A comparison of patient-controlled analgesia fentanyl and alfentanil for labour analgesia

Predicting Maternal-Fetal Disposition of Fentanyl Following Intravenous and Epidural Administration Using Physiologically Based Pharmacokinetic Modeling

Fentanyl is an opioid analgesic used to treat obstetrical pain in parturient women through epidural or intravenous route, and unfortunately can also be abused by pregnant women. Fentanyl is known to cross the placental barrier, but how the route of administration and time after dosing affects maternal-fetal disposition kinetics at different stages of pregnancy is not well characterized. To address this knowledge gap, we developed a maternal-fetal physiologically based pharmacokinetic (mf-PBPK) model for fentanyl to evaluate the feasibility to predict the maternal and fetal plasma concentration-time profiles of fentanyl after various dosing regimens. As fentanyl is typically given via the epidural route to control labor pain, an epidural dosing site was developed using alfentanil as a reference drug and extrapolated to fentanyl. Fetal hepatic clearance of fentanyl was predicted from CYP3A7-mediated norfentanyl formation in fetal liver microsomes (intrinsic clearance = 0.20 ± 0.05 µl/min/mg protein). The developed mf-PBPK model successfully captured fentanyl maternal and umbilical cord concentrations after epidural dosing and was used to simulate the concentrations after intravenous dosing (in a drug abuse situation). The distribution kinetics of fentanyl were found to have a considerable impact on the time course of maternal:umbilical cord concentration ratio and on interpretation of observed data. The data show that mf-PBPK modeling can be used successfully to predict maternal disposition, transplacental distribution, and fetal exposure to fentanyl. SIGNIFICANCE STATEMENT: This study establishes the modeling framework for predicting the time course of maternal and fetal exposures of fentanyl opioids from mf-PBPK modeling. The model was validated based on fentanyl exposure data collected during labor and delivery after intravenous or epidural dosing. The results show that mf-PBPK modeling is a useful predictive tool for assessing fetal exposures to fentanyl opioid therapeutic regimens and potentially can be extended to other drugs of abuse.

Intrapartum opioid analgesia and childhood neurodevelopmental outcomes among infants born preterm

BACKGROUND

There are concerns regarding neurobehavioral changes in infants exposed to parenteral opioids during labor; however, long-term neurodevelopment remains unstudied.

OBJECTIVE

We aimed to examine the association between parenteral opioids used as labor analgesia and perinatal outcomes and childhood neurodevelopment until 2 years of age among infants born prematurely. We hypothesized that intrapartum exposure to parenteral opioids is associated with impaired neurodevelopment and adverse perinatal outcomes.

STUDY DESIGN

This was a secondary analysis of a multicenter, randomized controlled trial assessing magnesium for the prevention of cerebral palsy in infants at risk for preterm birth. Women delivering a singleton, nonanomalous, live infant before 37 weeks' gestation were considered for inclusion. Women were excluded if they had missing exposure or primary outcome data, were exposed to general anesthesia, or reported use of heroin or unspecified illicit drugs. Women reporting use of nonopioid illicit drugs such as cocaine and marijuana were not excluded. Groups were compared based on exposure or nonexposure to parenteral opioids (intravenous or intramuscular) used as labor analgesia. The primary outcome was any psychomotor or mental developmental delay at 24 months according to the Bayley Scales of Infant Development II. Secondary outcomes were the Bayley Scales of Infant Development II subdomains and adverse perinatal outcomes. Multivariable logistic regression models were performed and adjusted odds ratios with 95% confidence intervals were estimated.

RESULTS

Of the 1404 women included, 535 (38%) received parenteral opioids as labor analgesia. Women receiving parenteral opioids were more likely to be younger, Hispanic, and present with cervical dilation ≥4 cm. Parenteral opioid recipients had lower rates of illicit nonopioid drug or tobacco use, a lower rate of cesarean delivery, lower educational level and were less likely to be undergoing induction. Women receiving parenteral opioids who underwent cesarean delivery were less likely to do so because of a nonreassuring fetal status. In the unadjusted and adjusted analyses, there were no significant differences in the primary outcomes of psychomotor or mental developmental delay at 2 years of age (adjusted odds ratio, 0.96; confidence interval, 0.76-1.20). The only significant difference in secondary outcomes was a shorter O₂ requirement duration in the parenteral opioid group (2 vs 4 days; P=.002).

CONCLUSION

Among a population of preterm infants vulnerable to neurologic impairment, intrapartum exposure to parenteral opioids was not associated with an increased risk for neurodevelopmental delay up to 2 years of age, nor did these infants have worse perinatal outcomes.

Parenteral opioids for maternal pain management in labour

BACKGROUND

Parenteral opioids (intramuscular and intravenous drugs including patient-controlled analgesia) are used for pain relief in labour in many countries throughout the world. This review is an update of a review first published in 2010.

OBJECTIVES

To assess the effectiveness, safety and acceptability to women of different types, doses and modes of administration of parenteral opioid analgesia in labour. A second objective is to assess the effects of opioids in labour on the baby in terms of safety, condition at birth and early feeding.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (11 May 2017) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials examining the use of intramuscular or intravenous opioids (including patient-controlled analgesia) for women in labour. Cluster-randomised trials were also eligible for inclusion, although none were identified. We did not include quasi-randomised trials. We looked at studies comparing an opioid with another opioid, placebo, no treatment, other non-pharmacological interventions (transcutaneous electrical nerve stimulation (TENS)) or inhaled analgesia.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the quality of each evidence synthesis using the GRADE approach.

MAIN RESULTS

We included 70 studies that compared an opioid with placebo or no treatment, another opioid administered intramuscularly or intravenously or compared with TENS applied to the back. Sixty-one studies involving more than 8000 women contributed data to the review and these studies reported on 34 different comparisons; for many comparisons and outcomes only one study contributed data. All of the studies were conducted in hospital settings, on healthy women with uncomplicated pregnancies at 37 to 42 weeks' gestation. We excluded studies focusing on women with pre-eclampsia or pre-existing conditions or with a compromised fetus. Overall, the evidence was graded as low- or very low-quality regarding the analgesic effect of opioids and satisfaction with analgesia; evidence was downgraded because of study design limitations, and many of the studies were underpowered to detect differences between groups and so effect estimates were imprecise. Due to the large number of different comparisons, it was not possible to present GRADE findings for every comparison.For the comparison of intramuscular pethidine (50 mg/100 mg) versus placebo, no clear differences were found in maternal satisfaction with analgesia measured during labour (number of women satisfied or very satisfied after 30 minutes: 50 women; 1 trial; risk ratio (RR) 7.00, 95% confidence interval (CI) 0.38 to 128.87, very low-quality evidence), or number of women requesting an epidural (50 women; 1 trial; RR 0.50, 95% CI 0.14 to 1.78; very low-quality evidence). Pain scores (reduction in visual analogue scale (VAS) score of at least 40 mm: 50 women; 1 trial; RR 25, 95% CI 1.56 to 400, low-quality evidence) and pain measured in labour (women reporting pain relief to be "good" or "fair" within one hour of administration: 116 women; 1 trial; RR 1.75, 95% CI 1.24 to 2.47, low-quality evidence) were both reduced in the pethidine group, and fewer women requested any additional analgesia (50 women; 1 trial; RR 0.71, 95% CI 0.54 to 0.94, low-quality evidence).There was limited information on adverse effects and harm to women and babies. There were few results that clearly showed that one opioid was more effective than another. Overall, findings indicated that parenteral opioids provided some pain relief and moderate satisfaction with analgesia in labour. Opioid drugs were associated with maternal nausea, vomiting and drowsiness, although different opioid drugs were associated with different adverse effects. There was no clear evidence of adverse effects of opioids on the newborn. We did not have sufficient evidence to assess which opioid drug provided the best pain relief with the least adverse effects.

AUTHORS' CONCLUSIONS

Though most evidence is of low- or very-low quality, for healthy women with an uncomplicated pregnancy who are giving birth at 37 to 42 weeks, parenteral opioids appear to provide some relief from pain in labour but are associated with drowsiness, nausea, and vomiting in the woman. Effects on the newborn are unclear. Maternal satisfaction with opioid analgesia was largely unreported. The review needs to be examined alongside related Cochrane reviews. More research is needed to determine which analgesic intervention is most effective, and provides greatest satisfaction to women with acceptable adverse effects for mothers and their newborn.

Efficacy and side effects of intravenous remifentanil patient-controlled analgesia used in a stepwise approach for labour: an observational study

BACKGROUND

Remifentanil has a suitable pharmacological profile for labour analgesia. In this prospective, observational study, intravenous patient-controlled analgesia with remifentanil, using stepwise bolus doses without background infusion, was examined during the first and second stages of labour. Outcomes were pain reduction, maternal satisfaction, maternal and neonatal side effects and remifentanil metabolism in the neonate.

METHODS

Parturients with normal term singleton pregnancies were recruited. The initial remifentanil bolus dose was 0.15 μg/kg, increasing in steps of 0.15 μg/kg, with a 2-min lock-out. Pain scores using a 100 mm visual analogue scale, systolic and diastolic blood pressures, respiratory rate and maternal sedation were recorded every 15 min. Maternal oxygen saturation and heart rate were monitored continuously. Neonatal data included Apgar scores, clinical examination, naloxone use, resuscitation, umbilical cord blood gases and remifentanil concentrations.

RESULTS

Forty-one parturients were enrolled. Pain scores were significantly reduced in the first 3 h of patient-controlled analgesia use compared to baseline, and at the end of the first and second stages of labour (P<0.05). Maximal pain reduction was 60% (P<0.01). One patient had inadequate pain relief and converted to epidural analgesia. The mean highest dose of remifentanil was 0.7 μg/kg [range 0.3-1.05]. Ninety-three percent of patients were satisfied with their analgesia. The lowest oxygen saturation was 91% and the lowest respiratory rate was 9 breaths/min. Eleven parturients (27%) received supplemental oxygen due to oxygen saturations <92%. Maternal sedation was moderate, and neonatal data reassuring.

CONCLUSIONS

Remifentanil intravenous patient-controlled analgesia provides adequate pain relief and high maternal satisfaction during the first and second stages of labour. Maternal sedation and respiratory depression may occur, but no serious neonatal side effects were recorded. Careful monitoring is mandatory.

Parenteral opioids for maternal pain relief in labour

BACKGROUND

Parenteral opioids are used for pain relief in labour in many countries throughout the world.

OBJECTIVES

To assess the acceptability, effectiveness and safety of different types, doses and modes of administration of parenteral opioids given to women in labour.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2010) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials examining the use of intramuscular or intravenous opioids (including patient controlled analgesia) for women in labour. We looked at studies comparing an opioid with placebo or another opioid.

DATA COLLECTION AND ANALYSIS

At least two review authors independently assessed study eligibility, collected data and assessed risk of bias.

MAIN RESULTS

We included 54 studies involving more than 7000 women that compared an opioid with placebo or another opioid administered intramuscularly or intravenously. The 54 studies reported on 27 different comparisons, and for many outcomes only one study contributed data. Overall the evidence was of poor quality regarding the analgesic effect of opioids, satisfaction with analgesia, adverse effects and harm to women and babies. There were few statistically significant results. Many of the studies had small sample sizes, and low statistical power. Overall, findings indicated that parenteral opioids provided some pain relief and moderate satisfaction with analgesia in labour, although up to two-thirds of women who received opioids reported moderate or severe pain and/or poor or moderate pain relief one or two hours after administration. Opioid drugs were associated with maternal nausea, vomiting and drowsiness, although different opioid drugs were associated with different adverse effects. There was no clear evidence of adverse effects of opioids on the newborn. We did not have sufficient evidence to assess which opioid drug provided the best pain relief with the least adverse effects.

AUTHORS' CONCLUSIONS

Parenteral opioids provide some relief from pain in labour but are associated with adverse effects. Maternal satisfaction with opioid analgesia was largely unreported but appeared moderate at best. We did not examine the effectiveness and safety of parenteral opioids compared with other methods of pain relief in labour and this review needs to be examined alongside related Cochrane reviews. More research is needed to determine which analgesic intervention is most effective, and provides greatest satisfaction to women with acceptable adverse events for mothers and their newborns.

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.

Analgesia for labour: a survey of Norwegian practice - with a focus on parenteral opioids

BACKGROUND

During the last two decades, epidural analgesia has become 'a gold standard' for labour pain in most Western countries. Newer short-acting opioids given systemically represent an alternative for adequate pain relief without using regional techniques. With this survey, we wish to explore how Norwegian hospitals practice labour analgesia, especially their use of systemic opioids.

METHODS

A questionnaire was sent to the head of all 46 registered Norwegian labour units in 2005. The questionnaire focused on epidural and the use of systemic opioids. In 2008, the same questionnaire was sent to the 19 largest units reporting >1000 births a year, seeking updated information.

RESULTS

Forty-three of the 46 original questionnaires were returned. An epidural frequency of 25.9% was registered. For epidural treatment, bupivacaine was the preferred local anaesthetic, while sufentanil was the opioid of choice for the majority of units. Pethidine was the most commonly used opioid for systemic administration (77%). All units reported nurse administration of systemic opioids. The intramuscular route was most commonly used, either alone (58%) or in combination with an intravenous (i.v.) administration (34%). Only one unit used i.v. fentanyl. There were only minor changes with the repeated survey, except for one large unit, which reported over a 50% increase in the epidural frequency.

CONCLUSION

In Norway, the frequency of epidural for labour analgesia is still relatively low, but seems to be increasing. Systemic opioids are often used instead of or as a supplement. Clinical practice seems to be conservative, and newer short-acting opioids are seldom used systemically.

Intravenous dexmedetomidine as an adjunct for labor analgesia and cesarean delivery anesthesia in a parturient with a tethered spinal cord

For parturients desiring labor analgesia who have contraindications to neuraxial techniques, intravenous opioid-based patient-controlled analgesia (IVPCA) offers a reasonable alternative, although incomplete analgesia and maternal and neonatal respiratory depression can occur. Dexmedetomidine, a highly selective alpha(2) agonist with negligible placental transfer, may be a valuable adjunct to IVPCA by providing additional analgesia without the respiratory depression associated with increasing opioid usage. The successful use of a dexmedetomidine infusion as an adjunct to unsatisfactory fentanyl IVPCA is reported in a 31-year-old parturient with spina bifida occulta and a tethered spinal cord reaching L5-S1. Dexmedetomidine significantly improved the analgesic quality; increased sedation was observed, but the patient was easily rousable to verbal stimuli. No episodes of maternal hypotension or bradycardia, or fetal heart rate irregularities occurred. Cesarean delivery was required for prolonged first stage of labor and presumed chorioamnionitis; it was conducted under general anesthesia during which the dexmedetomidine infusion was continued. A healthy baby boy was delivered with normal Apgar scores and no discernible neurobehavioral or other deficits.

The use of remifentanil in obstetrics

Remifentanil has been proposed as the most suitable systemic opioid for use in obstetrics. Although the onset and offset are rapid, it cannot achieve maximum effect within the time period of a single uterine contraction. Nevertheless, it provides worthwhile analgesia mainly for the first stage of labor with consistently high maternal satisfaction. Maternal oxygen desaturation limits the dose and suitable monitoring during use is advised. As an adjunct to general anesthesia, it is successful in blunting responses to airway manipulation and providing hemodynamic stability in high-risk women. Neonatal effects when used in labor are minimal, but when combined with general anesthesia neonatal depression is unpredictable and more likely with an infusion dose greater than 0.1 microg/kg/min.

Options for systemic labor analgesia

PURPOSE OF REVIEW

This article reviews the challenging practice of systemic analgesia as an alternative to epidural analgesia for labor pain, and places remifentanil within the context of opioid analgesics suitable for managing for labor pain.

RECENT FINDINGS

Although systemic opioids have long been used for labor analgesia, they have become less popular because of frequent maternal and neonatal side effects. Recently, their efficacy has been questioned. Patient-controlled intravenous analgesia with fentanyl or sufentanil is currently the method of choice for achieving analgesia during early labor, when epidural analgesia is not feasible. Remifentanil has been suggested as the opioid of choice for labor analgesia, having the advantage of easy administration, predictable pharmacokinetics, and improved neonatal outcomes. The position of remifentanil in obstetric analgesia is now better understood, as reflected by the increasing number of reported studies describing its use.

SUMMARY

Remifentanil is now gaining popularity. Remifentanil may be more suitable than other traditional opioids for inducing labor analgesia. Careful monitoring of the parturient and the newborn is recommended, however, to mitigate the potential for maternal and neonatal hypoxemia.

American gastroenterological association institute technical review on the use of gastrointestinal medications in pregnancy

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Institute Clinical Practice and Economics Committee. The paper was approved by the Committee on February 22, 2006 and by the AGA Institute Governing Board on April 20, 2006.

Sedation and analgesia for gastrointestinal endoscopy during pregnancy

Endoscopy during pregnancy raises the unique issue of fetal safety. Endoscopic medications comprise a significant component of fetal risks from endoscopy. Before endoscopy, the gastroenterologist or anesthesiologist should evaluate the potential fetal risks of sedation and analgesia, identify any contraindications to endoscopy, stabilize the maternal medical status as necessary, and correct maternal hypoxia or hypotension. The mother should be informed about the potential teratogenic risks of endoscopic medications during pregnancy. Patients who receive sedation and analgesia should be monitored during endoscopy by continuous electrocardiography, continuous pulse oximetry, and intermittent sphygmomanometry, as well as by the pulse and respiratory rate. General principles of sedation and analgesia during pregnancy include use of the minimal effective dose, avoidance of unnecessary medications, and preferable use of Food and Drug Administration category B medications.

Alternatives à l'analgésie péridurale au cours du travail

Many systemic techniques, so-called "alternatives" to labor epidural analgesia, have been described: they are all poorly effective and some are associated with significant maternal and neonatal side effects. Nonetheless, these techniques can provide good maternal satisfaction. Accordingly, they are indicated when epidural analgesia is contraindicated or unavailable. Administration of systemic opioids mandates maternal respiratory supervision, oxygen supplementation and/or pulse oxymetry. Systemic opioids may also decrease fetal heart rate variability and produce neonatal respiratory depression; naloxone administration to the neonate is therefore widely indicated. Pethidine should be abandoned because it can produce prolonged neonatal respiratory depression. Nalbuphine produces less nausea/vomiting and less long lasting neonatal respiratory depression. Intravenous PCA fentanyl or sufentanil is presently the method of choice during early labor. Alfentanil seems less effective and may produce more neonatal side effects. Intravenous PCA remifentanil is the most effective technique, but safe administration may be problematic during intermittent supervision usually implemented in labour ward. Nitrous oxide 50% provides little pain relief. Nonetheless, it is associated with few side effects, quite good maternal satisfaction and can be quickly implemented during advanced painful labor. It is not recommended to add it to systemic opioid (except under continuous supervision by the anaesthetic team), because of an increased incidence of maternal desaturation. The use of a subanaesthetic concentration of sevoflurane has been described recently; it is more effective than nitrous oxide. However, guidelines for safe implementation in labor ward remain to be determined.

Patient-controlled analgesia with fentanyl provides effective analgesia for second trimester labour: a randomized controlled study

PURPOSE

To examine dose and lockout intervals for effective fentanyl patient-controlled analgesia (PCA) in second trimester genetic termination of pregnancy, and compare three different fentanyl PCA regimes with morphine PCA.

METHODS

In a double-blind randomized study, 60 ASA physical status I-II patients received one of three fentanyl PCAs or morphine PCA. Labour was induced with prostaglandins and PCA use continued until delivery. Within two hours following delivery, four visual analogue scales (VAS) were administered measuring anticipated pain, pain relief in labour and delivery, and overall satisfaction. The drug delivery/demand ratio for two hours preceding delivery was obtained from the PCA pump. The outcome variables were analyzed using the Chi square test and analysis of variance as appropriate.

RESULTS

The delivery/demand ratio was 0.71 +/- 0.27 (mean +/- standard deviation) for morphine; 0.67 +/- 0.21 for fentanyl 50 micro g, lockout six-minute; 0.63 +/- 0.21 for fentanyl 25 micro g, lockout three-minute; and 0.81 +/- 0.17 for fentanyl 50 micro g, lockout three-minute groups. We found no significant differences among the four groups with respect to using delivery/demand ratio as a measure of pain relief. Morphine had the highest rate of side effects compared to fentanyl. There was strong evidence of differences among groups with regard to patient satisfaction and expected pain, and moderate evidence of differences in the delivery and labour pain scores.

CONCLUSION

This study found PCA fentanyl 50 micro g with a lockout period of six minutes provided satisfactory analgesia for second trimester labour.

Effects of obstetric analgesics and anesthetics on the neonate : a review

Most anesthetic and analgesic agents in current use traverse the placental barrier in varying degrees, but are well tolerated by the fetus if judiciously administered. For labor analgesia, many options are available. Systemic administration of opioids and sedatives is one such option. Repeated maternal administration of opioids such as pethidine (meperidine) results in significant fetal exposure and neonatal respiratory depression. Patient-controlled analgesia with synthetic opioids such as fentanyl, alfentanil, and the new ultra-short-acting remifentanil may be used for labor analgesia in selected patients. Other options for labor analgesia include epidural and combined spinal-epidural techniques. With such techniques, neonatal exposure to opioids and sedatives can be minimized or totally avoided. While limiting the fetal exposure to the harmful effects of depressant drugs, epidural anesthesia and/or analgesia improves placental perfusion and oxygenation of the fetus, which is beneficial, especially in conditions such as pregnancy-induced hypertension. Regional blocks are also administered for the majority of cesarean deliveries because of the overwhelming and unequivocal evidence of maternal and fetal safety compared with general anesthesia for this indication. However, in some instances, administration of general anesthesia is unavoidable. Neonatal respiratory depression with low Apgar scores, and umbilical arterial and venous pH associated with general anesthesia, is often transient. A properly administered anesthetic, whether regional or general, has no significant adverse fetal or neonatal effects.

Parenteral opioids for labor analgesia

Labor pain relief is an important aspect of women's health that has historically been neglected. Epidural analgesia is the only consistently effective method of labor pain relief and has recently undergone substantial improvements to address the concerns of both parturients and obstetric care providers. With increased physician awareness, these recent advances are becoming more widely accepted and routinely available for all laboring parturients. Unfortunately, an increasing number of women are presenting to maternity wards with an absolute contraindication to epidural labor analgesia. The present review will provide an outline of the recent developments in parenteral analgesic options which complement modern epidural analgesic techniques. Protocols for the initiation of "state-of-the-art" parenteral analgesic techniques are provided as a guide to facilitate effective, modern, parenteral labor analgesia.

Newer techniques of labor analgesia

In maternity units in which central neuraxial techniques are frequently used, newer methods of epidural drug delivery (continuous infusion, patient-controlled) are well established and combined spinal-epidural analgesia is commonly used. Continuous spinal analgesia has reemerged as a useful approach after accidental dural puncture. Lumbar sympathetic block has been revisited and the safety of paracervical nerve block improved. The analgesic properties of systemic opioid in labor are poor, but PCIA at least has psychological benefits and allows rapid drug titration. PCIA is again under investigation because of the potent antinociceptive effects of the short-acting mu-opioid agonist, remifentanil. The premixing of nitrous oxide and a subanesthetic concentration of volatile anesthetic for patient-controlled administration has been tested under control of midwifery staff and without direct medical supervision.

The fetal safety and clinical efficacy of gastrointestinal endoscopy during pregnancy

More than 12,000 pregnant patients in the United States per annum have conditions that are normally evaluated by EGD. More than 6000 pregnant patients in the United States per annum have conditions that are normally evaluated by sigmoidoscopy or colonoscopy. About one thousand more have symptomatic choledocholithiasis during pregnancy, which is a strong indication for endoscopic sphincterotomy in nonpregnant patients. Endoscopy during pregnancy raises the unique issue of fetal safety. Endoscopic medications comprise a significant component of fetal endoscopic risks. Safety of EGD during pregnancy has been examined in a case-controlled study of 83 patients, a mailed survey of 73 patients, and 28 case reports. Safety of sigmoidoscopy during pregnancy has been examined in a case-controlled study of 46 patients, a mailed survey of 13 patients, and 10 case reports. Safety of therapeutic ERCP during pregnancy has been analyzed in studies of 23, 10, 6, and 5 patients, and in 32 case reports. These studies suggested that EGD, sigmoidoscopy, and ERCP should be performed when strongly indicated: EGD for significant upper gastrointestinal bleeding, sigmoidoscopy for nonhemorrhoidal rectal bleeding, and ERCP for symptomatic choledocholithiasis when sphincterotomy is contemplated. PEG and colonoscopy are currently considered experimental during pregnancy because of insufficient data on fetal safety. Several cases of PEG and colonoscopy were successfully performed during pregnancy. Performance of endoscopy during pregnancy should increase with further technical refinements, and greater awareness of procedure safety.

Anaesthesia and analgesia for the critically ill parturient

Anaesthetic and analgesic techniques in the critically ill are determined largely by the nature of the presenting illness. The commonest conditions likely to present as life-threatening emergencies are pre-eclampsia, obstetric haemorrhage, cardiac disease and severe sepsis. Issues dictating choice of anaesthetic technique are the patient's ability to maintain her airway, coagulation status, intravascular volume and haemodynamic dependence upon sympathetic drive, and requirements for ventilatory support and intensive care. Fetal well-being is an issue in the antepartum period, uteroplacental blood flow should be maintained and hypotension avoided. Maternal survival takes priority, however, and occasionally general anaesthetic techniques must be used which lead to neonatal respiratory depression and requirement for ventilatory support. Anaesthesia itself is associated with known hazards. The risks of each technique must be balanced against possible benefits in the context of the presenting illness.

Patient-controlled intravenous analgesia using remifentanil in the parturient

PURPOSE

To show the use of the short acting opioid remifentanil for labour analgesia when epidural analgesia is considered to be contraindicated.

CLINICAL FEATURES

After Ethics Committee approval and informed consent, six patients (36-40 wk gestation), in whom epidural analgesia was considered contraindicated (women refusing regional analgesia, presenting with coagulation or platelet abnormalities or sepsis) benefited from patient-controlled intravenous analgesia (PCIA) with remifentanil. The Abbott Lifecare patient-controlled analgesia (PCA) pump with remifentanil 50 microg x ml(-1) was set to deliver remifentanil continuous background infusion of 0.05 microg x kg(-1) x min(-1) and 25 microg boluses with a five minutes lockout period. The PCIA was started when the parturients experienced regular painful contractions (cervical dilatation of at least 4 cm) and stopped just before delivery (cervix fully dilated). Maternal monitoring included non-invasive blood pressure measurements, heart rate, percutaneous arterial oxyhemoglobin saturation and respiratory rate. Percutaneous fetal heart rate was continuously monitored. All patients remained alert or sleepy but easily arousable and were satisfied with their analgesia. No particular side effects have been noticed. Apgar scores were between 6 and 10.

CONCLUSION

Remifentanil PCIA combining low continuous background infusion and small bolus doses is an alternative when epidural analgesia in labour is contraindicated. Under careful anesthesia monitoring, the technique seems to be safe for both mother and baby, at least when delivery occurs at or near the normal term of pregnancy.