Safety of nighttime 2-hour suspension of Basal insulin in pump-treated type 1 diabetes even in the absence of low glucose

Ketone-Based Alert System for Insulin Pump Failures

BACKGROUND

An increasing number of individuals with type 1 diabetes (T1D) manage glycemia with insulin pumps containing short-acting insulin. If insulin delivery is interrupted for even a few hours due to pump or infusion site malfunction, the resulting insulin deficiency can rapidly initiate ketogenesis and diabetic ketoacidosis (DKA).

METHODS

To detect an event of accidental cessation of insulin delivery, we propose the design of ketone-based alert system (K-AS). This system relies on an extended Kalman filter based on plasma 3-beta-hydroxybutyrate (BOHB) measurements to estimate the disturbance acting on the insulin infusion/injection input. The alert system is based on a novel physiological model capable of simulating the ketone body turnover in response to a change in plasma insulin levels. Simulated plasma BOHB levels were compared with plasma BOHB levels available in the literature. We evaluated the performance of the K-AS on 10 in silico subjects using the S2014 UVA/Padova simulator for two different scenarios.

RESULTS

The K-AS achieves an average detection time of 84 and 55.5 minutes in fasting and postprandial conditions, respectively, which compares favorably and improves against a detection time of 193 and 120 minutes, respectively, based on the current guidelines.

CONCLUSIONS

The K-AS leverages the rapid rate of increase of plasma BOHB to achieve short detection time in order to prevent BOHB levels from rising to dangerous levels, without any false-positive alarms. Moreover, the proposed novel insulin-BOHB model will allow us to understand the efficacy of treatment without compromising patient safety.

Restoring normal islet mass and function in type 1 diabetes through regenerative medicine and tissue engineering

Type 1 diabetes is characterised by autoimmune-mediated destruction of pancreatic β-cell mass. With the advent of insulin therapy a century ago, type 1 diabetes changed from a progressive, fatal disease to one that requires lifelong complex self-management. Replacing the lost β-cell mass through transplantation has proven successful, but limited donor supply and need for lifelong immunosuppression restricts widespread use. In this Review, we highlight incremental advances over the past 20 years and remaining challenges in regenerative medicine approaches to restoring β-cell mass and function in type 1 diabetes. We begin by summarising the role of endocrine islets in glucose homoeostasis and how this is altered in disease. We then discuss the potential regenerative capacity of the remaining islet cells and the utility of stem cell-derived β-like cells to restore β-cell function. We conclude with tissue engineering approaches that might improve the engraftment, function, and survival of β-cell replacement therapies.

Fear of hypoglycemia in children with type 1 diabetes and their parents: Effect of pump therapy and continuous glucose monitoring with option of low glucose suspend in the CGM TIME trial

To determine if pump therapy with continuous glucose monitoring offering low glucose suspend (LGS) decreases fear of hypoglycemia among children with type 1 diabetes and their parents. The CGM TIME trial is a multicenter randomized controlled trial that enrolled 144 children with type 1 diabetes for at least 1 year (mean duration 3.4 ± 3.1 years) starting pump therapy (MiniMed™ Veo™, Medtronic Canada). CGM (MiniMed™ Enlite™ sensor) offering LGS was introduced simultaneously or delayed for 6 months. Hypoglycemia Fear Scale (HFS) was completed by children ≥10 years old and all parents, at study entry and 12 months later. Simultaneous and Delayed Group participants were combined for all analyses. Subscale scores were compared with paired t-tests, and individual items with paired Wilcoxon tests. Linear regression examined association with CGM adherence. 121/140 parents and 91/99 children ≥10 years had complete data. Mean Behavior subscale score decreased from 21.1 (SD 5.9) to 17.2 (SD 6.1) (p < .001) for children, and 20.7 (SD 7.5) to 17.4 (7.4) (p < .001) for parents. Mean Worry subscale score decreased from 17.9 (SD 11.9) to 11.9 (SD 11.4) (p < .001) for children, and 23.1 (SD 13.2) to 17.6 (SD 10.4) (p < .001) for parents. Median scores for 10/25 child items and 12/25 parent items were significantly lower at 12 months (p < .001). Linear regression found no association between HFS scores and CGM adherence. Insulin pump therapy with CGM offering LGS significantly reduced fear of hypoglycemia not related to CGM adherence in children with type 1 diabetes and their parents.

Air occlusion in insulin pumps of children and adolescents with type 1 diabetes

Background Insulin pumps are a frequently used technology among youth with type 1 diabetes. Air bubbles within insulin pump tubing are common, preventing insulin delivery and increasing the risk of large glycemic excursions and diabetic ketoacidosis (DKA). We sought to determine the prevalence of air bubbles in insulin pump tubing and identify factors associated with clinically significant air bubbles. Methods Fifty-three subjects were recruited over 65 office visits. The insulin pump tubing was visualized, and any air bubbles were measured by length. The length of air bubbles was then converted to time without insulin at the lowest basal rate. Generalized linear model (GLM) was used to determine the associations between air bubble size and other variables. Results Of the 65 encounters, 45 had air bubbles in the tubing. Five (5/65 = 7.7%) encounters had a time without insulin of more than 60 min. Air bubble size was inversely correlated with time since infusion set change (p < 0.001), and directly correlated with age of the subject (p = 0.049). Conclusions Significantly more air bubbles were found in the tubing of insulin pumps soon after infusion set change and with older subjects, suggesting a relationship with the technique of filling the insulin cartridge and priming the tubing.

A Review of Predictive Low Glucose Suspend and Its Effectiveness in Preventing Nocturnal Hypoglycemia

To evaluate the effectiveness of predictive low glucose suspend (PLGS) systems within sensor-augmented insulin infusion pumps at preventing nocturnal hypoglycemia in patients with type 1 diabetes (DM1), we performed a systematic review and meta-analysis of randomized crossover trials. Pubmed and Google Scholar were searched for randomized crossover trials, published between January 2013 and July 2018, in nonpregnant outpatients with DM1, which compared event rates during PLGS overnight periods and non-PLGS overnight periods. The primary outcome was the proportion of overnight periods with one or more hypoglycemic measurement. When available, individual patient data were used to assess the effect of clustering measurements within patients. Four studies (272 patients, 10,735 patient-nights: 5422 PLGS and 5313 non-PLGS) were included in the meta-analysis. Two studies reported patient-level data that permitted assessment of the effect of clustering measurements within patients. The effect on the risk difference was minimal. The proportion of overnight periods with one or more episodes of hypoglycemia was 19.6% for the PLGS periods and 27.8% for the non-PLGS periods. Based on the pooled estimate, PLGS overnight periods were associated with an 8.8% lower risk of hypoglycemia (risk difference -0.088; 95% CI -0.119 to -0.056, I² = 67.4%, τ² = 0.0006, 4 studies). PLGS systems can reduce nocturnal hypoglycemic events in patients with DM1.

The hypoglycemia-prevention effect of sensor-augmented pump therapy with predictive low glucose management in Japanese patients with type 1 diabetes mellitus: a short-term study

Aims/introduction

The predictive low glucose management (PLGM) system was introduced in March 2018 in Japan. Although there are some reports demonstrating the benefit of PLGM in preventing hypoglycemia, no data are currently available in Japanese patients with type 1 diabetes mellitus (T1DM). The aim of the present study is to evaluate the effect of PLGM with sensor-augmented pump therapy in the prevention of hypoglycemia in Japanese patients.

Materials and methods

We included 16 patients with T1DM who used the MiniMed^®640G system after switching from the MiniMed^®620G system. We retrospectively analysed the data of the continuous glucose monitoring system in 1 month after switching to MiniMed^®640G.

Results

The area under the curve (AUC) of hypoglycemia of < 70 mg/dL was lowered from 0.42 ± 0.43 mg/dL day to 0.18 ± 0.18 mg/dL day (P = 0.012). Correspondingly, the duration of severe hypoglycemia (< 54 mg/dL) was reduced significantly from 15.3 ± 21.7 min/day to 4.8 ± 6.9 min/day (P = 0.019). The duration of hypoglycemia was reduced, but the reduction was not significant. Regarding the AUC for hyperglycemia > 180 mg/dL and the duration of hyperglycemia did not change. With the PLGM function, 79.3% of the predicted hypoglycemic events were avoided.

Conclusions

The hypoglycemia avoidance rate was comparable to those in previous reports. In addition, we demonstrated that PLGM can markedly suppress severe hypoglycemia without deteriorating glycemic control in Japanese T1DM patients. It is necessary to further investigate the effective use of the PLGM feature such as establishing a lower limit and the timing of resumption.

A Technological Revolution: The Integration of New Treatments to Manage Type 1 Diabetes

Intensive insulin treatment and frequent self-monitoring of blood glucose (SMBG) have been recognized as pillars of diabetes treatment. Many patients with type 1 diabetes (T1D) struggle to achieve targeted glycemic control. Technology has vastly changed how these tenets to treatment can occur. Continuous subcutaneous insulin infusion (CSII) pumps and continuous glucose monitoring (CGM) can be used in place of their counterparts, multiple daily injections and SMBG. We present a review of CSII, CGM, and of different levels of integration among these two therapies, ranging from low glucose suspension devices to hybrid closed loop insulin delivery. Analysis of the various tools, their effect on glycemic control, and a guide to integrate them into pediatric clinical practice is presented. Although a cure for T1D remains the ultimate goal, technology holds the promise of keeping youth with T1D in targeted control and minimize the burden of this chronic medical condition. [Pediatr Ann. 2019;48(8):e311-e318.].

Ketone production in children with type 1 diabetes, ages 4-14 years, with and without nocturnal insulin pump suspension

OBJECTIVE

To compare the frequency of elevated morning blood ketone levels according to age in 4-14 year olds with type 1 diabetes following overnight use of an automated low glucose insulin suspension system, or following control nights when the system was not used.

RESEARCH DESIGN AND METHODS

For 28 children ages 4-9 years and 54 youth ages 10-14 years, elevation of morning blood ketone levels was assessed using the Precision Xtra Ketone meter following 1155 and 2345 nights, respectively. Repeated measures logistic regression models were used to compare age groups for blood ketone level elevation following control nights (system not activated) and following intervention nights with and without insulin suspension.

RESULTS

Elevated morning blood ketones (≥0.6 mmol/L) were present following 10% of 580 control nights in the 4-9 year olds compared with 2% of 1162 control nights in 10-14 year olds (P < 0.001). Likewise, the frequency was greater following intervention nights in the younger age group (13% of 575 nights vs 2% of 1183 nights, P < 0.001). A longer duration of pump suspension resulted in a higher percentage of mornings with elevated blood ketones in the younger age group (P = 0.002), but not in the older age group (P = 0.63). The presence of elevated morning ketone levels did not progress to ketoacidosis in any subject.

CONCLUSIONS

Elevated morning blood ketones are more common in younger children with type 1 diabetes with or without nocturnal insulin suspension. Care providers need to be aware of the differences in ketogenesis in younger age children relative to various clinical situations.

Multivariable Adaptive Artificial Pancreas System in Type 1 Diabetes

PURPOSE OF REVIEW

The review summarizes the current state of the artificial pancreas (AP) systems and introduces various new modules that should be included in future AP systems.

RECENT FINDINGS

A fully automated AP must be able to detect and mitigate the effects of meals, exercise, stress and sleep on blood glucose concentrations. This can only be achieved by using a multivariable approach that leverages information from wearable devices that provide real-time streaming data about various physiological variables that indicate imminent changes in blood glucose concentrations caused by meals, exercise, stress and sleep. The development of a fully automated AP will necessitate the design of multivariable and adaptive systems that use information from wearable devices in addition to glucose sensors and modify the models used in their model-predictive alarm and control systems to adapt to the changes in the metabolic state of the user. These AP systems will also integrate modules for controller performance assessment, fault detection and diagnosis, machine learning and classification to interpret various signals and achieve fault-tolerant control. Advances in wearable devices, computational power, and safe and secure communications are enabling the development of fully automated multivariable AP systems.

Prevention of Hypoglycemia With Predictive Low Glucose Insulin Suspension in Children With Type 1 Diabetes: A Randomized Controlled Trial

OBJECTIVE

To investigate whether predictive low glucose management (PLGM) of the MiniMed 640G system significantly reduces the rate of hypoglycemia compared with the sensor-augmented insulin pump in children with type 1 diabetes.

RESEARCH DESIGN AND METHODS

This randomized, two-arm, parallel, controlled, two-center open-label study included 100 children and adolescents with type 1 diabetes and glycated hemoglobin A_1c ≤10% (≤86 mmol/mol) and using continuous subcutaneous insulin infusion. Patients were randomly assigned to either an intervention group with PLGM features enabled (PLGM ON) or a control group (PLGM OFF), in a 1:1 ratio, all using the same type of sensor-augmented insulin pump. The primary end point was the number of hypoglycemic events below 65 mg/dL (3.6 mmol/L), based on sensor glucose readings, during a 14-day study treatment. The analysis was performed by intention to treat for all randomized patients.

RESULTS

The number of hypoglycemic events below 65 mg/dL (3.6 mmol/L) was significantly smaller in the PLGM ON compared with the PLGM OFF group (mean ± SD 4.4 ± 4.5 and 7.4 ± 6.3, respectively; P = 0.008). This was also true when calculated separately for night (P = 0.025) and day (P = 0.022). No severe hypoglycemic events occurred; however, there was a significant increase in time spent above 140 mg/dL (7.8 mmol/L) in the PLGM ON group (P = 0.0165).

CONCLUSIONS

The PLGM insulin suspension was associated with a significantly reduced number of hypoglycemic events. Although this was achieved at the expense of increased time in moderate hyperglycemia, there were no serious adverse effects in young patients with type 1 diabetes.

Modeling Day-to-Day Variability of Glucose-Insulin Regulation Over 12-Week Home Use of Closed-Loop Insulin Delivery

Parameters of physiological models of glucose-insulin regulation in type 1 diabetes have previously been estimated using data collected over short periods of time and lack the quantification of day-to-day variability. We developed a new hierarchical model to relate subcutaneous insulin delivery and carbohydrate intake to continuous glucose monitoring over 12 weeks while describing day-to-day variability. Sensor glucose data sampled every 10-min, insulin aspart delivery and meal intake were analyzed from eight adults with type 1 diabetes (male/female 5/3, age 39.9 ± 9.5 years, BMI 25.4 ± 4.4kg/m², HbA1c 8.4 ± 0.6% ) who underwent a 12-week home study of closed-loop insulin delivery. A compartment model comprised of five linear differential equations; model parameters were estimated using the Markov chain Monte Carlo approach within a hierarchical Bayesian model framework. Physiologically, plausible a posteriori distributions of model parameters including insulin sensitivity, time-to-peak insulin action, time-to-peak gut absorption, and carbohydrate bioavailability, and good model fit were observed. Day-to-day variability of model parameters was estimated in the range of 38-79% for insulin sensitivity and 27-48% for time-to-peak of insulin action. In conclusion, a linear Bayesian hierarchical approach is feasible to describe a 12-week glucose-insulin relationship using conventional clinical data. The model may facilitate in silico testing to aid the development of closed-loop insulin delivery systems.

The artificial pancreas: evaluating risk of hypoglycaemia following errors that can be expected with prolonged at-home use

AIMS

Artificial pancreas systems show benefit in closely monitored at-home studies, but may not have sufficient power to assess safety during infrequent, but expected, system or user errors. The aim of this study was to assess the safety of an artificial pancreas system emulating the β-cell when the glucose value used for control is improperly calibrated and participants forget to administer pre-meal insulin boluses.

METHODS

Artificial pancreas control was performed in a clinic research centre on three separate occasions each lasting from 10 p.m. to 2 p.m. Sensor glucose values normally used for artificial pancreas control were replaced with scaled blood glucose values calculated to be 20% lower than, equal to or 33% higher than the true blood glucose. Safe control was defined as blood glucose between 3.9 and 8.3 mmol/l.

RESULTS

Artificial pancreas control resulted in fasting scaled blood glucose values not different from target (6.67 mmol/l) at any scaling factor. Meal control with scaled blood glucose 33% higher than blood glucose resulted in supplemental carbohydrate to prevent hypoglycaemia in four of six participants during breakfast, and one participant during the night. In all instances, scaled blood glucose reported blood glucose as safe.

CONCLUSIONS

Outpatient trials evaluating artificial pancreas performance based on sensor glucose may not detect hypoglycaemia when sensor glucose reads higher than blood glucose. Because these errors are expected to occur, in-hospital artificial pancreas studies using supplemental carbohydrate in anticipation of hypoglycaemia, which allow safety to be assessed in a controlled non-significant environment should be considered as an alternative. Inpatient studies provide a definitive alternative to model-based computer simulations and can be conducted in parallel with closely monitored outpatient artificial pancreas studies used to assess benefit.

Automated insulin pump suspension for hypoglycaemia mitigation: development, implementation and implications

In type 1 diabetes (T1D), insulin replacement therapy should ideally replicate endogenous insulin secretion, but achieving this goal requires frequent adjustments to insulin delivery based on glucose levels and trends, carbohydrate intake and physical activity. An overriding concern for people taking insulin is hypoglycaemia, which remains the most feared consequence of insulin therapy and limits therapy intensification options. Although fully automated systems that achieve consistent euglycaemia in T1D remain an elusive goal, improvements in continuous glucose monitoring (CGM) sensors and control algorithms have enabled semi-automated systems that lower the risk of hypoglycaemia, especially nocturnal hypoglycaemia. The present review focuses on an important advance in insulin delivery systems: the use of CGM data to stop insulin delivery in the presence of hypoglycaemia. Although conceptually simple, this strategy represents a critical step in the journey toward a fully closed-loop artificial pancreas; the next steps in this journey are also discussed.

Hypoglycemia Reduction and Changes in Hemoglobin A1c in the ASPIRE In-Home Study

BACKGROUND

ASPIRE In-Home randomized 247 subjects with type 1 diabetes to sensor-augmented pump therapy with or without the Threshold Suspend (TS) feature, which interrupts insulin delivery at a preset sensor glucose value. We studied the effects of TS on nocturnal hypoglycemia (NH) in relation to baseline hemoglobin A1c (A1C) and change in A1C during the study.

MATERIALS AND METHODS

NH event rates and mean area under curve (AUC) of NH events were evaluated at different levels of baseline A1C (<7%, 7-8%, and >8%) and at different levels of changes in A1C (less than -0.3% [decreased], -0.3% to 0.3% [stable], and >0.3% [increased]), in the TS Group compared with the Control Group (sensor-augmented pump only).

RESULTS

In the TS Group, 27.9% of the NH events were accompanied by a confirmatory blood glucose value, compared with 39.3% in the Control Group. Among subjects with baseline A1C levels of <7% or 7-8%, those in the TS Group had significantly lower NH event rates than those in the Control Group (P=0.001 and P=0.004, respectively). Among subjects with decreased or stable A1C levels, those in the TS Group had significantly lower NH event rates, and the events had lower AUCs (P≤0.001 for each). Among subjects with increased A1C levels, those in the TS Group had NH events with significantly lower AUCs (P<0.001).

CONCLUSIONS

Use of the TS feature was associated with decreases in the rate and severity (as measured by AUC) of NH events in many subjects, including those with low baseline A1C levels and those whose A1C values decreased during the study period. Use of the TS feature can help protect against hypoglycemia in those wishing to intensify diabetes management to achieve target glucose levels.

Experience with the Enlite sensor in a multicenter pediatric study

PURPOSE

The purpose of this article is to outline the experience of certified diabetes educators (CDEs) using the Enlite continuous glucose monitoring sensor system in a pediatric multicenter randomized controlled trial. Continuous glucose monitoring (CGM) is becoming popular as a tool for educators and families to improve glycemic control. CGM can be a valuable educational tool to demonstrate to the user the impact of insulin dosing and effects of physical activity, food intake, and other life events such as work, illness, and stress on their glycemic control. The authors will share education tips and practical applications for diabetes educators to facilitate education and sustained use of Enlite glucose sensors in children and adolescents using insulin pump therapy.

CONCLUSIONS

The Enlite glucose sensor is a comfortable and user-friendly device. Improvements to both the insertion device and the Enlite glucose sensor have resulted in improved level of comfort on insertion and with ongoing wear, which may translate into greater adherence and effectiveness.

Accuracy of a new patch pump based on a microelectromechanical system (MEMS) compared to other commercially available insulin pumps: results of the first in vitro and in vivo studies

The JewelPUMP™ (JP) is a new patch pump based on a microelectromechanical system that operates without any plunger. The study aimed to evaluate the infusion accuracy of the JP in vitro and in vivo. For the in vitro studies, commercially available pumps meeting the ISO standard were compared to the JP: the MiniMed® Paradigm® 712 (MP), Accu-Chek® Combo (AC), OmniPod® (OP), Animas® Vibe™ (AN). Pump accuracy was measured over 24 hours using a continuous microweighing method, at 0.1 and 1 IU/h basal rates. The occlusion alarm threshold was measured after a catheter occlusion. The JP, filled with physiological serum, was then tested in 13 patients with type 1 diabetes simultaneously with their own pump for 2 days. The weight difference was used to calculate the infused insulin volume. The JP showed reduced absolute median error rate in vitro over a 15-minute observation window compared to other pumps (1 IU/h): ±1.02% (JP) vs ±1.60% (AN), ±1.66% (AC), ±2.22% (MP), and ±4.63% (OP), P < .0001. But there was no difference over 24 hours. At 0.5 IU/h, the JP was able to detect an occlusion earlier than other pumps: 21 (19; 25) minutes vs 90 (85; 95), 58 (42; 74), and 143 (132; 218) minutes (AN, AC, MP), P < .05 vs AN and MP. In patients, the 24-hour flow error was not significantly different between the JP and usual pumps (-2.2 ± 5.6% vs -0.37 ± 4.0%, P = .25). The JP was found to be easier to wear than conventional pumps. The JP is more precise over a short time period, more sensitive to catheter occlusion, well accepted by patients, and consequently, of potential interest for a closed-loop insulin delivery system.

Quantification of the glycemic response to microdoses of subcutaneous glucagon at varying insulin levels

OBJECTIVE

Glucagon delivery in closed-loop control of type 1 diabetes is effective in minimizing hypoglycemia. However, high insulin concentration lowers the hyperglycemic effect of glucagon, and small doses of glucagon in this setting are ineffective. There are no studies clearly defining the relationship between insulin levels, subcutaneous glucagon, and blood glucose.

RESEARCH DESIGN AND METHODS

Using a euglycemic clamp technique in 11 subjects with type 1 diabetes, we examined endogenous glucose production (EGP) of glucagon (25, 75, 125, and 175 μg) at three insulin infusion rates (0.016, 0.032, and 0.05 units/kg/h) in a randomized, crossover study. Infused 6,6-dideuterated glucose was measured every 10 min, and EGP was determined using a validated glucoregulatory model. Area under the curve (AUC) for glucose production was the primary outcome, estimated over 60 min.

RESULTS

At low insulin levels, EGP rose proportionately with glucagon dose, from 5 ± 68 to 112 ± 152 mg/kg (P = 0.038 linear trend), whereas at high levels, there was no increase in glucose output (19 ± 53 to 26 ± 38 mg/kg, P = NS). Peak glucagon serum levels and AUC correlated well with dose (r2 = 0.63, P < 0.001), as did insulin levels with insulin infusion rates (r2 = 0.59, P < 0.001).

CONCLUSIONS

EGP increases steeply with glucagon doses between 25 and 175 μg at lower insulin infusion rates. However, high insulin infusion rates prevent these doses of glucagon from significantly increasing glucose output and may reduce glucagon effectiveness in preventing hypoglycemia when used in the artificial pancreas.

Closed-loop system in the management of diabetes: past, present, and future

Intensive insulin therapy (IIT) has been shown to reduce micro- and macrovascular complications in patients with type 1 diabetes mellitus (T1DM). However, IIT is associated with a significant increase in severe hypoglycemic events, resulting in increased morbidity and mortality. Optimization of glycemic control without hypoglycemia (especially nocturnal) should be the next major goal for subjects on insulin treatment. The use of insulin pumps along with continuous glucose monitors (CGMs) has made it easier but requires significant resources and patient education. Research is ongoing to close the loop by integrating the pump and the CGM using different algorithms. The currently available closed-loop system is the threshold suspend. Steps needed to achieve a near-perfect closed-loop are (1) a control-to-range system that will reduce the incidence and/or severity of hyper- and/or hypoglycemia by adjusting the insulin dose and (2) a control-to-target system, a fully automated or hybrid system that sets target glucose levels to individual needs and maintains glucose levels throughout the day using insulin (unihormonal) alone or with other hormones such as glucagon or possibly pramlintide (bihormonal). Future research is also focusing on better insulin delivery devices (pumps), more accurate CGMs, better predictive algorithms, and ultra-rapid-acting insulin analogs to make the closed-loop system as physiological as possible.

A randomized trial of a home system to reduce nocturnal hypoglycemia in type 1 diabetes

OBJECTIVE

Overnight hypoglycemia occurs frequently in individuals with type 1 diabetes and can result in loss of consciousness, seizure, or even death. We conducted an in-home randomized trial to determine whether nocturnal hypoglycemia could be safely reduced by temporarily suspending pump insulin delivery when hypoglycemia was predicted by an algorithm based on continuous glucose monitoring (CGM) glucose levels.

RESEARCH DESIGN AND METHODS

Following an initial run-in phase, a 42-night trial was conducted in 45 individuals aged 15-45 years with type 1 diabetes in which each night was assigned randomly to either having the predictive low-glucose suspend system active (intervention night) or inactive (control night). The primary outcome was the proportion of nights in which ≥1 CGM glucose values ≤60 mg/dL occurred.

RESULTS

Overnight hypoglycemia with at least one CGM value ≤60 mg/dL occurred on 196 of 942 (21%) intervention nights versus 322 of 970 (33%) control nights (odds ratio 0.52 [95% CI 0.43-0.64]; P < 0.001). Median hypoglycemia area under the curve was reduced by 81%, and hypoglycemia lasting >2 h was reduced by 74%. Overnight sensor glucose was >180 mg/dL during 57% of control nights and 59% of intervention nights (P = 0.17), while morning blood glucose was >180 mg/dL following 21% and 27% of nights, respectively (P < 0.001), and >250 mg/dL following 6% and 6%, respectively. Morning ketosis was present <1% of the time in each arm.

CONCLUSIONS

Use of a nocturnal low-glucose suspend system can substantially reduce overnight hypoglycemia without an increase in morning ketosis.

Frequency of morning ketosis after overnight insulin suspension using an automated nocturnal predictive low glucose suspend system

OBJECTIVE

To assess the effect of overnight insulin pump suspension in an automated predictive low glucose suspend system on morning blood glucose and ketone levels in an attempt to determine whether routine measurement of ketone levels is useful when a closed-loop system that suspends insulin delivery overnight is being used.

RESEARCH DESIGN AND METHODS

Data from an in-home randomized trial of 45 individuals with type 1 diabetes (age range 15-45 years) were analyzed, evaluating an automated predictive low glucose pump suspension system in which blood glucose, blood ketone, and urine ketone levels were measured on 1,954 mornings.

RESULTS

One or more pump suspensions occurred during 744 of the 977 intervention nights (76%). The morning blood ketone level was ≥0.6 mmol/L after 11 of the 744 nights (1.5%) during which a pump suspension occurred and 2 of the 233 nights (0.9%) during which there was no suspension compared with 11 of 977 control nights (1.1%). The morning blood ketone level was ≥0.6 mmol/L after only 2 of 159 nights (1.3%) with a pump suspension exceeding 2 h. Morning fasting blood glucose level was not a good predictor of the presence of blood ketones.

CONCLUSIONS

Routine measurement of blood or urine ketones during use of an automated pump suspension system using continuous glucose monitoring, whether threshold based or predictive, is not necessary. Recommendations for checking ketone levels should be no different when a patient is using a system with automated insulin suspension than it is for conventional diabetes self-management.