Continuous Subcutaneous Insulin Infusion Csii Therapy Using An External Insulin Pump

External insulin pumps have gained popularity because of increased flexibility of dosing, improved glycemic control and a lower incidence of hypoglycemia when compared with traditional insulin injection methods (5,6,45-48). However, CSII requires that patients count carbohydrates, SMBG frequently and carefully control caloric intake to avoid hypoglycemia and excessive weight gain. Failure to deliver rapid-acting insulin (due to pump malfunction, catheter occlusion or catheter disconnection) can lead to hyperglycemia and ketoacidosis within several hours, because of the small depot of sc insulin (two to four units) during typical basal CSII therapy (25,33,45).

Although pumps can deliver basal and bolus doses of rapid-acting insulin (insulin Lispro or insulin Aspart in the USA) into the sc tissue with great precision, initial absorption into the circulation can be delayed up to 20 min, with 30% to 50% intra-subject variability (31,32,34,35). Large bolus doses and high basal rates are associated with a four to 10 unit depot of sc insulin. Once delivered into the sc tissue, the depot of rapid-acting insulin may not be completely absorbed into the circulation for 2-4 h. This highlights a major limitation of CSII insulin therapy; plasma insulin levels will continue to rise for several hours even if the patient attempts to decrease the actions of insulin by stopping the delivery of insulin (35,45).

Doyle et al. performed a prospective randomized clinical trial in patients with type 1 diabetes comparing pump therapy with Lispro insulin (CSII) and multiple dose therapy using Lispro and Glargine insulin (MDI). Fifty percent of the patients managed with CSII achieved near-normal BG control (HbA1c < 7%), compared to only 12% of patients managed with MDI (46). In another randomized clinical trial, Rudolph et al. (49) demonstrated a 74% reduction in the incidence of severe hypoglycemia in type 1 diabetic patients managed with CSII compared to MDI.

Modern pumps are small, light weight, water-resistant, reliable and highly programmable. Advanced pumps manufactured by Medtronic Diabetes and Smiths-Medical communicate wirelessly with a patient's SMBG meter, while an Animas Corporation pump has a detailed library of meals and an algorithm that calculates an optimal meal bolus dose of rapid-acting insulin. Improved estimation of meal carbohydrate content leads to decreased postprandial hyperglycemia (36). Several pumps have an "insulin on board" feature that estimates the future glucose-lowering effect of delivered insulin to prevent the patient from injecting additional insulin when a large amount is already present in the subcutaneous depot. The inadvertent stacking of meal or correction boluses of rapid-acting insulin often leads to hypoglycemia (28,33,46,47).

Medtronic Diabetes recently received FDA approval for a device that combines the Guardian RT continuous glucose monitoring system with an insulin pump (Fig. 7). Patients are able to utilize the real-time glucose and insulin trend data to improve BG control with meals, exercise and sleep (19,20,22). This exciting technology is limited because the patient must frequently look at the CGM display, thus clinical decisions about therapy are made intermittently. Future devices may "close the loop" during sleep or continuously throughout the day.

FIGURE 7 Medtronic Diabetes (Guardian REALTime) CGM System. Distal tip of needle-type glucose sensor is implanted into the subcutaneous tissue of the abdomen. Glucose data is sent wirelessly from telemetry module to insulin pump. Glucose data displayed on y-axis and time of day on x-axis. CGMS is open-loop system, requiring patient initiated SMBG for change in insulin dose (www.medtronicdiabetes.com).

FIGURE 7 Medtronic Diabetes (Guardian REALTime) CGM System. Distal tip of needle-type glucose sensor is implanted into the subcutaneous tissue of the abdomen. Glucose data is sent wirelessly from telemetry module to insulin pump. Glucose data displayed on y-axis and time of day on x-axis. CGMS is open-loop system, requiring patient initiated SMBG for change in insulin dose (www.medtronicdiabetes.com).

Insulet Corporation recently commercialized an insulin pump that separates the insulin delivery system from the programmer and display. The small, lightweight and disposable insulin "pod" attaches to the skin with an adhesive and self-inserts the infusion needle with minimal discomfort. Patient comfort and convenience are improved by eliminating the need for an infusion catheter and tubing (Fig. 8). (www.animas.com, www.medtronicdiabetes.com,www.roche.com, www.smiths-medical.com,www.insulet.com.)

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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