a glucose analytical section. BG was referenced against a Yellow Springs Instrument (YSI) laboratory analyzer. Sampling errors for automated blood draws were assessed by calculating the percent of failed draws, and BG data were analyzed using the Bland and Altman technique.

RESULTS

Out of 498 total sample draws, unsuccessful draws were categorized as follow: 11 (2.2%) were due to autosampler technical problems, 21 (4.2%) were due to catheter-related failures, and 37 (7.4%) were BG meter errors confirmed by a glucometer-generated error code. Blood draw difficulties or failures related to the catheter site (e.g., catheter occlusion or vein collapse) occurred in 6/15 (40%) subjects. Mean BG bias versus YSI was 0.20 +/- 12.6 mg/dl, and mean absolute relative difference was 10.4%.

CONCLUSIONS

Automated phlebotomy can be performed in healthy subjects using this prototype BG monitor. The BG measurement technology had suboptimal accuracy based on a YSI reference. A more accurate BG point-of-care testing meter and strip technology have been incorporated into the future version of this monitor. Development of such a monitor could alleviate the burden of frequent BG testing and reduce the risk of hypoglycemia in patients on insulin therapy.

Clinical need for continuous glucose monitoring in the hospital

Automation and standardization of the glucose measurement process have the potential to greatly improve glycemic control, clinical outcome, and safety while reducing cost. The resources required to monitor glycemia in hospitalized patients have thus far limited the implementation of intensive glucose management to patients in critical care units. Numerous available and up-and-coming technologies are targeted for the hospital patient population. Advantages and limitations of these devices are discussed herewith in.

Social, organizational, and contextual characteristics of clinical decision support systems for intensive insulin therapy: a literature review and case study

INTRODUCTION

Evaluations of computerized clinical decision support systems (CDSS) typically focus on clinical performance changes and do not include social, organizational, and contextual characteristics explaining use and effectiveness. Studies of CDSS for intensive insulin therapy (IIT) are no exception, and the literature lacks an understanding of effective computer-based IIT implementation and operation.

RESULTS

This paper presents (1) a literature review of computer-based IIT evaluations through the lens of institutional theory, a discipline from sociology and organization studies, to demonstrate the inconsistent reporting of workflow and care process execution and (2) a single-site case study to illustrate how computer-based IIT requires substantial organizational change and creates additional complexity with unintended consequences including error.

DISCUSSION

Computer-based IIT requires organizational commitment and attention to site-specific technology, workflow, and care processes to achieve intensive insulin therapy goals. The complex interaction between clinicians, blood glucose testing devices, and CDSS may contribute to workflow inefficiency and error. Evaluations rarely focus on the perspective of nurses, the primary users of computer-based IIT whose knowledge can potentially lead to process and care improvements.

CONCLUSION

This paper addresses a gap in the literature concerning the social, organizational, and contextual characteristics of CDSS in general and for intensive insulin therapy specifically. Additionally, this paper identifies areas for future research to define optimal computer-based IIT process execution: the frequency and effect of manual data entry error of blood glucose values, the frequency and effect of nurse overrides of CDSS insulin dosing recommendations, and comprehensive ethnographic study of CDSS for IIT.

Intraoperative glycemic control procedures and the use of an artificial pancreas

Strict intraoperative glycemic control can significantly decrease the incidence of postoperative infection; however, anesthesiologists must carefully control blood glucose levels as well as properly manage the respiratory and cardiovascular systems. However, standard blood glucose measurement systems and insulin dosing algorithms, which are necessary for achieving strict glycemic control, have not yet been developed. An artificial pancreas (STG-22^TM; Nikkiso Co., Tokyo, Japan) is considered a highly accurate blood glucose monitoring system capable of closed-loop control of blood glucose. The device has, however, many problems to be addressed since it is a large and expensive system with little versatility, and it requires a large amount of blood to be collected. Therefore, the development of less invasive and inexpensive systems with future technological progress is greatly anticipated.

What is artificial endocrine pancreas? Mechanism and history

The artificial endocrine pancreas is a feedback control instrument that regulates insulin delivery on a minute-by-minute basis according to measured blood glucose levels. Only one type of bedside-type artificial endocrine pancreas is now available in Japan: STG-22 (Nikkiso Co. Ltd., Japan). In the insulin infusion algorithm, insulin is infused on the basis of its proportional and derivative actions, to blood glucose concentrations with a constant time delay. The bedside-type artificial endocrine pancreas has been proven to be useful not only as a therapeutic tool for diabetes mellitus, but also as an elegant research tool for investigating the pathophysiology of the disease, by using the euglycemic hyperinsulinemic glucose clamp technique. The wearable type of closed-loop system has been developed recently. The breakthrough is the establishment of a needle-type glucose sensor. The development of closed-loop glycemic control systems that enable long-term physiological regulation has focused on implantable devices. Much effort has been expended to realize these devices.

Relationship between perioperative glycemic control and postoperative infections

Perioperative hyperglycemia in critically ill surgery patients increases the risk of postoperative infection (POI), which is a common, and often costly, surgical complication. Hyperglycemia is associated with abnormalities in leukocyte function, including granulocyte adherence, impaired phagocytosis, delayed chemotaxis, and depressed bactericidal capacity. These leukocyte deficiencies are the cause of infection and improve with tight glycemic control, which leads to fewer POIs in critically ill surgical patients. Tight glycemic control, such as intensive insulin therapy, has a risk of hypoglycemia. In addition, the optimal targeted blood glucose range to reduce POI remains unknown. Since 2006, we have investigated tight perioperative blood glucose control using a closed-loop artificial endocrine pancreas system, to reduce POI and to avoid hypoglycemia. In this Topic Highlight, we review the relationship between perioperative glycemic control and POI, including the use of the artificial pancreas.

Perioperative intensive insulin therapy using artificial endocrine pancreas in patients undergoing pancreatectomy

Perioperative glycemic control is important for reducing postoperative infectious complications. However, clinical trials have shown that efforts to maintain normoglycemia in intensive care unit patients result in deviation of glucose levels from the optimal range, and frequent attacks of hypoglycemia. Tight glycemic control is even more challenging in those undergoing pancreatic resection. Removal of lesions and surrounding normal pancreatic tissue often cause hormone deficiencies that lead to the destruction of glucose homeostasis, which is termed pancreatogenic diabetes. Pancreatogenic diabetes is characterized by the occurrence of hyperglycemia and iatrogenic severe hypoglycemia, which adversely effects patient recovery. Postoperatively, a variety of factors including surgical stress, inflammatory cytokines, sympathomimetic drug therapy, and aggressive nutritional support can also affect glycemic control. This review discusses the endocrine aspects of pancreatic resection and highlights postoperative glycemic control using a closed-loop system or artificial pancreas. In previous experiments, we have demonstrated the reliability of the artificial pancreas in dogs with total pancreatectomy, and its postoperative clinical use has been shown to be effective and safe, without the occurrence of hypoglycemic episodes, even in patients after total pancreatectomy. Considering the increasing requirement for tight perioperative glycemic control and the recognized risk of hypoglycemia, we propose the use of an artificial endocrine pancreas that is able to monitor continuously blood glucose concentrations with proven accuracy, and administer automatically substances to return blood glucose concentration to the optimal narrow range.

Problems associated with glucose toxicity: Role of hyperglycemia-induced oxidative stress

Glucose homeostasis deficiency leads to a chronic increase in blood glucose concentration. In contrast to physiological glucose concentration, chronic superphysiological glucose concentration negatively affects a large number of organs and tissues. Glucose toxicity means a decrease in insulin secretion and an increase in insulin resistance due to chronic hyperglycemia. It is now generally accepted that glucose toxicity is involved in the worsening of diabetes by affecting the secretion of β-cells. Several mechanisms have been proposed to explain the adverse effects of hyperglycemia. It was found that persistent hyperglycemia caused the functional decline of neutrophils. Infection is thus the main problem resulting from glucose toxicity in the acute phase. In other words, continued hyperglycemia is a life-threatening risk factor, not only in the chronic but also the acute phase, and it becomes a risk factor for infection, particularly in the perioperative period.

Perioperative insulin therapy using a closed-loop artificial endocrine pancreas after hepatic resection

Postoperative hyperglycemia is common in critically ill patients, even in those without a prior history of diabetes mellitus. It is well known that hyperglycemia induced by surgical stress often results in dysregulation of liver metabolism and immune function, impairing postoperative recovery. Current evidence suggests that maintaining normoglycemia postoperatively improves surgical outcome and reduces the mortality and morbidity of critically ill patients. On the basis of these observations, several large randomized controlled studies were designed to evaluate the benefit of postoperative tight glycemic control with intensive insulin therapy. However, intensive insulin therapy carries the risk of hypoglycemia, which is linked to serious neurological events. Recently, we demonstrated that perioperative tight glycemic control in surgical patients could be achieved safely using a closed-loop glycemic control system and that this decreased both the incidence of infection at the site of the surgical incision, without the appearance of hypoglycemia, and actual hospital costs. Here, we review the benefits and requirements of perioperative intensive insulin therapy using a closed-loop artificial endocrine pancreas system in hepatectomized patients. This novel intensive insulin therapy is safe and effectively improves surgical outcome after hepatic resection.

Effect of intensive insulin therapy using a closed-loop glycemic control system in hepatic resection patients: a prospective randomized clinical trial

OBJECTIVE Intensive insulin therapy (IIT) reduces morbidity and mortality in patients in surgical intensive care units. The aim of this study is to assess the effect of IIT using a closed-loop system in hepatectomized patients. RESEARCH DESIGN AND METHODS Patients were randomly assigned to receive IIT using a closed-loop system: an artificial pancreas (AP group) or conventional insulin therapy using the sliding-scale method (SS group). RESULTS The incidence of surgical-site infection in the AP group was significantly lower than that in the SS group. The length of hospitalization required for patients in the AP group was significantly shorter than that in the SS group. CONCLUSIONS Total hospital costs for patients in the AP group were significantly lower than for patients in the SS group. IIT using a closed-loop system maintained near-normoglycemia and contributed to a reduction in the incidence of SSI and total hospital costs due to shortened hospitalization.