Ever since the introduction of insulin glargine (Lantus; Aventis Pharmaceuticals Inc. Kansas City, Missouri), many of my patients have noticed a significant improvement in their diabetes control. I'm wondering if there is much of a need for insulin pumps any longer?
Response from M. James Lenhard, MD, 03/13/2003
In 1993, the Diabetes Control and Complications Trial (DCCT) definitively showed that achieving and maintaining glucose values as close to normal as possible in people with type 1 diabetes will prevent the development and slow the progression of microvascular complications. In the years following the release of the DCCT, there was a rapid increase in the number of prescriptions for insulin pumps. Continuous subcutaneous insulin infusion (CSII) continued to become increasingly common throughout the 1990s. CSII allows the user to program increases or decreases in insulin infusion based on patterns or perceived needs. In addition to providing multiple programmable basal rates, CSII allows the user to choose from several "types" of mealtime boluses. The insulin can be delivered quickly or stretched out over a protracted time in an attempt to mimic the normal pancreatic secretion of insulin.
In 2000, insulin glargine was approved for use as a basal insulin. It has become very popular for patients with type 1 diabetes. Studies have suggested that the basal insulin profile obtained from glargine is superior to NPH or Ultralente insulin, with a reduction in the incidence of hypoglycemia. Many patients have reported significant success with glargine, and it has been dubbed the "poor man's pump." So which method is optimal?
Unfortunately, there are no long-term studies comparing CSII with glargine. It would appear that for many patients with type 1 diabetes, there is little compelling reason to use anything other than glargine to supply basal insulin. Cost, availability on formularies, the inability to mix it with other kinds of insulin, and rare adverse reactions may lead some patients to stick with NPH, but for the majority, glargine will be superior.
Over the last 2 decades numerous studies have shown that CSII helped to achieve the goal of maintaining glucose levels as close to the normal range as is safely possible. Many studies compared CSII to conventional therapy (For example: 2 split and mixed injections per day). The best comparisons between CSII and standard insulin injections are studies using multiple daily injections (MDI). There are several advantages and disadvantages of CSII.
Advantages of CSII
Glycemic control: Most studies have shown that CSII provides as good and often better glycemic control than does intensive diabetes management with MDI. Most studies suggest that the improvement is modest. For example, 1 study of 107 patients with type 1 diabetes treated with MDI that were switched to CSII had a decline in the mean HbA1c from 7.6 to 7.1%.
Hypoglycemia: The reduction in the variability of glucose levels and severe hypoglycemia may be reduced as much as 4-fold with CSII in comparison with MDI, with no discernible reduction in glycemic control. This decrease in hypoglycemic events has been accompanied by an increase in self-reported warning symptoms of hypoglycemia, as well as by an increase in counterregulatory hormonal responses to hypoglycemia. Severe hypoglycemia has now become an accepted indication for initiation of CSII therapy, and may be the greatest advantage offered by CSII.
Other metabolic factors and diabetes complications: CSII has been shown to cause improvement or slowing of diabetic nephropathy, peripheral and autonomic neuropathy, retinopathy, hypertriglyceridemia and hypoalphalipoproteinemia, and diabetic changes in transplanted kidneys.
Lifestyle flexibility: The improvement in lifestyle may be the most important reason for the patient who chooses CSII. The ability to increase flexibility in moment-to-moment living is the reason most frequently cited by individuals who have chosen CSII. The increased flexibility that is allowed may be fueling the upsurge in patient demand for CSII more than any other factor.
Disadvantages of CSII
As recently as 1990, some authorities asserted that "the use of CSII is discouraged in routine clinical practice," suggesting instead that it be limited to specific subsets of patients with type 1 diabetes. There are several potential disadvantages of CSII.
Diabetic ketoacidosis: There is no subcutaneous depot of long-acting insulin with CSII. If the flow of the regular, short-acting insulin is interrupted, ketonemia and diabetic ketoacidosis can develop more rapidly and more frequently with CSII.
Hypoglycemia: Although hypoglycemia is generally less common with CSII than with MDI, proper use of the insulin pump requires the user to monitor glucose frequently and to work with the diabetes team to program the appropriate basal infusion rates. Without patient cooperation, hypoglycemia may occur.
Catheter-site infection and contact dermatitis: The most common complication associated with CSII is infection at the infusion site. This is one of the most common causes listed for discontinuation of CSII, but most cases can be prevented with close attention to hygiene.
In addition to the advantages and disadvantages listed, there are several special situations where CSII may be preferred. Some children and adolescents have improved acceptance of their diabetes and better glycemic control when CSII is used. Pregnant women with type 1 diabetes may find less variability in their blood glucose levels. People with type 1 diabetes who engage in regular vigorous exercise often appreciate the ability to control their insulin infusion very precisely.
The key to success with CSII involves the appropriate selection and training of individuals. For the successful use of CSII, a skilled and motivated health care delivery team is required, and a thorough evaluation and training of the CSII candidate is necessary prior to implementation. There is also a need for on-going close contact between the pump user and the health care team. For many patients, the disadvantages and costs of CSII outweigh the advantages. In this group, MDI using insulin glargine may prove to be equally effective.
M. James Lenhard, MD,
Medical Director, Weight Management
Program, Preventative Medicine and Rehabilitation Institute and Chief,
Section of Endocrinology, Christiana Care Health Systems, Wilmington, Delaware.
1. Ratner RE, Hirsch IB, Neifing JL, Garg SK, Mecca TE, Wilson CA. Less hypoglycemia with insulin glargine in intensive insulin therapy for type 1 diabetes: US Study Group of Insulin Glargine in Type 1 Diabetes. Diabetes Care. 2000; 23:639-643. Abstract
2. Lenhard MJ, Reeves GD. Continuous subcutaneous insulin infusion: a comprehensive review of insulin pump therapy. Arch Intern Med. 2001;161:2293-2300. Abstract
3. Rudolph JW, Hirsch IB. Assessment of therapy with continuos subcutaneous insulin infusion in an academic diabetes clinic. Endocr Pract. 2002;8:401-405.
4. Selam J-L, Charles MA. Devices for insulin administration. Diabetes Care. 1990;13:955-979. Abstract
Medscape Diabetes & Endocrinology 5(1), 2003. © 2003 Medscape