| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
* From the Departments of Anaesthesia, Singapore General Hospital, and
the KK Women and Children’s Hospital, Singapore.
Address correspondence to: Dr. Sebastian M.H. Chua, Department of Anaesthesia, Singapore General Hospital, Outram Rd, Singapore 169608. Phone: 65-6321-4220; Fax: 65-6224-1792; E-mail: sebnjess{at}singnet.com.sg
 |
Abstract |
|---|
 TOP Abstract IntroductionMethodsResultsDiscussionReferences |
|---|
Methods: CSE was instituted in 42 nulliparous parturients at the L3 to 4 level with intrathecal (IT) fentanyl 25 µg followed by an epidural test dose of 3 mL of 1.5% lidocaine. These parturients were then randomly assigned to receive either epidural CIB (n = 21) or CEI (n = 21) with 0.1% ropivacaine and fentanyl 2 µg·mL–1. For the CIB, 5 mL boluses were given hourly, with the first bolus 30 min postinduction. CEI at the rate of 5 mL·hr–1 was initiated in the minute after CSE. The duration of analgesia, pain score, degree of sensorimotor block were compared.
Results: From Kaplan Meier survival analysis, the duration of analgesia was significantly longer in CIB (mean survival time 239 ± SD 24 min vs 181 ± 17, P < 0.05 using log rank test). During the first three hours postblock, the median sensory block to cold was higher in CIB (P < 0.05, Mann U Whitney test) but no difference in blood pressure was detected [P > 0.05, repeated measure analysis of variance (RMANOVA)]. The serial pain scores were lower in the CIB (P < 0.05, RMANOVA).
Conclusion: CIB prolonged the duration and improved the quality of analgesia. CIB could have resulted in an improved spread of analgesics in the epidural space or encouraged a direct passage of infusate into the IT space. This could have also rendered a higher sensory block to cold in the CIB group. CIB is a good alternative to CEI for the maintenance of epidural analgesia after CSE.
|
Introduction |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
In this study, we aimed to compare the efficacy of CEI with CIB in the maintenance of epidural analgesia after the induction of CSE during early labour. We hypothesized that the potentially improved spread of analgesic solution in the epidural space during CIB could, to a greater degree than CEI, prolong the duration of analgesia rendered by the initial IT component of CSE.
|
Methods |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
After obtaining written informed consent, 0.5 L lactated Ringer’s solution was infused iv before CSE and a preblock pain score on the VAS was taken. Preblock systolic blood pressure (SBP) was measured non-invasively on the right arm (DINAMAP, Critikon, Tampa, FL, USA) with the parturients supine but with a left lateral tilt effected by placing a wedge under the right hip. The parturients were then randomly assigned by the blind opaque envelope technique to receive either epidural CIB (n = 21) or CEI (n = 21). Prior to CSE, all fetal heart rate tracings were confirmed to be reactive by the attending obstetrician. Continuous fetal heart tracings were then monitored closely for the first 30 min postblock.
CSE was instituted in the sitting position. The epidural space was identified at the L3 or L4 level in the midline with an 18-G Tuohy needle by using the loss of resistance to air technique, followed by dural puncture with a 27-G pencil-point needle through the Tuohy needle (Espocan, B.Braun, Melsungen, Germany). All the blocks were performed by the principal investigator (S.M.H.C.). After ensuring a free flow of cerebrospinal fluid, fentanyl 25 µg was injected intrathecally and the spinal needle removed. A multiorificed 20-G epidural catheter was then inserted and a length of 3 cm was left in the epidural space. After confirming the absence of blood on aspiration,3 a ‘test dose’ of 3 mL of 1.5% lidocaine (Xylocaine, Astrazeneca, Sodertalje, Sweden) was injected into the catheter. If blood was detected on aspirating the catheter, the epidural catheter would be removed and resited. The parturient would be excluded from the study and the sealed envelope would be made available for a second randomization.
The parturients were then positioned supine with a left lateral tilt. Motor block was assessed every five minutes for the first half-hour postblock and every hour after CSE. The modified Bromage scale [0 = no impairment; 1 = unable to raise the extended leg but able to move knees and feet; 2 = unable to raise extended leg as well as flex knees, able to move foot; 3 = not able to flex ankle, feet or knees (complete block)] was used to assess lower limb motor block. Similarly, SBP was recorded every five minutes for the first half-hour postblock and every 15 min subsequently. The lowest SBP at the end of every hour after time 0 was recorded. In the presence of motor block to a degree greater than Bromage 1 and/or a reduction of SBP 
30% from the baseline value during the first ten minutes postblock, the subject would be withdrawn from the study because of possible subdural or subarachnoid catheter placement.
The time of completion of the injection of the ‘test dose’ was defined as time 0. All the parturients received a solution of ropivacaine 0.1% plus fentanyl 2 µg·mL–1 for the maintenance of epidural analgesia. The Graseby 9200 pump (SIMS Graseby, Watford, United Kingdom) was employed for CIB. The initial 5 mL bolus was administered 30 min after time 0, followed by 5 mL boluses every hour thereafter. As the highest rate of delivery afforded by the pump was 100 mL·hr–1, each epidural bolus was delivered over three minutes. For CEI, a rate of 5 mL·hr–1 was initiated one minute after time 0 by using a Terumo syringe pump (Terumo Corporation, Tokyo, Japan).
For half an hour after time 0, VAS was taken every ten minutes and then every hour after the block. The level of sensory block to cold was assessed using ice ten minutes after time 0 and hourly after CSE. All data were collected by an anesthesiologist who was not involved in instituting the block.
The time when patients requested supplemental analgesia while on either epidural maintenance regimen was defined as time END. Duration of analgesia was the difference between time END and time 0. Parturients who delivered prior to the loss of analgesia were excluded at the time of delivery but accounted for in the Kaplan Meier survival analysis for duration of analgesia. If the VAS was greater than 10, 20 min after time 0, the block would be labelled as ‘ineffective’ and the parturient would be excluded from further analysis. Pain ‘rescue’ medication in the form of 5 mL aliquots of ropivacaine 0.2% would then be given epidurally followed by a continuous infusion of 0.1% ropivacaine plus 2 µg·mL–1 fentanyl at the rate of 10 mL·hr–1.
The sample size was computed to detect a 30-min difference (
= 0.05, ß = 0.2) in the duration of analgesia. The following tests were used for the comparison of data between the two groups: log rank test for survival analysis of the duration of analgesia, Student’s t test for parametric data, Mann U Whitney test for non-parametric data; Fisher’s exact test for proportions and repeated measures ANOVA for pain score and lowest blood pressure. Results are expressed as mean (with standard deviation) or median (with range). A value of P < 0.05 was considered statistically significant.
|
Results |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
). All parturients completed the study and none was excluded due to the possible subdural/subarachnoid placement of the epidural catheter. There were also no ‘ineffective’ blocks. There were no new ominous or non-reactive fetal heart rate changes requiring an emergent delivery in the first 30 min postblock.
|
). Four parturients in CIB and five in CEI delivered without the need for supplemental analgesia (P > 0.05, Fisher’s exact test). The CIB group displayed a significantly lower pain score than CEI (P < 0.05, repeated measure ANOVA) during the first three hours (Figure 2). The hourly consumption of epidural bupivacaine + fentanyl solution prior to the loss of analgesia or delivery was similar between the two groups (mean 5.2 mL·hr–1 ± SD 0.6 for CIB vs 5.0 ± 0.5 for CEI, P > 0.05).
|
|
). None of the parturients had a decline of SBP > 20% of the preblock value prior to time END. Two parturients, one in each group had some lower limb motor block, not greater than Bromage 1.
|
|
Discussion |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
Experimentally, a greater spread of infusate from a multiorificed catheter was found when intermittent boluses were used instead of a continuous infusion, despite a similar rate of infusion.2 Moreover, when a continuous infusion was used, there was practically no flow through the distal hole, whereas when intermittent bolusing was used, the infusate flowed out from all the holes. Hogan also suggested that the use of intermittent boluses could produce a more uniform epidural block than a continuous infusion due to the difference of injectate pressure, based on his study in human cadavers.5
In another study on epidural analgesia during labour, intermittent bolusing was also found to reduce analgesic requirements and the need for additional top-up boluses.6 The authors attributed this to a higher driving pressure associated with intermittent boluses. In that study, a common 10.5 mL·hr–1 basal infusion/bolusing rate was used. We suggest that the higher sensory block and longer duration of analgesia in the CIB group results from the improved spread of analgesics in the epidural space, secondary to a higher driving pressure. However, we are unable to substantiate this, as we did not measure changes in epidural pressure with either regimen used in our study.
We induced analgesia by CSE. Continual bolusing, with its attendant greater driving pressure, could also have an arguably more profound epidural volume expansion (EVE) effect than a slow continuous infusion. A rapid injection of saline into the epidural space after subrachnoid administration of local anesthetics has been found to promote the cephalad spread of sensory block, a technique called ‘EVE’.7 The contribution of a greater EVE effect from continual bolusing in the first hours after CSE induction could have played a role to enhance the sensory block and the quality of analgesia.
Shortly after CSE induction by the IT injection of local anesthetics, the epidural injection of local anesthetics has been found to enhance cephalad spread of the block more rapidly than the epidural injection of the same volume of saline.8 Similarly, a bolus of local anesthetic through a catheter in the epidural space has been found to result in a greater degree of sensorimotor block in the event of a prior intentional dural puncture during CSE.9 This has been attributed to some degree of direct migration of analgesics into the subarachnoid space through the dural rent post CSE. Intuitively, the higher driving pressure associated with continual bolusing could, potentially, facilitate the magnitude of this flux. This could also have been partially responsible for the higher sensory block in CIB in our study. More research is required in this regard.
The low concentration and rate of epidural infusion/boluses used may have been responsible for the overall lack of change of SBP and the low incidence of motor block (only 2/42 parturients had any degree of lower limb motor block) in our study. The use of low dose epidural infusion/boluses resulted in a majority of parturients requiring supplemental analgesia before reaching the second stage of labour. The use of higher doses of infusion/boluses could have prolonged the duration of analgesia induced by CSE,4 albeit at the expense of a higher number of parturients with greater sensory and motor blocks.6 Even though the sensory block reached a high dermatomal level, it did not ascend during the study and there was no corresponding motor impairment or respiratory depression. The extent of sensory block could have been confounded by the action of IT fentanyl on opioid receptors.10
In conclusion, in labouring parturients, the use of epidural CIB was more effective than CEI in prolonging analgesia induced by IT fentanyl. This was associated with lower pain scores and a higher sensory block in CIB. CIB appears to be a good alternative to CEI for the maintenance of labour epidural analgesia.
|
Footnotes |
|---|
|
References |
|---|
|
TOPAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
2 Kaynar AM, Shankar KB. Epidural infusion: continuous or bolus? (Letter). Anesth Analg 1999; 89: 534.
3 Norris MC, Ferrenbach D, Dalman H, et al. Does epinephrine improve the diagnostic accuracy of aspiration during labor epidural analgesia? Anesth Analg 1999; 88: 1073–6.
4 Beilin Y, Nair A, Arnold I, et al. A comparison of epidural infusions in combined spinal/epidural technique for labor analgesia. Anesth Analg 2002; 94: 927–32.
5 Hogan Q. Distribution of solution in the epidural space: examination by cryomicrotome section. Reg Anesth Pain Med 2002; 27: 150–6.[Medline]
6 Bhavani-Shankar K, Malov S, Hurley R, Datta S. Do rapidly administered intermittent epidural boluses provide better labor analgesia? Anesthesiology 2000; 93(Suppl): A1071.
7 Picard J, Crowhurst JA, Plaat F. Failure to achieve consistent anesthesia could be attributed to technique (Letter). Reg Anesth Pain Med 2001; 26: 588.[Medline]
8 Stienstra R, Dilrosun-Alhadi BZ, Dahan A, van Kleef JW, Th Veering B, Burm AG. The epidural "top-up" in combined spinal-epidural anesthesia: the effect of volume versus dose. Anesth Analg 1999; 88: 810–4.
9 Leighton BL, Arkoosh VA, Huffnagle S, Huffnagle HJ, Kinsella SM, Norris MC. The dermatomal spread of epidural bupivacaine with and without prior intrathecal sufentanil. Anesth Analg 1996; 83: 526–9.[Abstract]
10 Riley ET, Ratner EF, Cohen SE. Intrathecal sufentanil for labor analgesia: do sensory changes predict better analgesia and greater hypotension? Anesth Analg 1997; 84: 346–51.[Abstract]
This article has been cited by other articles:
 |
|
 |
|
  A. T. Sia, Y. Lim, and C. Ocampo A Comparison of a Basal Infusion with Automated Mandatory Boluses in Parturient-Controlled Epidural Analgesia During Labor Anesth. Analg., March 1, 2007; 104(3): 673 - 678. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. D. W. Fettes, C. S. Moore, J. B. Whiteside, G. A. Mcleod, and J. A. W. Wildsmith Intermittent vs continuous administration of epidural ropivacaine with fentanyl for analgesia during labour Br. J. Anaesth., September 1, 2006; 97(3): 359 - 364. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. A. Wong, J. T. Ratliff, J. T. Sullivan, B. M. Scavone, P. Toledo, and R. J. McCarthy A randomized comparison of programmed intermittent epidural bolus with continuous epidural infusion for labor analgesia. Anesth. Analg., March 1, 2006; 102(3): 904 - 909. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. A.E. Shephard The changing pattern of anesthesia, 1954-2004: a review based on the content of the Canadian Journal of Anesthesia in its first half-century: [La transformation du modele de l'anesthesie, 1954-2004 : une revue fondee sur le contenu du premier demi-siecle du Journal canadien d'anesthesie] Can J Anesth, March 1, 2005; 52(3): 238 - 248. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
