Nitrous oxide for labor analgesia: Utilization and predictors of conversion to neuraxial analgesia.

We examined the characteristics of women who choose nitrous oxide for labor analgesia and identified factors that predict conversion from nitrous oxide to labor neuraxial analgesia. Retrospective descriptive study. Labor and Delivery Ward. 146 pregnant women who used nitrous oxide for analgesia during labor and delivery between September 2014 and September 2015. Chart review only. Demographic, obstetric, and intrapartum characteristics of women using nitrous oxide were examined. Multivariable logistic regression was performed to identify factors associated with conversion from nitrous oxide to neuraxial analgesia. Data are presented as n (%), median [IQR], adjusted relative risk (aRR), and 95% confidence intervals (CI) as appropriate. During the study period, 146 women used nitrous oxide for labor analgesia (accounting for 3% of the total deliveries). The majority (71.9%) of women who used nitrous oxide were nulliparous, and over half (51.9%) had expressed an initial preference for "nonmedical birth." The conversion rate to neuraxial blockade was 63.2%, compared to a concurrent institutional rate of 85.1% in women who did not use nitrous oxide. Factors associated with conversion from nitrous oxide to neuraxial blockade were labor induction (aRR=2.0, CI 1.2-3.3) and labor augmentation (aRR=1.7, CI 1.0-2.9). Only a small number of women opted to use nitrous oxide during labor, analgesia was minimal, and most converted to neuraxial analgesia. Women with induced and augmented labors should be counseled about the increased likelihood that they will convert to neuraxial analgesia.

Sutton CD ，Butwick AJ ，Riley ET ，Carvalho B ... -  《-》

Nitrous Oxide Use During Labor: Satisfaction, Adverse Effects, and Predictors of Conversion to Neuraxial Analgesia.

Women desire safe and effective choices for pain management during labor. Currently, neuraxial and opioid analgesia are the most common methods used in the United States. The purpose of this study was to investigate demographic characteristics, safety, and satisfaction in a cohort of parturients who used inhaled nitrous oxide (N2 O) analgesia and to determine predictors of conversion from N2 O to neuraxial analgesia. This was a prospective chart review study. Individuals aged at least 18 years who used inhaled N2 O during the first or second stage of labor between March 1, 2016, and July 23, 2017, on the labor and delivery unit of one academic medical center (N = 463) and their neonates were included. Data describing maternal and neonatal factors are reported. Logistic regression and chi-square tests were used to model the effects of oxytocin augmentation, labor induction, parity, prior cesarean birth, pre-N2 O cervical dilatation, and post-N2 O cervical dilatation on the odds of conversion from N2 O to neuraxial analgesia. In this cohort, 31% who chose N2 O for analgesia did not convert to any other analgesic method. Significant positive predictors for conversion from N2 O to neuraxial analgesia included labor induction (odds ratio [OR], 2.9; 95% CI, 1.7-5.0), oxytocin augmentation (OR, 3.1; 95% CI, 1.6-6.0), and labor after cesarean (OR, 6.4; 95% CI, 2.5-16.5). Multiparity (OR, 0.4; 95% CI, 0.2-0.6) and post-N2 O cervical dilatation (OR, 0.8; 95% CI, 0.7-0.9) were negative predictors. Adverse effects related to N2 O use during labor were rare (8%) and were not a significant reason for conversion to neuraxial analgesia. Parturients had moderately high satisfaction with N2 O for pain management (11-point scale, mean [SD], 7.4 [2.9]). Five-minute Apgar scores were 7 or greater in 97.8% of the newborns. Understanding predictors of conversion from inhaled N2 O to neuraxial analgesia may assist perinatal care providers in their discussions with women about analgesia options during labor. N2 O is a useful, safe option for labor analgesia in the United States.

Nodine PM ，Collins MR ，Wood CL ，Anderson JL ，Orlando BS ，McNair BK ，Mayer DC ，Stein DJ ... -  《-》

Does nitrous oxide labor analgesia influence the pattern of neuraxial analgesia usage? An impact study at an academic medical center.

To compare the rate of epidural use before and after the implementation of nitrous oxide (N2O). Data were obtained from a nursing database of N2O usage and our obstetric anesthesia database. We compared 8 months before and 8 months after the introduction of N2O. It was available 24 h/d, 7 d/wk, consistent with neuraxial analgesia availability. Epidural utilization before and after introduction of N2O was compared using χ2 analysis. Labor and delivery floor. Total number of births over the study period was 8539: 4315 pre-N2O and 4224 post-N2O. The rate of epidural usage was 77% pre-N2O and 74% after N2O (P= not significant, χ2). A total of 762 patients used N2O. Monthly analysis showed no change in pattern of neuraxial analgesia use in post-N2O period compared with the pre-N2O period. The introduction of N2O for labor analgesia was not associated with any change in our rate of labor epidural utilization. Under the conditions of our study, these results suggest that N2O does not discourage neuraxial use for labor pain relief.

Bobb LE ，Farber MK ，McGovern C ，Camann W ... -  《-》

Nitrous Oxide During Labor: Maternal Satisfaction Does Not Depend Exclusively on Analgesic Effectiveness.

Richardson MG ，Lopez BM ，Baysinger CL ，Shotwell MS ，Chestnut DH ... -  《-》

A qualitative analysis of parturients' experiences using nitrous oxide for labor analgesia: It is not just about pain relief.

A vast majority of women who choose nitrous oxide for labor report high satisfaction despite variable analgesic effectiveness. We analyzed comments provided by women who used nitrous oxide for labor, to identify determinants of satisfaction in this population, and to better understand reasons for continuing with nitrous oxide despite variable analgesic effectiveness. We conducted qualitative content analysis of comments in a quality improvement database of routine follow-up assessments of women who delivered vaginally, using nitrous oxide as the sole labor analgesic. An inductive grounded approach was used and emergent themes and subthemes were identified. Of 6507 vaginal deliveries over 34 months in 2011-2014, 753 (12%) used nitrous oxide as their sole analgesic. Analysis of 264 clarifying comments yielded six emergent themes. Parturients cited nonanalgesic benefits of nitrous oxide use (relaxation, distraction, focus on breathing), as well as partial analgesic effects that they deemed to be sufficient, or consistent with their expectations. Numerous women described their nitrous oxide experience as consistent with their birth plan, including 14 who equated it with natural childbirth. Several comments described nitrous oxide as a vital component of the parturients' birth experience. Some described using nitrous oxide when neuraxial analgesia was not possible. Side effects were identified, as were difficulties using the apparatus/mask. Analysis highlighted importance of timely administration upon request and attention to technical aspects. Among parturients who choose nitrous oxide as their sole labor analgesic, determinants of satisfaction are more variable than previously understood, and extend beyond analgesia.

Richardson MG ，Raymond BL ，Baysinger CL ，Kook BT ，Chestnut DH ... -  《-》