Effects of IV Opioids during Labor

by | May 14, 2024


Today’s video is all about the use of IV opioids during labor for pain relief.  As a reminder, here is our disclaimer and terms of use.

You’ll learn:

  • Which IV opioids during labor are most commonly used
  • What studies have found about the safety and effectiveness of IV opioids during labor
  • The potential pros and cons of using IV opioids during labor

Watch, Read or Listen:

To read, please view the transcript below. To listen, subscribe to our podcast:  iTunes  |  Spotify  | YouTube

References and Resources
  • American College of Obstetricians and Gynecologists (2019). Obstetric analgesia and anesthesia. Practice Bulletin No. 209. Obstet Gynecol: e208 – 225. Click here.
  • American Society of Anesthesiologists (ASA). Types of Pain Relief in Labor and Delivery. Click here.  
  • Cai, M., Liu, J., Lei, X.F., et al. (2023) Remifentanil at a relatively elevated dose in active phase is safe and more suitable than fixed lower dose for intravenous labor analgesia. J Pain Res 16: 2543-2552. Click here.
  • Declercq, E. R., Sakala, C., Corry, M. P., et al. (2013). Listening to mothers III: Pregnancy and birth. New York: Childbirth Connection. Click here.
  • Khalil, H., Abedalmajeed, S., Momani, A., et al. (2021). Effect of epidural versus parenteral opioid analgesia on labor pain and maternal and neonatal outcomes among Jordanian women: A retrospective study. Malaysian J Medicine and Health Sciences 17: 245-250. Click here.
  • Li, J., Cai, J., Li, J., et al. (2023). Efficacy of remifentanil intravenous patient-controlled analgesia in singleton parturients during the second stage of labor: A single-arm, prospective study. International Medical Case Reports Journal 16: 673-678. Click here.
  • Muchatuta, N. A., & Kinsella, S. M. (2013). Remifentanil for labour analgesia: time to draw breath? Anaesthesia 68:231. Click here.
  • Murray, H., Hodgkinson, P., & Hughes, D. (2019). Remifentanil patient-controlled intravenous analgesia during labour: A retrospective observational study of 10 years’ experience. Intl J Obstet Anes 39: 29–34. Click here.
  • Nanji, J. A., & Carvalho, B. (2020). Pain management during labor and vaginal birth. Best Practice & Research. Clinical Obstet Gyn 67: 100–112. Click here.
  • NHS Choices. (2023). Pain relief in labor. Available at http://www.nhs.uk/conditions/pregnancy-and-baby/pages/pain-relief-labour.aspx
  • Obstetrics & Gynecology Opioid Prescribing Guidelines (2018). Prescribing Guidelines for Pennsylvania Available here.
  • Ohashi, Y., Baghirzada, L., Sumikura, H., et al. (2016). Remifentanil for labor analgesia: A comprehensive review. J. Anesth 30(6): 1020-1030. Click here.
  • Phillips, S. N., Fernando, R., Girard, T. (2017). Parental opioid analgesia: Does it still have a role? Best Practice & Research Clinical Anaesthesiology 31(1): 3-14. Click here.
  • Smith, A., Laflamme, E., & Komanecky, C. (2021). Pain Management in Labor. American Fam Physician 103(6), 355–364. Click here.
  • Smith, L. A., Burns, E., & Cuthbert, A. (2018). Parenteral opioids for maternal pain management in labour. Cochrane Database of Systematic Reviews CD007396. Click here.
  • Stocki, D., Matot, I., Einav, S., et al. (2014). A randomized controlled trial of the efficacy and respiratory effects of patient-controlled intravenous remifentanil analgesia and patient-controlled epidural analgesia in laboring women. Anesth Analg;118(3):589-97. Click here.
  • Stourac, P., Kosinova, M., Harazim, H., et al. (2016). The analgesic efficacy of remifentanil for labour. Systemic review of the recent literature. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 160(1): 30-38. Click here.
  • Thorbiörnson, A., da Silva Charvalho, P., Gupta, A., et al. (2020). Duration of labor, delivery mode and maternal and neonatal morbidity after remifentanil patient-controlled analgesia compared with epidural analgesia. European J Obstet Gynecol Reproduct Biol 6: 100106. Click here.
  • Ullman, R., Smith, L. A., Burns, E., et al. (2010). Parenteral opioids for maternal pain management in labour. Cochrane Database of Systematic Reviews 9: CD007396. Click here.
  • Van de Velde, M. and Carvalho, B. (2016). Remifentanil for labor analgesia: An evidence-based narrative review. Intl J Obstet Anesth 25: 66–74. Click here.
  • Weibel, S., Jelting, Y., Afshari, A., et al. (2017). Patient-controlled analgesia with remifentanil versus alternative parenteral methods for pain management in labour. Cochrane Database of Systematic Reviews 4: CD011989. Click here.

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View the transcript

Dr. Rebecca Dekker

Hi everyone, in today’s video we’re going to talk about IV opioids for pain management during labor. Welcome to the Evidence Based Birth® Podcast. My name is Rebecca Dekker, and I’m a nurse with my PhD and the founder of Evidence Based Birth®. Join me each week as we work together to get evidence-based information into the hands of families and professionals around the world. As a reminder, this information is not medical advice. See ebbirth.com/disclaimer for more details. 

Did you know that here at Evidence Based Birth® we have an Instructor program where you can apply to teach official EBB classes to parents and pros? We only open applications for the EBB instructor program once per year… and this year we are opening on May 30 through June 28 only! So if you’ve ever wished you could teach the EBB Childbirth Class for parents, or the EBB Comfort Measures Workshop or Savvy Birth Workshop for nurses and doulas, this is your chance to apply! Just go to ebbirth.com/instructor to learn more and sign up for a live Q & A about the program. Also, have you ever wished you could easily give Evidence Based Birth® handouts to your clients or colleagues? About a month ago, we introduced brand new, color-printed EBB tearaway pads to make it super easy for you to give evidence handout topics to others. These tear away pads sold out almost immediately! So, we ordered another batch and you can now get them in the EBB shop. Just go to ebbirth.com/shop to order your bundle of tearaway pads before they sell out again! And with that, we’re going to get started with today’s episode, all about injectable opioids for pain management during labor. Are you ready to get started? Alright, let’s go!

Injectable opioids, also known as narcotics, are a medication method for managing pain during labor. These medicines can be injected into a vein, which we call intravenous, or injected into a muscle, which we call intramuscular injections, or an IM injection. Both IV and IM medications are known as parenteral medications, which are systemic, meaning they spread throughout your entire body, and these are designed to help you with pain without making you numb, and without you losing the ability to move your body around. This is in a bit of contrast to epidural medication, which does numb you from the waist down, and can, if it’s given in higher doses, make it more difficult for you to move. In 2018, researchers from California found that of the 2000 mothers in that survey, about 16% were given parenteral opioids during a vaginal birth and 24% during a Cesarean birth. 

So which opioids are most commonly used during labor? So there are several. They include pethidine, fentanyl, remifentanil, nalbuphine, butorphanol, also known as Stadol, and morphine. Around the world, pethidine, which is also known as Demerol or meperidine, is the most common opioid used in an injectable way during labor. The American Congress of Obstetricians and Gynecologists, or ACOG, does not recommend use of pethidine or Demerol because it easily crosses the placenta into the fetus, and it can take a week after the baby is born for the drug to leave the baby’s body. So pethidine is rarely used in the United States. Another note about pethidine and one of its main drawbacks is that, compared to epidurals, pethidine has much lower satisfaction scores and it causes more severe sedation and drowsiness. Remifentanil and fentanyl are opioids that are both suitable for something called patient-controlled analgesia. 

A PCA pump is when you are hooked up to IV tubing and a special pump that can deliver medication when you, as the patient, press a little button. There’s safety features built into these pumps so that they can’t be tampered with and to prevent you from receiving too much medication. Both Remifentanil and fentanyl can be used in these PCA pumps because they have a short medication half-life, which means that they only last for a short time in the body. So the half-life is the length of time that it would take for half of the drug to leave your circulation. So it makes sense that you could use these medications and just push a little button to give you a small dose whenever you need it. It only lasts a short time. If you need it again, you press the button again. And sometimes there’s a maintenance drip where the provider orders it to be continuously delivered through the IV tubing. Nalbuphine, also known as Nubain, is another common opioid for use during labor, but some clinicians do not prefer Nubain because it can slow down labor, even cause labor to stall out. Nubain does cross the placenta within five minutes of administration, and within 15 minutes, about 10 to 16% of the dose has entered the baby’s blood circulation. 

However, because of the type of opioid it is, it’s what we call a mixed agonist antagonist, it is less likely to suppress your breathing or your baby’s breathing because of how the medication works. Butorphanol, also known as Stadol, is another mixed agonist antagonist. And so it’s also commonly offered during labor because it’s less likely to suppress your breathing or your baby’s breathing after birth. Now, Stadol does last a little bit longer in your body than Fentanyl and Remifentanil. It can take as long as four to 10 hours to clear this medication out of your system. Morphine is another option, but it’s not used as much because in order to be effective, it needs a pretty high dose, and therefore there’s a higher risk of side effects. 

So not all these medications are available in all hospitals. Every hospital has the medications that they prefer to use. And sometimes there’s also shortages of different medications. So which medication might be offered to you depends on what they have available and what they’re used to commonly administering. The dose also depends on the type of medicine they’re using and how it’s given, whether through an IV or through an IM injection. And some medications will last longer in your body than others. Now, the ideal opioid for use for pain management during labor would start to work very quickly, provide lasting pain relief, and have no unwanted side effects for you or your baby. Unfortunately, none of the opioids that we have right now meet these criteria. Basically, every opioid can cross the placenta and cause side effects in the fetus, which can then affect them after they’re born. And these potential side effects are more common and more severe with injectable opioids. 

We do commonly give opioids through an epidural, but those are typically a much smaller dose and they’re less likely to be getting into your system or the baby’s system. It’s more of a local effect. Because of the side effects that I mentioned of injectable opioids, they’re not typically given late in labor. So they are typically not seen during the pushing phase or when you’re getting close to nine or 10 centimeters dilated. This is because they’re worried about the medication lingering in the baby’s system after they’re born and maybe suppressing the baby’s breathing. However, Remifentanil is unique in that it’s thought to be safer to administer towards the end of labor. And I found two small studies that looked at the effects of Remifentanil in the second stage of labor, meaning the pushing phase. One was a case series in which researchers concluded that Remifentanil given by a PCA pump could effectively relieve pain from severe uterine contractions in the second stage and that this was a safe thing to do. 

The second study found that giving a slightly higher dose of Remifentanil during the active phase of labor when you’re 6 centimeters or more dilated was safe and reduced the pain score. Because of this, Remifentanil is growing in popularity and I’ll talk a little bit more about it later on. So what is the research evidence on injectable opioids during labor? Well, in 2018, researchers published a Cochrane review, where they looked at all of the research up until that time point on injectable opioids during labor. The review included 70 randomized controlled trials with more than 8,000 participants. Most of the studies were looking at the IM injections or the intramuscular injections, and they found that the medication effect on pain relief after one to two hours was considered poor to moderate. Most participants in these studies reported still having moderate or even severe pain, one to two hours after the dose was given. And satisfaction scores were largely not tracked. There were some side effects reported in this study, including nausea, vomiting, and drowsiness. There was no evidence of any bad long-term health outcomes for newborns, but this is likely because these adverse outcomes long-term are rare anyway, so it’s pretty hard to capture in a study. 

However, they did see short-term side effects for babies in the study, and these were well-documented in randomized trials. The short-term side effects included changes in the baby’s heart rate while the baby was still in utero and changes in early neurological scores of the baby’s behavior right after birth. But of all the opioid medications that researchers have studied for use during labor, remifentanil seems to be becoming the most popular. And right now, most of the research that’s coming out on injectable opioids during labor is focused on this one medication. So as I mentioned earlier, Remifentanil is only given as an IV medication through a PCA pump. It starts working really fast within 20 seconds, but it only lasts three or four minutes. So you have to have a dose pretty frequently in order for you to get any lasting effect. One study found that getting IV Remifentanil lessened people’s need for an epidural compared to IM pethidine or Demerol. Compared to some of the other medications, Remifentanil carries less risk of breathing problems for the baby, but it does appear to have a higher risk of breathing problems for the birthing person. In terms of rare side effects, when it’s used with PCA or pushing the button to get pain relief, there have been at least four case reports of respiratory or cardiac arrest when the birthing person stopped breathing or their heart stopped. Because of these four cases that were reported, in general, when nurses, doctors, and midwives are administering this medication, they’re supposed to follow a long list of safety precautions, including having one-to-one nursing monitoring, continuous oxygen monitoring, continuous carbon dioxide monitoring, and having an anesthesiologist on site and resuscitation equipment available. 

So anybody who’s receiving remifentanil during labor should have one nurse who’s taking care of only them. They also need some special precautions on the PCA pump. There needs to be a lockout or a wait time between when you can push the button from one time to the next, and the lockout interval for remifentanil should be at least two to three minutes. There was a Cochrane review published by Weeble et al. in 2017 that was comparing remifentanil to other injectable opioids for use during labor, and they also compared remifentanil to an epidural. They found 20 randomized controlled trials with about 3,500 participants total, and they found very low quality evidence that people using IV, patient-controlled remifentanil, reported stronger pain relief at one hour, requested fewer additional pain medications, and were more satisfied with pain relief compared to those receiving other injectable opioids. However, compared to the group receiving epidurals, spinals, or combined spinal epidurals, the remifentanil group did have higher pain scores, required more additional pain medications, and had lower patient satisfaction. 

Some researchers have proposed that the reason remifentanil seems to be better than the other injectable opioids is more because it’s being used in the PCA pump, where you’re pushing the button to get your pain relief. That’s because, in general, PCA pumps tend to have higher satisfaction scores, which makes sense because then you’re in control of your own pain relief. Another benefit of remifentanil, I mentioned it’s short half-life, it’s actually an ultra-short half-life, which is really useful for labor because there’s less concern for side effects for the baby after birth. So let’s sum up the pros and cons of injectable opioids for pain management during labor. Basically, the pros are that injectable opioids tend to be universally available around the globe for pain management. They’re affordable, fast, they work fairly quickly. In contrast to epidurals, which are still not available in some parts of the world, injectable opioids are less expensive than epidurals, less invasive, and they do provide some element of pain management, although it’s not the best. They have not been shown to increase the risk of Cesarean. 

And in general, injectable opioids can be a decent option for families who want some kind of medication for pain relief but do not want an epidural or spinal, or maybe cannot have an epidural or spinal for medical reasons. For example, if labor is moving too quickly, or if you have low platelets, or there’s some other medical reason that an epidural cannot be given. Injectable opioids have also been shown to be linked to shorter labors compared to epidurals. That’s probably because epidurals are known to lengthen the labor process. 

Now let’s talk about the cons. The main drawbacks of injectable opioids include the fact that they’re not that effective. So the pain relief might be poor or moderate and the pain relief might be unreliable. So they’re not guaranteed to work. In contrast, epidurals are more effective at managing pain with fewer side effects for the newborn because you have a lower risk of medications from the epidural getting into the baby’s circulation. There are a lot of potential side effects with injectable opioids. You might feel nauseous, they might make you vomit or feel drowsy or dizzy. They can also cause breathing problems, pauses in your breathing, confusion, forgetfulness, sedation, or slowed reflexes. These side effects could interfere with your ability to nurse your baby shortly after birth and they might not be the best option if you are rapidly dilating or you’re really close to delivery and they don’t want the medications to be in the baby’s system when the baby is born. 

There also have been rare cases of cardiac or pulmonary arrest with injectable opioids and this is one reason why one-to-one nursing care and monitoring are so important. For the newborn, all opioids have been shown to cross the placenta and can get into the baby’s circulation. So potential harms include changes to the baby’s heart during labor, which could potentially lead to a need for a C-section, slowed breathing after birth, and low Apgar scores. Apgar scores are a way we check the baby’s health rate at birth. Also, the baby may be born limp and drowsy and have reduced suckling reflexes at birth, which may make it harder to get started on the right foot with lactation. Rarely these medications can have serious life-threatening side effects for babies, including respiratory depression at birth, maybe not breathing, low muscle tone, or a severe slowing of the baby’s heart rate. 

Specifically, meperidine, also known as pethidine or Demerol is not recommended by many organizations because it has a very long half-life in newborns and meperidine cannot be treated with naloxone. Many of you are probably familiar with naloxone or Narcan. That’s the medication approved by the FDA to reverse opioid overdose. Speaking of more long-term opioid use, both butorphanol and nalbuphine are mixed agonist antagonists, and so they should be avoided if you’ve been regularly taking opioids in the past. Having butorphanol and nalbuphine given to you in labor if you have been on opioids or treatment for opioid addiction might trigger sudden withdrawal symptoms or minimize the pain management effect. In terms of alternatives, we talked about epidurals and spinals and we have a different separate video on that, but there is an alternative medication option called paracetamol. This is an injectable form of Tylenol and there’s some newer research on that. 

Also, nitrous oxide or a mixture of laughing gas and oxygen and we cover that in a separate video and podcast as well. In terms of non-medication pain management techniques, there are a lot of options and in fact at EBB, we have a Pocket Guide to comfort measures for labor and birth that covers the medications. But then actually most of the Pocket Guide includes the non-medication alternatives such as acupressure, birthing positions, doulas, water birth, TENS machines and more. So, there are a ton of options if you educate yourself in terms of staying comfortable, either to use before you have pain medication or in place of pain medication or a lot of those comfort measures you can use alongside pain medication. And in fact, sometimes combining different methods of pain relief can be really helpful during labor. 

So what’s the bottom line? In summary, most of the research evidence does not support one IV opioid over another for use during labor, but evidence is starting to point to remifentanil as perhaps being the most effective option and maybe the best alternative to an epidural in terms of medication pain relief for labor. However, epidurals and spinals and combined spinal epidurals are considered the gold standard for managing pain during labor if you’re going to have medications. But injectable opioids do offer some benefits to people who do not want an epidural or spinal or cannot have one for medical reasons. Remifentanil seems to have the fewest side effects for babies in terms of breathing problems, but it appears to have more side effects for birthing people in terms of breathing issues. So if you are receiving remifentanil or any injectable opioid during labor, it’s important that the people taking care of you are following the safety precautions, that you have one-on-one nursing care and that your oxygen levels are being monitored. 

So that’s it all for our updated video and podcast episode about injectable opioids for pain management during labor. I hope you found it helpful. We’re going to keep updating these pain management videos as well as we’re going to be showcasing some real-life interviews with families who’ve tried different pain management strategies. So thanks again for listening and we’ll see you next week. Bye!

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