4. Discussion
NRS pain, NRS, pain
MINOR, RECRUITMENT
New insights gained from this research are as follows: (1) effectiveness of nitrous oxide and pethidine/midazolam is comparable for pain relief in minor gynecologic procedures; (2) patients’ satisfaction is also not significantly different between the two groups; (3) side effects of nitrous oxide is significantly lower when compared to those in pethidine/midazolam group; and (4) patients in nitrous oxide group had significantly faster recovery time. However, though the discharge scores were better with statistical significance in the group of nitrous oxide, one or two points of scores might not be clinically significant. Nevertheless, this study supports that inhaled nitrous oxide could be an alternative analgesic technique for minor gynecologic operative procedures, which would improve patients’ comfort and tolerance to the procedures and health care quality without serious side effects.To the best of our knowledge, this is the first study that evaluated the effectiveness and safety of nitrous oxide as pain relief during minor gynecologic procedures. Accordingly, this study could not be perfectly compared with other previous studies on the effectiveness of nitrous oxide. Nevertheless, our finding seems in agreement with that reported by Schneider et al. [Interestingly, both methods in this study were not highly effective in pain relief for minor gynecologic operations (NRS pain scores of 5–6, interpreted as moderate pain relief). Nevertheless, most patients expressed high satisfaction with the procedures. This might be associated with rapid recovery, no serious side effects, short operation time, and probably acceptability of moderate pain relief among our patients. In fact, our results are consistent with those reported by Thongrong et al. [The strengths of this study include: (1) no selection bias at recruitment. This was due to the nature of randomized controlled trials in which known and unknown confounders were equally allocated to both groups, as confirmed by the similar baseline and clinical data; (2) as conducted in a single center, the same standard protocol of care was provided to all patients; (3) exclusion of the women who had a history of prior gynecologic procedure such as curettage because it might alter the pain threshold; and (4) all main outcomes were assessed using the well-validated metric tool; NRS as well as post-anesthesia discharge scoring system.The weaknesses of this study are as follows: (1) Because of the apparent difference in the methods of drug administration, both participants and care providers could not be blinded to the groups of study, possibly resulting in a bias in the subjective assessment of pain scoring and other outcomes. (2) The types of procedures were heterogeneous and did not include some other important gynecologic procedures such as loop electrosurgical excision procedure or hysteroscopic polypectomy, etc. (3) The sedative effects after the procedure might still persist and affect the capability in pain scoring. (4) Though the sample size was adequate for primary outcomes, it might be relatively small for some rare side effects of both medications. Of note, the pain scores in the nitrous oxide group seemed to be slightly higher, though not significantly different. Thus, it is possible that studies with larger sample sizes or high power of test might express a significance of such a small difference if it existed. Nevertheless, such a small difference, if it existed, was unlikely to have a clinical impact.Based on our findings, because of the comparable effectiveness to intravenous sedation for pain relief and its safety as well as rapid recovery, it is reasonable to use nitrous oxide for pain control during the uncomplicated short minor gynecological procedure. Advantages of nitrous oxide include its low cost and non-burdensome training of clinic staff. Additionally, nitrous oxide sedation has a rapid onset, quickly reversible with the administration of 100% oxygen, and delivery of the gas is noninvasive. However, because of some weaknesses mentioned above, larger randomized controlled trials are needed to confirm our results. In health systems that do not have the resources for analgesia sedation or anesthesia supervised by an anesthesiologist for such minor gynecological procedures, the use of nitrous oxide appears to be a second-rate alternative.