It's easy to live a Flexible Life
..with Medtronic Insulin Pump Therapy

EVOLUTION OF INSULIN PUMP THERAPY

The idea of continuous insulin delivery first emerged in the early 1960s when Dr Arnold Kadish from Los Angeles fashioned a device that would permit such insulin delivery. This device was the size of an army backpack making it impractical for everyday use. The consensus that insulin replacement should be more physiologic grew during the 70s, leading investigators to further pursue how to achieve this, first by employing continuous intravenous insulin delivery, and then by the more practical means of continuous subcutaneous insulin infusion (CSII).

In 1978, Keen and Pickup from Guy's Hospital, London first reported the successful use of portable pumps for CSII (followed in 1979 by Tamborlane and Felig of Yale). These early studies demonstrated that CSII, when used with self-monitoring of blood glucose, could feasibly achieve near normal glycaemic control. This became known as "Intensive Insulin Therapy".

These early insulin pumps - though a vast improvement on the Kadish device - were bulky, being the size of a house brick and weighing up to 400grams. Their batteries needed to be recharged or changed on a regular basis, they had few safety alarms, offered very little flexibility in the rate of basal insulin delivery, and used infusion sets with metal needles, which required the use of diluted insulin.

Technical issues such as syringe and tubing blockages, over-delivery of insulin and needle dislodgment were widely reported.

These problems led to clinical complications including, hypoglycaemia, diabetic ketoacidosis (DKA) and needle site infection, resulting in only limited acceptance throughout the 80s by both clinicians and patients.

CSII in the DIABETES CONTROL and COMPLICATIONS TRIAL (DCCT STYDY)

During the years of the DCCT ran, and certainly by its completion in 1993, many of the inherent "equipment related" problems of CSII had begun to be addressed by advancements in technology. Pumps had become smaller (to "pager size"), with multiple in-built safety alarms, were more compatible with buffered insulins, had long-life batteries and were easier to use. Plastic catheter type infusion sets had also been developed, dramatically reducing the problem of site infection.

During the DCCT study, 59 percent of intensively-treated subjects tried CSII for some period of time, with 34 percent using CSII on an on-going, long-term basis. In 1992, the last full year of the study, 42 percent of subjects used CSII and achieved 0.2 to 0.4 percent lower HbA1C levels than those subjects using multiple daily injections (MDI). This improvement can best be explained by the rationale that CSII, provides a more physiologic mode of insulin delivery by utilising a continuous baseline infusion ("basal rate") of short acting regular insulin supplemented by mealtime boluses.

The DCCT investigators, during the presentation of results, stated that CSII facilitated glycaemic control and provided greater flexibility in lifestyle.

These findings, and the widespread implementation of intensive therapy, reawakened interest in pumps and the potential advantages of CSII.

ADVANTAGES AND UTILITY OF CSII

Today’s insulin pumps provide a wide range of basal and bolus delivery options with memory and alarms. The insulin is stored inside a reservoir in the pump and delivered to the patient by means of an infusion set implanted into the subcutaneous tissue of the abdomen.

The insertion cannula is either a teflon cannula or a stainless steel needle that is replaced by the patient every 3 days. The patient is able to disconnect from the pump temporarily for bathing or exercise.

The major advantages of CSII when compared with multiple daily injections, are derived primarily from its pharmokinetic effects which include:

  • Using only rapid-acting regular insulin, which appears to provide a more consistent, reproducible absorption pattern. Absorption variance from 10-52 percent occurs with each injected dose of intermediate -acting insulin compared to 2.8 percent with regular insulin over a 24-hour period. This variability accounts for 80 percent of the change in the amplitude of glucose excursions from day to day. (Lauritzen et al 1983)

  • Using only one body region (abdomen) for insulin delivery, which avoids interregional variation of insulin absorption. These differences have been attributed to blood flow. Absorption is fastest from the abdomen, followed by the arm, buttocks and thigh.

  • A minimal insulin depot or pool to reduce risk of mobilisation during exercise thereby reducing the risk of exercise-related hypoglycaemia.

Other advantages include:

  • The ability to separate out basal and bolus rates (like a normal pancreas does naturally). This allows a patient to separate out metabolic needs (about 50 percent of insulin requirement) from meal requirements. The basal rate is pre-programmed, constant, and can be easily altered to reflect the changing background need for insulin.

  • The precision of insulin delivery with CSII (one tenth unit increments). This cannot be matched by a multiple injection mode of delivery.

  • The ability to program bolus doses to be delivered over a chosen period to allow for the slower digestion of some foods.

  • The feeling of a more "normal" lifestyle for some users. Pump users are able to experience a degree of freedom in the timing of meals, work, school, sleep and physical activity not possible with MDI. Having this freedom without loss of diabetes control is thought to be a major reason for the decreased depression and greater perception of self-efficacy found among pump users. This is particularly so with some children and adolescents (currently the largest expanding group of pump users worldwide).

CLINICAL INDICATORS FOR CSII

The primary medical indication for insulin pump therapy is to achieve better control of blood glucose levels and thereby reduce the risk for long-term diabetic complications.

According to the American Diabetes Association and the Australian Diabetes Society, the accepted level of HbA1C as a measure of good glycaemic control is </=7.0%.

Clinical indicators where CSII has proven beneficial are:

  • unpredictable or inconsistent control utilising intensive insulin management (i.e. MDI). These people have often been given the labels of "hard to control", "labile" or "brittle".

  • severe recurrent hypoglycaemia including hypoglycaemia unawareness

  • Dawn phenomenon

  • early signs of nephropathy, neuropathy, retinopathy

  • gastroparesis

  • pre conception or during pregnancy

  • extreme insulin sensitivity

  • allergy to intermediate/long acting insulin

  • antibody-mediated insulin resistance

PATIENT SELECTION

  • technical ability to accurately perform blood glucose monitoring and operate the insulin pump

  • intellectual ability to learn and retain information

  • motivation toward self-management

  • availability of support systems

  • evidence that the individual has accepted the self-care responsibilities associated with diabetes

  • effective coping patterns

Careful candidate selection is crucial to the successful use of an insulin pump.
It is recommended that pump therapy is best implemented with the support of a team of healthcare professionals who are trained in all aspects of diabetes management and CSII.