If pain is a problem the injections can be given through an indwelling catheter (eg Insuflon®) instead of sticking the child's skin. The insulin is then injected through a rubber membrane.

Our present policy is to give all pre-school children the injections with the help of indwelling catheters. Older children and adolescents are offered to try this method during their first week of subcutaneous injections. We take all the blood glucose tests from an intravenous cannula. These procedures ensure as little pain as possible at the onset of the child's life-long disease. Painless injections have made it less complicated for the family to cope with their crisis reaction and has facilitated their participation in the diabetes education program. After a week or so the child has had time to adjust psychologically and to learn technically the correct injection techniques and can then try regular injections. When discharged from the hospital the children have their free choice of method of injection. Twenty to 25 percent continue with indwelling catheters while the others choose to start with regular injections. Insuflon is even used by many adults who find the injections painful or uncomfortable.

Using indwelling catheters will facilitate the use of multiple injection treatment for small children and will make it easier for those who are not used to giving injections to give insulin, like grandparents, baby-sitters or day-care staff. It will also be easier to give an extra injection when needed since it will not imply more pain for the child. For example, sometimes it is difficult to know how much a small child will eat and it is then better to give half the insulin dose before the meal and perhaps give some extra insulin after the meal depending on how much the child actually eats.

We have not found that more children continue to use indwelling catheters when introducing them at the onset of diabetes, compared to our earlier policy which was to offer indwelling catheters only to those who had problems with injections. However, children using indwelling catheters are probably at less risk for needle-phobia if they are spared frightful injections during the initial period of their disease.

One study showed that in particular the younger patients using indwelling catheters and multiple injection treatment would have found this method more difficult to accept if indwelling catheters had not been available (1).

Children and adolescents find that they can take injections without indwelling catheters after a shorter or longer period of time. Many, especially teenagers, use indwelling catheters on and off, often taking a break during the summer, when they prefer a nice suntan on their abdomen.

When should Insuflon be replaced?

The average time between replacements is 4 - 5 days (2). Some patients will be quite comfortable replacing it once a week while others may need replacement twice a week. Disinfection with alcohol is recommended before inserting the catheter to minimize the risk for infection.

Which insulin can be given in Insuflon

Small children usually use the same indwelling catheter both for short-acting insulin at mealtimes and for bed-time insulin of NPH-type (e.g. Insulatard, Humulin NPH, Isuhuman Basal). However, if a longer action time of the bedtime insulin is desirable it is better to give it as a separate injection in the thigh. Older children usually accept this without any problems. It is not advisable to mix insulins of Lente-type (e.g. Monotard, Humutard) with short-acting insulin to give in the catheter since part of the short-acting effect will vanish. However, if the patient already is doing well mixing these types of insulin there should be no disadvantage giving them through an indwelling catheter.

Dead space

The dead space of the catheter (the hollow inside that will be filled with insulin with the first injection) is half a unit of insulin in a clinical setting.

For most older children and adults 0.5 U more or less will not make any practical difference. Because 1 drop of insulin of 100 U/ml roughly equals one unit, there are small margins of error if the child's entire dose is only 1 or 2 units. With such small doses we use insulin of 40 U/ml. Many patients prefer to add one extra unit with the first injection after replacing an indwelling catheter. This is OK if they are aware that they will be getting an extra 0.5 U in this way.

When administering the bedtime insulin the catheter will already be filled with short-acting insulin. This will partly be exchanged for intermediate-acting insulin during the injection. Remaining in Insuflon will be a mixture of approximately 0.3 units of bedtime insulin and 0.2 units of short-acting insulin. In practice, these tiny amounts of insulin are usually insignificant.

High blood glucose after a few days use?

Sometimes the blood-glucose level will rise after a few days use of an indwelling catheter. If this happens on a regular basis, there are often signs of lipohypertrophy present. We then instruct to replace the indwelling catheter at shorter intervals. X-ray studies of catheters have shown a delayed absorption in some cases of lipohypertrophy but normal in others. (3). The short- and long-term metabolic control were not altered when using Insuflon during a 2-month cross-over study. (4).

Studies of insulin pump users have shown both an unchanged insulin absorption during 5 days' use (5) and an increased absorption after 3 days' of using of the same injection site. Studies from Finland with indwelling catheters show no change in insulin absorption during 5 days of use. (7). A Swedish study using radio-actively labelled insulin did not show any change in absorption during 4 days' use of indwelling catheters. (8).

Most patients will have impaired home test results from time to time without knowing the exact reason. This will, of course, also happen to patients using indwelling catheters. As a measure of caution we instruct patients to replace the catheter whenever this happens, although the catheter itself is usually not the cause of the increased blood glucose level.

Infection and redness

We have seen a very low frequency of infections requiring antibiotic treatment (1/140 patient months or 1/850 used catheters).Infection of the catheter canal in the subcutaneous tissue is recognized by redness and/or pain around the insertion site. If you have problems with redness or infections at the insertion site we recommend that you use chlorhexidine in alcohol (or similar disinfectant) for skin disinfection and hand washing. Don't use products containing a skin moistener since this causes the adhesive to come loose.

Redness and/or itching can be caused by an allergic reaction to the adhesive. Application of 1 % hydrocortisone cream usually helps. It the problem continues we have successfully used a stoma type adhesive (such as Compeed® or Duoderm®). Cut a hole for the catheter hood before applying it. Itching can also be caused by perspiration in hot weather or during sports activities. The itching usually disappears when one stops sweating.

1) Hanas R, Ludvigsson J. Experience of pain from insulin injections and needle-phobia in young patients with IDDM. Practical Diabetes 1997;14:95-99.

2) Hanas R, Ludvigsson J. Side effects and indwelling times of subcutaneous catheters for insulin injections: A new device for injecting insulin with a minimum of pain in the treatment of insulin-dependent diabetes mellitus. Diabetes Res Clin Pract 1990; 10:73-83.

3) Hanas R, Ludvigsson J, Stanke C-G, Östberg H. X-ray appearance of the indwelling catheter when using Insuflon for insulin injections. Abstracts of the 17th Annual Meeting of ISGD, Hormone Research 1991; 35:58.

4) Hanas R, Ludvigsson J. Metabolic control is not altered when using indwelling catheters for insulin injections. Diabetes Care 1994;17:716-18.

5) Olsson PO, Arnqvist H, Asplund J. No pharmacokinetic effect of retaining the infusion site up to four days during continuous subcutaneous insulin infusion therapy. Diabet Med 6/1993;10:477-80.

6) Liu D, Moberg E, Wredling R, Lins PE, Adamson U. Insulin absorption is faster when keeping the infusion site in use for three days during continuous subcutaneous insu-lin infusion. Diabetes Res Clin Pract 1991;12:19-24.

7) Käär ML, Mäenpää J, Knip M. Insulin administration via a subcutaneous catheter. Diabetes Care 1993;16:1412-13.

8) Hanas, R. Carlsson S, Frid A, Ludvigsson J. Unchanged insulin absorption after 4 days' use of subcutaneous indwelling catheters for insulin injectons. Diabetes Care 1997;20:487-90.