Chapter 5 Discussion
5.5 Study limitation
This is the first study about the determinants of ineffectiveness epidural analgesia of labor pain in Taiwan.
We acknowledge several limitations in our conclusions. First, the numeric rating
scale is a single quantitative dimension of pain intensity and couldn’t reveal the complex multidimensional phenomenon of pain. Acute pain such as labor pain is considered to have at least two dimensions, a sensory and an affective or distress component3. For example, anxiety, fear of pain, and psychological factors are commonly associated with pain and can’t be distinguished by only NRS. Parturients may confuse these negative emotions with pain sensation and pronounce they are painful. Many methods of measuring pain in a more objective way have been developed such as McGill pain questionnaire, which Chinese translation edit is validated, and currently development Present Behavioral Intensity Scale may be a choice to evaluate labor pain.
Second, an arbitrary definition of ineffectiveness of epidural painless labor was used in our study. In our experience of management acute pain including, the NRS is used to confirm clinical nursing judgment as to the need for further intervention32. NRS less than three document that the goal of analgesia has been achieved.
Third, there might be some factors related to ineffectiveness of painless labor didn’t include in our analyses. For example, technique factors mentioned in previous studies were not recorded and analysis in our study. The two major causes of inadequate block were found to be transforaminal escape of the catheter tip, and persistent unilateral block associated with an obstructive barrier in the epidural space in Collier et al.’s study
of epidurogram52. Thus the incidence of paresthesia during epidural placement, the catheter migration after delivery, the unilateral analgesia may be important factors.
Forth, participates in our study are limited in one medical center in Taipei City.
There may be limitations for extrapolating. The characteristics of parturients in other hospital in Taiwan may differ from our hospital. For example the age, education level and income may higher than other rural hospitals and clinics. Second the regimens of epidural painless labor may be different in drugs and concentrations. Although there are limitations exist, to apply our results in a population similar to our participants is appropriate.
5.6 Conclusion
Our results revealed that factors associated with ineffectiveness of epidural analgesia of labor pain are cervical dilatation velocity, type of loading drugs and type of continue drugs. Improvement of effectiveness and of epidural analgesia of painless labor could be aimed at these factors. And more factors to be concluded in analyses are suggested in further investigation.
Figure 1-1 Comparison of the intensity of labor pain with other clinical pain syndromes.
(From Melzack R. Pain 1984;19:321-37)
Figure 2-1 The linear relationship between VAS and NRS of obstetrical pain. (From Hartrick CT. Pain Pract 2003;3(4):310-6)
Figure 3-1 The Portex ® epidural minipack (system 1, clear catheter, 3 lateral eyes. Portex Ltd.
CT21 6JL, UK) (From website of Smiths medical ASD Inc.)
Figure 3-2 The place and position of epidural catheter insertion.
11 parturients were excluded:
2 had intrauterine death,
9 had epidural catheter replaced
Parturients using epidural analgesia,
Record of epidural painless in three parturients couldn’t be found
Eligible 1001 parturients
Training group, n=500 Validating group, n=501
Figure 3-3 Results of data collection.
Figure 4-1 Trend of usage rate of epidural painless labor.
0 5 10 15 20 25
9401 3 5 7 9 11
9501 3 5 7 9 11
年月
百分比
Figure 4-2 The distribution of NRS before the epidural catheter insertion (upper figure), 30 minutes after epidural drugs administration (middle figure), and the maximum NRS of pain during labor after epidural painless labor (lower figure).
NRS in 0 min
Figure 4-3 ROC (receiver operating characteristic) curve of logistic regression model for predict ineffectiveness epidural painless labor.
Chapter 5 Discussion
AUC (area under ROC curve)= 0.6712
Table 4-1 The demographic data of training and validating group
Training group Validating group P-value (two tail)
Mother age 30.04±3.8 30.08±4.06 0.9108
Mother height (cm) 160.08±4.99 160.27±4.71 0.5439 Mother weight (kg) 67.83±9.21 67.94±8.28 0.8506 Gestation weeks 38.97±1.29 39.04±1.29 0.4052 Newborn height (cm) 50.11±3.92 50.18±2.01 0.5818 Newborn weight (kg) 3174.71± 3180.13±363.45 0.8182
Table 4-2 Univariate analysis of two groups (NRS>3 and NRS<=3) using t-test for continuous variables
and chi-square test or Fisher’s exact test for categorical variables. * p<0.1 # Fisher’s exact test
NRS<=3 (N=370, 74%) NRS>3 (N=130, 26%) p-value
Mother age 29.989(29.593-30.385) 30.214(29.591-30.837) 0.5615 Mother height 159.96(159.47-160.46) 160.4(159.48-161.32) 0.393
Mother weight 67.77(66.81-68.73) 68.01(66.49-69.53) 0.7999
Education (above college) 74.15% 82.95% 0.227
Gestation age 39.02(38.88-39.15) 38.85(38.65-39.04) 0.199
Newborn weight 3185.4(3145.8-3225.0) 3144.9(3081-3208.8) 0.298
Newborn height 50.16(49.96-50.37) 49.98(49.64-50.31) 0.3553
Newborn sex (male) 54.67% 53.49% 0.8169
Children number (first) 86.18% 86.26% 0.294
OP presentation 2.98%(11) 1.51%(2) #0.5291
Apgar score at 1 min 8.61(8.53-8.69) 8.67(8.53-8.81) 0.4516
Apgar score at 5 min 8.96(8.93-8.98) 8.95(8.91-9.00) 0.8442
Stage1 310.7(283.74-337.67) 264.43(218.47-310.39) *0.0847
Stage2 77.40(68.17-86.64) 75.58(64.93-88.23) 0.9234
Cervivle dilatation in 0 min 2.55(2.44-2.66) 2.50(2.32-2.67) 0.6417 Cervicle dilatation in 30 min 2.91(2.76-3.07) 3.25(2.93-3.57) *0.0407 Cervicle dilatation velocity 0.67(0.46-0.89) 1.52(0.46-2.05) *0.0006
Use of Mepedipine 14.57% 19.53% 0.1872
Instrumentation delivery 21.69% 11.25% *0.0256
C/S rate 70(18.97%) 24(18.46%) 0.8701
Loading drug *#<0.0001
Non 0.82%(3) 0
Lidocaine 41.58%(153) 54.2%(71)
Bupivacaine 2.45(9) 9.16%(11)
Ropivacaine 55.16%(203) 36.64%(48)
Loading with Fentanyl 86.96%(320) 75.57%(99) *0.0023
Loading volume 11.25(10.89-11.60) 10.73(10.10-11.35) 0.1194
Continue drug *#0.0015
Bupivacaine 0.81%(3) 6.11%(8)
Ropivacaine 99.19%(366) 93.89%(122)
Satisfaction(very satisfy) 51.49% 21.77% *<0.0001
Anesthesiologist(VS) 59.51% 52.67% 0.1736
Table 4-3 Multivariate analysis using logistic regression.
Odds ratio 95% CI P-value
Fentanyl (with Fentanyl) 0.729 0.409-1.299 0.2841
Stage 1 (<300 mins) 1.338 0.830-2.157 0.2315
Cervical dilatation at 30 min (>3cm) 0.875 0.553-1.385 0.5696 Cervical dilatation velocity (>1cm/hour) 2.333 1.400-3.889 *0.0012
Loading drug (non or Lidocaine or
Bupivacaine) 1.827 1.150-2.904 *0.0108
Continue drug (Bupivacaine) 5.546 1.386-22.195 *0.0155
Table 4-4 Stepwise logistic regression to select model of prediction ineffectiveness of epidural painless labor.
Parameter Estimate Standard error Chi-square Pr>Chi-square
Intercept -1.6458 0.1765 869384 <0.0001
Cervical dilatation (>1cm/hour) 0.8404 0.2377 12.4985 0.0004
Loading drugs (non or Lidocaine
or Bupivacaine)
0.6710 0.2154 9.7081 0.0018
Continue drugs (Bupivacaine) 1.8274 0.6977 6.8611 0.0088
References
1. Melzack R. The myth of painless childbirth. Pain 1984;19(4):321-37.
2. Brown ST, Campbell D, Kurtz A. Characteristics of labor pain at two stages of cervical dilation. Pain 1989;38(3):289-95.
3. Brownridge P. The nature and consequences of childbirth pain. European Journal of Obstetrics, Gynecology, and Reproductive Biology 1995;59:S9-15.
4. American Collage of Obstetricians and Gynecologists Committee Opinion No.295:
pain relief during labor. Obstetrics and Gynecology 2004;104(1):213.
5. American Collage of Obstetricians and Gynecologists committee opinion. No.339:
Analgesia and cesarean delivery rates. Obstetrics and Gynecology 2006;107(6):1487-8.
6. Lowe NK. The nature of labor pain. American Journal of Obstetrics and Gynecology 2002;186:S16-24.
7. Zhang J, Yancey MK, Klebanoff MA, Schwarz J, Schweitzer D. Does epidural analgesia prolong labor and increase risk of cesarean delivery? A natural experiment.
American Journal of Obstetrics and Gynecology 2001;185(1):128-34.
8. Carvalho B, Wang P, Cohen SE. A survey of labor patient-controlled epidural anesthesia practice in California hospitals. International Journal of Obstetric Anesthesia 2006;15(3):217-22.
9. Hess PE, Pratt SD, Lucas TP, et al. Predictors of breakthrough pain during labor epidural analgesia. Anesthesia and Analgesia 2001;93(2):414-8.
10. Khor LJ, Jeskins G, Cooper GM, Paterson-Brown S. National obstetric anaesthetic practice in the UK 1997/1998. Anaesthesia 2000;55(12):1168-72.
11. Palot M, Chale JJ, Colladon B, et al. Anesthesia and analgesia practice patterns in French obstetrical patients. Annales francaises d'anesthesie et de reanimation 1998;17(3):210-9.
12. Palot M, Leymarie F, Jolly DH, Visseaux H, Botmans-Daigremont C, Mariscal-Causse A. Request of epidural analgesia by women and obstetrical teams in four French areas. Part II: Management of epidural analgesia. Annales francaises d'anesthesie et de reanimation 2006;25(6):569-76.
13. Meuser T, Wiese R, Molitor D, Grond S, Stamer UM. A survey of labour pain management in Germany. Schmerz (Berlin, Germany) 2008;22(2):184-90.
14. Chan YK, Ng KP. A survey of the current practice of obstetric anaesthesia and analgesia in Malaysia. The Journal of Obstetrics and Gynaecology Research 2000;26(2):137-40.
15. Lee BB, Chen PP, Ngan Kee WD. Status of obstetric epidural analgesia services in Hong Kong public hospitals: postal questionnaire survey. Hong Kong Medical Journal. 2003;9(6):407-14.
16. Fan ZT, Gao XL, Yang HX. Popularizing labor analgesia in China. International Journal of Gynaecology and Obstetrics. 2007;98(3):205-7.
17. Chan YK, Ng KP. A survey of regional analgesia and anaesthesia for obstetrics in selected countries in the Far East. International Journal of Obstetric Anesthesia 2000;9(4):225-32.
18. Chang KY, Chan KH, Chang SH, Yang MC, Chen TH. Decision analysis for epidural labor analgesia with Multiattribute Utility (MAU) model. The Clinical Journal of Pain 2008;24(3):265-72.
19. Fridh G, Gaston-Johansson F. Do primiparas and multiparas have realistic expectations of labor. Acta obstetricia et gynecologica Scandinavica 1990;69(2):103-9.
20. Melzack R, Kinch R, Dobkin P, Lebrun M, Taenzer P. Severity of labour pain:
influence of physical as well as psychologic variables. Canadian Medical Association Journal 1984;130(5):579-84.
21. Ranta P, Jouppila P, Spalding M, Jouppila R. The effect of maternal obesity on labour and labour pain. Anaesthesia 1995;50(4):322-6.
22. Ranta P, Spalding M, Kangas-Saarela T, et al. Maternal expectations and experiences of labour pain--options of 1091 Finnish parturients. Acta anaesthesiologica Scandinavica 1995;39(1):60-6.
23. Conell-Price J, Evans JB, Hong D, Shafer S, Flood P. The development and validation of a dynamic model to account for the progress of labor in the assessment of pain. Anesthesia and Analgesia 2008;106(5):1509-15.
24. Sizer AR, Nirmal DM. Occipitoposterior position: associated factors and obstetric outcome in nulliparas. Obstetrics and Gynecology 2000;96:749-52.
25. Le Coq G, Ducot B, Benhamou D. Risk factors of inadequate pain relief during epidural analgesia for labour and delivery. Canadian Journal of Anaesthesia 1998;45(8):719-23.
26. Chang KY, Dai CY, Ger LP, et al. Determinants of patient-controlled epidural analgesia requirements: a prospective analysis of 1753 patients. The Clinical Journal of Pain 2006;22(9):751-6.
27. Bijur PE, Silver W, Gallagher EJ. Reliability of the visual analog scale for measurement of acute pain. Acad Emerg Med 2001;8(12):1153-7.
28. Bijur PE, Latimer CT, Gallagher EJ. Validation of a verbally administered numerical rating scale of acute pain for use in the emergency department. Acad Emerg Med 2003;10(4):390-2.
29. Gallagher EJ, Liebman M, Bijur PE. Prospective validation of clinically important changes in pain severity measured on a visual analog scale. Annals of Emergency Medicine 2001;38(6):633-8.
30. Li L, Liu X, Herr K. Postoperative pain intensity assessment: a comparison of four scales in Chinese adults. Pain Medicine 2007;8(3):223-34.
31. Price DD, McGrath PA, Rafii A, Buckingham B. The validation of visual analogue scales as ratio scale measures for chronic and experimental pain. Pain 1983;17(1):45-56.
32. Hartrick CT, Kovan JP, Shapiro S. The numeric rating scale for clinical pain measurement: a ratio measure? Pain Pract 2003;3(4):310-6.
33. Graninger EM, McCool WP. Nurse-midwives' use of and attitudes toward epidural analgesia. Journal of Nurse-Midwifery 1998;43(4):250-61.
34. Ciment J. US women asked to pay for epidurals in advance. BMJ 1999;318(7187):828.
35. Atherton MJ, Feeg VD, el-Adham AF. Race, ethnicity, and insurance as determinants of epidural use: analysis of a national sample survey. Nursing Economic 2004;22(1):6-13, 3.
36. Hodnett ED. Pain and women's satisfaction with the experience of childbirth: a systematic review. American Journal of Obstetrics and Gynecology 2002;186:S160-72.
37. Anim-Somuah M, Smyth R, Howell C. Epidural versus non-epidural or no analgesia in labour. Cochrane database of systematic reviews 2005(4):CD000331.
38. Hwa HL, Chen LK, Chen TH, Lee CN, Shyu MK, Shih JC. Effect of availability of a parturient-elective regional labor pain relief service on the mode of delivery.
Journal of the Formosan Medical Association 2006;105(9):722-30.
39. Cheek TG, Samuels P, Miller F, Tobin M, Gutsche BB. Normal saline i.v. fluid load decreases uterine activity in active labour. British Journal of Anaesthesia 1996;77(5):632-5.
40. Mussat P, Dommergues M, Parat S, et al. Congenital chylothorax with hydrops:
postnatal care and outcome following antenatal diagnosis. Acta Paediatr 1995;84(7):749-55.
41. To WW, Li IC. Occipital posterior and occipital transverse positions: reappraisal of the obstetric risks. The Australian & New Zealand Journal of Obstetrics &
Gynaecology 2000;40(3):275-9.
42. Michael S, Richmond MN, Birks RJ. A comparison between open-end (single hole) and closed-end (three lateral holes) epidural catheters. Complications and quality of sensory blockade. Anaesthesia 1989;44(7):578-80.
43. Rowlands S, Permezel M. Physiology of pain in labour. Bailliere's Clinical Obstetrics and Gynaecology 1998;12(3):347-62.
44. Wuitchik M, Bakal D, Lipshitz J. Relationships between pain, cognitive activity and epidural analgesia during labor. Pain 1990;41(2):125-32.
45. Halpern SH, Walsh V. Epidural ropivacaine versus bupivacaine for labor: a meta-analysis. Anesthesia and Analgesia 2003;96(5):1473-9.
46. Sah N, Vallejo M, Phelps A, Finegold H, Mandell G, Ramanathan S. Efficacy of ropivacaine, bupivacaine, and levobupivacaine for labor epidural analgesia. Journal of Clinical Anesthesia 2007;19(3):214-7.
47. Zink W, Graf BM. Benefit-risk assessment of ropivacaine in the management of postoperative pain. Drug Safety 2004;27(14):1093-114.
48. George MJ. The site of action of epidurally administered opioids and its relevance to postoperative pain management. Anaesthesia 2006;61(7):659-64.
49. Lee BB, Ngan Kee WD, Lau WM, Wong AS. Epidural infusions for labor analgesia:
a comparison of 0.2% ropivacaine, 0.1% ropivacaine, and 0.1% ropivacaine with fentanyl. Regional Anesthesia and Pain Medicine 2002;27(1):31-6.
50. Klostergaard KM, Terp MR, Poulsen C, Agger AO, Rasmussen KL. Labor pain in relation to fetal weight in primiparae. European Journal of Obstetrics, Gynecology, and Reproductive Biology 2001;99(2):195-8.
51. Martino V, Iliceto N, Simeoni U. Occipito-posterior fetal head position, maternal and neonatal outcome. Minerva Ginecologica 2007;59(4):459-64.
52. Collier CB. Why obstetric epidurals fail: a study of epidurograms. International Journal of Obstetric Anesthesia 1996;5(1):19-31.
53. MarucciM, Cinnella G, Perchiazzi G, Brienza N, Fiore T. Patient-requested neuraxial analgesia for labor. Anesthesiology 2007;106:1035-45.