- Email: [email protected]
Does nitrous oxide labor analgesia influence the pattern of neuraxial analgesia usage? An impact study at an academic medical center
Journal of Clinical Anesthesia (2016) 35, 54–57
Original contribution
Does nitrous oxide labor analgesia influence the pattern of neuraxial analgesia usage? An impact study at an academic medical center☆,☆☆ Lesley E. Bobb MD (Fellow in Obstetric Anesthesia)a,1,2,3 , Michaela K. Farber MD, MS (Assistant Professor of Anesthesia)a,1,3,4 , Catherine McGovern RN, CNM (Clinical Educator)b,3,5,6 , William Camann MD (Associate Professor of Anesthesia)a,⁎,3,7,8 a
Department of Anesthesiology, Perioperative, and Pain Medicine, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115 Center for Labor and Birth, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115
b
Received 2 October 2015; revised 28 May 2016; accepted 8 July 2016
Keywords: Neuraxial analgesia; Nitrous oxide
Abstract Study objective: To compare the rate of epidural use before and after the implementation of nitrous oxide (N2O). Design: 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. Setting: Labor and delivery floor. Main results: 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.
☆
Funding: This work was not funded by the National Institutes of Health, Howard Hughes Medical Institute, Medical Research Council, or Wellcome Trust. IRB: IRB contact—Fred Syllien: (617) 424-4124, [email protected]. ⁎ Corresponding author at: Department of Anesthesiology, Perioperative, and Pain Medicine, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115. Tel.: +1 617 732 8220; fax: +1 617 264 6841. E-mail addresses: [email protected] (L.E. Bobb), [email protected] (M.K. Farber), [email protected] (C. McGovern), [email protected] (W. Camann). 1 Contribution: This author helped analyze the data and prepare the manuscript. 2 Attestation: Lesley E. Bobb approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript. 3 Conflicts of interest: none. 4 Attestation: Michaela K. Farber approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript. 5 Contribution: This author helped collect the data and prepare the manuscript. 6 Attestation: Catherine McGovern approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript. 7 Contribution: This author designed the study, helped conduct the study, helped collect and analyze the data, and helped prepare the manuscript. 8 Attestation: William Camann approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript. William Camann is the archival author. ☆☆
http://dx.doi.org/10.1016/j.jclinane.2016.07.019 0952-8180/© 2016 Elsevier Inc. All rights reserved.
Influence of nitrous oxide on neuraxial analgesia use in labor
55
Conclusion: 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. © 2016 Elsevier Inc. All rights reserved.
1. Introduction Several options are available for pharmacologic and nonpharmacologic pain relief during labor and delivery (L&D). Personal preference and available resources often dictate what any particular woman will use for intrapartum pain relief [1]. The inhalation of nitrous oxide (N2O) for labor analgesia has recently undergone resurgence in popularity in the United States, although this technique has long been widely used in many other countries [2-4]. N2O may be used in early labor, in late labor, or as a bridge to other methods of analgesia for patients who are undecided about neuraxial or other analgesic methods. The influence of N2O on the utilization patterns of other forms of labor analgesia, particularly neuraxial techniques, has not been studied in the setting of a large American maternity hospital. We sought to examine how the introduction of N2O would influence the pattern of neuraxial labor analgesia at our institution.
2. Methods Brigham & Women's Hospital is a tertiary-care academic medical center in Boston performing approximately 7000 deliveries per year. Before August 2014, various modes of labor analgesia were available including intravenous opioids, epidural analgesia, and combined spinal-epidural analgesia. In August 2014, we began to offer N2O in addition to the other modalities. After August 2014, both N2O and neuraxial analgesia were available 24 h/d, 7 d/wk. For the implementation of N2O to laboring patients, the L&D nursing staff underwent thorough orientation about N2O, including its indicated use for labor analgesia, appropriate patient counseling, and safe operation of the N2O delivery system. Neuraxial analgesia was provided on patient request by a dedicated team of anesthesiology residents or fellows under the direct supervision of an attending obstetric anesthesiologist. The obstetric anesthesiology team was present on the L&D unit 24 h/d, with no service responsibility elsewhere in the hospital. The labor epidural technique was either an epidural dosed with 15-20 mL bupivacaine 0.125% with fentanyl 2 μg/mL or a combined spinal-epidural technique dosed with bupivacaine 1.67 mg and fentanyl 16.7 μg followed by a basal rate of bupivacaine 0.125% with fentanyl 2 μg/mL at 6 mL/h. Patient-controlled epidural dosing was a 6-mL demand dose with 15-minute lockout interval. N2O was supervised by the L&D nursing staff per an institutional policy established by
our multidisciplinary L&D management team. N2O was selfadministered by patients via a Pro-Nox (Carestream Medical, Langley, British Columbia, Canada) delivery system (N2O:O2 50%:50%) with its proper use monitored by the L&D nursing team. We compared the utilization of neuraxial labor analgesia and N2O usage during the 8-month period before (December 2013-July 2014) and for 8 months after (August-January 2015) the introduction of N2O. The utilization of N2O for labor analgesia was obtained from a nursing database of N2O usage. The utilization of neuraxial analgesia for labor was obtained from our anesthesia departmental database. Anesthetic utilization in the before and after periods was compared using χ2 analysis. We also tabulated the cesarean delivery rate across both time periods.
3. Results The total number of births over the study period was 8539: 4315 in the pre-N2O period (December 2013-July 2014) and 4224 in the post-N2O period (August 2014-March 2015). The utilization of epidural analgesia pre-N2O was 77% compared with 74% in the post-N2O period (P= .24, χ2). A total of 762 parturients used N2O. Month-to-month analysis showed no change in pattern of neuraxial analgesia use during the pre-N2O and post-N2O periods (Fig. 1). No change in monthly birth rate or cesarean delivery rate was observed between the study periods.
4. Discussion The primary finding of our study was that the new availability of N2O for labor analgesia on our L&D unit was not associated with a change in neuraxial labor analgesia use. We also observed no change in the overall birth or cesarean delivery rate. Our method of analysis is often referred to as a “catastrophe theory,” “impact study,” “sentinel event analysis,” or “natural experiment.” Requirements for this type of analysis include the rapid introduction of a new event, with an otherwise stable patient population and practice patterns. Analysis then consists of tabulation of a particular outcome in the before and after periods. Such analysis has been used for investigation of the influence of labor epidural analgesia on various labor outcomes, such as incidence of cesarean delivery [5], maternal fever [6], or fetal head malposition [7]. This method of
56
L.E. Bobb et al. 650 600 550 500 450 400 350 300 250 200 150 100 50 0
Total Births (n) Nitrous Use (n) Epidural use (n) Epidural Rate (%) Cesarean rate (%)
Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
2014
Fig. 1
Epidural, nitrous usage, and birthing data from December 2013 to March 2015.
analysis examines overall hospital-wide outcomes or resource utilization and does not assess individual patient outcomes. Therefore, although we identified no change in neuraxial labor analgesia utilization with the implementation of N2O analgesia, whether N2O use was predominantly among women who were committed to nonneuraxial pain relief techniques or natural childbirth, or was used by women as an adjunct before receiving epidural pain relief is unknown. Further studies are required to delineate which patients are choosing N2O and whether they opt for additional analgesia during labor. Nonetheless, our results are valuable on a policy-making or administrative level, as anesthetic staffing requirements on an L&D unit depend on accurate estimation of how various resources will be used in the aggregate setting. Nitrous oxide has been widely used for many years in other countries, but until recently, its utilization in the United States has been sparse [2-4]. The main reason for this was the lack of an FDA-approved delivery system. In 2012, this obstacle was overcome, and several vendors began to produce affordable, portable, safe systems with effective scavenging and venting devices to enable administration of N2O on L&D units and other settings. Although widely used in other countries, the actual evidence to support the analgesic efficacy of N2O during labor is surprisingly weak [4]. Our results may reflect the poor analgesic effects of N2O, but further study of specific analgesic patterns in our patients (N2O alone vs N2O with an epidural vs epidural without N2O) is required to confirm this hypothesis. Further studies are also required to determine the effect of N2O use in labor on overall maternal satisfaction as well as the temporizing effect of N2O on the initiation of epidural analgesia and the stages of labor. The use of, or avoidance of, various pain relief options during L&D is a very personal decision. Effective pain relief is only one aspect of a satisfying L&D experience [8]. For many women, complex interactions of prenatal expectations, coping, emotions, labor support resources, individual pain thresholds, and other multifactorial components contribute to the decisions to use various methods or combinations of pharmacologic and/or nonpharmacologic pain relief [8-11]. N2O may play an important role in maternal satisfaction about their labor experience.
The main alternative to neuraxial labor analgesia in the United States has traditionally been systemic opioids [1]. However, systemic opioid administration is associated with a variety of both maternal and fetal adverse effects, including nausea, sedation, fetal heart rate abnormalities, and neonatal depressant effects, including neurobehavioral findings and difficulty with initiation of breastfeeding [12]. In contrast, N2O has effects that are remarkably transient, with very brief onset and rapid offset of effect, minimal long-lasting maternal sedative properties, and no reported influence on Apgar scores or fetal heart rate patterns [2-4]. Thus, even considering the relatively mild analgesic properties of N2O, its role as an adjunct or alternative to other, more traditional labor pain relief modalities is appealing. Neither N2O nor systemic opioids are considered a substitute for the “criterion standard” demonstrated by neuraxial analgesia. Even with the implementation of advanced delivery systems (ie, patient controlled) and newer opioids (ie, remifentanil), intravenous opioid labor analgesia remains inferior in efficacy and safety compared with neuraxial analgesia [13-15]. Likewise, N2O does not provide the degree of analgesia even remotely similar to that of a neuraxial block. But, for a variety of reasons, not every woman wants, needs, or is able to receive neuraxial analgesia during labor. The ability to offer N2O as an alternative to opioids, with fewer opioid-related adverse effects, may be valuable. In conclusion, our results suggest that availability of N2O does not influence neuraxial analgesia use for labor pain relief. Further investigation is warranted to assess precisely why N2O did not change our pattern of neuraxial analgesia use, whether N2O analgesia impacts overall maternal satisfaction, and how N2O may be most effectively used as an adjunct to existing labor analgesic techniques.
References [1] Amin-Somuah M, Smyth R, Jones L. Epidural versus non-epidural or no analgesia in labour. Cochrane Database Syst Rev 2011;12, CD000331.
Influence of nitrous oxide on neuraxial analgesia use in labor [2] Likis FE, Andrews JC, Collins MR, et al. Nitrous oxide of the management of labor pain: a systematic review. Anesth Analg 2014; 118:153-67. [3] Rosen MA. Nitrous oxide for relief of labor pain: a systematic review. Am J Obstet Gynecol 2002;186(5 Suppl.):S110-26. [4] Likis FE, Andrews JA, Collins MR, et al. Nitrous oxide for the management of labor pain. Comparative effectiveness review no. 67 (prepared by the Vanderbilt Evidence-Based Practice Center under contract no. 290-2007-10065-I). Agency for Healthcare Research and Quality: Rockville, MD; 2012. [5] Segal S, Su M, Gilbert P. The effect of a rapid change in availability of epidural analgesia on the cesarean delivery rate: a meta-analysis. Am J Obstet Gynecol 2000 Oct;183:974-8. [6] Yancey MK, Zhang J, Schwarz J, Dietrich CS III, Klebanoff M. Labor epidural analgesia and intrapartum maternal hyperthermia. Obstet Gynecol 2001;98:763-70. [7] Yancey MK, Zhang J, Schweitzer DL, Schwarz J, Klebanoff MA. Epidural analgesia and fetal head malposition at vaginal delivery. Obstet Gynecol 2001;97:608-12. [8] Kannan S, Jamison RN, Datta S. Maternal satisfaction and pain control in women electing natural childbirth. Reg Anesth Pain Med 2001;26:468-72. [9] Carvalho B, Zheng M, Aiono-Le Tagaloa L. A prospective observational study evaluating the ability of prelabor psychological tests to predict
[10]
[11]
[12]
[13]
[14]
[15]
57 labor pain, epidural analgesic consumption, and maternal satisfaction. Anesth Analg 2011;119:632-4010. Trout KK. The neuromatrix theory of pain: implications for selected nonpharmacological methods of pain relief for labor. J Midwifery Womens Health 2004;49:482-8. Attanasio L, Kozhimannil KB, Jou J, McPherson ME, Camann WR. Women's experiences with neuraxial labor analgesia in the listening to mothers II survey: a content analysis of open-ended responses. Anesth Analg 2015;121:974-80. Fernando R, Jones T. Systemic analgesia: parenteral and inhalational agents. Chestnut's obstetric anesthesia: principles and practice. 4th ed. Philadelphia: Mosby/Elsevier; 2009. p. 415-27 [Ch. 22]. Liu ZQ, Chen XB, Li HB, Qiu MT, Duan T. A comparison of remifentanil parturient-controlled intravenous analgesia with epidural analgesia: a meta-analysis of randomized controlled trials. Anesth Analg 2014;118: 598-603. Birnbach DJ, Ranasinghe JS. Is remifentanil a safe and effective alternative to neuraxial labor analgesia? It all depends. Anesth Analg 2014;118: 491-3. Kranke P, Girard T, Lavand'homme P, et al. Must we press on until a young mother dies? Remifentanil patient-controlled analgesia in labour may not be suited as a “poor man's epidural”. BMC Pregnancy Childbirth 2013;13:139.
Original contribution
Does nitrous oxide labor analgesia influence the pattern of neuraxial analgesia usage? An impact study at an academic medical center☆,☆☆ Lesley E. Bobb MD (Fellow in Obstetric Anesthesia)a,1,2,3 , Michaela K. Farber MD, MS (Assistant Professor of Anesthesia)a,1,3,4 , Catherine McGovern RN, CNM (Clinical Educator)b,3,5,6 , William Camann MD (Associate Professor of Anesthesia)a,⁎,3,7,8 a
Department of Anesthesiology, Perioperative, and Pain Medicine, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115 Center for Labor and Birth, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115
b
Received 2 October 2015; revised 28 May 2016; accepted 8 July 2016
Keywords: Neuraxial analgesia; Nitrous oxide
Abstract Study objective: To compare the rate of epidural use before and after the implementation of nitrous oxide (N2O). Design: 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. Setting: Labor and delivery floor. Main results: 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.
☆
Funding: This work was not funded by the National Institutes of Health, Howard Hughes Medical Institute, Medical Research Council, or Wellcome Trust. IRB: IRB contact—Fred Syllien: (617) 424-4124, [email protected]. ⁎ Corresponding author at: Department of Anesthesiology, Perioperative, and Pain Medicine, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115. Tel.: +1 617 732 8220; fax: +1 617 264 6841. E-mail addresses: [email protected] (L.E. Bobb), [email protected] (M.K. Farber), [email protected] (C. McGovern), [email protected] (W. Camann). 1 Contribution: This author helped analyze the data and prepare the manuscript. 2 Attestation: Lesley E. Bobb approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript. 3 Conflicts of interest: none. 4 Attestation: Michaela K. Farber approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript. 5 Contribution: This author helped collect the data and prepare the manuscript. 6 Attestation: Catherine McGovern approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript. 7 Contribution: This author designed the study, helped conduct the study, helped collect and analyze the data, and helped prepare the manuscript. 8 Attestation: William Camann approved the final manuscript and attests to the integrity of the original data and the analysis reported in this manuscript. William Camann is the archival author. ☆☆
http://dx.doi.org/10.1016/j.jclinane.2016.07.019 0952-8180/© 2016 Elsevier Inc. All rights reserved.
Influence of nitrous oxide on neuraxial analgesia use in labor
55
Conclusion: 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. © 2016 Elsevier Inc. All rights reserved.
1. Introduction Several options are available for pharmacologic and nonpharmacologic pain relief during labor and delivery (L&D). Personal preference and available resources often dictate what any particular woman will use for intrapartum pain relief [1]. The inhalation of nitrous oxide (N2O) for labor analgesia has recently undergone resurgence in popularity in the United States, although this technique has long been widely used in many other countries [2-4]. N2O may be used in early labor, in late labor, or as a bridge to other methods of analgesia for patients who are undecided about neuraxial or other analgesic methods. The influence of N2O on the utilization patterns of other forms of labor analgesia, particularly neuraxial techniques, has not been studied in the setting of a large American maternity hospital. We sought to examine how the introduction of N2O would influence the pattern of neuraxial labor analgesia at our institution.
2. Methods Brigham & Women's Hospital is a tertiary-care academic medical center in Boston performing approximately 7000 deliveries per year. Before August 2014, various modes of labor analgesia were available including intravenous opioids, epidural analgesia, and combined spinal-epidural analgesia. In August 2014, we began to offer N2O in addition to the other modalities. After August 2014, both N2O and neuraxial analgesia were available 24 h/d, 7 d/wk. For the implementation of N2O to laboring patients, the L&D nursing staff underwent thorough orientation about N2O, including its indicated use for labor analgesia, appropriate patient counseling, and safe operation of the N2O delivery system. Neuraxial analgesia was provided on patient request by a dedicated team of anesthesiology residents or fellows under the direct supervision of an attending obstetric anesthesiologist. The obstetric anesthesiology team was present on the L&D unit 24 h/d, with no service responsibility elsewhere in the hospital. The labor epidural technique was either an epidural dosed with 15-20 mL bupivacaine 0.125% with fentanyl 2 μg/mL or a combined spinal-epidural technique dosed with bupivacaine 1.67 mg and fentanyl 16.7 μg followed by a basal rate of bupivacaine 0.125% with fentanyl 2 μg/mL at 6 mL/h. Patient-controlled epidural dosing was a 6-mL demand dose with 15-minute lockout interval. N2O was supervised by the L&D nursing staff per an institutional policy established by
our multidisciplinary L&D management team. N2O was selfadministered by patients via a Pro-Nox (Carestream Medical, Langley, British Columbia, Canada) delivery system (N2O:O2 50%:50%) with its proper use monitored by the L&D nursing team. We compared the utilization of neuraxial labor analgesia and N2O usage during the 8-month period before (December 2013-July 2014) and for 8 months after (August-January 2015) the introduction of N2O. The utilization of N2O for labor analgesia was obtained from a nursing database of N2O usage. The utilization of neuraxial analgesia for labor was obtained from our anesthesia departmental database. Anesthetic utilization in the before and after periods was compared using χ2 analysis. We also tabulated the cesarean delivery rate across both time periods.
3. Results The total number of births over the study period was 8539: 4315 in the pre-N2O period (December 2013-July 2014) and 4224 in the post-N2O period (August 2014-March 2015). The utilization of epidural analgesia pre-N2O was 77% compared with 74% in the post-N2O period (P= .24, χ2). A total of 762 parturients used N2O. Month-to-month analysis showed no change in pattern of neuraxial analgesia use during the pre-N2O and post-N2O periods (Fig. 1). No change in monthly birth rate or cesarean delivery rate was observed between the study periods.
4. Discussion The primary finding of our study was that the new availability of N2O for labor analgesia on our L&D unit was not associated with a change in neuraxial labor analgesia use. We also observed no change in the overall birth or cesarean delivery rate. Our method of analysis is often referred to as a “catastrophe theory,” “impact study,” “sentinel event analysis,” or “natural experiment.” Requirements for this type of analysis include the rapid introduction of a new event, with an otherwise stable patient population and practice patterns. Analysis then consists of tabulation of a particular outcome in the before and after periods. Such analysis has been used for investigation of the influence of labor epidural analgesia on various labor outcomes, such as incidence of cesarean delivery [5], maternal fever [6], or fetal head malposition [7]. This method of
56
L.E. Bobb et al. 650 600 550 500 450 400 350 300 250 200 150 100 50 0
Total Births (n) Nitrous Use (n) Epidural use (n) Epidural Rate (%) Cesarean rate (%)
Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
2014
Fig. 1
Epidural, nitrous usage, and birthing data from December 2013 to March 2015.
analysis examines overall hospital-wide outcomes or resource utilization and does not assess individual patient outcomes. Therefore, although we identified no change in neuraxial labor analgesia utilization with the implementation of N2O analgesia, whether N2O use was predominantly among women who were committed to nonneuraxial pain relief techniques or natural childbirth, or was used by women as an adjunct before receiving epidural pain relief is unknown. Further studies are required to delineate which patients are choosing N2O and whether they opt for additional analgesia during labor. Nonetheless, our results are valuable on a policy-making or administrative level, as anesthetic staffing requirements on an L&D unit depend on accurate estimation of how various resources will be used in the aggregate setting. Nitrous oxide has been widely used for many years in other countries, but until recently, its utilization in the United States has been sparse [2-4]. The main reason for this was the lack of an FDA-approved delivery system. In 2012, this obstacle was overcome, and several vendors began to produce affordable, portable, safe systems with effective scavenging and venting devices to enable administration of N2O on L&D units and other settings. Although widely used in other countries, the actual evidence to support the analgesic efficacy of N2O during labor is surprisingly weak [4]. Our results may reflect the poor analgesic effects of N2O, but further study of specific analgesic patterns in our patients (N2O alone vs N2O with an epidural vs epidural without N2O) is required to confirm this hypothesis. Further studies are also required to determine the effect of N2O use in labor on overall maternal satisfaction as well as the temporizing effect of N2O on the initiation of epidural analgesia and the stages of labor. The use of, or avoidance of, various pain relief options during L&D is a very personal decision. Effective pain relief is only one aspect of a satisfying L&D experience [8]. For many women, complex interactions of prenatal expectations, coping, emotions, labor support resources, individual pain thresholds, and other multifactorial components contribute to the decisions to use various methods or combinations of pharmacologic and/or nonpharmacologic pain relief [8-11]. N2O may play an important role in maternal satisfaction about their labor experience.
The main alternative to neuraxial labor analgesia in the United States has traditionally been systemic opioids [1]. However, systemic opioid administration is associated with a variety of both maternal and fetal adverse effects, including nausea, sedation, fetal heart rate abnormalities, and neonatal depressant effects, including neurobehavioral findings and difficulty with initiation of breastfeeding [12]. In contrast, N2O has effects that are remarkably transient, with very brief onset and rapid offset of effect, minimal long-lasting maternal sedative properties, and no reported influence on Apgar scores or fetal heart rate patterns [2-4]. Thus, even considering the relatively mild analgesic properties of N2O, its role as an adjunct or alternative to other, more traditional labor pain relief modalities is appealing. Neither N2O nor systemic opioids are considered a substitute for the “criterion standard” demonstrated by neuraxial analgesia. Even with the implementation of advanced delivery systems (ie, patient controlled) and newer opioids (ie, remifentanil), intravenous opioid labor analgesia remains inferior in efficacy and safety compared with neuraxial analgesia [13-15]. Likewise, N2O does not provide the degree of analgesia even remotely similar to that of a neuraxial block. But, for a variety of reasons, not every woman wants, needs, or is able to receive neuraxial analgesia during labor. The ability to offer N2O as an alternative to opioids, with fewer opioid-related adverse effects, may be valuable. In conclusion, our results suggest that availability of N2O does not influence neuraxial analgesia use for labor pain relief. Further investigation is warranted to assess precisely why N2O did not change our pattern of neuraxial analgesia use, whether N2O analgesia impacts overall maternal satisfaction, and how N2O may be most effectively used as an adjunct to existing labor analgesic techniques.
References [1] Amin-Somuah M, Smyth R, Jones L. Epidural versus non-epidural or no analgesia in labour. Cochrane Database Syst Rev 2011;12, CD000331.
Influence of nitrous oxide on neuraxial analgesia use in labor [2] Likis FE, Andrews JC, Collins MR, et al. Nitrous oxide of the management of labor pain: a systematic review. Anesth Analg 2014; 118:153-67. [3] Rosen MA. Nitrous oxide for relief of labor pain: a systematic review. Am J Obstet Gynecol 2002;186(5 Suppl.):S110-26. [4] Likis FE, Andrews JA, Collins MR, et al. Nitrous oxide for the management of labor pain. Comparative effectiveness review no. 67 (prepared by the Vanderbilt Evidence-Based Practice Center under contract no. 290-2007-10065-I). Agency for Healthcare Research and Quality: Rockville, MD; 2012. [5] Segal S, Su M, Gilbert P. The effect of a rapid change in availability of epidural analgesia on the cesarean delivery rate: a meta-analysis. Am J Obstet Gynecol 2000 Oct;183:974-8. [6] Yancey MK, Zhang J, Schwarz J, Dietrich CS III, Klebanoff M. Labor epidural analgesia and intrapartum maternal hyperthermia. Obstet Gynecol 2001;98:763-70. [7] Yancey MK, Zhang J, Schweitzer DL, Schwarz J, Klebanoff MA. Epidural analgesia and fetal head malposition at vaginal delivery. Obstet Gynecol 2001;97:608-12. [8] Kannan S, Jamison RN, Datta S. Maternal satisfaction and pain control in women electing natural childbirth. Reg Anesth Pain Med 2001;26:468-72. [9] Carvalho B, Zheng M, Aiono-Le Tagaloa L. A prospective observational study evaluating the ability of prelabor psychological tests to predict
[10]
[11]
[12]
[13]
[14]
[15]
57 labor pain, epidural analgesic consumption, and maternal satisfaction. Anesth Analg 2011;119:632-4010. Trout KK. The neuromatrix theory of pain: implications for selected nonpharmacological methods of pain relief for labor. J Midwifery Womens Health 2004;49:482-8. Attanasio L, Kozhimannil KB, Jou J, McPherson ME, Camann WR. Women's experiences with neuraxial labor analgesia in the listening to mothers II survey: a content analysis of open-ended responses. Anesth Analg 2015;121:974-80. Fernando R, Jones T. Systemic analgesia: parenteral and inhalational agents. Chestnut's obstetric anesthesia: principles and practice. 4th ed. Philadelphia: Mosby/Elsevier; 2009. p. 415-27 [Ch. 22]. Liu ZQ, Chen XB, Li HB, Qiu MT, Duan T. A comparison of remifentanil parturient-controlled intravenous analgesia with epidural analgesia: a meta-analysis of randomized controlled trials. Anesth Analg 2014;118: 598-603. Birnbach DJ, Ranasinghe JS. Is remifentanil a safe and effective alternative to neuraxial labor analgesia? It all depends. Anesth Analg 2014;118: 491-3. Kranke P, Girard T, Lavand'homme P, et al. Must we press on until a young mother dies? Remifentanil patient-controlled analgesia in labour may not be suited as a “poor man's epidural”. BMC Pregnancy Childbirth 2013;13:139.