Introduction

Intramuscular injections are one of the most commonly used modalities for pharmacological treatments such as vaccines, analgesia, corticosteroids, and hormonal therapies.1-3 More than 12 billion intramuscular injections are administered annually throughout the world, with nurses working in hospital and community settings performing this medical procedure daily as part of their role.4 The process of intramuscular injections involves the drug being introduced into the muscle tissue.5,6 Due to the vascularity of the muscle, absorption of the drug via the intramuscular route is faster than through the subcutaneous method. Additionally, some medications contain constituents that may be an irritant to the subcutaneous tissue; however, if administered intramuscularly, these injections cause less irritation, but are still painful.2,7

Despite intramuscular injections being commonly used for administration of parenteral medications and with the procedure considered a simple technique, pain from intramuscular injections is the most commonly reported side effect.1,6 There are two main causes for intramuscular injection pain: penetration of the needle and the chemical reaction of the medication entering the muscle.1,5,7 Pain receptors at the skin and pressure receptors at the muscle are where the pain of an intramuscular injection is registered. Past experiences of painful intramuscular injections create an emotional and cognitive negative imprint that have the ability to raise a fear response due to the previous experience. The needle phobia can deter patients from seeking medical treatment in the future.1,8

The gate control theory of pain introduced in 1965 by Melzack and Wall9 proposes that when a pain signal is transmitted to the spinal cord through the central nervous system, a gating mechanism in the dorsal horns of the spinal cord can either inhibit or facilitate those pain signals passing to the brain.10-12 Therefore, the gating mechanism has the ability to send an impulse through the A-delta nerve fibers to either open or close the gate in the spinal cord.10,12 According to the gate control theory of pain, a physical stimulation technique, such as pressure or rubbing, of the injection site prior to administration of the injection stimulates small A-delta nerve fibers. The physical stimulation works by closing the gate to the painful transmission since the stimulation signals get to the spinal cord first.10-12 Using a physical stimulation technique to reduce pain due to injections therefore correlates with the gate control theory of pain. Pressure (non-painful stimuli) applied to the injection site prior to administration of an injection inhibits the transmission of the painful stimuli (injection).

Numerous randomized controlled trials (RCTs) and clinical trials have addressed the non-pharmacological (pressure, distraction, and cold intensity) and pharmacological methods (topical and local anesthetics) of pain reduction during intramuscular injection.5,13-22 Some studies have published conflicting results. An RCT demonstrated that the use of a shot blocker (manual pressure device) to the injection site was effective at reducing pain intensity but increased patients anxiety levels.21 Similarly, a clinical trial indicated that acupressure significantly reduced the pain experienced by intramuscular injections.22 Conversely, when exploring the effect of music and pressure on pain intensity from intramuscular injection, music was found to be effective in reducing pain whereas applying pressure demonstrated no effect.20

Reducing patients' pain from intramuscular injections is important for the continued development of the patient and nurse relationship.8 The challenge for the nurse is in exploring alternate methods to reduce pain from intramuscular injections, as this will increase patient satisfaction.2 Currently, several methods are used to alleviate this pain, and research continues to explore the most effective techniques.

A preliminary search of PROSPERO, MEDLINE, the Cochrane Database of Systematic Reviews, and the JBI Database of Systematic Reviews and Implementation Reports was conducted, and three systematic reviews that assessed strategies for reducing pain were identified.5,23,24 The first review reported on establishing best practice guidelines for administration of intramuscular injections, but did not assess the quality of the included papers.5 The second review was published in 2010; however, it was undertaken only for adults receiving immunization.23 The third review synthesized the evidence of the effectiveness of vibratory stimulation on reducing needle-related pain in children.24 Therefore, the objective of this review is to evaluate the effectiveness of physical stimulation on injection pain in adults receiving intramuscular injections.

Review question

Is physical stimulation effective in reducing intramuscular procedural pain in adults?

Inclusion criteria

Participants

The review will consider studies that include adults aged 18 years and over receiving intramuscular injections. Studies undertaken on children will be excluded. Studies evaluating pain levels in patients receiving subcutaneous, intradermal, and intravenous injection will also be excluded.

Interventions

This review will consider studies of interventions that use physical stimulation during intramuscular injections. It will include any physical stimulation strategies used during intramuscular injections, including devices, skin tapping, manual pressure, massage, pinch, and traction. Physical stimulation strategies related to temperature, such as hot and cold compresses, will be excluded.

Comparators

This review will consider studies that compare the intervention to a control group or no treatment or other strategies.

Outcomes

This review will consider studies that include pain during intramuscular injection administration as an outcome. Only studies that evaluate pain using validated tools such as pain scales will be included.

Types of studies

This review will consider both experimental and quasi-experimental study designs including RCTs, non-randomized controlled trials, and before and after studies.

Methods

The proposed systematic review will be conducted in accordance with JBI methodology for systematic reviews of effectiveness.25 The protocol has been registered in PROSPERO (CRD42020168586).

Search strategy

The search strategy will aim to locate both published and unpublished studies. An initial limited search of MEDLINE and CINAHL was undertaken to identify articles on the topic. The text words contained in the titles and abstracts of relevant articles, and the index terms used to describe the articles were used to develop a full search strategy for MEDLINE (see Appendix I). The search strategy, including all identified keywords and index terms, will be adapted for each included information source. The reference lists of all studies selected for critical appraisal will be screened for additional studies.

The databases to be searched include: MEDLINE (PubMed), Embase, CINAHL, the Cochrane Library, and Cochrane Central Register of Controlled Trials. The search for unpublished studies will include Google Scholar, Dissertation Abstracts International, ProQuest Dissertations and Theses, and MedNar. The trial registers to be searched will include ClinicalTrials.gov. Studies published in English will be included. Studies published from database inception until the current date will be included.

Study selection

Following the search, all identified citations will be collated and uploaded into EndNote X8 (Clarivate Analytics, PA, USA) and duplicates removed. Titles and abstracts will then be screened by two independent reviewers for assessment against the inclusion criteria for the review. Potentially relevant studies will be retrieved in full and their citation details imported into the JBI System for the Unified Management, Assessment and Review of Information (JBI SUMARI; JBI, Adelaide, Australia).26 The full text of selected citations will be assessed in detail against the inclusion criteria by two independent reviewers. Reasons for exclusion of full-text studies that do not meet the inclusion criteria will be recorded and reported in the systematic review. Any disagreements that arise between the reviewers at each stage of the study selection process will be resolved through discussion or with a third reviewer. The results of the search will be reported in full in the final systematic review and presented in a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram.27

Assessment of methodological quality

Eligible studies will be critically appraised by two independent reviewers at the study level for methodological quality in the review using standardized critical appraisal instruments from JBI for experimental and quasi-experimental studies.25 Authors of papers will be contacted to request missing or additional data for clarification, where required. Any disagreements that arise will be resolved through discussion or with a third reviewer. The results of the critical appraisal will be reported in narrative form and in a table.

All studies, regardless of the results of their methodological quality, will undergo data extraction and synthesis (where possible).

Data extraction

Data will be extracted from studies included in the review by two independent reviewers using the standardized JBI data extraction tool.26 The data extracted will include specific details about the populations, study methods, interventions, and outcomes of significance to the review objective. Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer. Authors of papers will be contacted to request missing or additional data, where required.

Data synthesis

Studies will, where possible, be pooled in statistical meta-analysis using JBI SUMARI. Effect sizes will be expressed for dichotomous data as odds ratios or risk ratios, and for continuous data, weighted (or standardized) final post-intervention mean differences along with their 95% confidence intervals. Heterogeneity will be assessed statistically using the standard [chi]² and I² tests. The choice of model (random or fixed effects) and method for meta-analysis will be based on the guidance by Tufanaru et al.25 Subgroup analyses will be conducted where there are sufficient data to investigate the various physical strategies for injection pain reduction. Where statistical pooling is not possible, the findings will be presented in narrative form, including tables and figures, to aid in data presentation where appropriate. A funnel plot will be generated to assess publication bias if there are 10 or more studies included in a meta-analysis. Statistical tests for funnel plot asymmetry will be performed where appropriate.28

Assessing certainty in the findings

The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach29 for grading the certainty of evidence will be followed and a Summary of Findings will be created using GRADEpro GDT (McMaster University, ON, Canada). The Summary of Findings will present the following information where appropriate: absolute risks for the treatment and control, estimates of relative risk, and a ranking of the quality of the evidence based on the risk of bias, directness, heterogeneity, precision, and risk of publication bias of the review results. The outcome reported in the Summary of Findings will be pain.

Appendix I: Search strategy

MEDLINE (PubMed)

Search conducted: 4 November 2019

References