Nitrous oxide for pain management of first-trimester instrumental termination of pregnancy under local anaesthesia and/or minimal sedation: A systematic review and meta-analysis

Background: Inhalation of nitrous oxide and oxygen (N2O/O-2) is used to reduce pain that is spontaneous or induced by procedures. N2O/O-2 could be useful in the treatment of the pain in first-trimester termination of pregnancy performed under local anaesthesia and/or minimal sedation (FTOPL). Objective: To evaluate the usefulness of N2O/O-2 to reduce pain in FTOPL. Search strategy: Electronic databases including PubMed, Embase, and MEDLINE were searched using keywords. Study selection: All studies comparing the use of N2O/O-2 versus a placebo in the management of pain during FTOPL during the first trimester were included. Of the 199 studies identified, four were deemed eligible for this meta-analysis. Data collection: The extracted results were perioperative pain, immediate and delayed postoperative pain, anxiety scores, and the secondary effects (nausea, vomiting). The data were analysed using Comprehensive Meta-Analysis software version 2.2.064. Main results: There was a significant difference in favour of N2O/O-2 for perioperative pain (p = 0.006; SMD = - 0.31; 95 % CI, -0.54 - -0.09). No difference was found, however, in postoperative pain, nor was there a difference in the secondary effects (nausea, vomiting) (p = 0.61). A significant decrease in postoperative anxiety scores was seen in the pooled placebo group (p = 0.049; SMD = 0.41; and 95 % CI, 0.001-0.83). Conclusions: N2O/O-2 reduces the pain of FTOPL. N2O/O-2 could be recommended in FTOPL. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study found that N2O/O2 was effective in reducing perioperative pain during first-trimester pregnancy termination, but did not show significant differences in postoperative pain or secondary effects compared to a placebo. However, a significant decrease in postoperative anxiety scores was observed in the placebo group.