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.

Abstract Background Inhalation of nitrous oxide and oxygen (N2O/O2) is used to reduce pain that is spontaneous or induced by procedures. N2O/O2 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/O2 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/O2 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/O2 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/O2 reduces the pain of FTOPL. N2O/O2 could be recommended in FTOPL.