A self-controlled study of the effect of continuous subcutaneous insulin infusion on diabetic neuropathy

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.

Insulin pump therapy: a meta-analysis

OBJECTIVE

To conduct a meta-analysis of the metabolic and psychosocial impact of continuous subcutaneous insulin infusion (CSII) therapy on adults, adolescents, and children.

RESEARCH DESIGN AND METHODS

Studies were identified and data regarding study design, year of publication, sample size, patient's age, diabetes duration, and duration of CSII therapy were collected. Means and SDs for glycohemoglobin, blood glucose, insulin dosages, and body weight for CSII and comparison conditions were subjected to meta-analytic procedures. Data regarding pump complications and psychosocial functioning were reviewed descriptively.

RESULTS

A total of 52 studies, consisting of 1,547 patients, were included in the meta-analysis. Results indicate that CSII therapy is associated with significant improvements in glycemic control (decreased glycohemoglobin and mean blood glucose). A descriptive review of potential complications of CSII use (e.g., hypoglycemia, diabetic ketoacidosis [DKA], pump malfunction, and site infections) suggests a decreased frequency of hypoglycemic episodes but an increased frequency of DKA in studies published before 1993.

CONCLUSIONS

CSII therapy is associated with improved glycemic control compared with traditional insulin therapies (conventional therapy and multiple daily injections) and does not appear to be associated with significant adverse outcomes. Additional studies are needed to further examine the relative risks of CSII therapy, including the potential psychosocial impact of this technologically advanced therapy.

Management of diabetic neuropathy

The only strategy shown to be consistently beneficial in the treatment of diabetic neuropathy is meticulous control of blood glucose. The largest study of the effects of glycemic control on progression of neuropathy was the Diabetes Control and Complications Trial, which enrolled 1,500 patients. Meticulous control of blood glucose by multiple injections or continuous subcutaneous infusion both delayed the onset of neuropathy and slowed its progression. A weakness of this and other studies of the effect of glycemic control is that they used surrogate measures of improvement (or slowing of progression) of neurologic function. Most used sensory and motor nerve conduction studies and some used vibration perception thresholds. Whether such measures correlate reliably with neuropathy symptom scores, neurologic examination, quality-of-life measures, neuropathic complications (foot ulcers and amputation), and mortality remains controversial. Also, most studies of tight glycemic control do not address the complications of more intensive therapy, among them severe hypoglycemia. Severe hypoglycemia can precipitate acute painful neuropathy, and it markedly increases axonal degeneration in experimental diabetic neuropathy. Finally, all studies have been confined to patients with mild neuropathy; some patients had no clinical evidence of neuropathy. Whether benefit can accrue to patients with more advanced neuropathy is not known. The most physiologic means of achieving glycemic control is through pancreas transplantation; this can result in significant improvement in clinical and electrophysiologic measures of motor and sensory function and slightly improve autonomic function. Strategies to reduce the metabolic consequences of hyperglycemia on nerves and to enhance axonal regeneration are needed to supplement careful glycemic control. Aldose reductase inhibitors hold promise for reducing metabolic nerve injury, but further study is needed.

Effects of methylcobalamin on diabetic neuropathy

We studied the clinical and neurophysiological effects of methylcobalamin on patients with diabetic neuropathy. In a double-blind study, the active group showed statistical improvement in the somatic and autonomic symptoms with regression of signs of diabetic neuropathy. Motor and sensory nerve conduction studies showed no statistical improvement after 4 months. The drug was easily tolerated by the patients and no side effects were encountered.