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[Usefulness of continuous glucose monitoring system (CGMS) in monitoring glycaemic profile in small children with diabetes type 1].

BACKGROUND: Improved methods of diabetes therapy result in a near normoglycaemic state in many patients. This leads however unfortunately to more frequent hypoglycaemic incidents. Particularly small children, whose nervous system is not fully mature, are at high risk of central nervous system damage in case of hypoglycaemia. A new method of detail monitoring of glycaemia provides CGMS system. OBJECTIVES: The aim of the study was to compare the glycaemic profile, with high attention to hypoglycaemia in groups of young and older children with diabetes type 1, using CGMS and routine glucose meter. MATERIAL AND METHODS: We studied 32 children with diabetes type 1. Children were divided into groups: group I--small children, n=17 (<7 yrs of age), mean age 5,8 years, with disease duration--2,46 years, with mean HbA1c level--7,22%, and group II--older children, n=15 (>10 years of age), mean age--12 years, with disease duration--3 years, with HbA1c level--7,21%. Continuous glucose monitoring system (CGMS), by MiniMed, was applied in outpatient or hospital conditions, after short training of patient and parents; together with routine glucose meter measurements, 4-8 times/24 hours. In 9 patients from small children group CGMS was repeated after 2 months. RESULTS: Hypoglycaemic incidents detected with CGMS were similar in both groups: 4,6 in I group vs. 4,2 in II group (ns). Hypoglycaemic incidents found with meter were lower in I group--1,6 vs. 2,3 in II group (ns). Mean hypoglycaemic time/24 hour was longer in small children group: 101 min vs. 74 min in group II (p<00,05). In I group we found higher number of hypoglycaemic incidents during the night compared to group II--1,7 vs. 0,8 (p<00,05) and longer duration of night hypoglycaemia: in I group--56 min vs. 32 min in group II (p<00,05). Repeated CGMS study in 9 children from I group revealed decreased mean time of hypoglycaemia/24 hours from 134 min/24 h to 90 min/24 h (p<00,05) and decreased time of night hypoglycaemia from 65 min to 40 min (p<00,05), with a comparable number of hypoglycaemic incidents. Hypoglycaemic incidents found with routine meter measurements in small children were 1,6 vs. 4,6 hypoglycaemia found with CGMS (p<00,05), in the older children group routine measurement found 2,3 hypoglycaemia vs. 4,2 detected with CGMS (ns). CONCLUSIONS: 1. CGMS can be particularly usefull in monitoring glucose profile and detecting hypoglycaemia incidents, mainly nocturnal in small children. 2. CGMS allows to verify meal dose of insulin and to decrease postprandial hyperglycaemia. 3. Modification of insulin therapy on the base of CGMS helps to decrease the time of hypoglycaemia and hyperglycemia, particularly during the night.

Age Factors↗

Evaluation of a new real-time blood continuous glucose monitoring system in pregnant women without gestational diabetes. A pilot study.

The incidence of gestational diabetes mellitus (GDM) has reached epidemic proportions in the United States, affecting 200,000 pregnant women annually. Controversies exist regarding whether the glucose levels used to diagnose GDM in pregnancy should be lowered since similar fetal complications are seen in women with GDM as well as in nondiabetic women. Although GDM has been extensively studied, the effects of the earlier stage of glucose intolerance are not well understood. The objectives of this descriptive, comparative, correlational pilot study include assessment of real-time blood glucose concentrations in women (20) with idiopathic macrosomia and/or polyhydramnios but with a normal baseline glucose screening test. This group was compared to pregnant women (20) without idiopathic macrosomia and/or polyhydromnios as confirmed by normal ultrasounds (controls). All subjects had a normal screeing test and/or a 3-hour Glucose Tolerance Test earlier in the pregnancy and wore a continuous glucose monitoring system for 72 hours. No adverse maternal complications were seen. Neonatal complications included macrosomia, shoulder dystocia, and hyperbilirubinemia. There was no significant association between real-time blood glucose levels and adverse maternal or fetal/neonatal complications. There is little evidence available regarding real-time physiologic glycemic levels in pregnant women. The findings of our pilot study provide baseline data for the design of a larger study to compare blood glucose levels and complications in euglycemic women and compare to women with those impaired glucose tolerance.

Adult↗

Continuous glucose monitoring: long-term implantable sensor approach.

Problems with existing glucose monitoring technology have resulted in poor compliance with recommended monitoring guidelines by patients with diabetes. To achieve the goal of tight glucose control by patients with diabetes, a long-term implantable glucose sensor should meet the following functional requirements: it should be a one-time minimally invasive implantable with a wireless external unit; provide on-demand real-time glucose levels and trends; operate for up to 12 months after implantation with infrequent recalibration; contain built-in hypoglycemic and hyperglycemic alarms; and have an ergonomically designed, external, wearable user interface. Measurements of glucose in interstitial fluid (ISF) can be used for long-term monitoring. A novel approach to continuous and long-term glucose sensing could be based on measuring the changes in fluorescence of glucose-sensitive indicator molecules. To measure these changes in fluorescence a miniature optoelectronic device with a glucose sensitive indicator could be implanted subcutaneously for long-term remote operation. The fluorescence-based glucose sensing process is reversible and does not consume glucose. The combination of fluorescence-based glucose detection, sensor miniaturization and the use of biomaterials, inducing neovascularization at the implant site, opens the opportunity for achieving the requirements for long-term, continuous and convenient glucose monitoring.

Blood Glucose↗

Comparison of a needle-type and a microdialysis continuous glucose monitor in type 1 diabetic patients.

OBJECTIVE: We examined the reliability of two continuous glucose sensors in type 1 diabetic patients at night and during rapid glucose excursions and verified the hypothesized nocturnal hypoglycemic drift of the needle-type sensor (CGMSgold) and delay of the microdialysis sensor (GlucoDay). RESEARCH DESIGN AND METHODS: Blood was sampled overnight twice per hour in 13 patients. Rapid-acting insulin was given subcutaneously 30 min after breakfast. Sampling once per minute started 45 min after breakfast and 75 min after insulin injection for 30 min, with the aim of determining peak and nadir glucose values. Mean absolute differences (MADs) between sensor and blood glucose values were calculated. Sensor curves were modeled for all patients using linear regression. Horizontal and vertical shifts of sensor curves from the blood glucose curves were assessed. A vertical shift indicates sensor drift and a horizontal shift sensor delay. RESULTS: Drift was minimal in the needle-type and microdialysis sensors (-0.02 and -0.04 mmol/l). Mean +/- SD delay was 7.1 +/- 5.5 min for the microdialysis sensor (P < 0.001). MAD was 15.0% for the needle-type sensor and 13.6% for the microdialysis sensor (P = 0.013). After correction for the 7-min delay, the microdialysis MAD improved to 11.7% (P < 0.0001). CONCLUSIONS: The microdialysis sensor was more accurate than the needle-type sensor, with or without correction for a 7-min delay. In contrast to the previous version, the current needle-type sensor did not exhibit nocturnal hypoglycemic drift. Continuous subcutaneous glucose sensors are valuable adjunctive tools for glucose trend analyses. However, considering the large MADs, individual sensor values should be interpreted with caution.

Blood Glucose↗

The first use of live continuous glucose monitoring in patients on extracorporeal life support.

BACKGROUND: Evidence suggests that glycemic control provides clinical benefit to critically ill patients. The Extracorporeal Glucose Monitoring System (EGMS), Medtronic Minimed, Northridge, CA) has been developed to measure real-time, continuous blood glucose concentrations in patients on extracorporeal bypass. This pilot study reports the first in vitro and in vivo evaluations of EGMS in an extracorporeal circuit. METHODS: In an in vitro study, three EGMS sensors were inserted in a neonatal extracorporeal circuit. Circuit blood glucose levels were altered by saline dilution and dextrose infusion. EGMS sensors were then inserted into the venous return limb of the extracorporeal circuit in a cohort of six critically ill infants on extracorporeal life support (ECLS). Continuous glucose measurements were compared with laboratory and bedside glucose values at predefined intervals. Linear regression analyses and the Clarke error grid were constructed to analyze device accuracy. RESULTS: All three in vitro EGMS sensors recorded real-time data without interruption for 48 h. EGMS glucose measurements closely correlated with reference levels (R (2) = 0.93). EGMS glucose values demonstrated an approximate 7-10 min lag while glucose concentrations were rapidly changing. Eight EGMS devices were inserted into six neonates on ECLS on day of life 6 +/- 3. EGMS correlated well with laboratory glucose (R2 = 0.61) and bedside glucose during a hyperinsulinemic euglycemic clamp (R2 = 0.78). On the Clarke error grid, 98% of readings were within zones A and B using laboratory glucose as reference, and 100% were within zones A and B using bedside glucose measurements. Blood glucose range during the in vitro study was 19-295 mg/dL and during the in vivo study was 80-257 mg/dL. CONCLUSIONS: This pilot study suggests that EGMS is a reliable tool for measuring continuous blood glucose in critically ill patients connected to an extracorporeal circuit, although important limitations exist. Potential applications of this technology include intensive glucose monitoring in patients on ECLS, cardiopulmonary bypass, and renal replacement therapy.

Blood Glucose↗

[How I explore...glycemic kinetics by continuous glucose monitoring].

The improvement of diabetic patients' glycaemic status requires an increase of fingerstick blood glucose measurements. Among the possibilities available to assess diabetes' control, we will consider new systems of continuous interstitial glucose monitoring. After a brief description of the devices presently commercialized, we will discuss their indications and their limitations, as well as their future prospects in a possible "closed loop" insulin delivery according to blood glucose level.

Blood Glucose↗

[Continuous glucose monitoring: a critical appraisal after one year experience].

Conventional assessment of glycemic control in diabetes mellitus (DM) includes blood glucose attention to glycemia and glycated hemoglobin levels. Recently, we introduced the continuous glucose-monitoring test (CGM) (Medtronic Minimed-CGMS System Gold). Here we describe our experience with this methodology over the year 2004. A total of 141 CGM tests were performed over this period of time. Overall, 88% (n= 124) patients were diabetics (DM), 99 of them were insulin users. We found a strong correlation between glucose values obtained by CGM and capillary glucose measures (r= 0.926; p< 0.005). In diabetic patients, nocturnal hypoglycemia (< 50 mg/dL) was identified in approximately 35% (n= 44), hyperglycemic patterns (> 220 mg/dL) at specific times of day in approximately 44% and sustained hyperglycemia throughout the whole monitoring period in thirteen cases (10%). Twelve tests were performed to investigate the occurrence of hypoglycemia in non-diabetic subjects. Two tests came out very suggestive of "dumping", and in one case the CGMS supported the hypothesis of insulinoma. Partial monitoring interruptions have occurred in 15% of all tests. We concluded that CGMS is a useful methodology to investigate glycemic fluctuations, and it is also an important tool to adjust therapy in diabetic patients.

Adolescent↗

A predictive tool for the self-management of diabetes (Librae): evaluation using a continuous glucose monitoring system.

AIMS: Diabetes self-management involves a difficult balancing act between insulin, food and exercise. The challenge is to develop innovative, validated algorithms to aid patient decision-making and optimize glycaemic control. 'Librae' is a computerized diabetes simulator in diary format, developed as an educational predictive tool for patients, reducing 'trial and error' by allowing patients to simulate and experiment with dietary or insulin adjustments on a 'body double'. We have evaluated the predictive ability of Librae using continuous blood glucose monitoring (CGMS). METHODS: Patients with Type 1 Diabetes attending the Paediatric Clinic were invited to use 'Librae' for 1 week and were then fitted with a CGMS for 72 h. The predictive ability of 'Librae' was compared with concurrent data obtained from the CGMS. RESULTS: Seven thousand nine hundred and sixty paired blood glucose values were obtained from the 11 patients who completed the study. 'Librae' underestimated the measured CGMS values, the error having a positive mean of 0.35 mmol/l (95% confidence interval 0.22-0.48 mmol/l). However, Librae tended to overestimate at low levels of blood glucose readings, and underestimate at high levels of blood glucose readings. CONCLUSION: The modelled values of 'Librae' correlated well with the CGMS data, but clinically unacceptable errors occurred at extremes of blood glucose levels. Concurrent CGMS recordings have provided a large data set to modify and improve the existing Librae model and patient feedback has led to improvements in its usability. Librae may provide a useful tool to improve diabetes self-management education and optimize glycaemic control.

Adolescent↗

Switch to multiple daily injections with insulin glargine and insulin lispro from continuous subcutaneous insulin infusion with insulin lispro: a randomized, open-label study using a continuous glucose monitoring system.

OBJECTIVE: To evaluate the safety and efficacy of the transition from a continuous subcutaneous insulin infusion (CSII) regimen with insulin lispro to 1 of 2 dose regimens of multiple daily injections (MDI) with insulin lispro and insulin glargine in patients with type 1 diabetes. METHODS: The study group consisted of 38 patients with type 1 diabetes who had been using CSII with insulin lispro for > or =6 months. These patients were randomized to receive insulin glargine at a dose equal to (group 1:1) or 1.2 times (group 1:1.2) the mean of their total daily CSII basal insulin dose. Data were obtained by continuous interstitial glucose measurement at baseline and for 7 days of MDI. RESULTS: The switch to MDI was associated with a transient deterioration in glycemic control on day 1 in the 1:1 treatment group, which stabilized thereafter. Glucose variability did not increase significantly from baseline in either group on days 1 and 2 after the switch in treatment but increased significantly on day 4 in the 1:1 group for mean amplitude of glucose excursion and in the 1:1.2 group for SD, M-value, and mean amplitude of glucose excursion. Rates of hypoglycemia did not change significantly in either study group after the switch in treatment, but the 1:1 group showed a trend toward less nocturnal hypoglycemia. There were no episodes of severe hypoglycemia, and patients in both groups experienced significantly less time at glucose values <70 mg/dL on day 1 after the switch in comparison with baseline. CONCLUSION: MDI with insulin glargine and insulin lispro provide a safe transition for patients taking "pump holidays" without clinically significant disruptions of glycemic control. The recommended dose of insulin glargine after the switch in treatment is equal to the total daily basal dose on CSII.

Adolescent↗

Continuous glucose monitoring and external insulin pump: towards a subcutaneous closed loop.

The development of an artificial pancreas for the treatment of type 1 diabetes is a highly desired endeavour for type 1 diabetic patients, physicians, scientists and engineers. The development of the first miniaturized external pumps in the 70s and the pharmacokinetic properties of short acting insulin analogues, closer to physiology, have raised hopes for the elaboration of such a device. Recent technological progress in the development of continuous glucose sensors, have improved the reliability and accuracy of these devices. This has led to the development of prototypes of closed-loop system based on the combination of a continuous monitor, a control algorithm, and an insulin pump. This review focuses on the SC-SC approach, employing subcutaneous glucose monitoring and subcutaneous insulin delivery. The feasibility of this solution has been proven at a small scale, but remains to be confirmed in the home setting. Intermediate solutions, such as semi-automatic systems, might be immediately valuable.

Blood Glucose↗

Microdialysis of subcutaneous adipose tissue in vivo for continuous glucose monitoring in man.

Subcutaneous adipose tissue extracellular glucose was investigated in vivo in man with a microdialysis technique. A small dialysis probe (4 or 10 x 0.5 mm) was implanted subcutaneously, and was perfused continuously with a micro-infusion pump. Dialysate samples were collected in 15-min periods. A transient yield of ATP was recorded immediately after insertion of the probe; thereafter ATP was almost undetectable. During steady-state conditions the tissue dialysate glucose concentration remained constant for at least 2 h, which indicated that there was no drainage of glucose from the interstitial fluid to the tissue dialysate. Simultaneous dialysis of venous blood and subcutaneous fat in rats showed that the recovery of glucose from the adipose tissue interstitial fluid to the dialysate was only 20% of that from blood. However, in vivo dialysis of human adipose tissue with glucose-containing solutions produced an equilibrium with the extracellular space at a glucose concentration that was similar to the blood glucose concentration. After oral glucose ingestion and following i.v. insulin and glucose administration the relative variations in subcutaneous glucose closely resembled those in blood glucose. It is concluded that the subcutaneous implantation of the presently used small dialysis device causes only minor and transient traumatic effects. The dialysis recovery of glucose is lower in adipose tissue than in blood. However, the relative kinetics of subcutaneous tissue dialysate glucose are closely related to variations in the blood glucose concentration, and thus may be used for monitoring of glycaemic control in man.

Adipose Tissue↗

Continuous glucose monitoring and control in a rotating wall perfused bioreactor.

A glucose control system consisting of a single in-line glucose sensor, concentrated glucose solution, and computer hardware and software were developed. The system was applied to continuously control glucose concentrations of a perfusion medium in a rotating wall perfused vessel (RWPV) bioreactor culturing BHK-21 cells. The custom-made glucose sensor was based on a hydrogen peroxide electrode. The sensor continuously and accurately measured the glucose concentration of GTSF-2 medium in the RWPV bioreactor during cell culture. Three sets of two-point calibrations were applied to the glucose sensor during the 55-day cell culture. The system first controlled the glucose concentration in perfusing medium between 4.2 and 5.6 mM for 36 days and then at different glucose levels for 19 days. A stock solution with a high glucose concentration (266 mM) was used as the glucose injection solution. The standard error of prediction (SEP) for glucose measurement by the sensor, compared to measurement by the Beckman glucose analyzer, was +/-0.4 mM for 55 days.

Animals↗

Towards continuous glucose monitoring: in vivo evaluation of a miniaturized glucose sensor implanted for several days in rat subcutaneous tissue.

A miniaturized amperometric, enzymatic, glucose sensor (outer diameter 0.45 mm) was evaluated after implantation in the subcutaneous tissue of normal rats. A simple experimental procedure was designed for the long-term assessment of the sensor's function which was performed by recording the current during an intraperitoneal glucose load. The sensor was calibrated by accounting for the increase in the current during the concomitant increase in plasma glucose concentration, determined in blood sampled at the tail vein. This made it possible to estimate the glucose concentration in subcutaneous tissue. During the glucose load, the change in subcutaneous glucose concentration followed that in blood with a lag time consistently shorter than 5 min. The estimations of subcutaneous glucose concentration during these tests were compared to the concomitant plasma glucose concentrations by using a grid analysis. Three days after implantation (n = 6 experiments), 79 estimations were considered accurate, except for five which were in the acceptable zone. Ten days after implantation (n = 5 experiments), 101 estimations were accurate, except for one value, which was still acceptable. The sensitivity was around 0.5 nA.mmol-1.l-1 on day 3 and day 10. A longitudinal study on seven sensors tested on different days demonstrated a relative stability of the sensor's sensitivity. Finally, histological examination of the zone around the implantation site revealed a fibrotic reaction containing neocapillaries, which could explain the fast response of the sensor to glucose observed in vivo, even on day 10. We conclude that this miniaturized glucose sensor, whose size makes it easily implanted, works for at least ten days after implantation into rat subcutaneous tissue.

Animals↗