Objective: sterile water injections are a simple, safe, effective, non-pharmacological technique for relieving back pain in labour, however the number of injections required to achieve optimal analgesia is unknown. The objective of this trial was to evaluate the degree and duration of analgesia provided by a single injection of sterile water, compared to four injections. Design: randomised controlled non-inferiority trial.
Participants and setting: three hundred and five women in labour at term, requesting analgesia for back pain were recruited from two metropolitan hospitals in Brisbane, Australia. Intervention: participants were randomly assigned to receive either one (n=147) or four (n=158) sterile water injections.
Outcome measures: difference in self-reported pain measured using a visual analogue scale (VAS) between baseline and 30. mins post-intervention. The clinically acceptable margin of difference was defined as ≤1. cm on the VAS between the single injection compared to four injection technique. Secondary outcomes include VAS score on injection and 10, 60, 90 and 120. mins post-intervention, analgesia use, mode of birth and maternal satisfaction.
Findings: the mean difference in the pre and post (30. mins) injection scores between two groups was -1.48. cm (95% CI -2.10, -0.86) in favour of the FI technique, however the injection pain associated with the FI was significantly greater than that of the SI technique (p<0.001). There were no significant differences between the two groups in terms of other analgesic use, mode of birth or maternal satisfaction.
Conclusion: the four injection technique was associated with increased level of analgesia at 30. mins post-intervention compared to the single injection, but also a greater degree of injection pain.