1 Department of Anaesthesia, University of Stellenbosch and Tygerberg Academic Hospital Private Bag 3, Tygervallei 7505, Western Cape, South Africa. 2 Department of Anaesthesia, University of Toronto and Sunnybrook and Womens Health Sciences Centre, Womens College Campus, 76 Grenville Street, Toronto, Ontario, M5S 1B2 Canada *Corresponding author
Accepted for publication: April 11, 2002
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Abstract |
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Methods. All randomized controlled trials that compared PCEA, without background infusion, with CEI were sought from the literature. These were rated for quality using a validated, five-point scale. The primary outcome was the number of patients who received anaesthetic interventions. Secondary outcomes included the dose of local anaesthetic, incidence of motor block, quality of analgesia, obstetric and safety outcomes. Where feasible, the data were combined using meta-analytical techniques. For dichotomous data, the risk difference (RD) and 95% confidence intervals (CI) were calculated. For continuous data, the weighted mean differences (WMD) were calculated. The differences were statistically significant when the 95% CI excluded 0.
Results. Nine studies comprised of 640 patients were found. There were fewer anaesthetic interventions in the PCEA group (RD, 27%; 95% CI, 1836%; P<0.00001). This group also received less local anaesthetic (WMD, 3.92; 95% CI, 5.38 to 2.42; P<00001) and less motor block (RD, 18%; 95% CI, 631%; P=0.003). Both methods were safe for mother and newborn.
Conclusion. Patients who receive PCEA are less likely to require anaesthetic interventions, require lower doses of local anaesthetic and have less motor block than those who receive CEI. Future research should be directed at determining differences in maternal satisfaction and obstetric outcome.
Br J Anaesth 2002; 89: 45965
Keywords: analgesia, obstetric; analgesia, patient-controlled; analgesic techniques, epidural; safety, techniques
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Introduction |
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Continuous epidural infusion (CEI) of local anaesthetics was introduced into common clinical practice in the 1980s. While the technique has circumvented a number of difficulties,2 it is not ideal. Many patients still required clinician-initiated top-ups and experienced unacceptably dense motor block in the lower extremities. Although many combinations of infusion rates and various concentrations of local anaesthetics and additives have been investigated, these problems persist.
Patient-controlled epidural analgesia (PCEA) for relief of labour pain was first described by Gambling in 1988.3 This technique allowed the patient to control the dose of epidural medication as labour and pain patterns changed. It also allowed for individualization of drug dosage by the patient, allowing her to trade off therapeutic effects (e.g. complete pain relief) and side-effects (e.g. motor block). However, the equipment needed for PCEA may be more expensive than CEI. Also, more time is required to educate both the patient and staff about the appropriate use of the medication and equipment.
Many studies have been performed comparing PCEA with CEI. The purpose of this systematic review is to compare the efficacy and safety of PCEA with that of CEI for maintenance of labour analgesia.
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Methods |
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We used the following search terms as key words and text words: Patient-controlled, labour analgesia, anaesthesia (excluding anaesthesia for Caesarean section) and pregnancy. Alternative spellings of the search terms were also used. No language restriction was applied. The last search was done on the September 20, 2001. Additional reports were identified from reference lists of retrieved reports and review articles.
We included published RCTs in healthy parturients that used the same local anaesthetic and additives for both the study and control group. Furthermore, we only included RCTs that had no continuous background infusion in the PCEA group. We excluded abstracts of scientific meetings, unpublished observations and correspondence.
Each report meeting the inclusion criteria, was read independently by each of the authors and assigned a quality score according to a previously published, validated scale.4 This scale consists of three items and has a maximum possible score of five. When the report was described as randomized, one point was given. If the randomization process was appropriate an extra point was given. The original point for randomization was lost if randomization was inappropriate (e.g. if it was based on date of birth). One point was given when a study was described as blinded. If blinding was inappropriate this point was lost, but an extra point was gained if blinding was appropriate. If all patients randomized were fully accounted for another point was given. The final quality score for each article was reached by the authors by means of consensus.
The primary outcome of the study was the number of patients who received anaesthetic interventions during the maintenance of labour analgesia. Secondary outcomes included the dose of local anaesthetic, the incidence of motor block, the quality of analgesia and maternal satisfaction. Obstetric and neonatal outcomes included the length of labour, rate of Caesarean section, the rate of instrumental deliveries and the incidence of low Apgar scores at 1 and 5 min. Other outcomes included the incidence of hypotension, high block, nausea, pruritus and shivering.
Data were recorded independently by two of the authors (M.V. and G.J.) and discrepancies resolved by reinspection of the original articles. The data were entered into the statistical program (S.H.H) and rechecked (M.V.).
Where feasible, meta-analytical techniques, using a random effects model were used (Metaview software, Revman 4.1, Cochrane Library, Oxford, UK). For dichotomous data, the risk difference (RD) and 95% confidence intervals (95% CI) were calculated. For continuous data, the weighted mean difference and 95% CI were calculated. We considered the results statistically significant if the 95% CI excluded 0. The 2 test was used to calculate heterogeneity and a P-value of <0.05 was regarded as significant. Where meta-analysis was not appropriate, the results of the individual studies were reported. We also performed a sensitivity analysis on the primary outcome on the basis of the quality score (02 vs 3 or more).
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Results |
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Table 1 details the quality score, the obstetric population studied, the number of patients involved in each group and drugs used for maintenance in PCEA and CEI groups. None of the studies reported the incidence of induced and spontaneous labour. All measured outcomes, as well as those that were significantly different, are shown.
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In addition to reporting the number of patients who required no interventions, three studies reported the total number of clinician top-ups in the CEI group compared with PCEA. Tan and colleagues8 found a significantly higher number in the CEI group than in the PCEA group (120 top-ups in 84 women compared with 49 in 75 women, respectively). Curry and colleagues11 reported 27 top-ups in 30 patients who received CEI compared with only two top-ups in 30 patients who received PCEA (P<0.001). Sia and colleagues15 reported six top-ups in 20 patients in the CEI group compared with three top-ups in 20 patients in the PCEA group during the first stage of labour (P=0.4).
Drug dose
The dose (mg h1) of local anaesthetic administered to patients receiving CEI was significantly greater than those in the PCEA group (Table 2). All studies that measured this outcome reported the same result regardless of whether bupivacaine or ropivacaine was used. The addition of opioid to the maintenance solution (either fentanyl or sufentanil) did not make a difference to this outcome. Because different regimen were used, this outcome is heterogeneous (P<0.0001) even though all studies favoured the PCEA group (Fig. 2).
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Tan and colleagues8 reported that patients receiving PCEA were more likely to have no motor weakness compared with those having CEI, based on repeated assessments of each patient (P<0.01). The incidence of complete immobility of the lower extremities was not different between groups (4.5 vs 2.9%; ns). Two other studies found no difference between groups in dense motor block as defined by Bromage scores of 2 or 3.12 13
Analgesia
Labour analgesia was measured at intervals using a visual or verbal analogue score (VAS) in seven studies,915 and the number of distressing pain episodes in one.7 These results were either displayed in graphic form or described qualitatively. The VAS scores were not different between groups in any of the studies. The numbers of distressing pain episodes were also similar. Finally, pain scores, when classified as mild, moderate or severe, were the same in both groups.10
One study specifically reported VAS scores for pain in the second stage of labour and found no difference between groups.10 A second study reported that complete or good analgesia was also not significantly different between groups.7 However, in this study 16.9% of women suffered unacceptable pain in the PCEA group compared with 2.8% in the CEI group (P=0.01).
Patient satisfaction
Overall patient satisfaction with the method of analgesia, using a VAS score, was reported in five studies.911 14 15 The data from four of these could be combined (Table 2). One study reported maternal satisfaction using a VAS scale at various times during labour and reported the data in graphical form, but did not report an overall score.14 One study reported patient satisfaction with analgesia.7 These studies did not show a difference in maternal satisfaction between groups.
Obstetric and neonatal outcomes
The total length of labour (in minutes) was reported in three studies911 and there was no difference between the groups. Similarly there was no difference in the duration of first stage of labour12 13 or second one.7 12 13 15 None of the studies reported a difference in the incidence of Caesarean section or instrumental delivery between groups. The incidence of low Apgar scores at 1 and 5 min after birth was low and similar in each group (Table 2).
Other outcomes
There was no difference between groups in the incidence of hypotension or high block (as described by any of the authors). The incidence of pruritus, shivering and nausea were similar in each group (Table 2).
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Discussion |
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The need for unscheduled clinician interventions is an important outcome for a number of reasons, apart from simple convenience. Additional drug doses require opening the closed system and may increase the risk of infection. Furthermore, it is usual for the clinician to use an increased drug dose compared with that available to the patient. If this dose is misplaced (either in the intravascular or intrathecal space), toxicity might result. Finally, because of the increased drug dose, motor block of the lower extremities may be more evident.
The use of less local anaesthetic is also an important advantage of PCEA. While this review did not show a difference in operative delivery between patients who received PCEA and those who received CEI, there is some evidence that drug dose may affect labour outcome. Recently, the COMET group17 in the United Kingdom have shown that there is an increased incidence of operative vaginal delivery when conventional doses of local anaesthetic (0.25% bupivacaine) are used in labour compared with low dose techniques. Furthermore, cumulative doses of opioids, which are often combined with local anaesthetics in the infusions, may result in mild neonatal depression.17 While none of the studies we have reviewed reported results from high doses of local anaesthetics, it may still be an advantage to use less of the drugs.
The differences in patient mobility were also consistent between groups when this outcome was measured. This consistency was present despite the numerous ways in which motor weakness of the lower extremities was reported and was likely to have been a result of the observed increase in local anaesthetic dosage in the CEI group. Of note, in one study that used 0.1% ropivacaine and fentanyl 2 µg ml1, all patients could walk. It is possible that by reducing the concentration of local anaesthetic sufficiently, the difference in motor block between PCEA and CEI may become insignificant.
Of interest, although many of the studies reported measures of maternal satisfaction, there was no consistent difference between PCEA and CEI. This may be due to a number of reasons. First, satisfaction with both forms of analgesia appeared to be extremely high. Therefore, even by combining the results of all studies, the sample size may be insufficient to demonstrate a difference. This is particularly true because of the numerous different methods used to measure satisfaction and the different times (during labour or the next day) at which the question was asked. Second, it is very difficult to accurately measure maternal satisfaction. Often satisfaction with a particular technique is confused with satisfaction with pain relief. However, satisfaction is multidimensional and other factors such as patient expectations, communication skills of the health care team and the obstetric outcome are far more important than analgesia per se.18 One study attempted to measure multiple aspects of satisfaction but still did not find any difference between groups.10
In this review, we found no difference between groups in the incidence of Caesarean section or instrumental vaginal delivery. Furthermore, there was no difference in the duration of either the first or second stages of labour. However, the studies were small and the total number of patients enrolled may have been insufficient. In addition, the combination of nulliparous and multiparous parturients in some of the studies would reduce the power to detect these outcomes. A single, large study with standardized obstetric management would be more likely to find a difference if it exists.
Both CEI and PCEA appear to be safe for the mother and neonate. The incidence of maternal side-effects and neonatal depression was extremely low in the studies that measured these outcomes. Maternal hypotension occurred in less than 3% of cases and a low 5 min Apgar score occurred in under 2% (Table 2). An extremely large series of patients would be required to determine if the two groups were different with respect to these outcomes.
In summary, PCEA for labour pain has several advantages when compared with CEI. These include a reduction in the number of unscheduled clinician top-ups, a reduction in the amount of drug used and a reduction in the amount of motor block of the lower extremities. Both methods are safe for the mother and newborn. More information is needed to determine which method of analgesia maintenance leads to a reduced need for obstetric intervention and better patient satisfaction.
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Acknowledgement |
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References |
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