The effect of intramuscular injection technique on injection associated pain; a systematic review and meta-analysis

Aim: To review the effect of different intramuscular injection (IMI) techniques on injection associated pain, in adults. Methods: The review protocol was registered on PROSPERO (CRD42019136097). MEDLINE, EMBASE, British Nursing Index and CINAHL were searched up to June 2020. Included studies were appraised and a meta-analysis, where appropriate, was conducted with a random effects model and test for heterogeneity. Standardised mean difference (SMD) with a 95% confidence interval in reported injection pain (intervention cf. control) was reported. Results: 29 studies were included in the systematic review and 20 studies in the meta-analysis. 13 IMI techniques were identified. 10 studies applied local pressure to the injection site. Of these, applying manual pressure (4 studies, SMD = -0.85[-1.36,-0.33]) and Helfer (rhythmic) tapping (3 studies, SMD = -2.95[-5.51,-0.39]) to the injection site reduced injection pain, whereas the use of a plastic device to apply local pressure to the skin (ShotBlocker) did not significantly reduce pain (2 studies, SMD = -0.51[-1.58,0.56]). Acupressure techniques which mostly involved applying sustained pressure followed by intermittent pressure (tapping) to acupressure points local to the injection site reduced pain (4 studies: SMD = -1.62[-2.80,-0.44]), as did injections to the ventrogluteal site compared to the dorsogluteal site (2 studies, SMD = -0.43[-0.81,-0.06]). There was insufficient evidence on the benefits of the ‘Z track technique’ (2 studies, SMD = -0.20[-0.41,0.01]) and the cold needle technique (2 studies, SMD = -0.73[-1.83,0.37]) on injection pain. The effect of changing the needle after drawing up the injectate on injection pain was conflicting and warming the injectate did not reduce pain. Limitations included considerable heterogeneity, poor reporting of randomisation, and possible bias in outcome measures from unblinding of assessors or participants. Conclusions: Manual pressure or rhythmic tapping over the injection site and applying local pressure around the injection site reduced IMI pain. However, there was very high unexplained heterogeneity between studies and risk of significant bias within small studies.