Analgesia with sevoflurane during labour: II. Sevoflurane compared with Entonox for labour analgesia † ‡

European Society of Anaesthesiology Task Force on Nitrous Oxide: a narrative review of its role in clinical practice

Nitrous oxide (N₂O) is one of the oldest drugs still in use in medicine. Despite its superior pharmacokinetic properties, controversy remains over its continued use in clinical practice, reflecting in part significant improvements in the pharmacology of other anaesthetic agents and developing awareness of its shortcomings. This narrative review describes current knowledge regarding the clinical use of N₂O based on a systematic and critical analysis of the available scientific literature. The pharmacological properties of N₂O are reviewed in detail along with current evidence for the indications and contraindications of this drug in specific settings, both in perioperative care and in procedural sedation. Novel potential applications for N₂O for the prevention or treatment of chronic pain and depression are also discussed. In view of the available evidence, we recommend that the supply of N₂O in hospitals be maintained while encouraging its economic delivery using modern low flow delivery systems. Future research into its potential novel applications in prevention or treatment of chronic conditions should be pursued to better identify its role place in the developing era of precision medicine.

Labor analgesia in South West Nigeria: Methods and self-reported effectiveness

Context:

Labor exposes many women to severe pain. Effective labor pain management is one of the prerequisites for a satisfying labor experience.

Aim:

The aim of this study was to assess the labor pain management practices and patients’ assessment of adequacy of pain relief in two tertiary hospitals in South West Nigeria.

Materials and Methods:

This was a cross-sectional study involving 132 pregnant women who had a noninstrumental vaginal delivery at the obstetric units of Babcock University Teaching Hospital and Olabisi Onabanjo University Teaching Hospital, between December 2017 and May 2018. A structured questionnaire was administered to women within 24 h of delivery to record details of labor and delivery, the form of labor analgesia administered and respondents’ perceived effectiveness of the analgesia. Data were analyzed using the IBM-SPSS statistics for Windows version 21.0 (IBM, Armonk, New York).

Results:

Sixty-six (50%) women rated labor pain to be severe. Thirty-eight women (28.8%) did not receive any pain relief during labor. Nonpharmacological pain management practices such as back massage, breathing exercises, and companionship were administered to 45(34.1%), 79(59.8%), and 45(34.1%) women, respectively. Nine women (6.8%) received intramuscular pentazocine (30 mg) for labor analgesia. There was a statistically significant association between use of back massage and severe labor pain perception (χ² = 4.080; P = 0.043). Self-reported effectiveness was highest among users of back massage (82.2%) and companionship (77.8%).

Conclusions:

There is a large unmet need for labor analgesia in South West Nigeria. Nonpharmacological pain management practices were the most frequently used methods, and most patients experienced reduction in severity of pain. There is need for improvements in obstetric analgesia services in our maternity units.

Non-Neuraxial Labor Analgesia: Options

Although it is the most effective method to treat labor pain, neuraxial analgesia may be undesired, contraindicated, unsuccessful, or unavailable. Providing safe choices for labor pain relief is a central goal of health care providers alike. Consequently, knowledge of the efficacy, clinical implementation, and side effects of various non-neuraxial strategies is needed to provide appropriate options for laboring patients. In addition to nonpharmacologic alternatives, inhaled nitrous oxide and systemic opioids represent two broad classes of non-neuraxial pharmacologic labor analgesia most commonly available. This review summarizes the current published literature for these non-neuraxial labor analgesic options.

Effect of Entonox for pain management in labor: A systematic review and meta-analysis of randomized controlled trials

Background and aim

Entonox was one of the important methods for pain management in the delivery process. In previous years some studies have assessed the effect of this method in Iran. In this regard, the aim of this study was to systematically review studies addressing the effect of Entonox for pain management in labor.

Methods

This systematic review and meta-analysis study was conducted in 2016. The required data was collected using keywords such as ”Entonox”, “nitrous oxide”, ”vaginal delivery”, ”pain relief”, “obstetric”, “labor pain”, and “labor analgesia”, from databases including Google scholar, PubMed, Science Direct, Magiran, SID, and Scopus, and hand-searching of related and valid journals and references of articles. Articles published from 2000 to 2016 were searched. To conduct meta-analysis, CMA:2 (Comprehensive Meta-analysis) was used.

Results

Finally, 14 articles were included in the study. Pain relief standard difference in mean between-groups was −1.01 (95% CI: −1.59 to −0.43, Q=148.5, df=8, p=0.02, I²=76) this difference was significant (p<0.05). The overall Apgar score standard difference in mean between-groups (Entonox vs. comparison) was 0.12 (95% CI: 0.01 to 0.23, Q=109.4, df=16, p=0.00, I²=85.3) this difference was significant (p<0.05). The results of mothers’ satisfaction rate show that mothers in Entonox group has a high level of satisfaction rate.

Conclusion

According to results of studies published in Iran, it seems that Entonox is an effective method for pain relief in vaginal delivery, as well as for improving infant Apgar score and mothers’ satisfaction rate. Pain relief through Entonox can be used as a strategy for cesarean section reduction plan in Iran.

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.

Opinion: Labour Analgesia in the Developing World; Why Not

The provision of western-style safe, highly effective labour analgesia requires levels of training, staffing and technology that make its applicability in the developing world in current circumstances questionable. This review examines the reasons.

A randomized controlled trial comparing Pentazocine and Chamomilla recutita for labor pain relief

BACKGROUND

Traditional birth attendants in Pakistan sometimes use a homeopathic remedy, Chamomilla for labor pain relief. Our study compares this homeopathic remedy for pain relief in labor with a commonly used parenteral analgesic in a hospital setting. No systematic study has been conducted previously to study the effect of chamomile, which may be affordable and available in community settings.

METHODS

A double blind randomized controlled trial was carried out at Islamic International Medical College Trust. Ninety-nine normal pregnant women were randomly assigned into three groups. Each group received one of the three trial drugs; Chamomile, Pentazocine or placebo. The efficacy of labor analgesia was assessed by using Visual Analogue Scale (VAS) for pain intensity. Indicators of maternal and child health were recorded as were adverse effects of the drugs.

RESULTS

Mean pain scores in the three groups were calculated and compared. The difference in mean VAS scores in Pentazocine and Chamomilla recutita group as compared with placebo was not statistically significant. No significant adverse effects were noticed in any group except slight headache and dizziness in three parturients in Pentazocine group.

CONCLUSION

Neither Pentazocine, or Chamomilla recutita offer substantial analgesia during labor.

Sevoflurane for analgesia-testing a modified vaporiser for delivery

The Diamedica Sevoflurane Inhaler (Diamedica UK Ltd, Bratton Fleming, UK) (DSI) is a breathing system which includes a modification of an existing vaporiser (Diamedica Draw-over Vaporiser, Diamedica UK Ltd, Bratton Fleming, UK), to enable the delivery of 0.8% sevoflurane. Previous studies have suggested that self-administered sevoflurane at sub-anaesthetic concentration can provide useful pain relief during the first stage of labour and that it may be more effective than Entonox. Further research and potential clinical use have been impeded by the lack of a practical delivery system. In this study, the performance of two versions of the DSI (DSI-1 and DSI-2) was investigated. DSI-1 was tested over a range of minute volumes (1 to 30 l/min) and ambient temperatures (10°C to 40°C). The sevoflurane output increased unacceptably with rising ambient temperature, therefore the design was modified to create the DSI-2. The results from testing this revised version are also described. Mean sevoflurane output from the DSI-2 was found to be within a clinically acceptable range at the minute volumes tested (0.78% to 0.88%) and ambient temperatures tested (0.69% to 0.9%). Based upon these results, the authors propose to undertake further studies of sevoflurane analgesia using the DSI-2.

Anaesthetic challenges and management during pregnancy: Strategies revisited

During pregnancy, an obstetrician can encounter various complications and sometimes require surgery or operative intervention for delivery. However, the role of anaesthesiologists during such clinical scenario is grossly under-estimated. Without any close coordination and team work among obstetricians, neonatologists and an anaesthesiologist, morbidity and mortality can increase during these surgical interventions. The clinical scenario can become more challenging if the parturient suffers from any comorbid diseases. The present article reviews some of the common challenging scenarios during pregnancy that an anaesthesiologist frequently encounters during routine practice. Anaesthetic management has been discussed briefly and separately for each trimester and post-partum period. The article also aims at gaining in-depth knowledge of these obstetrical and surgical emergencies so as to ensure close-knit team work among obstetricians, anaesthesiologists, intensivists and a neonatologist.

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.

Comparison of remifentanil: Entonox with Entonox alone in labor analgesia

Background:

We designed a study to evaluate the effectiveness of continuous low dose infusion of remifentanil adding to self-administration of entonox administered for pain relief during the active phase of first stage of labor.

Materials and Methods:

Thirty healthy term pregnant women recruited in our randomized double-blind, cross over study. They received the study medicines during two 30-min periods with a 15-min wash-out sequence after each period. Fifteen parturient used remifentanil as a single bolus dose followed by constant low dose infusion and self-administration of entonox (group R) during the first period and entonox and saline (group P) during the second period, while the remainder of the parturient used the drugs in a reverse order. Pain and Ramsay score, maternal and fetal hemodynamic, and ventilation were assessed during each intervention.

Results:

In this study, mean pain severity scores were 8 ± 0.9 before and 5.4 ± 1.7 after intervention in group P, and 7.8 ± 0.1, 3.5 ± 1.3 in group R, respectively. Mean pain severity difference was 2.6 ± 1.5 in group P, while 4.3 ± 1.5 in group R; so, use of entonox and remifentanil can decrease labor pain two times more in comparison with entonox/placebo (normal saline). However, hemodynamic and ventilation parameter in remifentanil/entonox period were same as in entonox/placebo period. No statistical differences were seen in mean Ramsay score between group R and P. There was no episode of maternal bradycardia, hypotension, or hypoxemia.

Conclusion:

Not only adding low dose infusion of remifentanil to self-administration of entonox was notable in labor pain reduction, it did n’t make more parturient and neonatal side-effects.

Effects of Propofol, Sevoflurane, Remifentanil, and (S)-Ketamine in Subanesthetic Concentrations on Visceral and Somatosensory Pain–evoked Potentials

Background:

Although electroencephalographic parameters and auditory evoked potentials (AEP) reflect the hypnotic component of anesthesia, there is currently no specific and mechanism-based monitoring tool for anesthesia-induced blockade of nociceptive inputs. The aim of this study was to assess visceral pain–evoked potentials (VPEP) and contact heat–evoked potentials (CHEP) as electroencephalographic indicators of drug-induced changes of visceral and somatosensory pain. Additionally, AEP and electroencephalographic permutation entropy were used to evaluate sedative components of the applied drugs.

Methods:

In a study enrolling 60 volunteers, VPEP, CHEP (amplitude N2-P1), and AEP (latency Nb, amplitude Pa-Nb) were recorded without drug application and at two subanesthetic concentration levels of propofol, sevoflurane, remifentanil, or (s)-ketamine. Drug-induced changes of evoked potentials were analyzed. VPEP were generated by electric stimuli using bipolar electrodes positioned in the distal esophagus. For CHEP, heat pulses were given to the medial aspect of the right forearm using a CHEP stimulator. In addition to AEP, electroencephalographic permutation entropy was used to indicate level of sedation.

Results:

With increasing concentrations of propofol, sevoflurane, remifentanil, and (s)-ketamine, VPEP and CHEP N2-P1 amplitudes decreased. AEP and electroencephalographic permutation entropy showed neither clinically relevant nor statistically significant suppression of cortical activity during drug application.

Conclusions:

Decreasing VPEP and CHEP amplitudes under subanesthetic concentrations of propofol, sevoflurane, remifentanil, and (s)-ketamine indicate suppressive drug effects. These effects seem to be specific for analgesia.

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.

Analgesia in Obstetrics

Background: An effective relief of labour pain has become an important part of obstetric medicine. Therefore regional nerve blocks, systemic analgesic and non-pharmacologic techniques are commonly used. This review article gives a summary of pathophysiology and anatomy of labour pain as well as advantages, disadvantages, risks and adverse reactions of analgesic techniques in newborns and parturients. Methods: We performed a selective literature search in Medline via PubMed using the search-terms "Analgesia" and "Obstetrics". We also included the current guidelines of the German Society for Anesthesiology and Intensive Care Medicine. Results: PDA and CSE are safe techniques for the relief of labour pain if contraindications are excluded. The risk for instrumental delivery but not for caesarean section is increased under neuraxial analgesia. PDA and CSE should be performed in an early stage of labour using low doses of local anaesthetics if possible. It is not necessary to wait for a defined cervical dilatation before starting neuraxial analgesia. Anesthesiologists and obstetricians should inform patients as soon as possible before the situation of stress during labour. Systemic opioid analgesia is a possible alternative for neuraxial techniques. Because of possible side effects systemic remifentanil analgesia should only be performed under continuous monitoring. Several nonpharmacologic methods can also relieve labour pain, but results of studies about their effectiveness are inconsistent.

Sevoflurane to alleviate pain on propofol injection

PURPOSE

Since the introduction of propofol, several drugs and methods have been used to alleviate the pain on its injection. This study was designed to evaluate the effect of adding sevoflurane 3% during preoxygenation in alleviation of pain on propofol injection.

METHODS

In this randomized single-blinded study, 100 patients were randomly allocated equally into five groups: sevoflurane-lidocaine-tourniquet (SLT), sevoflurane-lidocaine (SL), lidocaine-tourniquet (LT), lidocaine (L), and sevoflurane (S). Approximately 10 min before the induction of anesthesia, midazolam 1-2 mg was administered intravenously to all patients. All patients received fentanyl 1 µg/kg as pretreatment and a full induction dose of propofol. A blinded anesthesia nurse assessed pain and hand movements throughout the injection of propofol.

RESULTS

In the SLT group, all patients (100%) were pain free and had no hand movements. There was no significant difference in pain grade or in hand movements between the L and the S groups, or between the SLT and the SL groups. However, significant differences were observed in pain grade between the SLT and the L groups as well as between the SLT and the S groups. In addition, a significant difference in hand movement was observed only between the SLT and the S groups.

CONCLUSION

The addition of 3% sevoflurane at the time of preoxygenation for 1 min along with routine use of lidocaine-tourniquet completely prevented pain upon propofol injection, whereas sevoflurane by itself provided similar analgesia to premixed lidocaine with propofol.

Labour analgesia: Recent advances

Advances in the field of labour analgesia have tread a long journey from the days of ether and chloroform in 1847 to the present day practice of comprehensive programme of labour pain management using evidence-based medicine. Newer advances include introduction of newer techniques like combined spinal epidurals, low-dose epidurals facilitating ambulation, pharmacological advances like introduction of remifentanil for patient-controlled intravenous analgesia, introduction of newer local anaesthetics and adjuvants like ropivacaine, levobupivacaine, sufentanil, clonidine and neostigmine, use of inhalational agents like sevoflourane for patient-controlled inhalational analgesia using special vaporizers, all have revolutionized the practice of pain management in labouring parturients. Technological advances like use of ultrasound to localize epidural space in difficult cases minimizes failed epidurals and introduction of novel drug delivery modalities like patient-controlled epidural analgesia (PCEA) pumps and computer-integrated drug delivery pumps have improved the overall maternal satisfaction rate and have enabled us to customize a suitable analgesic regimen for each parturient. Recent randomized controlled trials and Cochrane studies have concluded that the association of epidurals with increased caesarean section and long-term backache remains only a myth. Studies have also shown that the newer, low-dose regimes do not have a statistically significant impact on the duration of labour and breast feeding and also that these reduce the instrumental delivery rates thus improving maternal and foetal safety. Advances in medical technology like use of ultrasound for localizing epidural space have helped the clinicians to minimize the failure rates, and many novel drug delivery modalities like PCEA and computer-integrated PCEA have contributed to the overall maternal satisfaction and safety.

Advances in labor analgesia

The pain of childbirth is arguably the most severe pain most women will endure in their lifetimes. The pain of the early first stage of labor arises from dilation of the lower uterine segment and cervix. Pain from the late first stage and second stage of labor arises from descent of the fetus in the birth canal, resulting in distension and tearing of tissues in the vagina and perineum. An array of regional nerve blocks, systemic analgesic, and nonpharmacologic techniques are currently used for labor analgesia. Nonpharmacologic methods are commonly used, but the effectiveness of these techniques generally lacks rigorous scientific study. Continuous labor support has been shown to decrease the use of pharmacologic analgesia and shorten labor. Intradermal water injections decrease back labor pain. Neuraxial labor analgesia (most commonly epidural or combined spinal-epidural) is the most effective method of pain relief during childbirth, and the only method that provides complete analgesia without maternal or fetal sedation. Current techniques commonly combine a low dose of local anesthetic (bupivacaine or ropivacaine) with a lipid soluble opioid (fentanyl or sufentanil). Neuraxial analgesia does not increase the rate of cesarean delivery compared to systemic opioid analgesia; however, dense neuraxial analgesia may increase the risk of instrumental vaginal delivery.

The management of breakthrough pain during labour

There is a long history of attempts to alleviate the pain of childbirth, particularly in Asian and Middle Eastern civilisations. In the UK, it was the administration of chloroform to Queen Victoria by John Snow in 1853 that is widely credited with popularizing the idea that labour pain should and could be treated. Medical analgesia is now well established around the globe with a wealth of research evidence describing methods, efficacy and complications. In this article, we define 'primary breakthrough pain' as the moment when a woman first requests analgesia during labour. The management of this can include simple emotional support, inhaled analgesics, parenteral opioids and epidural analgesia. 'Secondary breakthrough pain' can be defined as the moment when previously used analgesia becomes ineffective. We concentrate our discussion of this phenomenon on the situation when epidural analgesia begins to fail. Only epidural analgesia offers the potential for complete analgesia, so when this effect is lost the recipient can experience significant distress and dissatisfaction. The best strategy to avert this problem is prevention by using the best techniques for epidural catheterisation and the most effective drug combinations. Even then, epidurals can lose their efficacy for a variety of reasons, and management is hampered by the fact that each rescue manoeuvre takes about 30 minutes to be effective. If the rescue protocol is too cautious, analgesia may not be successfully restored before delivery, leading to patient dissatisfaction. We therefore propose an aggressive response to epidural breakthrough pain using appropriate drug supplementation and, if necessary, the placement of a new epidural catheter. Combined spinal epidural techniques offer several advantages in this situation. The goal is to re-establish analgesia within 1 hour. The primary aim of pain management during labour and delivery is to provide the level of comfort determined as acceptable to each individual woman. Some require little or no analgesia, while others demand complete abolition of pain. Whatever the individual's personal point of breakthrough pain is, supporting clinicians should respond logically and rapidly to re-establish analgesia using locally agreed protocols. This approach will maximize patient satisfaction and hopefully increase the pleasure and satisfaction of childbirth.

Influence of different remifentanil concentrations on the performance of the surgical stress index to detect a standardized painful stimulus during sevoflurane anaesthesia

BACKGROUND

Although measurement of cerebral hypnotic drug effect and muscle relaxation is common clinical routine during anaesthesia, a reliable measurement of the neurophysiological effects evoked by a painful stimulus is still missing. Recently, the surgical stress index (SSI) has been introduced as a surrogate measure of 'nociception'. The present study aimed to examine the influence of increasing remifentanil concentrations on the ability of SSI to detect a standardized painful stimulus during sevoflurane anaesthesia.

METHODS

Twenty-four patients received incremental or decremental doses of 0, 2, and 4 ng ml(-1) remifentanil effect-site concentration (Ce(remi)) during 0.7 MAC sevoflurane. Painful tetanic stimulation was applied at least 5 min after changing Ce(remi). SSI, heart rate (HR), response entropy (RE), state entropy (SE), RE-SE difference, and bispectral index (BIS) were obtained in each patient before and after stimulation. Further prediction of an author-defined response to painful stimulus was analysed.

RESULTS

SSI and BIS, but not HR, SE, RE, or RE-SE difference were significantly altered after stimulation. Change in SSI (Delta SSI) was significantly dependent on Ce(remi), as Delta SSI was [median (inter-quartile range)] 20 (15-31), 10 (1-19), and 3 (1-10) at 0, 2, and 4 ng ml(-1) Ce(remi). In 10 out of 63 cases, SSI detected response to stimulation, not detected by another variable. SSI was unable to predict movement after stimulation as P(K) value is 0.59 (0.09).

CONCLUSIONS

The SSI response to tetanic stimulation was dependent on the remifentanil concentration.

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.