Insulin injection users ‘at risk’ of lipohypertrophy

Almost 65 per cent of the 421,300 people who use insulin injection therapy in the UK could be at risk of developing lipohypertrophy (LH), according to new research.

Dr Kenneth Strass, who is director of safety in medicine at the European Medical Association (EMA), carried out the study and discovered that LH has also been reported as having a high prevalence in people who infuse insulin.

LH, which is a thickened, ‘rubbery’ swelling of tissue, is one of the most common complications of subcutaneous (SC). It can often be seen at injection or infusion sites but usually requires careful palpation to definitively diagnose.

The NDF Zorgstandaard, developed by the Nederlandse Diabetes Federatie, advises carers to check injection sites four times a year.

It is thought if the prevalence of LH is reduced, the clinical benefits could be enormous. They would include fewer frequent and unexplained hypoglycaemias, less glucose variability, reduced consumption of insulin and lower overall healthcare costs.

Repeated trauma

Histologically LH is characterised by increased adipocyte size and morphologic variability, accelerated metabolic activity of fat tissue and even adipocyte invasion of the dermis.

Clinically the practice of infusing or injecting insulin into LH leads to delayed or unpredictable absorption and glucose rises or instability.

Although the exact etiology of LH is unclear, associated factors that have been reported are repeated trauma to the same site by failing to rotate injections and the repeated use of a single needle. Failure to rotate infusion sites or leaving the cannula in situ longer than recommended may also have a promotional effect on LH.

A recent evaluation of the dermatological complications of insulin pump usage in 50 children and adolescents who were on this therapy for more than six months showed that 94 per cent had scars with a diameter <3 mm, 66 per cent had erythema not associated with nodules, 62 per cent had SC nodules and 42 per cent had LH.

In a much larger international survey among 14,012 pump users, 41.5 per cent reported skin problems, including LH, on a regular basis. These frequencies of LH are similar to those reported in insulin injecting patients.

In the largest survey to date of injecting practice covering 16 countries and 4352 patients, 47.9 per cent of people responded yes to the question: ‘Have you ever noticed swelling of fatty tissue or small bumps at your injection sites?’

Clinically harmful

Adolescents and children had higher incidences of these lesions than adults. The abdomen and thigh were the sites with the majority of LH, with buttocks having the least, but this seemed to only be a reflection of the frequency of injections at the respective body sites.

After palpating, nurses found and measured 614 abdominal LH in the population of 4352 patients. The average diameter of the palpated lesion was 4.2 cm (SD 3.2); size varied as a function of age, the younger the patient the smaller the mass.

In a recent Spanish study nearly 2/3 of injecting patients (64.4 per cent) had LH. There was a strong relationship between the presence of LH and non-rotation of sites, with correct rotation technique having the strongest protective value against LH.

Of the people who correctly rotated sites only 5 per cent had LH. Of patients with LH 98 per cent were observed to not rotate or to rotate incorrectly. LH was also related to needle reuse, with risk increasing significantly when needles were used > 5 times.

LH is associated with two annoying and clinically harmful symptoms: hypoglycaemia and glucose variability. In the Spanish study of those with LH,  39.1 per cent had unexplained hypoglycaemia and 49.1 per cent had glycemic variability; for those without LH these were present in only 5.9 per cent and 6.5 per cent respectively.

Correct rotation of injection sites means more than simply switching from right to left sides or back and forth from abdomen to thigh sites. It means inserting cannulae or placing injections at least 1 cm away from previously used sites. In order to rotate appropriately, peoples will need to expand the areas in which they inject, seeking tissue that has not previously been exposed to insulin.

This will involve using the entire surface of the abdomen, including the flanks. It means using the entire antero-lateral aspect of the thigh from the hip nearly to the knee. It may even involve use of the arm in certain patients.

By expanding injection areas we move into zones with significantly reduced SC fat depth. In order to avoid intramuscular (IM) injections it is important to use the shortest needle possible for injections and the shortest cannula possible for infusions.

The 4mm insulin pen needle has recently been shown to be safe and effective in all types of people, even obese ones (11-15). Use of such needles is an important advance not only in preventing IM deposition of insulin but in expanding injection sites so that better rotation habits are possible. These principals apply equally to infusion patients.

The main risk factors for LH are incorrect infusion and injection site rotation along with excessive needle reuse by injecting people. Addressing these issues involves enlightening professionals to the presence and risk of LH and better education of people.