Neonatal neurobehavioral effects of inhalation analgesia for vaginal delivery

Nitrous Oxide for Labor Analgesia: What We Know to Date

Background: Although nitrous oxide (N₂O) has been used since the 1880s for labor analgesia, its popularity has only recently increased in the United States. In 2011, only 3 centers in the country offered N₂O, but as of 2020, several hundred labor units have adopted its use.

Methods: We reviewed the literature and summarize the mechanism of action, clinical uses, and efficacy of N₂O for labor analgesia, as well as patient satisfaction related to its use.

Results: N₂O has several proposed mechanisms of action that make it a viable option for all 3 stages of labor and postpartum procedures. N₂O has been shown to be a safe option for both mom and baby during labor and delivery. Studies support N₂O as an analgesic for laboring. Even though 40% to 60% of women who use N₂O convert to a labor epidural analgesia, satisfaction surveys indicate that analgesia is not the only factor contributing to the use of N₂O during labor.

Conclusion: The use of N₂O has increased in labor and delivery units across the United States since 2011. Despite inferior analgesic properties compared to epidural analgesia, N₂O offers a safe alternative for many parturients who want a greater sense of control and mobility.

Should maternal anesthesia delay breastfeeding? A systematic review of the literature

Introduction

The importance and benefits of breastfeeding for the babies and mothers are well established and documented in the literature. However, it is frequent that lactating mothers need to undergo general or spinal anesthesia and, due to the lack of information, many of them interrupt breastfeeding after anesthesia. There are limited data available regarding anesthetics transfer to breast milk. This review aims to develop some considerations and recommendations based on available literature.

Methods

A systematic search of the literature was conducted by using the following health science databases: Embase, Lilacs, Pubmed, Scopus, and Web of Science. The latest literature search was performed on April 6^th, 2018. Additional literature search was made via the World Health Organization's website. We used the following terms for the search strategy: “Anesthesia” and “Breastfeeding”, and their derivatives.

Results

In this research, 599 registers were found, and 549 had been excluded by different reasons. Fifty manuscripts have been included, with different designs of studies: prospective trials, retrospective observational studies, reviews, case reports, randomized clinical trials, case–control, and website access. Small concentrations of the most anesthetic agents, are transferred to the breast milk; however, their administration seem to be safe for lactating mothers when administered as a single dose during anesthesia and this should not contraindicate the breastfeeding. On the other hand, high-doses, continuous or repeated administration of drugs increase the risk of adverse effects on neonates, and should be avoided. Few drugs, such as diazepam and meperidine, produce adverse effects on breastfed babies even in single doses. Dexmedetomidine seems to be safe if breastfeeding starts 24 h after discontinuation of the drug.

Conclusions

Most of the anesthetic drugs are safe for nursing mothers and offer low risk to the breastfed neonates when administered in single-dose. However, high-dose and repeated administration of drugs significantly increase the risk of adverse effects on neonates. Moreover, diazepam and meperidine should be avoided in nursing women. Finally, anesthesiologists and pediatricians should consider individual risk/benefit, with special attention to premature neonates or babies with concurrent diseases since they are more susceptible to adverse effects.

[Should maternal anesthesia delay breastfeeding? A systematic review of the literature]

INTRODUCTION

The importance and benefits of breastfeeding for the babies and mothers are well established and documented in the literature. However, it is frequent that lactating mothers need to undergo general or spinal anesthesia and, due to the lack of information, many of them interrupt breastfeeding after anesthesia. There are limited data available regarding anesthetics transfer to breast milk. This review aims to develop some considerations and recommendations based on available literature.

METHODS

A systematic search of the literature was conducted by using the following health science databases: Embase, Lilacs, Pubmed, Scopus, and Web of Science. The latest literature search was performed on April 6^th, 2018. Additional literature search was made via the World Health Organization's website. We used the following terms for the search strategy: "Anesthesia" and "Breastfeeding", and their derivatives.

RESULTS

In this research, 599 registers were found, and 549 had been excluded by different reasons. Fifty manuscripts have been included, with different designs of studies: prospective trials, retrospective observational studies, reviews, case reports, randomized clinical trials, case-control, and website access. Small concentrations of the most anesthetic agents, are transferred to the breast milk; however, their administration seem to be safe for lactating mothers when administered as a single dose during anesthesia and this should not contraindicate the breastfeeding. On the other hand, high-doses, continuous or repeated administration of drugs increase the risk of adverse effects on neonates, and should be avoided. Few drugs, such as diazepam and meperidine, produce adverse effects on breastfed babies even in single doses. Dexmedetomidine seems to be safe if breastfeeding starts 24h after discontinuation of the drug.

CONCLUSIONS

Most of the anesthetic drugs are safe for nursing mothers and offer low risk to the breastfed neonates when administered in single-dose. However, high-dose and repeated administration of drugs significantly increase the risk of adverse effects on neonates. Moreover, diazepam and meperidine should be avoided in nursing women. Finally, anesthesiologists and pediatricians should consider individual risk/benefit, with special attention to premature neonates or babies with concurrent diseases since they are more susceptible to adverse effects.

Nitrous oxide labor analgesia and pain relief memory in breastfeeding women

OBJECTIVE

The use of labor pain relief medications is a controversial issue that has engendered heated discussions among health care professionals about safety, interference with birthing, and breastfeeding.

METHODS

This is a case-control study with 62 puerperae treated with nitrous oxide and 124 control women (ratio 1:2), matched for age, gestational age, parity, delivery route, labor augmentation, and spinal regional analgesia. We tested anhedonia, anxiety, and depression symptoms at hospital discharge by The Edinburgh Postnatal Depression Scale (EPDS), and the intensity of nitrous oxide labor pain relief and satisfaction memory by a retrospective Visual Analog Scale (VAS, 0-10 Numeric Rating Scale) at a set cut off time of 3 months of a child's age.

RESULTS

Nitrous oxide use did not influence EPDS subscales upon discharge. Its use was instead associated with a lasting positive labor pain relief experience (VAS, 7.3 ± 2.2) in 83.5% of women, and labor satisfaction memory (VAS, 8.9 ± 1.8) in 90% of women, respectively, and with a significantly higher breastfeeding rates from the seventh day after discharge (p < .031), to the 1st (p < .043), and the third month of life (p < .016).

CONCLUSIONS

Nitrous oxide labor analgesia is associated with favorable effects on both women's psychoemotional experience of labor and breastfeeding success.

Should Nitrous Oxide Be Used for Laboring Patients?

Nitrous oxide, long used during labor in Europe, is gaining popularity in the United States. It offers many beneficial attributes, with few drawbacks. Cost, safety, and side effect profiles are favorable. Analgesic effectiveness is highly variable, yet maternal satisfaction is often high among the women who choose to use it. Despite being less effective in treating labor pain than neuraxial analgesic modalities, nitrous oxide serves the needs and preferences of a subset of laboring parturients. Nitrous oxide should, therefore, be considered for inclusion in the repertoire of modalities used to alleviate pain and facilitate effective coping during labor.

Maternal expectations and experiences of labor analgesia with nitrous oxide

BACKGROUND

Although there are various methods for painless delivery such as using entonox gas, most of the people are unfamiliar or concerned about it yet.

OBJECTIVES

The purpose of this study was to assess maternal expectations and experience of labor analgesia with nitrous oxide.

PATIENTS AND METHODS

In a clinical trial study, 98 pregnant women in active phase of delivery were studied randomly in two groups (intervention group = 49, control group = 49) after obtaining written consent. Efficacy, experience satisfaction, and also expectation of pregnant women about entonox gas in two groups were compared, likewise in intervention group before and after using entonox gas.

RESULTS

Most of the pregnant women receiving entonox gas had less labor pain (91.8%), and were satisfied with it (98%). The severity of pain in the most of entonox user was moderate level (46.94%), while for the control group it was severe (55.10%) which was significant, 40.82% of the mother in entonox group had a severe pain and 10.20% had a very severe pain, whereas in the control group (55.10%) of the mother had a severe pain and 26.53% of the had very severe pain (P = 0.004). efficacy of labor pain was in moderate level in most cases. 49% of pregnant women receiving gas described their experience as a good and excellent. 80.9% indicated that they will request the mentioned painless method in the future. The amount of suffering from gas side effects was mild in most patients of intervention group (63%). Expectations of the majority of pregnant women in intervention group (before receiving gas) and control group for painless delivery were weak (65.3%, 40.9%). The percentage of positive expectations had increased after receiving entonox gas (P = 0.01). There was a difference between the expectations of intervention group receiving entonox gas and control group (P = 0.001). Positive expectations were more in intervention group than the control group. Most differences of expectations in intervention group before and after receiving the gas were about higher efficacy (P = 0.001), more satisfaction (P = 0.001), fewer complications (P = 0.001), information about gas as painless delivery method (P = 0.02), and also previous experience of intolerable labor pain (P = 0.04).

CONCLUSIONS

This study has shown that using entonox gas caused less labor pain, favorable expectations and experiences and also more maternal satisfaction.

ABM clinical protocol #15: analgesia and anesthesia for the breastfeeding mother, revised 2012

A central goal of The Academy of Breastfeeding Medicine is the development of clinical protocols for managing common medical problems that may impact breastfeeding success. These protocols serve only as guidelines for the care of breastfeeding mothers and infants and do not delineate an exclusive course of treatment or serve as standards of medical care. Variations in treatment may be appropriate according to the needs of an individual patient.

Inhaled analgesia for pain management in labour

BACKGROUND

Many women would like to have a choice in pain relief during labour and also would like to avoid invasive methods of pain management in labour. Inhaled analgesia during labour involves the self-administered inhalation of sub-anaesthetic concentrations of agents while the mother remains awake and her protective laryngeal reflexes remain intact. Most of the agents are easy to administer, can be started in less than a minute and become effective within a minute.

OBJECTIVES

To examine the effects of all modalities of inhaled analgesia on the mother and the newborn for mothers who planned to have a vaginal delivery.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2012), ClinicalTrials.gov, and Current Controlled Trials (2 June 2012), handsearched conference proceedings from the American Society of Clinical Anesthesia (from 1990 to 2011), contacted content experts and trialists and searched reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials comparing inhaled analgesia with other inhaled analgesia or placebo or no treatment or other methods of non-pharmacological pain management in labour.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed trials for eligibility, methodological quality and extracted all data. Data were double checked for accuracy.

MAIN RESULTS

Twenty-six studies, randomising 2959 women, were included in this review.Inhaled analgesia versus a different type of inhaled analgesia Pain relief was measured using a Visual Analogue Scale (VAS) from 0 to 100 mm where 100 corresponds to the most relief. Pain intensity was measured using a VAS from 0 to 100 mm, where 0 corresponds to no pain at all and 100 corresponds to the worst pain. The highest score for pain relief is the most positive in contrast to 'pain intensity' in which the higher score is more negative. Flurane derivatives were found to offer better pain relief than nitrous oxide in first stage of labour as measured by a lower pain intensity score (average mean difference (MD) 14.39, 95% confidence interval (CI) 4.41 to 24.37, three studies, 70 women), also a higher pain relief score for flurane derivatives compared with nitrous oxide (average MD -16.32, 95% CI -26.85 to -5.79, two studies, 70 women). Substantial heterogeneity was found in the analyses of pain intensity (P = 0.003) and in the analysis of pain relief (P = 0.002).These findings should be considered with caution because of the questionable design of the included cross-over trials. More nausea was found in the nitrous oxide group compared with the flurane derivatives group (risk ratio (RR) 6.60 95% CI 1.85 to 23.52, two studies, 98 women).Inhaled analgesia versus placebo or no treatment Placebo or no treatment was found to offer less pain relief compared to nitrous oxide (average RR 0.06, 95% CI 0.01 to 0.34, two studies, 310 women; MD -3.50, 95% CI -3.75 to -3.25, one study, 509 women). However, nitrous oxide resulted in more side effects for women such as nausea (RR 43.10, 95% CI 2.63 to 706.74, one study, 509 women), vomiting (RR 9.05, 95% CI 1.18 to 69.32, two studies, 619 women), dizziness (RR 113.98, 95% CI 7.09 to 1833.69, one study, 509 women) and drowsiness (RR 77.59, 95% CI 4.80 to 1254.96, one study, 509 women) when compared with placebo or no treatment.There were no significant differences found for any of the outcomes in the studies comparing one strength versus a different strength of inhaled analgesia, in studies comparing different delivery systems or in the study comparing inhaled analgesia with TENS.Due to lack of data, the following outcomes were not analysed within the review: sense of control; satisfaction with childbirth experience; effect on mother/baby interaction; breastfeeding; admission to special care baby unit; poor infant outcomes at long-term follow-up; or costs.

AUTHORS' CONCLUSIONS

Inhaled analgesia appears to be effective in reducing pain intensity and in giving pain relief in labour. However, substantial heterogeneity was detected for pain intensity. Furthermore, nitrous oxide appears to result in more side effects compared with flurane derivatives. Flurane derivatives result in more drowsiness when compared with nitrous oxide. When inhaled analgesia is compared with no treatment or placebo, nitrous oxide appears to result in even more side effects such as nausea, vomiting, dizziness and drowsiness. There is no evidence for differences for any of the outcomes comparing one strength verus a different strength of inhaled analgesia, comparing different delivery systems or comparing inhaled analgesia with TENS.

Lidocaine hydrocarbonate and lidocaine hydrochloride for cesarean section: transplacental passage and neonatal effects

Twenty-six patients, ASA physical status 1, scheduled for elective cesarean section, were divided at random into two groups and received via an epidural catheter 20 ml of 2.2% lidocaine hydrocarbonate (17.3 mg.ml-1 lidocaine base) with 5 micrograms.ml-1 epinephrine freshly added (Group CO2 = 13 patients) or 20 ml of 2% lidocaine hydrochloride (17.3 mg.ml-1 lidocaine base) also with 5 micrograms.ml-1 epinephrine freshly added. Following clampage of the umbilical cord (at 40.1 +/- 4.9 min after the injection of lidocaine for the CO2 group and at 41.0 +/- 5.4 min for the HCl group), serum concentrations of lidocaine were measured both in the mother and in the umbilical vein. All newborns were examined by the same blinded pediatrician with Apgar scores at 1, 5 and 10 min and with Neurobehavioral Adaptive Capacity Scores (NACS) at 15 min, 2 h and 24 h. The concentrations of lidocaine in the serum were comparable in both groups: in the mothers 8.61 +/- 1.48 mumol.l-1 for the CO2 group vs 8.04 +/- 2.36 mumol.l-1 for the HCl group and in the newborns 3.86 +/- 0.84 mumol.l-1 for the CO2 group vs 3.92 +/- 0.95 mumol.l-1 for the HCl group. The ratio of umbilical vein to maternal vein concentrations of lidocaine was also similar in both groups: 0.45 +/- 0.07 for the CO2 group vs 0.54 +/- 0.24 for the HCl group. The percentage of newborns with a normal NACS (score > or = 35/40) was equal in both groups, i.e. 91% at 15 min and 2 h of life and 100% at 24 h of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk-benefit assessment of anaesthetic agents in the puerperium

A critical evaluation of anaesthetic agents in the puerperium is difficult because systematic, relevant studies are still lacking. Current knowledge of the effects of different agents used in labour and caesarean section indicates that significant residual effects on the mother and newborn are limited. In the early puerperium, based on physiological and/or hormonal changes, the mother could be more sensitive to inhalational anaesthetic agents and local analgesics. To date there is no evidence that any anaesthetic agent is excreted in breast milk in clinically significant amounts when given as a single dose. The only exception is perhaps in the case of very premature neonates whose mothers have had multidrug therapy before labour. Even then the importance of breast milk should be carefully assessed against possible adverse drug effect. However, repeated administration of long-acting benzodiazepines and continuous epidural administration of pethidine (meperidine) can have adverse effects on the neonate. The essential conclusion of this review is that breast-feeding is best. The different anaesthetic agents are excreted in the milk in amounts so low that detrimental effects on the neonate should not be expected.

Obstetric analgesia. Clinical pharmacokinetic considerations

All drugs used in obstetric analgesia are more or less lipophilic, their site of action is in the central nervous system, and they have good membrane penetrability in the fetomaternal unit. Thus the dose and method of administration as well as the duration of treatment are important clinical determinants of drug effects in the fetus and newborn. In the past, too much emphasis has been placed on fetomaternal blood concentration ratios of different agents; it is now appreciated that the extent of fetal tissue distribution and the neonatal elimination rate are pharmacokinetically much more important. Extensive fetal tissue distribution is reflected in a low fetomaternal drug concentration ratio, which may be followed by prolonged neonatal elimination of the drug. Currently, the most effective and safest method for obstetric analgesia is regional epidural administration of bupivacaine or lignocaine (lidocaine); only low doses are needed and the newborn is able to handle these agents efficiently. On the basis of pharmacokinetic and neurobehavioural assessments, inhalational anaesthetic agents appear to be more attractive than pethidine (meperidine) or benzodiazepines. Intermittent administration and fast pulmonary elimination of inhalational agents ensure that long-lasting residual effects are unlikely to occur. The kinetics of epidural and intrathecal opiates explain the problems associated with their use in obstetrics. Among the newer drugs used in obstetric analgesia, the properties of meptazinol and isoflurane appear interesting and these agents warrant further study. All drugs used in obstetric analgesia have a potentially detrimental effect on the neonate and, therefore, knowledge of fetal and neonatal pharmacokinetics is of importance to the clinician.

Delayed recovery of behavior after anesthesia in rats

Early, complete recovery from general anesthesia is of importance for outpatients, in resuscitation research and in behavior testing of neonates. A model was designed to study behavior during the first week of recovery from anesthesia in rats, using two methods: spontaneous and unrestrained locomotor activity was tested and passive avoidance of electroshock was studied in a two session, one trial model. Neurologic deficit and ease of handling were also tested. After anesthesia with halothane 1-2% in N2O/O2 for 30 min, spontaneous activity was reduced, compared with unanesthetized rats, for up to at least 48 h. On day 6 post-anesthesia, locomotor activity was recovered, and, on days 4 and 5, passive avoidance was unchanged. Neurologic deficits were absent after the first hour of recovery and ease of handling was unchanged.

CONCLUSION

Halothane and nitrous oxide have prolonged effects on locomotor behavior beyond the immediate post-anesthesia recovery period, at a time when neurologic deficit testing does not reveal any abnormalities. The model is suitable for the comparison of recovery from different anesthesia techniques in rats.

Enflurane as an analgesic in labour

A comparison of the analgesic efficacy of enflurane 1% in air with Entonox (50% nitrous oxide in oxygen) was performed in 20 consenting women during the first stage of labour. The two drugs were given in a random sequence to each woman, who also acted as her own control. Pain scores were significantly lower with enflurane than Entonox, although drowsiness scores were higher. No untoward effects were reported with either agent. The use of enflurane as an analgesic in the first stage of labour warrants further investigation.