Nitrous oxide for relief of labor pain: A systematic review

Inhalation analgesia with nitrous oxide versus other analgesic techniques in hysteroscopic polypectomy: a pilot study

STUDY OBJECTIVE

To show the decrease in pain and better tolerance to inhalation analgesia with a 50% equimolar mixture of nitrogen protoxide and oxygen in hysteroscopic polypectomy compared with paracervical anesthesia and a control group.

DESIGN

One hundred six patients scheduled for office hysteroscopy and polypectomy were divided into the following 3 groups: the control group, the nitrous oxide group, and the paracervical infiltration group. Patients were assigned sequentially (Canadian Task Force classification II-1).

SETTING

The study took place in a hysteroscopy outpatient clinic under the supervision of a gynecologist and 2 nurses trained to cooperate in the trial.

PATIENTS

One hundred six women from Area III of Madrid Community, Spain, who had been diagnosed with endometrial polyps at a gynecology office and were scheduled for office hysteroscopy and polypectomy agreed to participate in the study.

INTERVENTIONS

Patients in group 1 (control group) received no treatment. Group 2 received inhaled nitrous oxide and group 3 paracervical infiltration with 1% lidocaine.

MEASUREMENTS AND MAIN RESULTS

Pain was assessed using the visual analog scale (0-10). Pain perceived by patients was lower in the nitrous Oxide group (mean: 3.55 ± 0.60, median: 3) versus the control group (mean: 5.49 ± 1.88, median: 6, p < .05) and the paracervical infiltration group (mean: 4.22 ± 1.73, median: 5). Tolerance to pain, assessed by the medical staff using qualitative variables, was bad for the control group, very good for the nitrous oxide group, and good for the paracervical infiltration group (p < .05). There were no complications in 82% of the patients in the nitrous oxide group, whereas in the paracervical infiltration group, there were complications in more than 50% of the patients. No severe complications occurred.

CONCLUSION

Nitrous oxide is a safe and effective analgesic technique for polipectomy office hysteroscopy compared with the paracervical infiltration and control groups.

Nitrous oxide effect on relieving anxiety and pain in parturients under spinal anesthesia for caesarean section

Background:

Anxiety is an unpleasant experience that may have adverse effects on the process of anesthesia, cesarean delivery, recovery period and postoperative pain. Anxiety can also affect maternal satisfaction of the medical cares that provided by the medical team.

Objectives:

To compare the effects of inhalational 50% nitrous oxide (N₂O) with oxygen on reducing anxiety and pain in parturients who have undergone caesarean section under spinal anesthesia.

Patients and Methods:

In this double-blind clinical trial, 56 primigravid parturients were randomly assigned into two groups according to the operating list schedule. The experimental group received inhalational 50% N₂O three minutes before spinal anesthesia to the end of delivery. The control group received only oxygen. Flow meters were covered by a dark shield and monitored by an experienced nurse anesthetist. Pain and anxiety of patients were measured using visual analogue scale (VAS) by another nurse who was neither involved in the anesthetic process nor aware of the participants' allocation and inhalation agents. Data regarding sedation level, ephedrine use, nausea, vomiting, and neonate Apgar score were recorded as well.

Results:

Overall mean ± SD of anxiety VAS scores was 1.77 ± 1.5 in the experimental group and 3.12 ± 1.73 in the control groups (P = 0.003). The mean ± SD of pain VAS scores of the experimental and control groups were 0.82 ± 1.5 and 1.64 ± 1.45, respectively (P = 0.042). No significant differences were seen regarding blood oxygen saturation, neonate Apgar scores, total used ephedrine, operation time, delivery time, nausea, and vomiting between the two studied groups.

Conclusions:

Inhalation of 50% N₂O can significantly decrease anxiety (without clinically significant side effects) compared with O₂ inhalation in parturients who have undergone caesarean section under spinal anesthesia.

Nitrous oxide for the management of labor pain: a systematic review

BACKGROUND

We systematically reviewed evidence addressing the effectiveness of nitrous oxide for the management of labor pain, the influence of nitrous oxide on women's satisfaction with their birth experience and labor pain management, and adverse effects associated with nitrous oxide for labor pain management.

METHODS

We searched the MEDLINE, EMBASE, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases for articles published in English. The study population included pregnant women in labor intending a vaginal birth, birth attendees or health care providers who may be exposed to nitrous oxide during labor, and the fetus/neonate.

RESULTS

We identified a total of 58 publications, representing 59 distinct study populations: 2 studies were of good quality, 11 fair, and 46 poor. Inhalation of nitrous oxide provided less effective pain relief than epidural analgesia, but the quality of studies was predominately poor. The heterogeneous outcomes used to assess women's satisfaction with their birth experience and labor pain management made synthesis of studies difficult. Most maternal adverse effects reported in the literature were unpleasant side effects that affect tolerability, such as nausea, vomiting, dizziness, and drowsiness. Apgar scores in newborns whose mothers used nitrous oxide were not significantly different from those of newborns whose mothers used other labor pain management methods or no analgesia. Evidence about occupational harms and exposure was limited.

CONCLUSIONS

The literature addressing nitrous oxide for the management of labor pain includes few studies of good or fair quality. Further research is needed across all of the areas examined: effectiveness, satisfaction, and adverse effects.

Analgesia for childbirth: modern insights into an age-old challenge and the quest for an ideal approach

SUMMARY It is widely recognized that childbirth may be the most painful experience in a woman’s lifetime and that women have a right to relief. There are many options, but the efficacy of only a few is supported by robust evidence. Many influences determine which method of pain relief is chosen, including social and cultural factors, availability, cost and personal preference. Due to human diversity and the differing perspectives of consumers, obstetric care providers and health administrators, there is no such thing as ‘an ideal approach’. In resource-rich societies, major advances in parturient safety and outcome flow from technique development and better monitoring. Greater awareness of the negative impact of untreated pain and of the relevance of genetic, cultural and social factors motivates research into better predictive models, novel therapies and optimization of existing methods.

Effectiveness of nitrous oxide for postpartum perineal repair: a randomised controlled trial

OBJECTIVE

To compare the effectiveness of self-administered 50% nitrous oxide and conventional infiltrative anaesthesia with 1% prilocaine hydrochloride in postpartum perineal repair.

STUDY DESIGN

A total of 100 women were prospectively enrolled and randomised to receive either infiltrative anaesthesia or a self-administered nitrous oxide mixture (Livopan(©)) for pain relief during postpartum perineal suturing. Besides data concerning anaesthesia, characteristics of patients and labour were documented for statistical analysis. Pain experienced during perineal repair was assessed using the short form of the McGill Pain Questionnaire (SF-MPQ).

RESULTS

Forty-eight women received nitrous oxide and 52 underwent perineal suturing after infiltrative anaesthesia. There were no statistically significant differences regarding maternal age, body mass index (BMI), duration of pregnancy and suturing time between the groups. The most frequent birth injury was second-degree perineal laceration in the study group [22/48; 46%] and episiotomy in the control group [18/52; 35%]. Pain experienced during genital tract suturing and patients' satisfaction showed no statistically significant differences between the groups. Thirty-seven women in the study group and 47 in the control group were satisfied with the anaesthesia during perineal repair and would recommend it to other parturients [37/48, 77% vs. 47/52, 90%; p=0.0699).

CONCLUSION

Nitrous oxide self-administration during genital tract suturing after vaginal childbirth is a satisfactory and effective alternative to infiltrative anaesthesia.

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"

BACKGROUND

The epidural route is still considered the gold standard for labour analgesia, although it is not without serious consequences when incorrect placement goes unrecognized, e.g. in case of intravascular, intrathecal and subdural placements. Until now there has not been a viable alternative to epidural analgesia especially in view of the neonatal outcome and the need for respiratory support when long-acting opioids are used via the parenteral route. Pethidine and meptazinol are far from ideal having been described as providing rather sedation than analgesia, affecting the cardiotocograph (CTG), causing fetal acidosis and having active metabolites with prolonged half-lives especially in the neonate. Despite these obvious shortcomings, intramuscular and intravenously administered pethidine and comparable substances are still frequently used in delivery units. Since the end of the 90 ths remifentanil administered in a patient-controlled mode (PCA) had been reported as a useful alternative for labour analgesia in those women who either don't want, can't have or don't need epidural analgesia.

DISCUSSION

In view of the need for conversion to central neuraxial blocks and the analgesic effect remifentanil has been demonstrated to be superior to pethidine. Despite being less effective in terms of the resulting pain scores, clinical studies suggest that the satisfaction with analgesia may be comparable to that obtained with epidural analgesia. Owing to this fact, remifentanil has gained a place in modern labour analgesia in many institutions. However, the fact that remifentanil may cause harm should not be forgotten when the use of this potent mu-agonist is considered for the use in labouring women. In the setting of one-to-one midwifery care, appropriate monitoring and providing that enough experience exists with this potent opioid and the treatment of potential complications, remifentanil PCA is a useful option in addition to epidural analgesia and other central neuraxial blocks. Already described serious consequences should remind us not refer to remifentanil PCA as a "poor man's epidural" and to safely administer remifentanil with an appropriate indication.

SUMMARY

Therefore, the authors conclude that economic considerations and potential cost-savings in conjunction with remifentanil PCA may not be appropriate main endpoints when studying this valuable method for labour analgesia.

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.

Labor pain management other than neuraxial: what do we know and where do we go next?

Analgesia and coping with labor pain can prevent suffering during childbirth. Nonpharmacologic methods help women manage labor pain. Strong evidence is available for the efficacy of continuous one-to-one support from a woman trained to provide nonmedical care during labor, immersion in warm water during first-stage labor, and sterile water injected intracutaneously or subcutaneously at locations near a woman's lumbosacral spine to reduce back-labor pain. Sterile water injections also reduce the incidence of cesarean deliveries. Nitrous oxide labor analgesia is not potent, but helps women relax, gives them a sense of control, and reduces and distracts their perception of pain. It is inexpensive; can be administered and discontinued safely, simply, and quickly; has no adverse effects on the normal physiology and progress of labor; and does not require intensive monitoring or co-interventions. Parenteral opioids provide mild-to-moderate labor pain relief, but cause side effects. Although observational studies have found associations between maternal use of opioids and neonatal complications, little higher level evidence is available except that meperidine is associated with low Apgar scores. Patient-controlled intravenous administration of remifentanil provides better analgesia and satisfaction than other opioids, but can cause severe side effects; continuous monitoring of arterial oxygen saturation, anesthesia supervision, one-to-one nursing, and availability of oxygen are recommended. The demand for inexpensive, simple, safe but effective labor pain management for women will undoubtedly increase in places that lack wide access to it now.

Nitrous oxide as labor analgesia: clinical implications for nurses

A new interest in self-administered nitrous oxide for labor analgesia has emerged in recent years in the United States. It has been used widely in Europe for decades, with favorable results. The American College of Nurse-Midwives published a position statement in 2010 supporting the practice of self-administered nitrous oxide as an additional analgesia choice for laboring women. Recent literature on this subject has been directed toward midwives, obstetricians and/or anesthesiologists, with little emphasis for labor and delivery nurses. This article presents highlights of nursing care for women using self-administered nitrous oxide during labor and birth.

Pregnancy and birth outcomes of women with intellectual disability in Sweden: a national register study

OBJECTIVE

To investigate the antenatal health and demographic factors as well as pregnancy and delivery outcomes in women with intellectual disability (ID) in Sweden.

DESIGN

A population-based register study.

SETTING

The National Patient Register (NPR) linked to the Medical Birth Register (MBR).

SAMPLE

Women with ID classified as International Classification of Diseases (ICD) 8-10 who gave birth in 1999-2007 (n = 326), identified from the NPR linked to the MBR, were compared with all first-time, singleton mothers without ID or any other psychiatric diagnoses during this period in Sweden (n = 340 624).

METHODS

Population-based data were extracted from the NPR and the MBR.

MAIN OUTCOME MEASURES

Health and socio-demography at first antenatal visit, mode of delivery, pain relief during labor, preterm birth and discharge from hospital.

RESULTS

A higher proportion of women with ID were teenagers (18.4 vs. 3.3%), obese (20.1 vs. 8.6%) and single (36.6 vs. 6.2%) compared with women without ID, and women with ID smoked more often (27.9 vs. 7.9%). Women with ID had more often a preterm birth (12.2 vs. 6.1%), a cesarean section (CS) (24.5 vs. 17.7%) and used less nitrous oxide as pain relief during labor (59.5 vs. 75.8%). Women with ID had a higher risk for preterm birth [odds ratio (OR) 1.68], CS (OR1.55), non-use of nitrous oxide (OR 1.89) and discharge from hospital to a place other than home (OR 2.24).

CONCLUSION

Pregnant women with ID should be considered a risk group suggesting that better tailored pre- and intrapartum care and support are needed for these women.

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.

A newly developed scavenging system for administration of nitrous oxide during labour: safe occupational use

OBJECTIVE

Nitrous oxide (N(2) O) is routinely used as an analgesic in obstetrics during labour. Epidemiological studies have linked chronic occupational exposure to N(2) O to specific health problems, including reproductive risks. Occupational exposure limits (OELs) allow the use of N(2) O once appropriate preventive and safety measures have been taken. We assessed the effectiveness of a scavenger system (Anevac P-system®, Medicvent Heinen & Löwestein Benelux, Barneveld, the Netherlands) applied in N(2) O administration during labour in a midwifery-led birthing centre in the Netherlands.

METHODS

After informed consent, non-pregnant midwives were trained to administer N(2) O. N(2) O was delivered as a 50 : 50 mixture with oxygen and was self administered by the patient. The scavenging device, containing a double mask and a chin mask, was connected to the local evacuation system vented outside the building. Data on the 8-h time-weighted average (8-h TWA) as well as the 15-min TWA (15-min TWA) were obtained.

RESULTS

Thirteen patients were included. Six patients were included in the first study period. In this period the 8-h TWA was not exceeded, however, in all patients, the 15-min TWA occasionally exceeded the OELs. After four additional measures, seven patients were included. After implementation of these measures, the 8-h TWA and 15-min TWA never exceeded the OELs. System leakage was not observed during both study periods.

CONCLUSION

The Anevac P-scavenging system during N(2) O analgesia in labour prevents exceeding OELs in professional workers. The scavenging system appeared acceptable and effective, and can be considered in hospital settings that use N(2) O as analgesic during labour.

Pain management for women in labour: an overview of systematic reviews

BACKGROUND

The pain that women experience during labour is affected by multiple physiological and psychosocial factors and its intensity can vary greatly.  Most women in labour require pain relief. Pain management strategies include non-pharmacological interventions (that aim to help women cope with pain in labour) and pharmacological interventions (that aim to relieve the pain of labour).

OBJECTIVES

To summarise the evidence from Cochrane systematic reviews on the efficacy and safety of non-pharmacological and pharmacological interventions to manage pain in labour. We considered findings from non-Cochrane systematic reviews if there was no relevant Cochrane review.

METHODS

We searched the Cochrane Database of Systematic Reviews (The Cochrane Library 2011, Issue 5), The Cochrane Database of Abstracts of Reviews of Effects (The Cochrane Library 2011, Issue 2 of 4), MEDLINE (1966 to 31 May 2011) and EMBASE (1974 to 31 May 2011) to identify all relevant systematic reviews of randomised controlled trials of pain management in labour. Each of the contributing Cochrane reviews (nine new, six updated) followed a generic protocol with 13 common primary efficacy and safety outcomes. Each Cochrane review included comparisons with placebo, standard care or with a different intervention according to a predefined hierarchy of interventions. Two review authors extracted data and assessed methodological quality, and data were checked by a third author. This overview is a narrative summary of the results obtained from individual reviews.

MAIN RESULTS

We identified 15 Cochrane reviews (255 included trials) and three non-Cochrane reviews (55 included trials) for inclusion within this overview. For all interventions, with available data, results are presented as comparisons of: 1. Intervention versus placebo or standard care; 2. Different forms of the same intervention (e.g. one opioid versus another opioid); 3. One type of intervention versus a different type of intervention (e.g. TENS versus opioid). Not all reviews included results for all comparisons. Most reviews compared the intervention with placebo or standard care, but with the exception of opioids and epidural analgesia, there were few direct comparisons between different forms of the same intervention, and even fewer comparisons between different interventions. Based on these three comparisons, we have categorised interventions into: " What works" ,"What may work", and "Insufficient evidence to make a judgement".WHAT WORKSEvidence suggests that epidural, combined spinal epidural (CSE) and inhaled analgesia effectively manage pain in labour, but may give rise to adverse effects. Epidural, and inhaled analgesia effectively relieve pain when compared with placebo or a different type of intervention (epidural versus opioids). Combined-spinal epidurals relieve pain more quickly than traditional or low dose epidurals. Women receiving inhaled analgesia were more likely to experience vomiting, nausea and dizziness.When compared with placebo or opioids, women receiving epidural analgesia had more instrumental vaginal births and caesarean sections for fetal distress, although there was no difference in the rates of caesarean section overall. Women receiving epidural analgesia were more likely to experience hypotension, motor blockade, fever or urinary retention. Less urinary retention was observed in women receiving CSE than in women receiving traditional epidurals. More women receiving CSE than low-dose epidural experienced pruritus.  WHAT MAY WORKThere is some evidence to suggest that immersion in water, relaxation, acupuncture, massage and local anaesthetic nerve blocks or non-opioid drugs may improve management of labour pain, with few adverse effects.  Evidence was mainly limited to single trials. These interventions relieved pain and improved satisfaction with pain relief (immersion, relaxation, acupuncture, local anaesthetic nerve blocks, non-opioids) and childbirth experience (immersion, relaxation, non-opioids) when compared with placebo or standard care. Relaxation was associated with fewer assisted vaginal births and acupuncture was associated with fewer assisted vaginal births and caesarean sections.INSUFFICIENT EVIDENCEThere is insufficient evidence to make judgements on whether or not hypnosis, biofeedback, sterile water injection, aromatherapy, TENS, or parenteral opioids are more effective than placebo or other interventions for pain management in labour. In comparison with other opioids more women receiving pethidine experienced adverse effects including drowsiness and nausea. 

AUTHORS' CONCLUSIONS

Most methods of non-pharmacological pain management are non-invasive and appear to be safe for mother and baby, however, their efficacy is unclear, due to limited high quality evidence. In many reviews, only one or two trials provided outcome data for analysis and the overall methodological quality of the trials was low. High quality trials are needed.There is more evidence to support the efficacy of pharmacological methods, but these have more adverse effects. Thus, epidural analgesia provides effective pain relief but at the cost of increased instrumental vaginal birth.It remains important to tailor methods used to each woman's wishes, needs and circumstances, such as anticipated duration of labour, the infant's condition, and any augmentation or induction of labour.A major challenge in compiling this overview, and the individual systematic reviews on which it is based, has been the variation in use of different process and outcome measures in different trials, particularly assessment of pain and its relief, and effects on the neonate after birth. This made it difficult to pool results from otherwise similar studies, and to derive conclusions from the totality of evidence. Other important outcomes have simply not been assessed in trials; thus, despite concerns for 30 years or more about the effects of maternal opioid administration during labour on subsequent neonatal behaviour and its influence on breastfeeding, only two out of 57 trials of opioids reported breastfeeding as an outcome. We therefore strongly recommend that the outcome measures, agreed through wide consultation for this project, are used in all future trials of methods of pain management.

Nitrous oxide for analgesia in colonoscopy without sedation

BACKGROUND

Colonoscopy is associated with pain and discomfort, and intravenous analgesics and sedatives are widely used. There are several disadvantages regarding this practice, including risk of complications, resources demanded, and amnesia after sedation. In spite of promising results in previous studies, nitrous oxide is rarely used at endoscopy centers around the world.

OBJECTIVE

To investigate the efficiency of nitrous oxide versus placebo as an analgesic during colonoscopy without sedation.

DESIGN

A double-blind, randomized, placebo-controlled trial.

SETTING

The endoscopy unit at Oslo University Hospital Rikshospitalet, Oslo, Norway, between June 2006 and May 2008.

PATIENTS

This study involved patients undergoing elective colonoscopy.

INTERVENTION

Patients inhaled nitrous oxide or placebo on demand.

MAIN OUTCOME MEASUREMENTS

The participants filled in a questionnaire regarding their experiences with the examination. Pain was graded from 1 (no pain) to 4 (severe pain).

RESULTS

We recruited 199 patients. We randomized 97 patients to the nitrous oxide group and 102 to the control group. The groups were comparable regarding demographic factors. Median patient-reported pain was 2 in both the nitrous oxide group and the control group (interquartile range 2-3 in both groups). Additional sedatives and analgesics were given equally often and in similar doses in both groups. No side effects related to administration of nitrous oxide were reported.

LIMITATIONS

The questionnaire was returned by 76% of the patients. The study gas was given on demand, not continuously.

CONCLUSION

Nitrous oxide given intermittently is not an effective substitution for intravenous on-demand sedation and analgesics in the setting of colonoscopy without sedation.

Prevalence and management of acute pain in prehospital emergency medicine

BACKGROUND

Less is known about the prevalence of pain in prehospital emergency medicine than about pain in the emergency department. Objectives. To estimate the prehospital prevalence of pain and to identify the factors associated with oligoanalgesia.

METHODS

The mobile intensive care units of the emergency services of a Paris suburb conducted this prospective study. All consecutive patients aged 16 years or older who were able to self-assess pain were included around the clock over a period of 11 months in 2007.

RESULTS

Among the 2,279 included patients, 947 had acute pain (42% [95% confidence interval (CI) 40-44]). Pain was intense to severe in 64% of patients. Factors associated with acute pain were trauma (odds ratio [OR] = 2.9 [1.9-4.3]) and age under 75 years (OR = 2.2 [1.7-2.8]). Intense pain was significantly associated with pain of cardiac or traumatic origin. Among the 1,364 patients transported by the mobile units, 48% experienced acute pain (71% had intense to severe pain). An analgesic agent was administered to 73%. According to multivariate analysis, only gynecologic/obstetric emergencies were associated with inadequate treatment (OR = 0.2 [95% CI 0.1-0.6]). Overall, 51% of patients [46-56] experienced pain relief. The rate of pain relief was lowest in patients suffering from trauma or a gynecologic/obstetric disorder.

CONCLUSION

In our studied population, pain in prehospital emergency medicine affects 42% of patients. However, the rate varies widely according to the origin of the pain. Pain management is inadequate, as only one in two patients experiences relief.

Assisting informed decision making for labour analgesia: a randomised controlled trial of a decision aid for labour analgesia versus a pamphlet

BACKGROUND

Most women use some method of pain relief during labour. There is extensive research evidence available of pharmacological pain relief during labour; however this evidence is not readily available to pregnant women. Decision aids are tools that present evidence based information and allow preference elicitation.

METHODS

We developed a labour analgesia decision aid. Using a RCT design women either received a decision aid or a pamphlet. Eligible women were primiparous, > or = 37 weeks, planning a vaginal birth of a single infant and had sufficient English to complete the trial materials. We used a combination of affective (anxiety, satisfaction and participation in decision-making) and behavioural outcomes (intention and analgesia use) to assess the impact of the decision aid, which were assessed before labour.

RESULTS

596 women were randomised (395 decision aid group, 201 pamphlet group). There were significant differences in knowledge scores between the decision aid group and the pamphlet group (mean difference 8.6, 95% CI 3.70, 13.40). There were no differences between decisional conflict scores (mean difference -0.99 (95% CI -3.07, 1.07), or anxiety (mean difference 0.3, 95% CI -2.15, 1.50). The decision aid group were significantly more likely to consider their care providers opinion (RR 1.28 95%CI 0.64, 0.95). There were no differences in analgesia use and poor follow through between antenatal analgesia intentions and use.

CONCLUSIONS

This decision aid improves women's labour analgesia knowledge without increasing anxiety. Significantly, the decision aid group were more informed of labour analgesia options, and considered the opinion of their care providers more often when making their analgesia decisions, thus improving informed decision making.

TRIAL REGISTRATION

Trial registration no: ISRCTN52287533.

Do audio-guided decision aids improve outcomes? A randomized controlled trial of an audio-guided decision aid compared with a booklet decision aid for Australian women considering labour analgesia

OBJECTIVE

To assess the effectiveness of an audio-guided component: an audio-guided decision aid vs. a stand-alone booklet decision aid.

BACKGROUND

Despite extensive evaluation of decision aids in clinical settings the presentation style has not been properly assessed, and audio-guided decision aids are widely used although not supported by evidence-based research.

DESIGN

Randomized controlled trial.

SETTING AND PARTICIPANTS

Two obstetric hospitals in Sydney, Australia. A total of 395 pregnant women having their first baby and approximately > or =36 weeks of gestation, planning a vaginal birth of a single infant and with self-assessed English sufficiency to read and listen to English-presented material.

INTERVENTION

A decision aid for labour and childbirth analgesia that was presented in two ways: an audio-guided decision aid compared with a booklet only style decision aid.

MAIN OUTCOME MEASURES

Decisional conflict, knowledge and anxiety.

RESULTS

Although both groups improved their knowledge scores and decreased their decisional conflict there were no significant differences between groups: mean knowledge score - audio-guided group, 65.9 vs. booklet group, 64.3; mean difference, 1.7; 95% CI (-7.5, 4.2); mean decisional conflict score - audio-guided group, 23.6 vs. booklet group, 24.3; mean difference, 0.7; 95% CI (-1.4, 2.9). Acceptability and compliance were high.

DISCUSSION AND CONCLUSIONS

This evaluation highlights the lack of additional benefit in using audio-guided formats for presenting health information to consumers who are from a general English-speaking population. These results considered together with the increase in costs and work involved in producing audio components suggests that written and pictorial methods may be sufficient for decision aids aimed at a general audience.

The Pain of Labour

Labour is an emotional experience and involves both physiological and psychological mechanisms.The pain of labour is severe but despite this its memory diminishes with time.Labour pain has two components: visceral pain which occurs during the early first stage and the second stage of childbirth, and somatic pain which occurs during the late first stage and the second stage.The pain of labour in the first stage is mediated by T10 to L1 spinal segments, whereas that in the second stage is carried by T12 to L1, and S2 to S4 spinal segments.Pain relief in labour is complex and often challenging without regional analgesia.Effective management of labour pain plays a relatively minor role in a woman's satisfaction with childbirth.

Nitrous oxide for applying local anesthesia in nasal operations: a randomized placebo-controlled single-blinded study

CONCLUSIONS

In our study setting nitrous oxide (N(2)O) did not show any clinical benefit in discomfort experienced when applying local anesthesia for nasal operations. Further studies with longer inhalation times are needed to elucidate the role of N(2)O in application of local anesthesia in nasal surgery.

OBJECTIVES

N(2)O inhalation reduces the discomfort experienced in various medical procedures. The objective of this study was to assess the suitability of N(2)O inhalation before application of local anesthesia for nasal procedures in outpatient surgery.

PATIENTS AND METHODS

This was a prospective, randomized, single-blinded, placebo-controlled study at the Helsinki University Central Hospital, Finland. Ninety patients were randomly divided into three groups. Group A inhaled 10 breaths of 50% N(2)O/50% O(2) through a nasal mask with a Porter 2000 MXR scavenging system before application of local nasal anesthesia, group B inhaled room air through the same mask and group C received only local anesthesia. A visual analog scale was used to assess pain, nausea, and discomfort related to the application of nasal anesthesia.

RESULTS

The N(2)O inhalation was easy to perform and well tolerated. The N(2)O inhalation before applying local anesthesia for nasal operations did not show any significant additional benefit in reducing pain or discomfort.

The analgesic effect of inhalational Entonox for extracorporeal shock wave lithotripsy

Extracorporeal shock wave lithotripsy (ESWL) is a non-invasive procedure that allows urinary stones to be fragmented using acoustic shock waves. The impact of the shock waves causes transient stinging pain at the entry site as well as deep visceral discomfort, requiring analgesia during the procedure. The objective of this study was to compare the clinical efficacy of Entonox and pethidine for pain relief during outpatient ESWL. We randomized 150 outpatients undergoing elective ESWL into three groups of 50 patients, each group receiving inhalational Entonox, intravenous pethidine, or inhalational compressed air during ESWL. Quantitative evaluation of pain was performed according to a visual analogue scale (VAS), before and after the intervention. Analysis of variance (ANOVA) and paired t tests were used to compare VAS scores in the three groups, before and after the intervention. Entonox and pethidine decreased the pain score significantly, while compressed air did not. There was no significant difference between pain relief by Entonox and pethidine. This study demonstrates for the first time that inhalational Entonox is an effective analgesic regimen for ESWL. Entonox can be regarded as an appropriate alternative to analgesics like opioids in relieving pain during ESWL.

Involvement of the protein kinase Cγ isoform in development of tolerance to nitrous oxide–induced antinociception in mice

Prolonged exposure to nitrous oxide (N2O) results in development of acute tolerance to its antinociceptive effect. Cross-tolerance to N2O-induced antinociception is also observed in morphine-tolerant animals. Despite increasing evidence of tolerance development to N2O-induced antinociception, the details of the mechanisms that underlie this tolerance remain unknown. The present study was conducted to investigate the involvement of brain protein kinase C (PKC) isoform in these two types of tolerance to N2O-induced antinociception in mice. Prolonged exposure (41 min in total, including 30 min pre-exposure and 11 min of antinociceptive testing) to 70% N2O produced a reduction in N2O-induced antinociception, indicating development of acute tolerance. The prolonged exposure to 70% N2O caused an activation of PKCgamma isoform in the brain, but not the PKCepsilon isoform. Pretreatment with a PKCgamma-antisense oligonucleotide but not the corresponding mismatch oligonucleotide (i.c.v.) prevented the development of acute tolerance to N2O-induced antinociception. Chronic morphine treatment (10 mg/kg, s.c., b.i.d. for 5 days) resulted in development of tolerance to morphine-induced antinociception and cross-tolerance to N2O-induced antinociception. The development of tolerance to morphine and cross-tolerance to N2O were both inhibited by pretreatment with PKC inhibitor, chelerythrine (1 nmol, i.c.v.). Morphine-tolerant mice showed an activation of PKC within the brain, which was suppressed by pretreatment with chelerythrine (1 nmol, i.c.v.). Thus, activation of brain PKC, in particular, the PKCgamma isoform, appears to play an important role in the development of both acute tolerance and cross-tolerance to N2O-induced antinociception in mice.

Advances in understanding the actions of nitrous oxide

Nitrous oxide (N(2)O) has been used for well over 150 years in clinical dentistry for its analgesic and anxiolytic properties. This small and simple inorganic chemical molecule has indisputable effects of analgesia, anxiolysis, and anesthesia that are of great clinical interest. Recent studies have helped to clarify the analgesic mechanisms of N(2)O, but the mechanisms involved in its anxiolytic and anesthetic actions remain less clear. Findings to date indicate that the analgesic effect of N(2)O is opioid in nature, and, like morphine, may involve a myriad of neuromodulators in the spinal cord. The anxiolytic effect of N(2)O, on the other hand, resembles that of benzodiazepines and may be initiated at selected subunits of the gamma-aminobutyric acid type A (GABA(A)) receptor. Similarly, the anesthetic effect of N(2)O may involve actions at GABA(A) receptors and possibly at N-methyl-D-aspartate receptors as well. This article reviews the latest information on the proposed modes of action for these clinical effects of N(2)O.

Regional anaesthesia and perioperative outcome

PURPOSE OF REVIEW

The ongoing debate on the outcome benefits of regional anaesthesia and analgesia over general anaesthesia and systemic analgesia has led to a large number of recently published papers, in particular systematic reviews and meta-analyses that justify a review of the current status of the debate.

RECENT FINDINGS

Meta-analyses have shown consistently improved analgesia with epidural techniques, but the results are by far less consistent with regard to other outcomes, in particular morbidity and mortality. Specific outcomes in specific types of surgery, however, such as bowel recovery after abdominal surgery, can be improved by neuraxial blockade, which also remains the technique of choice for obstetric analgesia and anaesthesia. In certain indications, peripheral nerve blocks may have the potential to replace neuraxial blocks while maintaining the benefits of the regional technique, such as paravertebral blocks for thoracotomies.

SUMMARY

Although there are a considerable number of recent publications on the topic, the complex issues around the effect of regional anaesthesia on outcome is not completely resolved, possibly because the data are often not procedure specific. In addition, however, it may be that our current literature cannot provide a definitive answer.