Continuous subcutaneous insulin infusion:good blood glucose control for up to 4 days

Glycaemic control and novel technology management strategies in pregestational diabetes mellitus

Introduction

Pregestational diabetes (PGDM) is an increasingly common and complex condition that infers risk to both mother and infant. To prevent serious morbidity, strict glycaemic control is essential. The aim of this review is to review the glucose sensing and insulin delivering technologies currently available for women with PGDM.

Methods

We reviewed online databases for articles relating to technology use in pregnancy using a combination of keywords and MeSH headings. Relevant articles are included below.

Results

A number of technological advancements have improved care and outcomes for women with PGDM. Real time continuous glucose monitoring (rtCGM) offers clear advantages in terms of infants size and neonatal intensive care unit admissions; and further benefits are seen when combined with continuous subcutaneous insulin delivery (insulin pump) and algorithms which continuously adjust insulin levels to glucose targets (hybrid closed loop). Other advancements including flash or intermittent scanning CGM (isCGM) and stand-alone insulin pumps do not confer as many advantages for women and their infants, however they are increasingly used outside of pregnancy and many women enter pregnancy already using these devices.

Discussion

This article offers a discussion of the most commonly used technologies in pregnancy and evaluates their current and future roles.

Continuous subcutaneous insulin infusion (CSII) versus multiple insulin injections for type 1 diabetes mellitus

BACKGROUND

Type 1 diabetes is a metabolic disorder resulting from a defect in insulin secretion. Onset of type 1 diabetes mellitus may occur at any age and it is one of the most common chronic diseases of childhood and adolescence. Since there are no interventions known to prevent onset, it is vital that effective treatment regimes are available. Glycaemic control is maintained by replacement of insulin and may be in the form of 'conventional' insulin therapy (multiple injections per day) or continuous subcutaneous insulin infusion (CSII).

OBJECTIVES

To assess the effects of CSII compared to multiple insulin injections (MI) in people with type 1 diabetes mellitus.

SEARCH STRATEGY

Studies were obtained from electronic searches of The Cochrane Library, MEDLINE, EMBASE and CINAHL.

SELECTION CRITERIA

Studies were included if they were randomised controlled trials comparing CSII with three or more insulin injections per day (MI) in people with type 1 diabetes mellitus.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed risk of bias and extracted characteristics of included studies. Authors contacted study investigators to obtain missing information. Generic inverse variance meta-analyses using a random-effects model were performed.

MAIN RESULTS

Twenty three studies randomised 976 participants with type 1 diabetes to either intervention. There was a statistically significant difference in glycosylated haemoglobin A1c (HbA1c) favouring CSII (weighted mean difference -0.3% (95% confidence interval -0.1 to -0.4). There were no obvious differences between the interventions for non-severe hypoglycaemia, but severe hypoglycaemia appeared to be reduced in those using CSII. Quality of life measures suggest that CSII is preferred over MI. No significant difference was found for weight. Adverse events were not well reported, no information is available on mortality, morbidity and costs.

AUTHORS' CONCLUSIONS

There is some evidence to suggest that CSII may be better than MI for glycaemic control in people with type 1 diabetes. Non-severe hypoglycaemic events do not appear to be reduced with CSII. There is insufficient evidence regarding adverse events, mortality, morbidity and costs.

24-hour blood glucose profiles in insulin-dependent diabetics treated with intravenous insulin infusion systems. A comparison between closed- and open-loop systems

The aim of this study was to compare the 24-hour blood glucose profiles of insulin-dependent diabetics during treatment with preprogramed insulin delivery systems with those of patients on treatment with the artificial beta cell (Biostator). Mean blood glucose (MGB) was 4.4 +/- 0.5 mmol/l for 15 controls, 5.8 +/- 1.0 for 53 patients on open-loop and 6.0 +/- 0.6 for 20 patients on closed-loop treatment. MBG was significantly higher in diabetics than in non-diabetic, but the difference between the two diabetic populations was not significant. Mean amplitude of blood glucose excursion was 1.8 +/- 0.6, 4.3 +/- 1.3 and 3.5 +/- 0.8 mmol/l respectively, the difference between the diabetic groups being significant. No hypoglycemia was seen in patients during closed-loop treatment, whereas this was the case in 10 of 53 patients on treatment with open-loop systems. Physical exercise resulted in small but normal decreases in blood glucose without hypoglycemia. Plasma insulin was within the normal range during both regimes. It is concluded that blood glucose control during treatment with closed-loop system is superior to that during treatment with open-loop systems. However, under standard conditions i.v. insulin infusion with preprogramed pump devices resulted in blood glucose fluctuations comparable with those during Biostator treatment.

Short-term subcutaneous insulin infusion in diabetic children. Comparison with three daily insulin injections

Sixteen insulin-dependent diabetic children and adolescents were studied on intensified insulin treatment (3II) and during continuous subcutaneous insulin infusion (CSII). Mean blood glucose, M-value and 24-h glycosuria were similar in both types of treatment. Symptomatic hypoglycemia occurred more often in patients on 3II than CSII. With 3II we observed blood glucose peaks early in the morning confirming that better overnight control can be achieved by CSII.

The metabolic and hormonal response to acute normoglycaemia in type 1 (insulin-dependent) diabetes: studies with a glucose controlled insulin infusion system (artificial endocrine pancreas)

Twelve insulin deficient Type 1 (insulin-dependent) diabetic subjects were studied over an 11 1/2 h period during both subcutaneous insulin therapy and closed loop insulin delivery, using a glucose controlled insulin system (Biostator) programmed to maintain normoglycaemia. Results were compared with those from 21 age and weight-matched normal subjects. Using the Biostator, normoglycaemia was achieved in all diabetic subjects within 3.5 h and normal profiles maintained thereafter. Blood metabolite and hormone values were evaluated during the subsequent 8 h normoglycaemic period. Subcutaneous therapy resulted in abnormal glucose levels throughout the study period (mean 8 h value 8.3 +/- 0.7 compared with 5.6 +/- 0.3 mmol/l on feedback control and 5.5 +/- 0.1 mmol/l in normal subjects). The mean value of lactate and pyruvate over the final 8 h period was 25% higher in diabetic patients than in normal subjects with no difference between the two insulin treatments (blood lactate: 0.94 +/- 0.04 on subcutaneous insulin, 0.91 +/- 0.04 on feedback control and 0.74 +/- 0.03 mmol/l in control subjects). The pre-prandial peaks of blood glycerol and plasma non-esterified fatty acids were significantly decreased or absent during both feedback control and subcutaneous therapy in comparison with the normal subjects, whereas after the midday and evening meals, total ketone body levels were significantly higher in the diabetic patients. Peripheral serum free insulin levels were two-to fourfold greater in the diabetic than in the normal subjects. There were no significant differences between levels in diabetic patients receiving subcutaneous insulin or on the Biostator. Glucose turnover (1600-1800 h) was normal on feedback control (1.41 +/- 0.20 versus 1.55 +/- 0.18 mg X kg-1 X min-1 in the normal subjects) but was significantly decreased during subcutaneous insulin (1.04 +/- 0.09 mg X kg-1 X min-1). There was, in addition, a decrease in glucose recycling during both subcutaneous insulin therapy and feedback control in the diabetic subjects. These data suggest that although fine control of glucose metabolism both in terms of circulating concentrations and rates of production can be achieved by feedback-control, insulin infusion by the peripheral route is associated with significant metabolic abnormalities, at least in the short term. Longer term studies and examination of portal insulin delivery seem warranted.

Reversal of diabetic retinopathy by continuous subcutaneous insulin infusion: a case report

We report the case history of a 20-year-old diabetic girl with long-standing poorly controlled disease who presented with severe retinopathic features and who was treated with continuous subcutaneous insulin infusion (CSII). When first seen she had macular oedema and a visual acuity of 6/18 in her only eye, together with multiple blot haemorrhages and intraretinal microvascular abnormalities. Marked reversal of the retinal lesions occurred within 65 days of initiating SCII and after only 36 days of constant normoglycaemia. Subsequent good blood glucose control on conventional subcutaneous insulin injections has been achieved, and the retinopathy remains quiescent with a visual acuity of 6/5. We suggest that CSII may be a potentially useful method of arresting and reversing early diabetic retinopathy.

Continuous subcutaneous insulin infusion: comparison of plasma insulin profiles after infusion or bolus injection of the mealtime dose

To help optimize meal-time blood glucose control in diabetic patients by continuous subcutaneous insulin infusion we have studied plasma insulin profiles in six normal subjects, suppressing endogenous insulin secretion with somatostatin. Insulin was administered subcutaneously either as a bolus or by high-rate infusion. Mean infusion profiles were similar on the two occasions, with peak levels at 75 and 90 min respectively, and a linear decline to 34% and 36% of peak concentrations at 5 h. Bolus injection resulted in a faster rise in insulin concentration, more consistent with physiological requirements. It is concluded that bolus delivery would be similar in effect while mechanically simpler to achieve than infusion, when part of a dual rate subcutaneous infusion system. The dose should be given 30 min before meals, if peak insulin concentrations are to be coincident with those found physiologically. Insulin concentrations remain high in the post-absorptive phase.

Patient reactions to long-term outpatient treatment with continuous subcutaneous insulin infusion

Fourteen of the first 15 insulin-dependent diabetics to be treated in our unit by three weeks or more of outpatient continuous subcutaneous insulin infusion with a portable syringe pump completed a questionnaire about their reactions to the system. Motivation was more important to a favourable response than occupation or intelligence. Most patients thought that diabetic control was better with the pump than conventional injection treatment and several felt subjectively better. Features such as the greater flexibility of diet and insulin delivery rates during continuous subcutaneous infusion were appreciated. The most consistent adverse criticism was about the size of the device used, nearly all patients thinking that smaller and lighter infusion systems should be developed. Psychological reactions to the infusion and difficulties with interpersonal relationships were identified; these must be clearly appreciated and discussed with patients and family before and during treatment. Nine of the 14 patients said they would undertake continuous subcutaneous infusion for one year and a further two said they would do so if the infuser was smaller. These results provide guidance on future technological development of continuous subcutaneous insulin infusion and indicate that the major constraint to long-term trials of the present system is the size of the pump.

Management of severely brittle diabetes by continuous subcutaneous and intramuscular insulin infusions: evidence for a defect in subcutaneous insulin absorption

Severely brittle diabetes is defined as a rare subtype of insulin-dependent diabetes with wide, fast, unpredictable, and inexplicable swings in blood glucose concentration, often culminating in ketoacidosis or hypoglycaemic coma. To assess the role of inappropriate type, amount, or timing of insulin treatment and the route of administration as a cause of severe brittleness six patients with continuous subcutaneous insulin infusion, which provides a high degree of optimisation of dosage with exogenous insulin in stable diabetics. The glycaemic control achieved during continuous subcutaneous insulin infusion was compared with that during continuous intramuscular insulin infusion. Six patients with non-brittle diabetes were also treated by continuous subcutaneous insulin infusion. These patients achieved the expected improvement in glycaemic control (mean +/- SD plasma glucose concentration 5.1 +/- 2.3 mmol/l (92 +/- 41 mg/100 ml)), but not the patients with brittle diabetes remained uncontrolled with continuous subcutaneous infusion (13.6 +/- 5.8 mmol/1 (245 +/- 105 mg/100 ml) compared with 10.3 +/- 4.1 mmol/l (186 +/- 74 mg/100 ml) during treatment with optimised conventional subcutaneous injections). During continuous intramuscular infusion, however, glycaemic control in five of the patients with brittle diabetes was significantly improved (7.7 +/- 2.6 mmol/l (139 +/- 47 mg/100 ml). The remaining patient with brittle diabetes, previously safely controlled only with continuous intravenous insulin, did not respond to continuous intramuscular infusion. It is concluded that in five of the six patients with brittle diabetes studied here impaired or irregular absorption of insulin from the subcutaneous site played a more important part in their hyperlability than inappropriate injection strategies. This absorption defect was presumably bypassed by the intramuscular route.

Comparison between multi-injection and continuous subcutaneous insulin therapy in insulin-dependent diabetic inpatients

Circadian blood glucose profiles have been evaluated in 8 insulin-dependent diabetic inpatients on their usual home insulin therapy, on a 3-injection regimen (ultralente in the morning plus 3 injections of regular insulin at meals), on continuous subcutaneous insulin infusion by portable micropumps (Mill Hill 1001) and, again, on a 3-injection regimen at the same insulin dose as during continuous subcutaneous insulin infusion. The 3-injection regimen achieved a mean daily blood glucose level comparable to that obtained by continuous subcutaneous insulin infusion, even if significantly more insulin was needed. At comparable insulin doses, continuous subcutaneous insulin infusion provided a significantly lower mean daily blood glucose. Glycemic control at 0600 and 0800 was better during continuous subcutaneous insulin infusion. Low acceptance by the patients of the home use of portable micropumps was evidenced because of the practical and psychological problems involved.

The role of open-loop systems in the treatment of diabetes

In most insulin-dependent diabetics it is very difficult to achieve and maintain metabolic near-normalisation using conventional insulin injections. It is this deficiency which makes us still uncertain whether diabetic microangiopathy can be prevented, slowed or reversed by strict diabetic control.

Improvement of glucose homeostasis in insulin-dependent diabetics using a miniature insulin infusion pump with a fixed profile

Glucose homeostasis was studied in nine longstanding insulin-dependent diabetic patients using a portable pump for intravenous insulin infusion. The 24 h infusion dose was calculated from the conventional SC insulin treatment. The range of basal infusion rates was 2.5 to 15 mU/min and peak delivery rates were raised up to 16-fold from start of main meals for 30-60 minutes. Mean blood glucose improved from 12.0 +/- 2.4 to 6.4 +/- 1.0 mmol/l (SD) during infusion (p less than 0.01). Glucose excretion decreased from 23 g/24 h (range 1-42) to 4 g/24 h (range 0-14) (p less than 0.01). Mean amplitude of glycaemic excursions was significantly improved during infusion (from 8.9 +/- 4.8 to 4.7 +/- 0.9 mmol/l; p less than 0.01). No severe hypoglycaemic episodes or other adverse reactions were seen.

Long-term continuous subcutaneous insulin infusion in diabetics at home

6 insulin-requiring diabetics were treated at home with continuous, long-term, dual-rate subcutaneous insulin infusion (CSII) by means of a portable syringe pump. The duration of infusion was 48--111 days. Patients were initially stabilised on CSII in hospital and then allowed home, where capillary-blood glucose control was monitored by the patients with glucose-oxidase reagent strips. Patients diluted and changed their own insulin for the pump, adjusting the dose according to the control achieved. Mean (+/- SD) blood-glucose values ranged from 4.8 +/- 1.6 to 7.5 +/- 1.6 mmol/l. In 1 longstanding diabetic insulin requirements fell from 92 U/day to about 35 U/day on CSII. 2 newly diagnosed juvenile-onset diabetics were also infused: in 1 patient requirements fell to zero after 48 days and in the other the dose fell to 14 J/day after 51 days of CSII. No cannula-site infection or significant palpable lipodystrophy was experienced. Patients treated with "open-loop" systems have little or no insulin reserve: potential loss of control--for example, during intercurrent illness-demands careful metabolic monitoring and prompt correction.