Letters to the Editor: Letters & Announcements
First, we regret the significant lack of clarity with regard to maternal satisfaction in the conclusion of the abstract.1 We did find a trend that patient-controlled epidural anesthesia (PCEA) improved patient satisfaction (P = 0.06) but this did not reach statistical significance in our study. Because the data were both ordinal and not normally distributed, we applied a nonparametric (Kruskal-Wallis) test to analyze patient satisfaction scores. Previous studies comparing demand-only PCEA regimens versus PCEA regimens with basal infusion, albeit with some variations in methodologies, also demonstrated no difference in maternal satisfaction.2–4 However, these studies were not powered to detect a difference in maternal satisfaction. On the other hand, the meta-analysis by van der Vyver et al.5 did not address issues related to the comparison between PCEA regimens per se. Maternal satisfaction is often affected by a multitude of factors, as shown by Hodnett,6 but this was neither the focus nor aim of our study. Hence, we do not agree with Turkstra and Jones7 that the latter two references are contradictory to the findings of our study.
Second, we admit that our introductory paragraph should have been more explicit in expressing that the advantages rendered by PCEA could potentially have a positive influence on patient satisfaction. Indeed, Hodnett6 suggested that patient participation in decision making (patient autonomy) could have a positive impact on patient satisfaction. Similarly, the meta-analysis by van der Vyver et al.5 showed that patients on PCEA used less anesthetics and experienced less motor block, and the authors suggested that future studies should be directed toward assessing maternal satisfaction.
Third, we agree that the three regimens used in this study were based on our existing clinical practice, which in turn, was based on the principles proposed in a review article.8 In retrospect, it is reasonable to deduce that the regimen allowing a greater access to and flexibility in the use of local anesthetics could have resulted in an improved outcome with respect to analgesia. However, at the time of the study, we were also interested in whether greater local anesthetic consumption would concomitantly cause more side effects.
Fourth, the data for supplemental boluses were analyzed by using a nonparametric test (Kruskal-Wallis) and presented as median (min-max). We have included the raw data herewith for greater clarity (Table 1), which shows the incidence of breakthrough pain and the number of patients in each group.
Fifth, with regard to the confusion about the issue surrounding the analysis of the duration of effective analgesia, we had initially applied the statistically appropriate Kaplan-Meier analysis and treated parturients who had had vaginal or caesarean deliveries before the loss of analgesia as censored data. We found that the results greatly favored the regimen with the largest basal infusion even though the incidence of censored events was very high. We chose to do an additional nonparametric test to have a more conservative estimate of the effect size because this would better reflect the real-life situation with regard to the period of “painlessness.” This also yielded a similar result. In addition to the mean duration of analgesia (+sd), we include herewith the data of the respective median durations of analgesia (min-max range) for greater clarity.
Median Duration of Analgesia:
- Group 0: 230 min (13–1092)
- Group 5: 314 min (49–899)
- Group 10: 357 min (14–1020)
Sixth, we regret the typographical error. The revised P values for the duration of 2nd stage and total duration of labor are shown in Table 2.
Finally, we are grateful to Drs. Turkstra and Jones for highlighting this important publication on the use of mixed effect models, which we hope to incorporate in our future trials.9
Yvonne Lim, MBBS
Alex T. Sia
Department of Women’s Anesthesia
KK Women’s and Children’s Hospital
1.Lim Y, Ocampo CE, Supandji M, Teoh WH, Sia AT. A randomized controlled trial of three patient-controlled epidural analgesia regimens for labor. Anesth Analg 2008;107:1968–72
2.Bremerich DH, Waibel HJ, Mierdl S, Meininger D, Byhahn C, Zwissler BC, Ackermann H. Comparison of continuous background infusion plus demand dose and demand-only parturient-controlled epidural analgesia (PCEA) using ropivacaine combined with sufentanil for labor and delivery. Int J Obstet Anesth 2005;14:114–20
3.Petry J, Vercauteren M, Van Mol I, Van Houwe P, Adriaensen HA. Epidural PCA with bupivacaine 0.125%, sufentanil 0.75 microgram and epinephine 1/800.000 for labor analgesia: is a background infusion beneficial? Acta Anaesthesiol Belg 2000; 51:163–6
4.Vallejo MC, Ramesh V, Phelps AL, Sah N. Epidural labor analgesia: continuous infusion versus patient-controlled epidural analgesia with background infusion versus without a background infusion. J Pain 2007;8:970–5
5.van der Vyver M, Halpern S, Joseph G. Patient-controlled epidural analgesia versus continuous infusion for labour analgesia: a meta-analysis. Br J Anaesth 2002;89:459–65
6.Hodnett ED. Pain and women’s satisfaction with the experience of childbirth: a systematic review. Am J Obstet Gynecol 2002; 186:S160–S172
7.Turkstra TP, Jones PM. Is there evidence for improved maternal satisfaction with patient-controlled epidural anesthesia? Anesth Analg 2009;109:1344
8.D’Angelo R. New techniques for labor analgesia: PCEA and CSE. Clin Obstet Gynecol 2003;46:621–32
9.Shafer SL, Struys MM. Mixed effect modeling in analgesia trials. Anesth Analg 2008;107:9–10