Insulin Pump Therapy

Continuous Subcutaneous Insulin Infusion (CSII)

CSII Therapy is emerging as a treatment option for the entire spectrum of diabetes, from adults and children with type 1 diabetes to the elderly and patient with type 2 diabetes.1

The family physician may be the first person a patient with diabetes talks to about insulin pump therapy. The following may offer some useful information for that conversation.

A referral to a diabetes health care team will be needed to pursue this form of diabetes management. Use of CSII requires care by skilled professionals, careful selection of patients, meticulous patient monitoring and thorough patient education.

Indications and benefits:

Insulin pump therapy is the continuous delivery of rapid acting insulin at set and variable rates and is indicated for the management of diabetes in persons requiring insulin.

Rapid Acting insulin analogs (such as Lispro, and Humalog) are appropriate insulins for insulin infusion pumps. The stability of this insulin in pumps has been confirmed.2

The following benefits of pump therapy may achieve near normal glucose control and improve lifestyle flexibility:

• The ability to set and deliver fractional doses of insulin that match physiological needs.
• The ability to carbohydrate count and match food to insulin when food is eaten improves glucose control while allowing the normalization of lifestyle.
• Improvements in hypoglycemia awareness.
• Reduction of the incidence of severe hypoglycemia
• Ability to reduce risk of exercise induced hypoglycemia.
• Easier management of sick days.
• CSII can help improve metabolic control during pregnancy.

There are patients that are very structured about their diabetes self management. We may consider them as best candidates for pump therapy. However it is important to recognize that some people who manage their diabetes poorly may simply be frustrated or discouraged with multiple daily injections, demands of self care and not getting to their goals. They too may be candidates.

Patient candidates are:

• Strongly motivated to improve glucose control.
• Able and willing to self monitor ac and pc blood glucose.
• Willing to work with and follow-up with a health care team.
• Understand and demonstrate use of pump and protocols.

• The pump does not check blood sugars.
• Increased vigilance and self-care is often required of the pumper. Regular capillary, meter glucose monitoring is necessary for the user to make day to day decisions.
 
• Glucose testing four times a day is recommended with occasional extra 2- hour pc glucose tests to evaluate the pump settings.
 
• There are pumps available with continuous glucose sensing program capabilities, however even these systems require capillary glucose tests by the user to calibrate the sensor and to confirm extremes in glucose values prior to a treatment decision. The cost of the sensors to utilize this continuous glucose sensing feature is not yet covered by insurance and therefore does limit its use.

• Visual impairment would not exclude a person from managing their diabetes with a pump. A requirement would be that a reliable backup support person is educated in pump therapy along with them.
 
• The financial cost of an insulin pump along with the ongoing costs of disposable supplies to run the system is a barrier to those without insurance coverage. Some Canadian Provinces are covering the cost of pump therapy for children and youth with type 1 diabetes. (Saskatchewan, Ontario, NFLD and Labrador)

Contraindications:

• Insulin pump therapy is not recommended for people who are unwilling or unable to perform regular blood glucose tests daily.
 
• People unwilling to maintain follow-up care with their health professionals.

Basics of pump therapy:

The insulin infusion can be programmed to closely simulate pancreatic function by the delivery of rapid acting insulin in two ways:

• Basal rate: Background insulin delivered continuously by the pump throughout the day and night to cover the person's base metabolic need for insulin. Basal rates will vary at different times of the day. 
 
• Bolus: At the push of a button a calculated amount of insulin is given on demand by the user when food is eaten or to correct a high blood glucose value.

Advanced pump therapy involves detailed carbohydrate counting and the use of individual insulin sensitivity factor (ISF):

• Carbohydrate counting: allows the matching of food to insulin to prevent spikes in the post meal glucose. This is part of the education process leading to the initiation of insulin pump therapy and is best provided by a dietitian with knowledge in this area. At follow-up visits the insulin to carbohydrate ratio is examined for accuracy by reviewing the ac and pc glucose results and adjusted accordingly.
 
• Insulin Sensitivity Factor (ISF): allows a person on pump therapy to determine how to safely correct an elevated glucose with a specific bolus dose of insulin. Each individual's insulin sensitivity factor is determined by a formula after glucose has stabilized with the pump and glucose targets are met.

The formula for determining ISF:

100 divided by the total daily dose of insulin (basal + bolus) = the expected lowering effect of 1 unit of rapid insulin or (ISF)

Example of determining ISF and using it to correct an elevated glucose:

An individual uses average of 50 units total basal + bolus insulin per 24 hour period.

100 ÷ 50 units = 2 mmol/L drop in glucose with 1 unit of insulin.

↓

The ISF is 2.

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To correct an elevated glucose

↓

(Current BG - target BG) ÷ ISF = bolus insulin
(14 mmol - 6 mmol) ÷ 2 = 4 units insulin

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The pumper programs a 4 unit bolus and in 2 hours rechecks the glucose to assess the effectiveness or accuracy.

Mechanics:

• Pump: A battery operated computer like device, the size of a pager that stores and directs programmed settings. The settings are changed as needed based on blood glucose patterns.
 
• Reservoir: Similar to a syringe, it is filled with rapid insulin by the user every few days and loaded in to the pump.
 
• Infusion set: A thin, flexible latex free plastic tube connects to the insulin reservoir at one end through which insulin passes into a small catheter that is in the subcutaneous tissue at the other end. This is inserted and changed every few days by the user. There is no needle left under skin. It is comfortable and discreet. The infusion set can be quick-released from the injection catheter site allowing the user to be off the pump for short intervals for example swimming, showers and contact sports.

Safety:

Along with many other safety mechanisms the pump alerts the user with beeps or vibrations to indicate if a battery needs changing, if a reservoir is getting low or if the infusion line is occluded.

Pump therapy is as safe as multiple-injection therapy when recommended procedures are followed. Potential complications peculiar to pump therapy, however, must be explained to users. Undetected interruptions in insulin delivery may result in ketotic episodes more often and more quickly with CSII, which is of particular concern in pregnancy. Infections or inflammation at the needle site may also complicate CSII therapy but can be minimized by careful hygiene and frequent site changes.3

- Sarah Venedam RN CDE
Certified Insulin Pump Trainer

You can search for abstracts of the above references by following this link: PubMed