Novel use of local analgesia prior to intramuscular magnesium sulphate injection compared to mixed local analgesia with magnesium sulphate to reduce pain: a randomised crossover study in patients being managed for eclampsia and preeclampsia

Abstract

The World Health Organization (WHO) recommended addition of local anesthetic to reduce the intense pain of intramuscular injection of 50% Magnesium Sulphate (MgSO4) salt solution has been found to be ineffective. We tested whether giving the local anesthetic 5 min before the MgSO4 injection would reduce pain.We conducted a prospective cross-over trial where each participant with pre-eclampsia or eclampsia received sequential and mixed injection methods in random sequence during sequential MgSO4 administrations. Pain and preference were assessed using descriptive words, a numeric pain scale and direct comparison between the two injection methods. Differences were measured using the Wilcoxon signed rank test, risk ratios with 95% confidence intervals and the Chi squared or Fisher's test. The administration techniques were refined based on an initial pilot of 8 participants.We enrolled 49 consented participants and analysed data from 41 post-pilot participants The sequential injection method had a non-significantly lower mean pain score than the mixed injection method (3.1 vs. 3.3, p = 0.44). Severe pain was reported for 3/41 vs. 9/41, p = 0.12. The sequential injection method was perceived to be more painful by 13 (37%) vs. 22 (63%) participants (p = 0.03). The sequential injection was preferred by 21(60%) vs. 14 participants (40%) (p = 0.1).Our results consistently favoured the novel sequential injection method. The lack of statistical significance for most results is not surprising given the small sample size. Given the potential for clinically important benefits to women, a larger study to confirm these results is justified. https://pactr.samrc.ac.za/, Identifier (PACTR202201521544765).