insulin pumps

Insulin absorption and infusion site health

Considering that insulin pumps are new to more than a third of the population with type 1 diabetes in Canada, we continue to learn new positives as well as challenges in use of the therapy.

An emerging challenge is long-term infusion site health as it relates to absorption of insulin. In my experience, about one in four pump users have insulin absorption issues, which ultimately affect overall Diabetes control (A1c).

Signs and observations

• Increase in total daily dose of insulin over past year or more >/= 25%.

• Increasing A1c

• New onset insulin resistance diagnosis or medications
  (applies to those without significant weight gain).

In other words, if you have been on a pump for a while, and have noticed it takes more insulin to bring your glucose down then it used to and your A1c is not in range, this issue may apply.

What are the contributing factors?

Compared to injecting, placing an infusion set is tricky. Site rotation becomes limited to what you can reach with both hands. Usually, you need to see what you are doing clearly. This means pump users likely use half of 'injection-approved' site areas. (Injection approved like the back of arms, lower back or side of upper thigh).

Add to this the demand on the tissue for 3 days worth of absorption and the challenge emerges:

•  Most adult pump users alternate between sides of the abdomen.

The abdomen has the most consistent absorption and therefore is the most used whether injections or infusion sites.

The cost of replacing an infusion set means sets can be left in too long.

All of the above set the groundwork for the development of scar tissue, which ultimately affects the absorption of insulin.

Assessment

During a self-assessment of your infusion sites, you may notice:

•  Differences in one side of the abdomen from the other when gently pinching up along your infusion areas.

You have more than 2 past sites still trying to heal.

Your infusion set gets damp or seems to leak, as it gets closer to day 3.

The recommended cannula prime amount is not enough- usually have to take a non- food bolus to get the insulin absorption of your site "going".

More than one site infection requiring a course of antibiotics.

Treatment

As with injecting, areas of scar tissue are to be left alone / avoided. A challenge when using a pump! Development and frequency of site infections can also relate to the individual's immune defenses. Leaving in painful, red looking infusion sets in beyond the 3 days increases the risk o site infection- leading case of scar tissue.

If you wish to try new areas for infusion placement, be aware you may need to lower your insulin amounts as much as 25% to prevent hypoglycemia. You could try a temporary basal rate lowering with the usual meal bolus for simplicity until you are satisfied your usual rates apply in the new site area. More frequent glucose checks may be required while monitoring this change.

Routine use of a topical antiseptic ointment can help limit the risk of site infection beyond the basics of good hand washing and clean process of set placement. Expand the areas of use in your site rotation plan. Monitor your glucose response when using 'fresh' infusion areas. Talk to your diabetes team for tips or treatments to help you.

As we know, infusion sites are "prime real estate" and care is required to maintain a good number of effectively absorbing areas. Absorption of insulin becomes very limited in the presence of swelling due to infection and or scar tissue. People with frequent site issues may be infusing more insulin than they need. Glucose levels may increase initially due to lack of absorption and then as a result of inflammation and eventually, scar tissue.

For those who have been using a pump long-term adhesion may be less of an issue but site rotation can become more limited as a result of using these preferred sites. Our aim in this discussion is to share some tips, which have helped solve infusion site issues.

So let's talk about infusion sites! Some of the variables which relate to whether your site will last 3 days or 3 hours include:

1. location of the site is best in areas which are as protected as possible from being dislodged by moving alone. The sides of the body are more vulnerable to site dislodgement from movement and being caught on things than sites closer to your core.

2. Body hair can affect the longevity of an infusion site. If you can, use areas with the least amount of hair. Use products to remove hair instead of a razor to avoid later itch at the site. Apply hair removal product to the area a few days before placing the infusion site to decrease the likelihood of skin irritation under the new site.

3. Skin preparation process and adherence products. To maintain a site for 3 days, the site area should be clean and air-dried with the use of site preparation products unless you have sensitivities to these products. About one in 5 people seem to have skin sensitivities. If you have signs of skin sensitivities such as red itchy marked area where the tape was, or angry raised looking areas, speak to your diabetes care provider. Use the process of elimination to evaluate which compound is causing the problem if more than one product is being used. Sensitivity to one product does not translate to sensitivity to all. Some pump manufacturers provide samples of various site prep products.

4. Site change routines. Many people stretch their dollars worth out of a good infusion site. In general, the older the person and the longer duration of diabetes can extend their infusion sites longer than 3 days where children cannot. This is likely due to the blunting of the immune response to the cannula in adults than in children who's sites usually start failing after 48h as their body actively rejects the cannula. In all ages and stages, when a site becomes painful or uncomfortable to touch it's better to change it out. The pain means infection or irritability which result in the development of scar tissue.

5. Technique. There are many kinds of infusion sets in optional lengths and angles. It may be that there is some trial and error needed to find a product right for you. For example, some brands have stickier backing than others!

For some people the backing of their infusion set alone will carry them through to day 3. Success is often based on the site prep product used. Allow drying to at least "tacky" before applying the site. Use anti-perspirant spray if needed on the area a few hours before the site prep pad is used is one trick, which helps in the summer.

An occlusive dressing (looks like plastic wrap) can be used against the skin and does help anchor the infusion set, which is inserted directly through the dressing or a small hole in the center. This "sandwiching" technique helps hold the cannula securely. It will also prevent "set migration' when the site stretches over time and can cause a kinked cannula.

In the case of tape, more is not better. The added tape means the whole site becomes more vulnerable to dislodgement. Some people use a site prep pad to circle the perimeter of their infusion set occasionally to encourage the edges to stay down. Always go by your blood sugar no matter how beautiful or ugly and beat up your site looks!

Rarely, allergies to the cannula itself occur. The process to get to this point in troubleshooting is long painful and frustrating usually because it isn't the top of mind reason. The way to rule this out is to try a needle-based infusion set. This solution has been miraculous to those who were considering coming off of their pump due to this issue.
Jill Milliken RN CDE
Diabetes Nurse Specialist - Canada
insulin pumps > Insulin absorption and infusion site health