A comparison of pain levels following injections of hypotonic saline, sterile water or normal saline: A randomised trial
A comparison of pain levels following injections of hypotonic saline, sterile water or normal saline: A randomised trial in healthy adult females aged 18 to 45 years
The University of Queensland
90 participants
Jul 1, 2026
Interventional
Conditions
Summary
Sterile water injections are used by midwives to manage back pain during labour. The only side effect is the intense pain of the injections due to the lack of salt ions in sterile water. This placebo controlled double blind study aims to assess if a small concentration of salt added to the sterile water (0.2%) will reduce the pain of the injections. We hypothesize that the alternative low salt concentration solution will provide a more acceptable alternative to sterile water improving acceptability while maintaining clinical effectiveness.
Eligibility
Inclusion Criteria4
- Student enrolled at the University of Queensland
- Substantially healthy (self assessed)
- Aged between 18 – 45 years
- Female sex (at birth)
Exclusion Criteria4
- Pregnancy
- Chronic or ongoing pain
- Use of medication for depression, pain, or sleeping disorder 24?h before the experiment
- Smoking, physical activity, and intake of caffeinated beverages (coffee, tea, or energy drink (e.g., Red Bull)) 2 hrs before the experiment.
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Interventions
Intervention group 1: Participants in this group will receive two simultaneous injections of 0.2% sodium chloride solution into the intradermal layer of the skin above the posterior superior iliac spines (PSIS). The injections will done by two registered midwives trained in the procedure. The injections take less than 30 seconds to complete and are given once. The 0.2% sodium chloride solution will be achieved by mixing 0.2mls of 0.9% sodium chloride for injection with 0.8mls of sterile water for injection. The volume injected at each site will be 0.1- 0.3mls depending on the visual assessment of the resulting bleb. Consistency in site selection and procedural continuity will be monitored by the administering investigators. Intervention group 2: Sterile water. Participants in this group will receive two simultaneous injections of sterile water into the intradermal layer of the skin above the PSIS. The volume injected at each site will be 0.1-0.3 mls.
Locations(1)
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ACTRN12626000138381