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ORIGINAL ARTICLE
Year : 2022  |  Volume : 12  |  Issue : 2  |  Page : 150-154

Labor epidural analgesia: Comparison of intermittent boluses of ropivacaine with three different concentrations of fentanyl – A randomized controlled trial


Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, India

Date of Submission29-Oct-2021
Date of Acceptance04-Feb-2022
Date of Web Publication02-Sep-2022

Correspondence Address:
Dr. Nitu Puthenveettil
Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi-682041, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JOACC.JOACC_100_21

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  Abstract 


Background and Aims: Labor epidural analgesia can be provided with local anesthetics alone or in combination with opioids. The aim of this study was to compare the duration of analgesia, onset time, and obstetric and fetal outcomes with three different concentrations of fentanyl. Methods: This double-blinded trial was conducted on 75 parturients who delivered with epidural analgesia. They were randomly assigned to three groups by the closed envelope technique. Groups A, B, and C received a bolus dose of 20 ml 0.1% ropivacaine with 1 μgml-1, 1.5 μgml-1, and 2 μgml-1 fentanyl, respectively, as an initial epidural dose. The duration, time to onset of analgesia, top-up doses required, hemodynamics, fetal-maternal outcomes, and complications were compared. Results: The mean duration of analgesia with the first epidural dose was 57.4 ± 14.207, 121.52 ± 33.951, and 165.08 ± 34.271 min in the A, B, and C groups, respectively, with a P of <.001. There was a higher duration of analgesia in the B group than in the A group (p-value <.001), in the C group than in the B group (p. 016), and in the C group than in the A group (p-value <.001). The onset of analgesia was faster in the C group than in the A and B groups (7.960 ± 1.695, 6.800 ± 1.607, and 5.960 ± 1.645 min in groups A, B, and C, respectively, with a P of. 001). The number of epidural boluses required was 3.480 ± 0.509, 2.640 ± 0.489, and 2.120 ± 0.331 in the A, B, and C groups, respectively. Conclusion: Labor epidural analgesia with a higher concentration of fentanyl produces a prolonged and faster onset of analgesia with fewer requirements for top-up boluses.

Keywords: Epidural analgesia, fentanyl, labor analgesia, ropivacaine


How to cite this article:
Rahman S, Puthenveettil N, Jacob RA, Ravindran GC, Rajan S, Kumar L. Labor epidural analgesia: Comparison of intermittent boluses of ropivacaine with three different concentrations of fentanyl – A randomized controlled trial. J Obstet Anaesth Crit Care 2022;12:150-4

How to cite this URL:
Rahman S, Puthenveettil N, Jacob RA, Ravindran GC, Rajan S, Kumar L. Labor epidural analgesia: Comparison of intermittent boluses of ropivacaine with three different concentrations of fentanyl – A randomized controlled trial. J Obstet Anaesth Crit Care [serial online] 2022 [cited 2022 Oct 6];12:150-4. Available from: https://www.joacc.com/text.asp?2022/12/2/150/355340




  Introduction Top


Labor epidural analgesia decreases the metabolic demands during labor and can be provided with local anesthetics alone or in combination with opioids.[1],[2],[3] Adding opioids improves the analgesic quality and reduces the side effects as it allows reduction of the concentration of the local anesthetic.[4] The lipid-soluble opioid, fentanyl, is commonly used along with local anesthetics.[5],[6] This double-blinded, randomized control trial was done to compare the analgesic efficacy and side effects of three commonly used concentrations of epidural fentanyl with 0.1% ropivacaine in providing labor epidural analgesia. The primary objective was to assess the duration of adequate labor analgesia with the initial epidural bolus dose, with three different concentrations of fentanyl. The secondary objective was the comparison of the time to onset of analgesia, motor block, pruritus, sedation, instrumental delivery, conversion to cesarean sections, and fetal outcomes such as bradycardia, fetal acidosis, and neonatal Apgar score.


  Materials and Methods Top


This prospective double-blinded trial was performed after getting consent from the Institutional Ethics Committee (IEC-AIMS-2020-ANES-105) and Clinical Trials Registry – India clearance in 75 parturients who delivered in our hospital with labor epidural analgesia between August 2020 and September 2021. All consenting parturients of the American Society of Anesthesiologists, grade 2, having uncomplicated cephalic singleton pregnancy and expressing a desire of having a labor epidural were included in the study. Patients with bleeding disorders, hypersensitivity to drugs used in the study, low platelet counts, spinal column deformities, spine surgery, and sepsis and parturients who deliver before administering the second bolus dose were excluded from the study. Patients recruited were assigned randomly to three groups by the closed envelope technique [Figure 1]. It was a double-blinded study where the patient and the assessor were unaware of the group allocation. After taking the lot, the resident not involved in the data collection and analysis loaded the drugs into 20 ml unlabeled syringes and handed it over to the consultant anesthesiologist. The epidural was placed in active labor whenever the patient requested pain relief, and it was activated soon after. Pain assessment was performed using the visual analog scale by the consultant anesthesiologist prior to placement of the epidural catheter. After attaching monitors and securing an intravenous line, 500 ml of ringer lactate was infused. Under strict aseptic precautions, with the parturient positioned in a sitting position, the labor epidural catheter was inserted in the L3-4 intervertebral space using an 18-gauge epidural Tuohy needle. In the case of accidental intravascular or intrathecal placement, the patient was removed from the study and the catheter was recited. The epidural drug was injected in incremental boluses of 5 ml each. Parturients of groups A, B, and C received 20 ml 0.1% ropivacaine with 1 μgml-1, 1.5 μgml-1, and 2 μgml-1 fentanyl, respectively, as an initial epidural bolus dose. The same dose was used as a subsequent top-up on the patient's demand. The adequacy of pain relief was assessed after the first bolus dose by an anesthesiologist who was blinded to the dose used. Analgesia was adequate if the pain score was ≤3. The time to onset of analgesia was noted. It is the time taken for the first epidural bolus dose to achieve a visual analog score (VAS) of ≤3. In case there was no adequate analgesia within 15 min, another 10 ml of the same bolus drug was administered, and pain relief was re-assessed. If adequate pain relief was not achieved 15 minutes after the additional 10 ml, it was considered to be an epidural failure, and the patient was removed from the trial. The analgesic duration produced by the first epidural bolus dose was calculated as the time from the first bolus dose to the time taken for the request for the second bolus dose. Breen modified Bromage scale (BMBS: complete motor block; no motor block is Grade 1; up to Grade 6) was used to assess the lower limb weakness. The fall in mean blood pressure of >20% from the baseline (hypotension) was treated with a bolus dose of 50 μg IV phenylephrine. The heart rate was <50 bpm (bradycardia), and treatment was given with IV 0.6 mg atropine sulfate. Demographic data (age, height, and weight) and obstetric data at the initiation of labor epidural analgesia (dilatation of the cervix, parity, station, cervical effacement, and membrane status) were noted. Analgesia score, motor block, and vitals (heart rate, mean blood pressure) were noted at 0 (before the epidural), 10, 15, and 30 min and then every 30 min until delivery. The total number of top-ups, amount of ropivacaine and fentanyl used, injection to delivery interval, and maternal side effects such as motor block, pruritus, sedation, and nausea and vomiting were noted. Sedation assessment was performed using Ramsay's sedation score (Anxious, restless, agitated, -1, oriented, tranquil-2, responds to command-3, rapid response to glabellar tap-4, slow response to glabellar tap-5, absent response to light glabellar tap-6). A sedation score of more than 3 was considered significant. Labor was managed as per the institutional protocol, and the delivery mode was noted. A continuous cardiotocograph was used to monitor the fetal heart. The Apgar score was noted at 1 and 5 minutes. Fetal blood gas monitoring was also performed.
Figure 1: Consort flow diagram

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As there were no similar studies published, a pilot study was conducted with 10 patients in each group. Based on the results, the sample size was calculated. On evaluating the mean and standard deviation of duration of analgesia among group A (57.20 ± 17.53), group B (100.50 ± 31.14), and group C (151.4 ± 39.96), with 90% power and 99% confidence interval, the sample size was calculated as 10 per group for comparison between groups A and B, three per group for comparison between groups A and C, and 15 per group for comparison between groups B and C. We included a total of 25 parturients in each group. Statistical analysis was done using IBM, SPSS 20 (SPSS Inc, Chicago, USA). Mean ± SD (standard deviation) for continuous variables and percentages for categorical variables are used. To compare continuous variables among the groups, one-way ANOVA was used. Multiple comparisons were performed using the Bonferroni test. Chi-square was used to test the associations between categorical variables. A p of <.05 was considered statistically significant.


  Results Top


Demographic and obstetric parameters were comparable [Table 1]. Successful labor epidural analgesia was achieved in all groups with no failures. The mean analgesic duration with the first epidural dose demonstrated a significant difference among the three groups with 57.4 ± 14.207, 121.52 ± 33.951, and 165.08 ± 34.271 min in A, B, and C, respectively, with P <.001. In comparison between groups, a significantly higher duration of analgesia was noted in B than in A (p <.001), in C than in B (p-value. 016), and in C than in the A group (p <.001). The time of onset of analgesia was rapid in the C Group compared to that in the A and B groups and was 7.960 ± 1.695, 6.800 ± 1.607, and 5.960 ± 1.645 min in the A, B, and C groups, respectively, with a P of <.001. The number of epidural boluses required was 3.480 ± 0.509, 2.640 ± 0.489, and 2.120 ± 0.331 in the A, B, and C groups, respectively, with a P <.001 [Table 2]. The VAS scores and hemodynamic variables were comparable among the groups [Figure 2]. There was no incidence of bradycardia or hypotension requiring intervention in any parturient. Eight percent parturient in the A group and 12% in the B and C groups delivered by cesarean sections. One percent parturient in groups A and B and none in group C had instrumental delivery, which was comparable with a P of. 865. None of the patients had significant sedation or motor block. Pruritus was noted more in group C than in groups A and B, but this difference was statistically insignificant. Nausea and vomiting incidence were comparable between the groups [Table 3]. The fetal outcome assessed using Apgar score and fetal arterial blood gas showed no significant variation among the three groups [Table 4].
Table 1: Demographic Data

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Table 2: Comparison of duration, onset time of analgesia, and number of boluses

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Table 3: Mode of Delivery and side effects

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Table 4: Neonatal parameters

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Figure 2: Comparison of mean VAS scores

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  Discussion Top


All patients in the study had successful labor analgesia. Group C had a longer duration of analgesia than groups B and A. This difference in duration of analgesia could be because of the increased dose of fentanyl used (group C > group B > group A). Opioids are known to act along with local anesthetics to improve the duration and quality of epidural labor analgesia.[7] The duration of epidural analgesia with the local anesthetic was found to be prolonged by 50% by the addition of opioids.[8],[9] Reduction in the number of epidural boluses required leads to a decrease in the total amount of the local anesthetic used. Opioids such as fentanyl, sufentanil, and alfentanil are commonly used as adjuncts along with local anesthetics for providing labor analgesia.[4] Because of its lower lipid solubility, morphine is generally avoided in labor analgesia as it may cause respiratory depression in the later phase.[10] Similar to this study, Bang and colleagues demonstrated an increased duration of analgesia with an increasing dose of fentanyl.[4] The addition of hypobaric fentanyl to the local anesthetic renders the subsequent mixture more hypobaric. This could lead to greater cephalic spread resulting in prolonged analgesia. Administration of a larger dose of the epidural fentanyl will increase the concentration gradient and facilitate its faster entry into the spinal cord.

On comparing the onset time of analgesia, no major differences between groups A and B and between B and C were noted. However, we found a significant difference when group C was compared to group A, which could be because of the increased dose of fentanyl used. In a similar study by Sai and colleagues, 20, 50, and 100 μg of the epidural fentanyl were used with 10 ml of 0.08% bupivacaine. They found that the onset time was significantly lesser with higher doses of fentanyl. They also noted that increasing the fentanyl concentration did not increase maternal side effects or affect the mode of delivery and fetal Apgar scores.[11] We used ropivacaine as a local anesthetic in this study as it was found to have lesser cardiac toxicity and motor block. This permits the parturient to be ambulant. Several studies have shown that ropivacaine causes a lesser incidence of instrumental delivery and cesarean sections than bupivacaine.[12]

All parturients had a VAS score of ≤3 after 15 minutes. No parturient complained of numbness, and all were ambulant. After the onset of adequate analgesia, the average pain scores were comparable among the groups. Whenever the pain score went above 3, epidural top-up boluses were administered. In a study by Beilin and colleagues, the dose of ropivacaine for adequate analgesia was estimated as 0.2%. However, the addition of opioids as adjuncts reduces the local anesthetic concentration required to attain comparable analgesia.[13] Gupta et al.[14] compared 0.125% and 0.2% (15 ml) ropivacaine with 2 μgml-1 fentanyl and concluded that 0.2% ropivacaine with fentanyl resulted in a better onset and analgesic duration and lesser consumption of opioids. However, other studies have shown that combining 2 μgml-1 fentanyl with 0.1% ropivacaine provides as effective analgesia as 0.2% ropivacaine.[7] Hence, in our study, we used 0.1% ropivacaine in all the groups. In previous trials with intermittent doses, it was found that a volume of 20 ml provides prolonged and better analgesia than 15 ml without any adverse effects.[2],[15] These 20 ml boluses were given with the patient in a propped-up position to aid in more saddle spread of the block.

The different techniques of labor epidural analgesia available are intermittent top-up boluses, continuous infusion of the epidural, and parturient-controlled epidural analgesia.[16] The intermittent epidural boluses rather than continuous infusion have the benefit of lesser incidence of maternal motor block. It is also known to be associated with decreased incidence of cesarean delivery, higher maternal satisfaction, and decreased local anesthetic use when compared to continuous infusion.[17] A study comparing continuous labor epidural infusion and programmed intermittent boluses with levobupivacaine and sufentanil demonstrated increased incidence of muscle weakness and instrumental delivery with continuous infusion.[18] Epidural anesthesia was used for all patients who required cesarean sections in this study.

The adverse effects known to occur with epidural local anesthetics are motor block, bradycardia, hypotension, urinary retention, and paresthesia. None of these complications occurred in this study. There was no difference in incidence of cesarean or instrumental delivery among the groups. Studies have shown that the labor epidural was associated with an elevated risk of instrumental vaginal delivery.[19],[20] In a review by Gupta S and colleagues, sparing of motor fibers was noted when the concentration of local anesthetics was decreased by the addition of opioids.[21] Hector and colleagues compared the effects of 20 ml of bupivacaine, levobupivacaine, and ropivacaine given epidurally for labor analgesia and found that there was a linear trend of increasing motor blockade from ropivacaine to levobupivacaine to bupivacaine.[22]

The side effects usually encountered with opioid use are respiratory depression, vomiting, sedation, itching, and low scores of neonatal Apgar.[23] In this study, some patients had experienced nausea and pruritus, which was more with a higher dose of the opioid fentanyl. However, no considerable difference in the incidence was noted among the different groups. Vitals were comparable and none of the parturients had hypotension or bradycardia. All neonates in this study had comparable Apgar scores and arterial blood gas parameters. None of the babies required intensive care or ventilatory care.

This trial has a number of limitations. The stage of labor could have been taken into consideration while assessing the effects of epidural boluses. The labor epidural prolongs the second stage of labor, but in this study, we did not assess the effect of different doses of fentanyl on the duration of labor. The sensory level achieved by the block was also not assessed. Patients who underwent cesarean sections because of obstetric reasons were not excluded and might have affected the results. A bigger sample would have given better information on parturient and fetal outcomes. Studies with adjuncts other than opioids could be performed in the future.


  Conclusion Top


Labor epidural analgesia with a higher concentration of fentanyl produces a prolonged and faster onset of analgesia with fewer requirements for top-up boluses.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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