Abstract
Background
Recent trials demonstrated the safety and efficacy of sterile water injections to
provide relief from labour back pain. While four injections is the most common approach
variations in technique, such as employing two injections, are also used.
Aim
To determine if the analgesic effect of two sterile water injections is clinically
equivalent to four.
Methods
238 women in labour with a Visual Analogue Scale pain score (VAS) of 70 millimetres
(mm) (0 = no pain; 100 = worst pain imaginable) were randomised to two or four sterile
water injections. The primary outcome was pain measured on a VAS at 30 min post treatment.
A priori margin of equivalence was set at ±10 mm. Secondary outcomes included the
likelihood of achieving an at least 30% and 50% reduction in pain, birth and neonatal
outcomes.
Results
At 30 min post-injection the difference in VAS scores between the techniques was −5.97
(95% Confidence Interval [CI] −13.18–1.22). As the lower end of the CI exceeds the
margin of −10 mm equivalence was not demonstrated. Both techniques achieved an at
least 30% reduction in pain in over 75% of participants though duration of effect
was longer in the four injection group. There was no difference in other birth related
secondary outcomes.
Conclusion
Four injections provided a margin of benefit over two injections in level and duration
of analgesia.
Discussion
Four injections remains the technique of choice though two injections still provided
significant pain relief and would be suitable where it was not possible or desirable
to provide four.
Keywords
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Article info
Publication history
Published online: February 10, 2022
Accepted:
February 1,
2022
Received in revised form:
February 1,
2022
Received:
November 25,
2021
Identification
Copyright
© 2022 Australian College of Midwives. Published by Elsevier Ltd. All rights reserved.