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10/8/2016
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Nitrous Oxide for Labor Analgesia
Sandra Hoffman MS RNC-EFM
MPO 2016
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• Sandra Hoffman has no disclosures
Acknowledgements for program development: Lindsey Meier RN, Debbie Biffle RN, Dr Steven Dentz, Dr Sue Sendelbach
Images in this presentation are public domain images
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Disclosures
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OBJECTIVES
• Discuss history of nitrous oxide use for birth
• Describe candidates for nitrous oxide, and contraindications for use
• Discuss safe implementation of nitrous oxide for labor, as well as some of the potential barriers
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Nitrous Oxide: Some History
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• Discovered in 1771
• Analgesic potential for labor pain-1881 Russian MD Klikovich developed a machine that delivered 80% nitrous -20% oxygen
• Regular use for labor pain in 1934 with the creation of a device that allowed self administration
• 1961-Introduction of Entonox machine (50%/50% blend)
• As of 2014, only 19 hospitals and 14 birth centers were using or in the process of offering nitrous oxide to women in labor (Plenda 2014)
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Nitrous Oxide at the Present
• Most utilized gaseous anesthetic worldwide
• #1 utilized modality for labor analgesia worldwide
• UK- 60% of laboring women utilize N20
• Australia- 50% utilization
• Norway- offered at 85% of birthing centers
• Finland- 48% utilization
• More common than regional anesthesia worldwide (Rooks, 2007; STAKES 2006)
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& in the United States…
UCSF (over three decades)Vanderbilt (over three years)
Only recently widely available in the Twin Cities (Birthing centers and hospitals)
Growing consumer interest….
Why has it taken so long to catch on in the US?
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• Rooks: $$
• 61% of women who have singleton vaginal births in the U.S. receive regional anesthesia for labor pain. Epidurals are the most effective pain mgt modality.
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Nitrous Oxide: Why so long to adopt?
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• All women do not need or want regional anesthesia. Those who do are may be denied accessibility due to lack of or competing needs for the services of anesthesia professionals.
• This is especially true for women living in rural areas and delivering in institutions where anesthesia may not staff 24/7.
(Rooks, 2007)
Nitrous oxide may become increasingly in demand as the supply of anesthesiologists and nurse anesthetists to provide 24/7 access to labor epidurals and the need for some kind of relatively effective analgesia during labor (Rooks 2010)
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Nitrous Oxide
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Women want choices!
• Great adjunct for natural childbirth because it does not affect the fetus like narcotic analgesia
• Does not have the numbing effect of an epidural
• Has a calming effect which is helpful to relieve anxiety during labor
• Some women are not candidates for epidural
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Nitrous Oxide: What is it??
• Commonly known as “laughing gas”
• Colorless, tasteless, non-flammable gas
• Liquid at room temperature
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50% Nitrous Oxide/50% Oxygen used in labor is analgesia-not anesthesia!
• Analgesia or “minimal sedation” per American Society of Anesthesiologists (ASA)
• No special regulations or guidelines-”minimal risk”
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• Patient awake and alert
• Protective laryngeal reflexes intact
• Self administration
• Effect titrated by frequency and intensity of inhalation
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Analgesia…NOT Anesthesia
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According to the ACNM Position Statement on Nitrous Oxide 2010… “Women should have access to a variety of approaches to promote comfort and reduce pain throughout labor”
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Why Offer Nitrous Oxide in Labor?
“It is a fact that women in the United States have fewer options for childbirth pain management than women in Canada, Australia, and most of Western Europe.”
“Women in the United States need alternative ways to relieve labor pain.”
(Leeman et al., 2003; Marmor and Krol, 2002; Rooks, 2011)
Long history of safe use- over 50 years!
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• Rapid onset/offset• Low cost• Can be given at any point in labor
– (never “too late”)
• Does not diminish contractions or slow labor• No impact on the ability to push• No known effect on fetal heart rate or newborn APGARs • Allows for intact, but lessened, sensation of labor and
birth – (which is desired by many women)
• Procedural analgesia option: repairs, manual removal, manual OP rotation, tamponade balloon placement
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Advantages
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Nitrous Oxide Advantages
• Easy to set up quickly, and teach the patient how to use. Self administered
• Option for women who want minimal intervention, rapid onset of action
• May be able to postpone or avoid narcotics or epidural
• For normal, low risk, term patients- for those who cannot have an epidural…it’s another option!
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Nitrous Oxide Mechanism of Action: How Does it Work?
Exact mechanism is unknown
Increases the release of endorphins, dopamine, prolactin, and various endogenous opioids within the spinal cord and brain while decreasing the release of cortisol (Rooks 2011)
Anxiolysis-mediated by GABA (GABA plays the principal role in reducing neuronal excitability throughout the nervous system. )
Basically… N20 affects the brain which modulates pain stimuli by way of descending spinal cord nerve pathways.
(Gabbe, Niebyl, & Simpson, 2006; Rosen, 2002)
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Nitrous Oxide Mechanism of Action: How Does it Work?
• Nitrous oxide works by reducing the perception of pain and lowering anxiety levels.
• Resulting euphoria and dissociation may make pain more manageable.
• The ability to self administer nitrous oxide may help the woman feel more in control of pain (Zauderer 2016)
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Physiology: How Does it Work?
Enters body through inhalation, exits through exhalation
Onset is <60 seconds
Dose dependent for onset and effect
Very weak accumulation in fat/tissues (metabolism is 0.004%)
Elimination half-life is 5 minutes
(Gabbe, Niebyl, & Simpson, 2006; Rosen, 2002)
Excreted rapidly through the lungs…
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Nitrous Oxide: How does it work?
• Less than 1% of nitrous oxide is metabolized or stored in the body- over 99% is exchanged through exhalation
• No effect on uterine activity or the progress of labor
• Sensory and motor functions are not altered
• Maternal respiratory depression is not a risk factor from nitrous oxide alone
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Nitrous OxideIs it safe for the fetus or newborns?
• Potential neurotoxicity of anesthetic agents hasbeen topic of interest in recent years • phenomenon called “apoptosis” seen ONLY in animal studies when exposed to
extreme amount over long periods of time
• Also applies to sedatives, hypnotics, narcotics, and all anesthetic gases
• Nitrous oxide is one of a very long list of agents of interest in this regard
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Fetal/Newborn Effects
• Nitrous oxide crosses the placenta resulting in approximately 80% of the concentration of the maternal serum blood level accumulating in the fetus within 15 minutes
• Nitrous oxide quickly leaves the body upon the first few respirations of the newborn. It does not cause respiratory depression
• Studies have not shown an effect on the fetal heart rate, breastfeeding, APGAR or behavioral assessment scores
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What about use Preterm?
• Hemodynamic effect on maternal and fetal circulation: central vascular resistance in both were decreased by 30% with nitrous oxide inhalation
• Preterm fetuses are susceptible to ICH-use of nitrous oxide may increase the risk
Polvi et al Obstet Gynecol Vol 87 No 6, June 1996
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Nitrous OxideChallenges:
• Potential for – nausea (0-24%)
– Dizziness (6-23%)
• Dysphoria may be unacceptable to some women
• Mobility: – patient is limited by length of tubing on machine
• Not for women who desire complete pain relief
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• Can be used in any stage of labor, no time limit established in the literature
• Normal low risk patients >-37 weeks gest.
• Initial electronic fetal monitoring tracing reflects adequate oxygenation demonstrated by normal baseline rate, moderate variability, absence of recurrent variable or late decelerations, or prolonged decelerations. Intermittent auscultation or intermittent EFM may be used.
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Who may use Nitrous Oxide? (Allina)
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• If any concern for fetal status or category II EFM-continuous EFM should be done
• Minimal variability with recurrent variable or late decelerations that persists for >30 min despite intrauterine resuscitation efforts, any concern for fetal status, or Cat III EFM, discontinue nitrous oxide.
• Patient must be able to self administer nitrous oxide by holding her own mask without difficulty
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Use of Nitrous Oxide cont.
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• No need for continuous pulse oximetry- baseline reading only, reapply if any concerns
• 2 hours must pass after narcotic, benzodiazepine, or similar sedative medication before starting nitrous
• Epidural consent prior to nitrous use not needed, can be done just prior to the procedure.
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Other Care Considerations
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• No defined time limit for duration of use has been identified- provider order
• Nurse to remain with patient first 15 min, pt should be instructed to notify RN if she wants to get out of bed, must have someone in attendance if out of bed using nitrous
• Diffusion hypoxia- 100% oxygen by partial rebreather when discontinuing nitrous oxide for 5 min will prevent this
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Care Considerations
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• Cannot be used in combination with other agents –e.g. IV opioids within last 2 hours, sedatives, epidural (considered conscious sedation)
• Acutely intoxicated, or on Methadone, Buprenorphine, Suboxone
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Contraindications for use
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• Documented B12 deficiency, pernicious anemia.
• Patients with pneumothorax, bowel obstruction, recent ear or eye surgery where there is potential for accumulation in a closed space.
• Cannot or unable to hold face mask
• Patients with impaired oxygenation (<95% on room air)
• Patients may not use nitrous oxide in tub or shower
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Contraindications
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• Hx pneumothorax, acute asthma, emphysema, pulmonary hypertension, middle ear surgery or occlusion, current URI, COPD, cystic fibrosis, bowel obstruction, Crohn’s disease, graves disease, lupus erythematosus, increased intracranial pressure or intraocular surgery might not be candidates
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Relative Contraindications (provider to assess suitability)
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• The potential for nitrous oxide to accumulate in closed air spaces has been well documented
• Use caution before using it in women with a previous history of pneumothorax, retinal surgery, and recent middle ear or sinus infection.
• Retinal surgery is a particular concern- Visual loss has been identified in patients who got nitrous oxide after eye surgery involving gas injection into the eye.
Starr and Baysinger, Anesthesiology.theclinics.com 2013
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Use Caution…..
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Equipment
• Portable tanks (N20 and 02) or may use wall O2
• Blender device mixes 02 and N20 to
deliver a set 50:50% concentration
• Self administration by face mask with a demand
valve-only get the nitrous by inhalation
• Patient exhales into the mask, scavenging system
filters and diverts exhaled gas to wall suction.
Not exhaled into room air
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• Need buy-in from key stakeholders:-Anesthesia-OB Providers-Pediatric providers-All of the regulatory folks
• Staff and Provider Education: Toolkit (policy, consent, patient education, nitrous oxide articles, educational PowerPoints)
Excellent Video: Society for Obstetric Anesthesiahttps://www.youtube.com/watch?v=l90bFv5Lg8g.
RN’s complete an online education and hands on competency
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Implementation of a Nitrous Oxide Program
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• Self-administered Nitrous Oxide for an active laboring patient would be considered “Anxiolysis/Analgesia” – not moderate sedation.
• No H&P/H&P update required prior to initiation.
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Implementation: What does Joint Commission say about Nitrous Oxide for Labor Analgesia?
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• Provider assessment for suitability, H & P update (if required), order for use
• Informed consent documented
• Equipment check and proper set up
• Ensure no narcotics, sedatives, or benzodiazepines used prior to use
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Before Nitrous is Used
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• Continuous , 50% Nitrous Oxide/50% oxygen via Nitronox device.
• Intermittent or continuous self administration for labor analgesia and anxiolysis.
• Assess vital signs within 30 minutes of initiation of nitrous oxide, and per labor orders/policy. Assess pain and RASS scores q 1 hour.
• Wait 2 hours to begin nitrous oxide if narcotics, benzodiazepines, or similar sedative medications have been given.
• No concurrent administration of narcotics with nitrous oxide.
• Wait 5 minutes after nitrous oxide administration to administer narcotics.
• Discontinue nitrous oxide if any concerns regarding maternal or fetal status, and initiate necessary resuscitation measures. ( Contraindications to nitrous are patient with inability to hold their own facemask, patients who are intoxicated or have impaired consciousness, patients who have had intravenous opioids in the last 2 hours, those with pernicious anemia or documented B12 deficiency, anyone with oxygen saturations less than 95% on room air, or anyone taking methadone, buprenorphine, or suboxone.)
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Order Example
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• Proper use of mask-proper seal for inhalation and exhalation into the mask
• Patient must hold own mask-education is key!
• Call when getting up, someone in attendance when patient out of bed
• Educate re possible side effects (nausea, dizziness, dysphoria), report side effects
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Patient/Family Education
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Patient/Family Education
• Intermittent vs continuous use
• Peak analgesic effect lags the start of it’s administration by 50 seconds, uterine contractions typically peak 30 seconds after they start
• Educate that may not provide complete pain relief
• Elimination quickly via lungs (elimination half life 5 min)
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That’s a NO! If anyone else uses the mask-they will be escorted out and nitrous removed from the room
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Nitrous Oxide (Allina)Monitoring:
• RN in room for first 15 minutes to observe– thereafter, standard OB cares with intermittent external fetal
monitoring• Studies show that women breathing nitrous oxide have
higher O2 saturations than those breathing room air– continuous pulse oximetry is not indicated
• Nitrous oxide mixture is 50% oxygen/50% Nitrous oxide– room air 21%
• Mild desaturations do occur during active labor in all women, regardless of pain relief method used
**Any concerns- call OB provider
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• Biggest concern raised: apoptosis= programmed cellular death
-Dose is critical determining factor for risk from exposure (occupational and pt use)
-Apoptosis has only been demonstrated in animal studies when exposed to extreme amounts over long periods of time. (higher than amts typically used in general anesthesia)
-FDA 2007: after investigating “we have no evidence that supports detrimental CNS effect in pediatric patients/staff exposed. They recommend no changes
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Patient/Staff Safety
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• The effects on human fetuses or in children later in life who were exposed to nitrous oxide or other anesthetic agents in utero are unknown.
• Low concentrations and brief period to which a fetus would be exposed during labor (even a prolonged one) would be unlikely to result in a measureable effect even if such effects were later shown to be real.
(Starr and Baysinger, Anesthesiology.theclinics.com 2013
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? Neurotoxic effects
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• N2O oxidizes a physiologically active form of cobalmin (vit B12)- inactivating it
• Extremely high doses of N2O and/or long term exposure can cause bone marrow depression, macrocytic anemia, and neuropsychiatric disorders
• Effects reverse with time: Royston et al. research concluded that surgical (anesthetic doses) are at risk when receiving N2O >70% for >6 hrs.
• Conditions that reduce cobalmin (Crohns disease, celiac disease, gluten intolerance, pernicious anemia, strict vegan diet etc. increase risks of N2O exposure )
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Patient/Staff Safety: N2O effects on Cobalmin
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• Defined as: Arterial O2 saturation below 90%.
• When N2O and oxygen is stopped, the amount of O2 available to the lungs is 21%.
• N2O leaves the blood and enters alveoli faster than nitrogen can leave the alveoli to enter the blood- this causes a rapid rise in the amount of N2O in the alveoli reducing the amount of oxygen even lower than 20% for normal blood absorption
• O2 sat drops can occur (less likely with 50/50 mix), it is usually not significant in healthy populations.
• Administering 100% O2 when d/c’ing nitrous can prevent any issues-follow your own hospital policy
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Diffusion hypoxia???
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• NIOSH occupational exposure guidelines are <25 ppm/8 hrs (in Europe it’s <100 ppm)
• Periodic monitoring is done per institutional anesthetic gases policy
• No documented levels using Nitronox equipment have come close to 25 ppm
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Safety: N2O Monitoring/Exposure
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• There is a general lack of US data on maternal and fetal outcomes, and a specific lack of data on:-sense of control/satisfaction with the childbirth
experience-effect on mother/baby interaction-breastfeeding-admission to special care-infant outcomes at long term follow up-costs
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Need for Research
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Nitrous OxideIn Conclusion:• Nitrous is a great option for many laboring women
– Many women will desire and appreciate
• Some will not tolerate it d/t side effects
• Nitrous can be a useful tool in helping patients who desire a less-medicated birth
• Nitrous can provide pain relief for bedside procedures requiring analgesia or anxiolysis
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QUESTIONS?
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• AHRQ (2011). Evidence-based practice center systematic review protocol. Project title: Nitrous oxide for the management of labor pain. Retrieved from http://effectivehealthcare.ahrq.gov/index.cfm/search-for-guides-reviews-and-reports/?productid=675&pageaction=displayproduct
• American College of Nurse-Midwives. (2010). From the American College of Nurse-Midwives: Nitrous oxide for labor analgesia. Journal of Midwifery & Women’s Health, 55(3), 292– 296
• Collins, M. (2015). A case report on the anxiolytic properties of nitrous oxide during labor. Journal Of Obstetric, Gynecologic, & Neonatal Nursing: Clinical Scholarship For The Care Of Women, Childbearing Families, & Newborns, 44(1), 87-92. doi:10.1111/1552-6909.12522
• Khadem, N., Zirak, N., Soltani, G., Sahebdelfar, N., Sepehri Shamloo, A., & Ebrahimzadeh, S. (2013). Comparison of epidural versus entonox for labor analgesia in nulliparous women. 5-1, )1(1, نشریه جراحی و تروما . Retrieved form http://www.ijs.ir/
• King, T., Brucker, M., & Fahey, J. (2013). Varney’s nurse midwifery. Sudbury, MA: Jones and Bartlett Publishing.
• Klomp T, van Poppel M, Jones L, Lazet J, Di Nisio M, Lagro-Janssen ALM (2012). Inhaled
• analgesia for relieving pain during labour. Cochrane Reviews.
• Lederman, R. P., Lederman, E., & McCann, D. S. (1985). Anxiety and epinephrine in multiparous women in labor: relationship to duration of labor and fetal heart rate pattern. American Journal of Obstetrics and Gynecology, 153(8), 870-877. http://dx.doi.org/10.1016/0002-9378(85)90692-1
• Levinson, G., & Shnider, S. M. (1979). Catecholamines: The effects of maternal fear and its treatment on uterine function and circulation. Birth, 6(3), 167-174. http://dx.doi.org/10.1111/j.1523-536x.1979.tb01329.x
• Likis, F. E., Andrews, J. C., Collins, M. R., Lewis, R. M., Seroogy, J. J., Starr, S. A., ... & McPheeters, M. L. (2014). Nitrous oxide for the management of labor pain: a systematic review. Anesthesia & Analgesia, 118(1), 153-167. http://dx.doi.org/10
• Lindholm, A., & Hildingsson, I. (2015). Women's preferences and received pain relief in childbirth–A prospective longitudinal study in a northern region of Sweden. Sexual & Reproductive Healthcare, 6(2), 74-81. http://dx.doi.org/10.1016/j.srhc.2014.10.001
• Pasha, H., Basirat, Z., Hajahmadi, M., Bakhtiari, A., Faramarzi, M., & Salmalian, H. (2012). Maternal expectations and experiences of labor analgesia with nitrous oxide. Iranian Red Crescent Medical Journal, 14(12), 792. http://dx.doi.org/10.5812/ircmj.3470
• Pita, C., Pazmiño, S., Vallejo, M., Salazar-Pousada, D., Hidalgo, L., Pérez-López, F., & Chedraui, P. (2012). Inhaled intrapartum analgesia using a 50-50 % mixture of nitrous oxide-oxygen in a low-income hospital setting. Archives Of Gynecology & Obstetrics, 286(3), 627-631. doi:10.1007/s00404-012-2359-6
• Posner, G., Black, A., Jone, G., & Dy, J. (2013). Oxorn-Foote Human Labor & Birth. (6th Ed.) New York, NY: McGraw Hill.
• Rosen, M. (2000). Nitrous oxide for relief of labor pain: A systematic review. American Journal of Obstetrics and Gynecology. 186, 110-26
• Rosenstein, M., Flood, P., Thiet, M. P., Nakagawa, S., Bishop, J., & Cheng, Y. (2014). 598: The use of nitrous oxide analgesia during labor at a single institution in the United States. American Journal of Obstetrics and Gynecology, 1(210), S294-S295. http://dx.doi.org/10.1016/j.ajog.2013.10.631
• Rooks, J. P. (2007, May). Use of Nitrous Oxide in Midwifery Practice–Complementary, Synergistic, and Needed in the United States. Journal of Midwifery & Women's Health. pp. 186-189. http://dx.doi.org/10.1016/j.jmwh.2007.02.017.1097/01.aoa.0000455280.655.3
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References
