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Non-neuraxial analgesia during labour
OBSTETRIC ANAESTHESIA
Non-neuraxial analgesia during labour
Learning objectives After reading this article you should be aware: C of the non-neuraxial analgesics techniques that are employed to relieve pain in labour C that these techniques do not fully relieve the pain of labour and that some of the techniques are completely ineffective C that opioid analgesia can have a significant impact on the baby.
Geraldine O’Sullivan
Abstract Labour pain is one of the most severe pains known to man. Whilst neuraxial analgesia is the gold standard for achieving complete analgesia in labour, many women do not desire such high-tech pain relief. Many women want to be able to ‘cope with the pain of labour’ rather than annihilate the pain completely; for many of these women non-neuraxial techniques will suffice. This article evaluates many of the current non-neuraxial techniques that are employed in labour wards throughout the UK.
Hydrotherapy ‘All maternity units should provide women with the option to labour and deliver in water’. Labour party election manifesto e 2005, UK. There has been one major systematic review on the effects of immersion in water during labour.3 The systematic review included eight trials.
Keywords Analgesia; labour; non-neuraxial
Maternal outcome Meta-analysis of the trials showed that the use of water in the first stage of labour reduced the use of regional analgesia. There was no difference in the duration of the first and second stages of labour or the caesarean section rate.
Introduction Although neuraxial analgesia remains the gold standard for achieving analgesia in labour, many women prefer to employ less invasive techniques to relieve pain during labour. Factors influencing women’s decisions range from the influence of natural childbirth training, anxiety about the adverse effects of neuraxial analgesia to a genuine desire to have a medication-free delivery. In addition neuraxial techniques may be contra-indicated in specific medical conditions. It must be appreciated, and this fact needs to emphasized to women, that most non-neuraxial methods of analgesia will never provide complete pain relief during labour, but represent at best techniques that allow a woman ‘to cope’ with her labour pain. Alternatively the complete removal of pain does not necessarily mean a more satisfying birth experience for a woman.1
Neonatal outcomes Five trials reported on 5-minute Apgar scores and there were no differences in the number of infants with a score of less than seven at 5 minutes. Two trials reported on admission to the neonatal unit and found no difference. Immersion in water appears to reduce labour pain and therefore low-risk mothers should be advised to consider the use of hydrotherapy during labour. Hospitals and birthing centres should provide facilities for women to spend part or even all of their labour in a suitable bath/pool. Guidance should be provided on factors such as the temperature of the water, the use of concomitant analgesia and fetal monitoring. Complementary and alternative therapies4,5
Simple analgesic techniques
Acupuncture Chinese philosophy believes that our health is dependent on the body’s motivating energy, known as Qi, moving in a smooth and balanced way through a series of meridians beneath the skin. Qi consists of equal and opposite forces, Yin and Yang, and when these become unbalanced, illness can result. The flow of Qi can be disturbed by factors such as anxiety, stress and fear. The aim of acupuncture is to treat the whole person by regaining the equilibrium between the physical, emotional and spiritual aspects of the individual. Acupuncture is not in widespread use in China as a means of relieving pain in childbirth, and perhaps significantly no acupuncture points are described, in traditional Chinese literature, for pain relief in labour! Several randomized controlled trials (RCTs) have tried to evaluate the use of acupuncture as an analgesic in labour. These RCTs suggested that acupuncture improved pain scores and reduced the use of both parenteral opioid and epidural analgesia. However some of these RCTs had serious flaws, for example in
Support during labour A Cochrane review has specifically addressed the effect of continuous support for women during childbirth.2 Fifteen trials involving 12,791 women in 11 countries were evaluated in the review. The conclusion of the review was that women who had continuous one-to-one support during labour were: more likely to have a spontaneous vaginal birth less likely to require analgesia less likely to report dissatisfaction with their childbirth experience.
Geraldine O’Sullivan MD FRCA is a Consultant Anaesthetist at Guy’s and St Thomas’ NHS Foundation Trust, London, where she is lead clinician for obstetric anaesthesia. She is a past president of the Obstetric Anaesthetist’s Association (OAA). Her particular research interests include analgesia in labour and high-risk obstetrics. Conflicts of interest: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 11:7
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Ó 2010 Elsevier Ltd. All rights reserved.
OBSTETRIC ANAESTHESIA
1997.7 Articles included in this review were required to be full journal publications, to have documented pain outcomes, and to have included at least 10 patients in each treatment group. The review included 10 RCTs, among which three RCTs compared TENS with no TENS, seven RCTs compared TENS with sham TENS and one of the RCTs did both. The 10 studies involved 877 women; 436 women received active TENS and 441 women acted as controls (sham TENS or no treatment). No study recorded any difference in pain intensity or pain relief scores between TENS and controls. The need for additional analgesic interventions was reported in eight RCTs, and no evidence of difference was found. There were no reports of adverse events in the 10 RCTs. There is no evidence that TENS has any beneficial effect on labour pain.
some of the studies, the midwife performing the acupuncture was also clinically responsible for the patient and the patient only received other analgesics if ‘thought appropriate by the midwife’. Current evidence suggests that, in most women, acupuncture does not provide adequate analgesia throughout labour. However before a definite conclusion can be made further RCTs, which should include sham acupuncture, should be undertaken. Hypnosis Hypnosis has been practised during labour for over a century whilst a current unproven variant, hypnobirthing, is fashionable in some birth centres. Hypnosis is the induction of a deeply relaxed state, with increased susceptibility and suspension of critical faculties. Once in this state, sometimes called a hypnotic trance, patients are given therapeutic suggestions to encourage changes in behaviour or relief of symptoms. A very comprehensive systematic review of hypnosis for pain relief in labour, involving five RCTs and 14 non-randomized comparisons (NRCs), evaluating 8395 women was published in 2004.6 The meta-analysis showed that hypnosis significantly reduced the use of pharmacological pain relief in three trials (RR 0.51 [95% CI 0.28e0.98]) and the need for labour augmentation in two trials (RR 0.31 [95% CI 0.18e0.52]). However the authors of the meta-analysis acknowledge that the small numbers of patients, the lack of power analysis, and the statistically significant trial heterogeneity may have contributed to bias in the results of the meta-analysis. The widespread introduction of hypnosis as a means of reducing pain relief in labour cannot be recommended until further studies have been performed.
Pharmacological analgesia in labour Inhalational analgesia Inhalational analgesia is provided by inhalation of sub-anaesthetic concentrations of volatile agents, the aim being that the mother should remain conscious with preservation of her laryngeal reflexes. The technique first achieved fame and later gained widespread acceptance when John Snow administered chloroform to Queen Victoria for the births of her eighth and ninth children in 1853 and 1857. A variety of agents have been employed over the years including trichloroethylene (Trilene), methoxyflurane, isoflurane, but all have been abandoned. Sevoflurane has recently been evaluated as an analgesic in labour. However the only agent that has really survived the test of time is nitrous oxide, which is most commonly administered as Entonox (a 50:50 oxygen:nitrous oxide mixture). Administration is usually via a demand valve connected to a facemask or mouthpiece. Its popularity is probably related to its ease of administration, lack of smell, minimal effect on maternal consciousness and lack of effect on the progress of labour. A systematic review on the efficacy of N2O was published in 2002.8 Eleven RCTs were used to evaluate analgesic efficacy whilst adverse effects were determined from eight RCTs and eight observational studies. Seven studies described significant analgesia with N2O and interestingly in two studies women continued to use N2O even after the study period was over. Nausea and vomiting were reported as ranging from 5% to 36%. Neonatal Apgar scores were reported in four studies and no differences were shown. Therefore there is a moderate level of evidence to support the use of N2O in labour, in that N2O is effective for some women with no apparent adverse outcomes for either mother or baby. Training and practice in the use of nitrous oxide are essential if the maximum efficacy of this agent is to be achieved. Unfortunately the pollutant and greenhouse gas effect of nitrous oxide may result in its withdrawal within the next decade.
Non-pharmacological analgesic techniques Transcutaneous electrical nerve stimulation (TENS) TENS is a technique whereby low voltage electrical impulses are administered through electrodes that, for the relief of labour pain, are usually sited in the lower lumbar area (Figure 1). A systematic review on the efficacy of TENS was conducted in
Transcutaneous electrical nerve stimulation (TENS) in labour
Systemic opioid analgesia Worldwide systemic opioids are the main analgesics used during in labour. This is because opioids are readily available, cheap and easy to administer. Even in the USA, where epidural analgesia is universally available, opioids are still the main form of analgesia in labour.
Figure 1
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Ó 2010 Elsevier Ltd. All rights reserved.
OBSTETRIC ANAESTHESIA
Pethidine Since its introduction, without any trials, into obstetrics during the 1940s pethidine has been the chief opioid employed during labour. Its perceived analgesic efficacy probably owes as much to its sedative as to its analgesic effects. It was initially believed that pethidine caused little respiratory depression and that the effect on the fetus was minimal. Later studies demonstrated that the effect of pethidine and other opioids on the fetus was significant. A double-blind RCT, conducted in Hong Kong, compared intramuscular (IM) pethidine with an IM placebo (Figure 2). Ethical considerations demanded that the initial study period (after which rescue analgesia would be available) would be limited to 30 minutes to minimize the period during which patients would be exposed to a placebo. A reduction in pain scores was observed in the women who received pethidine (N ¼ 25), compared to those who had received placebo (N ¼ 25). Eight women in the group who received pethidine required no further analgesia compared with one in the control group ( p ¼ 0.01). Thirty minutes after drug administration the women were also asked to rate on a 5-point scale how satisfied they were with their analgesia (1 ¼ totally dissatisfied, 5 ¼ totally satisfied). Scores were higher for women in the pethidine group, although neither had very high scores (the median was two in the pethidine group and one in the placebo group). Therefore the poor efficacy of long acting systemic opioids during labour combined with their effects on the neonate suggests that women should not be encouraged to use these agents during labour.
Mean VAS pain scores as a function of time for pethidine (meperidine), remifentanil and fentanyl 10
VAS scores
8
Meperidine Fentanyl Remifentanil
0 0
1
2
3
4
5
6
Time (h) Vertical bars represent SD9; VAS, visual analogue scale
Figure 3
has been investigated in babies under 2 months and the half-life is similar to that found in adults. Patient-controlled remifentanil, fentanyl and pethidine in labour The analgesic efficacy of patient-controlled (PCA) pethidine, fentanyl and remifentanil was compared in a recent RCT.9 The women received either IV PCA remifentanil, 40 mg loading dose, a 40 mg bolus with a 2 min lockout and a maximum dose limit of 1200 mg/h (n ¼ 52), the pethidine group received a 49.5 mg loading dose, a 5 mg bolus with a 10 min lockout with a 10 min lockout and a maximum overall dose of 200 mg (n ¼ 53), whilst the fentanyl group received a 50 mg loading dose, a 20 mg bolus with a 5 min lockout and a maximum dose limit of 240 mg/h (n ¼ 54). Pain scores were assessed using a visual analogue scale (VAS) (0e10 cm), and sedation was assessed hourly using a 5-point scale, fetal outcome was also evaluated. The efficacy of pethidine, fentanyl and remifentanil PCA for labour analgesia varied from mild to moderate. Remifentanil provided better analgesia than meperidine and fentanyl PCA but only during the first hour of labour. In all groups, pain scores returned to pre-treatment values within 3 hours (Figure 3). Satisfaction scores were higher for remifentanil but it produced more sedation and pruritus. No significant differences were noted in the fetal heart rate Apgar scores or cord blood pH. Many of the studies assessing remifentanil in labour indicate that it can and does cause significant respiratory depression and thus currently its use mandates one-to-one nursing and monitoring with maternal pulse oximetry and fetal cardiotocography.
Visual analogue pain score (y axis) following pethidine and saline during labour Control
Visual analogue pain score
4 2
Remifentanil Neuraxial analgesia is contra-indicated in some women and not desired by others and thus remifentanil, a short acting m-opioid agonist, could be the opioid of choice for such women. It has a rapid onset of action and undergoes hydrolysis by non-specific tissue and blood esterases to almost completely inactive metabolites, which are eliminated in the urine. The context specific half-life is only 3 minutes. The pharmacokinetics of remifentanil
Pethidine
80
6
70 60 50 40 30 20 10
A
0 Baseline
15 min
30 min REFERENCES 1 Hodnett ED. Pain and women’s satisfaction with the experience of childbirth: a systematic review. Am J Obstet Gynecol 2002; 186: S160e72.
Br J Obstet Gynaecol 2004;111:648
Figure 2
ANAESTHESIA AND INTENSIVE CARE MEDICINE 11:7
272
Ó 2010 Elsevier Ltd. All rights reserved.
OBSTETRIC ANAESTHESIA
2 Hodnett ED, Gates S, Hofmeyr GJ, Sakala C. Continuous support for women during childbirth. Cochrane Database Syst Rev; 2003: CD003766. 3 Cluett ER, Nikodem VC, McCandlish RE, Burns EE. Immersion in water in pregnancy, labour and birth. The Cochrane Libr; 2004: CD000111. 4 Huntley AL, Coon JT, Ernst E. Complementary and alternative medicine for labor pain: a systematic review. Am J Obstet Gynecol 2004; 191: 36e44. 5 Smith CA, Collins CT, Cyna AM, Crowther CA. Complementary and alternative therapies for pain management in labour. Cochrane Database Syst Rev; 2005.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 11:7
6 Cyna AM, McAuliffe GL, Andrew MI. Hypnosis for pain relief in labour and childbirth: a systematic review. Br J Anaesth 2004; 93: 505e11. 7 Carroll D, Moore RA, Tramer MR, McQuay HJ. Transcutaneous electrical nerve stimulation does not relieve labor pain: updated systematic review. Contemp Rev Obstet Gynaecol 1997; 9: 205. 8 Rosen MA. Nitrous oxide for relief of labor pain: a systematic review. Am J Obstet Gynecol 2002; 186: S110e26. 9 Douma MR, Verwey RA, Kam-Endtz CE, et al. Obstetric analgesia; a comparison of patient-controlled meperidine, remifentanil and fentanyl in labour. Br J Anaesth 2010; 104: 209e15.
273
Ó 2010 Elsevier Ltd. All rights reserved.
Non-neuraxial analgesia during labour
Learning objectives After reading this article you should be aware: C of the non-neuraxial analgesics techniques that are employed to relieve pain in labour C that these techniques do not fully relieve the pain of labour and that some of the techniques are completely ineffective C that opioid analgesia can have a significant impact on the baby.
Geraldine O’Sullivan
Abstract Labour pain is one of the most severe pains known to man. Whilst neuraxial analgesia is the gold standard for achieving complete analgesia in labour, many women do not desire such high-tech pain relief. Many women want to be able to ‘cope with the pain of labour’ rather than annihilate the pain completely; for many of these women non-neuraxial techniques will suffice. This article evaluates many of the current non-neuraxial techniques that are employed in labour wards throughout the UK.
Hydrotherapy ‘All maternity units should provide women with the option to labour and deliver in water’. Labour party election manifesto e 2005, UK. There has been one major systematic review on the effects of immersion in water during labour.3 The systematic review included eight trials.
Keywords Analgesia; labour; non-neuraxial
Maternal outcome Meta-analysis of the trials showed that the use of water in the first stage of labour reduced the use of regional analgesia. There was no difference in the duration of the first and second stages of labour or the caesarean section rate.
Introduction Although neuraxial analgesia remains the gold standard for achieving analgesia in labour, many women prefer to employ less invasive techniques to relieve pain during labour. Factors influencing women’s decisions range from the influence of natural childbirth training, anxiety about the adverse effects of neuraxial analgesia to a genuine desire to have a medication-free delivery. In addition neuraxial techniques may be contra-indicated in specific medical conditions. It must be appreciated, and this fact needs to emphasized to women, that most non-neuraxial methods of analgesia will never provide complete pain relief during labour, but represent at best techniques that allow a woman ‘to cope’ with her labour pain. Alternatively the complete removal of pain does not necessarily mean a more satisfying birth experience for a woman.1
Neonatal outcomes Five trials reported on 5-minute Apgar scores and there were no differences in the number of infants with a score of less than seven at 5 minutes. Two trials reported on admission to the neonatal unit and found no difference. Immersion in water appears to reduce labour pain and therefore low-risk mothers should be advised to consider the use of hydrotherapy during labour. Hospitals and birthing centres should provide facilities for women to spend part or even all of their labour in a suitable bath/pool. Guidance should be provided on factors such as the temperature of the water, the use of concomitant analgesia and fetal monitoring. Complementary and alternative therapies4,5
Simple analgesic techniques
Acupuncture Chinese philosophy believes that our health is dependent on the body’s motivating energy, known as Qi, moving in a smooth and balanced way through a series of meridians beneath the skin. Qi consists of equal and opposite forces, Yin and Yang, and when these become unbalanced, illness can result. The flow of Qi can be disturbed by factors such as anxiety, stress and fear. The aim of acupuncture is to treat the whole person by regaining the equilibrium between the physical, emotional and spiritual aspects of the individual. Acupuncture is not in widespread use in China as a means of relieving pain in childbirth, and perhaps significantly no acupuncture points are described, in traditional Chinese literature, for pain relief in labour! Several randomized controlled trials (RCTs) have tried to evaluate the use of acupuncture as an analgesic in labour. These RCTs suggested that acupuncture improved pain scores and reduced the use of both parenteral opioid and epidural analgesia. However some of these RCTs had serious flaws, for example in
Support during labour A Cochrane review has specifically addressed the effect of continuous support for women during childbirth.2 Fifteen trials involving 12,791 women in 11 countries were evaluated in the review. The conclusion of the review was that women who had continuous one-to-one support during labour were: more likely to have a spontaneous vaginal birth less likely to require analgesia less likely to report dissatisfaction with their childbirth experience.
Geraldine O’Sullivan MD FRCA is a Consultant Anaesthetist at Guy’s and St Thomas’ NHS Foundation Trust, London, where she is lead clinician for obstetric anaesthesia. She is a past president of the Obstetric Anaesthetist’s Association (OAA). Her particular research interests include analgesia in labour and high-risk obstetrics. Conflicts of interest: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 11:7
270
Ó 2010 Elsevier Ltd. All rights reserved.
OBSTETRIC ANAESTHESIA
1997.7 Articles included in this review were required to be full journal publications, to have documented pain outcomes, and to have included at least 10 patients in each treatment group. The review included 10 RCTs, among which three RCTs compared TENS with no TENS, seven RCTs compared TENS with sham TENS and one of the RCTs did both. The 10 studies involved 877 women; 436 women received active TENS and 441 women acted as controls (sham TENS or no treatment). No study recorded any difference in pain intensity or pain relief scores between TENS and controls. The need for additional analgesic interventions was reported in eight RCTs, and no evidence of difference was found. There were no reports of adverse events in the 10 RCTs. There is no evidence that TENS has any beneficial effect on labour pain.
some of the studies, the midwife performing the acupuncture was also clinically responsible for the patient and the patient only received other analgesics if ‘thought appropriate by the midwife’. Current evidence suggests that, in most women, acupuncture does not provide adequate analgesia throughout labour. However before a definite conclusion can be made further RCTs, which should include sham acupuncture, should be undertaken. Hypnosis Hypnosis has been practised during labour for over a century whilst a current unproven variant, hypnobirthing, is fashionable in some birth centres. Hypnosis is the induction of a deeply relaxed state, with increased susceptibility and suspension of critical faculties. Once in this state, sometimes called a hypnotic trance, patients are given therapeutic suggestions to encourage changes in behaviour or relief of symptoms. A very comprehensive systematic review of hypnosis for pain relief in labour, involving five RCTs and 14 non-randomized comparisons (NRCs), evaluating 8395 women was published in 2004.6 The meta-analysis showed that hypnosis significantly reduced the use of pharmacological pain relief in three trials (RR 0.51 [95% CI 0.28e0.98]) and the need for labour augmentation in two trials (RR 0.31 [95% CI 0.18e0.52]). However the authors of the meta-analysis acknowledge that the small numbers of patients, the lack of power analysis, and the statistically significant trial heterogeneity may have contributed to bias in the results of the meta-analysis. The widespread introduction of hypnosis as a means of reducing pain relief in labour cannot be recommended until further studies have been performed.
Pharmacological analgesia in labour Inhalational analgesia Inhalational analgesia is provided by inhalation of sub-anaesthetic concentrations of volatile agents, the aim being that the mother should remain conscious with preservation of her laryngeal reflexes. The technique first achieved fame and later gained widespread acceptance when John Snow administered chloroform to Queen Victoria for the births of her eighth and ninth children in 1853 and 1857. A variety of agents have been employed over the years including trichloroethylene (Trilene), methoxyflurane, isoflurane, but all have been abandoned. Sevoflurane has recently been evaluated as an analgesic in labour. However the only agent that has really survived the test of time is nitrous oxide, which is most commonly administered as Entonox (a 50:50 oxygen:nitrous oxide mixture). Administration is usually via a demand valve connected to a facemask or mouthpiece. Its popularity is probably related to its ease of administration, lack of smell, minimal effect on maternal consciousness and lack of effect on the progress of labour. A systematic review on the efficacy of N2O was published in 2002.8 Eleven RCTs were used to evaluate analgesic efficacy whilst adverse effects were determined from eight RCTs and eight observational studies. Seven studies described significant analgesia with N2O and interestingly in two studies women continued to use N2O even after the study period was over. Nausea and vomiting were reported as ranging from 5% to 36%. Neonatal Apgar scores were reported in four studies and no differences were shown. Therefore there is a moderate level of evidence to support the use of N2O in labour, in that N2O is effective for some women with no apparent adverse outcomes for either mother or baby. Training and practice in the use of nitrous oxide are essential if the maximum efficacy of this agent is to be achieved. Unfortunately the pollutant and greenhouse gas effect of nitrous oxide may result in its withdrawal within the next decade.
Non-pharmacological analgesic techniques Transcutaneous electrical nerve stimulation (TENS) TENS is a technique whereby low voltage electrical impulses are administered through electrodes that, for the relief of labour pain, are usually sited in the lower lumbar area (Figure 1). A systematic review on the efficacy of TENS was conducted in
Transcutaneous electrical nerve stimulation (TENS) in labour
Systemic opioid analgesia Worldwide systemic opioids are the main analgesics used during in labour. This is because opioids are readily available, cheap and easy to administer. Even in the USA, where epidural analgesia is universally available, opioids are still the main form of analgesia in labour.
Figure 1
ANAESTHESIA AND INTENSIVE CARE MEDICINE 11:7
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Ó 2010 Elsevier Ltd. All rights reserved.
OBSTETRIC ANAESTHESIA
Pethidine Since its introduction, without any trials, into obstetrics during the 1940s pethidine has been the chief opioid employed during labour. Its perceived analgesic efficacy probably owes as much to its sedative as to its analgesic effects. It was initially believed that pethidine caused little respiratory depression and that the effect on the fetus was minimal. Later studies demonstrated that the effect of pethidine and other opioids on the fetus was significant. A double-blind RCT, conducted in Hong Kong, compared intramuscular (IM) pethidine with an IM placebo (Figure 2). Ethical considerations demanded that the initial study period (after which rescue analgesia would be available) would be limited to 30 minutes to minimize the period during which patients would be exposed to a placebo. A reduction in pain scores was observed in the women who received pethidine (N ¼ 25), compared to those who had received placebo (N ¼ 25). Eight women in the group who received pethidine required no further analgesia compared with one in the control group ( p ¼ 0.01). Thirty minutes after drug administration the women were also asked to rate on a 5-point scale how satisfied they were with their analgesia (1 ¼ totally dissatisfied, 5 ¼ totally satisfied). Scores were higher for women in the pethidine group, although neither had very high scores (the median was two in the pethidine group and one in the placebo group). Therefore the poor efficacy of long acting systemic opioids during labour combined with their effects on the neonate suggests that women should not be encouraged to use these agents during labour.
Mean VAS pain scores as a function of time for pethidine (meperidine), remifentanil and fentanyl 10
VAS scores
8
Meperidine Fentanyl Remifentanil
0 0
1
2
3
4
5
6
Time (h) Vertical bars represent SD9; VAS, visual analogue scale
Figure 3
has been investigated in babies under 2 months and the half-life is similar to that found in adults. Patient-controlled remifentanil, fentanyl and pethidine in labour The analgesic efficacy of patient-controlled (PCA) pethidine, fentanyl and remifentanil was compared in a recent RCT.9 The women received either IV PCA remifentanil, 40 mg loading dose, a 40 mg bolus with a 2 min lockout and a maximum dose limit of 1200 mg/h (n ¼ 52), the pethidine group received a 49.5 mg loading dose, a 5 mg bolus with a 10 min lockout with a 10 min lockout and a maximum overall dose of 200 mg (n ¼ 53), whilst the fentanyl group received a 50 mg loading dose, a 20 mg bolus with a 5 min lockout and a maximum dose limit of 240 mg/h (n ¼ 54). Pain scores were assessed using a visual analogue scale (VAS) (0e10 cm), and sedation was assessed hourly using a 5-point scale, fetal outcome was also evaluated. The efficacy of pethidine, fentanyl and remifentanil PCA for labour analgesia varied from mild to moderate. Remifentanil provided better analgesia than meperidine and fentanyl PCA but only during the first hour of labour. In all groups, pain scores returned to pre-treatment values within 3 hours (Figure 3). Satisfaction scores were higher for remifentanil but it produced more sedation and pruritus. No significant differences were noted in the fetal heart rate Apgar scores or cord blood pH. Many of the studies assessing remifentanil in labour indicate that it can and does cause significant respiratory depression and thus currently its use mandates one-to-one nursing and monitoring with maternal pulse oximetry and fetal cardiotocography.
Visual analogue pain score (y axis) following pethidine and saline during labour Control
Visual analogue pain score
4 2
Remifentanil Neuraxial analgesia is contra-indicated in some women and not desired by others and thus remifentanil, a short acting m-opioid agonist, could be the opioid of choice for such women. It has a rapid onset of action and undergoes hydrolysis by non-specific tissue and blood esterases to almost completely inactive metabolites, which are eliminated in the urine. The context specific half-life is only 3 minutes. The pharmacokinetics of remifentanil
Pethidine
80
6
70 60 50 40 30 20 10
A
0 Baseline
15 min
30 min REFERENCES 1 Hodnett ED. Pain and women’s satisfaction with the experience of childbirth: a systematic review. Am J Obstet Gynecol 2002; 186: S160e72.
Br J Obstet Gynaecol 2004;111:648
Figure 2
ANAESTHESIA AND INTENSIVE CARE MEDICINE 11:7
272
Ó 2010 Elsevier Ltd. All rights reserved.
OBSTETRIC ANAESTHESIA
2 Hodnett ED, Gates S, Hofmeyr GJ, Sakala C. Continuous support for women during childbirth. Cochrane Database Syst Rev; 2003: CD003766. 3 Cluett ER, Nikodem VC, McCandlish RE, Burns EE. Immersion in water in pregnancy, labour and birth. The Cochrane Libr; 2004: CD000111. 4 Huntley AL, Coon JT, Ernst E. Complementary and alternative medicine for labor pain: a systematic review. Am J Obstet Gynecol 2004; 191: 36e44. 5 Smith CA, Collins CT, Cyna AM, Crowther CA. Complementary and alternative therapies for pain management in labour. Cochrane Database Syst Rev; 2005.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 11:7
6 Cyna AM, McAuliffe GL, Andrew MI. Hypnosis for pain relief in labour and childbirth: a systematic review. Br J Anaesth 2004; 93: 505e11. 7 Carroll D, Moore RA, Tramer MR, McQuay HJ. Transcutaneous electrical nerve stimulation does not relieve labor pain: updated systematic review. Contemp Rev Obstet Gynaecol 1997; 9: 205. 8 Rosen MA. Nitrous oxide for relief of labor pain: a systematic review. Am J Obstet Gynecol 2002; 186: S110e26. 9 Douma MR, Verwey RA, Kam-Endtz CE, et al. Obstetric analgesia; a comparison of patient-controlled meperidine, remifentanil and fentanyl in labour. Br J Anaesth 2010; 104: 209e15.
273
Ó 2010 Elsevier Ltd. All rights reserved.