Skin blood perfusion and cellular response to insertion of insulin pen needles with different diameters

Abstract

Today most research on pen needle design revolves around pain perception statements through clinical trials, but these are both costly, timely, and require high sample sizes. The purpose of this study was to test if tissue damage, caused by different types of needles, can be assessed by evaluating skin blood perfusion response around needle insertion sites. Three common sized pen needles of 28G, 30G, and 32G as well as hooked 32G needles, were inserted into the neck skin of pigs and then removed. Laser Speckle Contrast Analysis was used to measure skin blood perfusion for 20 minutes after the insertions. Seven pigs were included in the study and a total of 118 randomized needle insertions were conducted. Histology was made of tissue samples inserted with 18G, 28G, and 32G needles, and stained to quantify red and white blood cell response. Based on area under curve, calculated for each individual blood perfusion recording and grouped according to needle type, skin blood perfusion response relates to needle diameter. The response was significantly higher after insertions with 28G and hooked 32G needles than with 30G (P < .05) and 32G (P < .01) needles. Histology results were not significant, but there was a trend of an increased response with increasing needle diameter. Skin blood perfusion response to pen needle insertions rank according to needle diameter, and the tissue response caused by hooked 32G needles corresponds to that of 28G needles. The relation between needle diameter and trauma when analyzing histology was also suggested.

Keywords: diabetes; injections; laser speckle contrast analysis; needle size; pen needles; tissue damage.

Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: KAP is enrolled as an industrial PhD student at Novo Nordisk A/S, CBJ is a consultant working for Novo Nordisk A/S, and NBM and JK are full-time employees of Novo Nordisk A/S.

© 2014 Diabetes Technology Society.

Figures

Figure 1.

Histology of tissue trauma 1 hour after needle insertion. (a) A scanned antihemoglobin stained histology slide with tissue containing the trauma of an 18G needle in the center of the tissue (arrow). (b) Same as a but with a trauma from a 32G needle. It is seen that the signal is much smaller than the signal from the 18G needle, and in this slide, only restricted to the epidermal layer. (c) Overlay image showing the complete segmentation of the slide as seen in a. The red overlay color denotes the morphological masks applied to exclude the epidermal layer as well as the local bleedings from the tissue removal procedure on the sides and bottom of the tissue. The green overlay color indicates presence of red blood cells. (d) Overlay image showing the complete segmentation of the 32G needle insertion seen in b.

Figure 2.

Summation images of tissue trauma caused by (a) the 18G needle and (b) the 32G needle exemplified in Figure 1. Each summed image contains 10 segmented and subfield divided histology slides. Each image is divided into 3 areas, 2 lateral and 1 center area. The mean value of the subfields in the 2 lateral areas represents the baseline value of the tissue. The signal is found in the center area, where the signal threshold is defined as the baseline value plus 2 standard deviations. The number of subfields qualifying as signal subfields is defined as the signal count of the center area.

Figure 3.

Blood perfusion following skin penetration. Averaged (mean ± SEM) skin blood perfusion profiles measured 0-20 minutes after needle insertion. Only 1 minute of the 3-minute baseline is included in the plot.

Figure 4.

AUC (mean with SEM) calculated from 0-20 minutes for all skin blood perfusion profiles, grouped by needle type. θ data groups significantly different from all other data groups. Statistics were performed on log-transformed data, but represented in this figure as original data. *Data groups significantly different with P < .05. **Data groups significantly different with P < .01.

Figure 5.

Quantified measures of immunohistochemically stained red blood cells and white blood cells, representing the needle induced tissue bleeding and inflammation, respectively. θ data group significantly different from all other data groups. The dots represent outliers defined as values with a distance from the median exceeding 1.5 times the interquartile range.