Open AccessInfluence of hypodermic needle dimensions on subcutaneous injection delivery – a pig study of injection deposition evaluated by CT scanning, histology, and backflow
Author(s) -
Ann Præstmark Juul Kezia,
Bengtsson Henrik,
Eyving Bente,
Kildegaard Jonas,
Lav Steffen,
Poulsen Mette,
Serup Jørgen,
Stallknecht Bente
Publication year - 2012
Publication title -
skin research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.521
H-Index - 69
eISSN - 1600-0846
pISSN - 0909-752X
DOI - 10.1111/j.1600-0846.2011.00592.x
Subject(s) - medicine , backflow , nuclear medicine , histology , subcutaneous tissue , hypodermic needle , ex vivo , deposition (geology) , staining , biomedical engineering , syringe , pathology , in vivo , mechanical engineering , psychiatry , engineering , inlet , paleontology , microbiology and biotechnology , sediment , biology
Background Thinner and shorter needles for subcutaneous administration are continuously developed. Previous studies have shown that a thinner needle causes fewer occurrences of painful needle insertions and that a shorter needle decreases the occurrence of painful intramuscular injections. However, little is known about local drug delivery in relation to needle length and thickness. This study aimed to compare deposition depth and backflow from three hypodermic needles of 3 mm 34 G (0.19 mm), 5 mm 32 G (0.23 mm), and 8 mm 30 G (0.30 mm) in length and thickness. Methods Ex vivo experiments were carried out on pigs, in neck tissue comparable to human skin at typical injection sites. Six pigs were included and a total of 72 randomized injections were given, i.e. 24 subcutaneous injections given with each needle type. Accordingly, 400 μL was injected including 70% NovoRapid ® (Novo Nordisk A/S, Bagsvμrd, Denmark) and 30% X enetix ® (Guerbet, Villepinte, France) contrast including 1 mg/mL Alcian blue. Surgical biopsies of injection sites were sampled and computer topographic ( CT )‐scanned in 3 D to assess deposition and local distribution. Biopsies were prepared and stained to evaluate deposition in comparison to the CT ‐scanning findings. The backflow of each injection was collected with filter paper. The blue stains of filter paper were digitized and volume estimated by software calculation vs. control staining. Results CT ‐scanning ( n = 57) and histology ( n = 10) showed that, regardless of injection depth, the bulk of the injection was in the subcutaneous tissue and did not propagate from subcutis into dermis. With the 8 mm 30 G needle all injections apart from one intramuscular injection were located in the subcutaneous layer. The volume depositions peaked in 4–5 mm depth for the 3 mm 34 G needle, in 5–6 mm depth for the 5 mm 32 G needle, and in 9–10 mm depth for the 8 mm 30 G needle. In general, injection depositions evaluated by histology and CT ‐scans compared well for the individual biopsies. The amount of backflow ( n = 69) from the 3 mm 34 G needle was smaller ( P < 0.05) as compared to the 5 mm 32 G and the 8 mm 30 G needles. Analysis showed a correlation between backflow and the needle's outer dimension with the needle diameter being the pivotal parameter. Furthermore, CT ‐scanning and histology confirmed that local propagation of the injection and final distribution followed a route of less mechanical resistance as determined by connective tissue barriers preset in the site of injection. Conclusion Needles as short as 3 mm efficiently delivered injections into the subcutaneous target. The amount of backflow was smaller with thinner needles. Local distribution was variable and determined by mechanical barriers preset in the tissue. CT ‐scans and histology were concordant.