Research paper
Assessment of distance from skin surface to muscle for evaluation of the risk of inadvertent intramuscular insulin injection at potential injection sites among patients attending a tertiary care children's hospital in Sri Lanka–an observational study

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Abstract

Background

Insulin therapy is essential for type 1 diabetes. While a reasonable glycemic control prevents complications, inadvertent intramuscular (IM) insulin injection results in hypoglycemia and fluctuations of blood glucose levels.

Objective

To assess the subcutaneous thickness (SCt) at the potential insulin injection sites, in order to determine the suitable needle length.

Methods

Diabetic and non-diabetic children (n = 125; aged 2–14 years) attending a tertiary care hospital were examined, after excluding those who had skin abnormality at the injection site, were hospitalized for > 3 days, or had any other chronic illnesses. Dermal thickness (Dt) and SCt at the potential insulin injection sites were measured with ultrasonography.

Results

The mean age of the patients was 8 years and 57% were boys; mean Dt was 2.1 ± 0.4 mm, SCt was 7.45.6 ± 3.7 mm, and maximum SCt was 29.8 mm in the anterior abdominal wall. SCt increased with age and by raising a skin fold (sf). There was no difference (P > 0.05) in Dt between genders, and limbs showed thinner Dt values than the abdomen. SCt changed with the injection site: it was the lowest in the thigh and the highest in the abdomen. SCt was thicker in females, with or without sf (P < 0.001). For all sites, IM risk was high for 15-mm needles: it was highest in the thighs (98%) and reduced to 86% with sf. IM risk was low for 5-mm needles: it was highest in the thigh (38%), and reduced to 12% with sf. Compared with girls (up to 42%), IM risk was higher for boys (up to 54%), even for 5-mm needles with a sf.

Conclusion

Using a short needle is recommended for children, particularly for boys. Regardless of the needle length, the raised sf technique is associated with reduced IM risk.

Introduction

Diabetes mellitus is classified into two subtypes: type 1 and type 2. Since insulin production is typically absent in type 1 diabetes (DM), subcutaneous insulin therapy is mandatory to achieve optimal glycemic control [1]. The optimum management of DM is a complex process that warrants both pharmacological and non-pharmacological approaches, such as subcutaneous insulin administration, diet and lifestyle modification, as well as behavioral and psychological counseling [2], [3]. Satisfactory glycemic control is key to preventing short- and long-term complications of diabetes, which is an unrealistic goal if the compliance to insulin therapy is poor [3].

The reasons for poor compliance with diabetes treatment are multifactorial, among which, the development of needle phobia due to pain and bleeding during insulin injections is eminent. Symptoms of hypoglycemia, a well-known side effect of insulin treatment, is another factor directly related to poor compliance and needle phobia [2], [4], [5], [6]. Intramuscular insulin injections (IM) or an accidental injection into a muscle is associated with symptomatic hypoglycemia and a variable degree of pain at the injection site. It is known that the incidence of IM injections is related to the skin thickness, the length of the insulin needle, and the insulin administration technique [4], [5], [7]. Although the suitable length of insulin needles is a widely discussed topic, only a few studies focused on the desired needle length for pediatric populations [5], [6], [8], [9], [10].

The ideal subcutaneous injection needle should have a high probability to enter and remain within the subcutaneous tissue. Therefore, it should be long enough to penetrate the dermal layer (low risk of intradermal injections) while being shorter than the skin-to-muscle distance (low risk of IM injections) [4]. In 90-degree injection technique, the needle is placed perpendicular to the skin surface. Hence, the dermal thickness and skin-to-muscle distance (skin thickness) measurements are crucial for determining the intradermal and intramuscular injection risks, respectively. Therefore, dermal thickness and skin thickness measurements determine the correct needle length for a particular patient. Ultrasonography is a reliable noninvasive technique to measure dermal and subcutaneous thicknesses, hence to assess the risk of intradermal and intramuscular injections [11].

Skin thickness in a child is affected by age, pubertal status, gender, body mass index (BMI), and the anatomical site. The racial variation described for skin thickness is probably related to the genetic influence on body composition [8], [12]. Due to the scarcity of data, the needle lengths prescribed for Sri Lankan children are based on Western reference values [13]. However, owing to racial variations, currently used needles may or may not be suitable for many children. This study aimed to evaluate the dermal and subcutaneous thicknesses of potential insulin injection sites of a selected pediatric population so as to determine the IM injection risk for different needle lengths, and thereby determine the suitable needle length.

Section snippets

Study population

The current study examined both diabetic (DM; n = 44) and non-diabetic children (n = 81) aged 2–14 years. Children with type 1 diabetes mellitus were recruited from the diabetic clinic at Lady Ridgeway Hospital for Children. Since the number of DM children attending the healthcare institution was inadequate, age- and sex-matched, non-diabetic children who presented for ultrasound scans at the same institution were recruited to strengthen the sample. All DM children were on subcutaneously

Results

The study examined children with type 1 DM (n = 44) and children without DM (n = 81) in two age groups: 2–6 years (n = 45) and 7–14 years (n = 80); the mean age was 8 ± 4 years. Of the children, 57% were boys, with no statistically significant age difference (P = 0.085) between girls and boys (Table 1, Table 2). A significant age difference was observed between the DM and non-DM groups (P < 0.05). As expected, a growth-related change in the study parameters was evident in all groups: weight, height, BMI,

Discussion

IM insulin injections can lead to fluctuations in blood glucose levels, needle phobia, and poor compliance to insulin treatment. The injection-related pain, which contributes to needle phobia, occurs when the highly innervated muscle is accidentally pricked. IM risk is known to be associated with the needle length [4], [5]. Therefore, selecting a needle with appropriate length (for subcutaneous insulin administration) is fundamental to achieve an optimal glycemic control [4], [7]. As a pioneer

Conclusion

An individualized approach in prescribing needles and injection sites, considering the age and gender of the child, would reduce the incidence of IM injections. Short insulin needles (5 mm or shorter) are suitable for children with type 1 DM, particularly for the 2–6-year age group, and for boys of any age. The anterior abdominal wall can be recommended as the preferable injection site, particularly for boys; for limb injections, use of a correct injection technique is mandatory. However,

Disclosure of interest

The authors declare that they have no competing interest.

Financial support

This research was not funded by any financial agent/group.

Ethical approval

Ethical approval was granted by the Ethics Review Committee, Faculty of Medicine University of Colombo, on 29.10.2015. Reference number EC-14-149.

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