Authors (including presenting author) :
CHAN SOY(1), LEUNG AYS(2), MOK MPH(3), LOOKM(4), AU SKY(5)
Affiliation :
(1)Princess Margaret Hospital (2)Yan Chai Hospital (3)United Christian Hospital (4)Prince of Wales Hospital (5)Pamela Youde Nethersole Eastern Hospital
Introduction :
Insulin therapy remains the cornerstone treatment in diabetes management. To obtain optimal absorption of insulin, insulin must be injected into subcutaneous (SC) tissue rather than intradermally and intramuscularly(IM). Hence, appropriate needle length with correct injection technique for insulin pen and syringe are crucial to ensure injecting insulin into SC tissue to achieve the expected insulin pharmacokinetics effect.
Objectives :
To recommend the optimal needle length for sc insulin injection in clinical practice
Methodology :
The literature was searched through PubMed, Ovid, CINANL, Cochrane Library and Google Scholar. It was restricted to full articles and the English language from 2012 to 2019. The keywords of insulin, injection technique, subcutaneous injections, and needle length were used. Among the 62 articles found, 8 articles met the criteria.
Result & Outcome :
Evidence demonstrated that the skin thickness is consistent across age groups ranging from 2-65 years old, sexes, and body mass indexes of 19 to 65 kg/m2, averaging 2.0 to 2.5mm. In contrast, the thickness of SC tissue varies by age, body site, BMI and gender. Median SC thickness ranges from 10.9mm at thigh, 12mm at arm, 14.7mm at abdomen to 16.9mm at buttock. The minimum SC thickness was < 3mm at thigh and < 5mm at other injection sites. Injecting at 90° without pinching up of skin, the estimated risks of injecting into the muscle were 25% and 9.7% respectively in thigh and abdomen when using a 8 mm-long needle, versus 10% and 2.8% for 6mm-long needle; and 1.6% and 0.3% for 4mm-long needle. Pinching up skinfold increased SC fat thickness (mm) by 83+/-6% to 192+/-16% in the abdomen and 22+/-6% in the thigh. No IM injection occurred in subjects occurred when using 6mm-needles and injecting at angled. The currently use 8mm-needle length insulin syringe for all ages and 6mm-needle length pen needle for children are too long and leading to increased IM risk. The shortest 6mm-needle length of insulin syringe and 4 or 5mm-needle length of pen needle are suitable for all people required insulin. When using insulin syringe with 6mm-needle length, it is recommended to inject at 45° angle or inject at 90° angle with skinfold.
