A comparison of the analgesic efficacy and safety of epidural bupivacaine with fentanyl and ropivacaine with fentanyl in abdominal surgery
Kumar Lakshmi MD , Meera Prabhaja Kumari, Rajan Sunil
Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences and Research Centre, Kochi, Kerala, India
Date of Submission 29-Nov-2014
Date of Acceptance 19-Jun-2015
Kumar Lakshmi
Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences and Research Centre, Kochi, 682 041 Kerala
Epidural bupivacaine remains the most widely used local anesthetic for postoperative pain relief, but ropivacaine is increasingly being used as it has less cardiac toxicity.
To compare the analgesic efficacy and safety of epidural bupivacaine with fentanyl versus ropivacaine with fentanyl during abdominal surgery and in the immediate postoperative period.
One hundred patients undergoing abdominal surgeries under general anesthesia with supplementary epidural analgesia were studied. Group B received an epidural infusion of 0.2% bupivacaine with fentanyl 2 mcg/ml at 6 ml/h intraoperatively and 0.1% bupivacaine with fentanyl 2 mcg/ml at 6 ml/h postoperatively. Group R received an epidural infusion of 0.2% ropivacaine with fentanyl 2 mcg/ml at 6 ml/h intraoperatively and 0.1% ropivacaine with fentanyl 2 mcg/ml at 6 ml/h postoperatively.
Intraoperative and postoperative heart rate and mean arterial pressure in both groups were comparable. Pain scores were significantly higher in group B postoperatively up to 24 h. The number of epidural topups required was comparable intraoperatively, but in the postoperative period, group B needed significantly more number of epidural topups. The requirement of rescue analgesia showed no significant difference intraoperatively and postoperatively between groups.
An epidural infusion of ropivacaine 0.2% with fentanyl provides better intraoperative and postoperative analgesia compared with bupivacaine 0.2% with fentanyl.
Keywords: bupivacaine, epidural analgesia, ropivacaine
Lakshmi K, Kumari MP, Sunil R. A comparison of the analgesic efficacy and safety of epidural bupivacaine with fentanyl and ropivacaine with fentanyl in abdominal surgery. Ain-Shams J Anaesthesiol 2015;8:623-7
Lakshmi K, Kumari MP, Sunil R. A comparison of the analgesic efficacy and safety of epidural bupivacaine with fentanyl and ropivacaine with fentanyl in abdominal surgery. Ain-Shams J Anaesthesiol [serial online] 2015 [cited 2023 Jan 27];8:623-7. Available from: http://www.asja.eg.net/text.asp?2015/8/4/623/172755
Among the most commonly used pain-relieving techniques, epidural local anesthetic or local anesthetic/opioid combinations are the most effective in providing pain relief after major surgical procedures. Evidence that epidural analgesia enhances the recovery process would lead to wider adoption of this method and better quality of care for surgical patients.
Successful selection of a drug for epidural anesthesia requires an understanding of the local anesthetic potency and duration as well as estimation of postoperative analgesia requirements. Although bupivacaine remains the most widely used long-acting local anesthetic, it can impair myocardial performance and conduction when systemic toxicity occurs. Ropivacaine is increasing being used as an epidural agent as it has less impact on cardiac conduction and frequency of arrhythmias than other local anesthetics at blood levels producing systemic toxicity. It provides a less intense motor block with a slightly shorter duration of action compared with bupivacaine.
Patients and methods
As no publication is available with the combination of drug and dosage used in this study, this can be considered a pilot study. This study was designed as a prospective, randomized, and nonblinded comparative study. Block randomization was used for the assignment of patients into two groups.
Sample size was selected on the basis of Cohen's d of published data. Cohen's d (mean of group 1-mean of group 2)/SD is used frequently to estimate sample sizes. A lower Cohen's d indicates a need for larger sample sizes and vice versa. As the total number of patients available during a period of one and a half years was approximately equal to 200, 100 patients were included in the study.
The study was carried out at the Amrita Institute of Medical Sciences and Research Centre, Kochi, India, from March 2012 to January 2014. After obtaining approval from the hospital ethical committee and informed consent from the patients, 100 ASA I and II patients undergoing elective abdominal surgeries under general anesthesia with supplementary epidural analgesia were recruited into the study. Patients were allocated randomly to two equal groups: group B (bupivacaine group) and group R (ropivacaine group).
Patients with coagulopathy or on anticoagulant therapy, skin infection at the injection site, high intracranial pressure, history of previous spinal surgery, spinal anomaly, and those on mechanical ventilation were excluded.
All patients were instructed to withhold solids 6 h before and clear liquids 2 h before surgery as per the standard guidelines for surgery.
Patients without clinical evidence of bowel obstruction received alprazolam 0.25 mg, metoclopramide 10 mg, and ranitidine 150 mg orally the previous night and on the morning of surgery.
All patients received anesthesia following a standardized anesthesia protocol. On arrival at the operation theater, a large bore intravenous cannula was inserted under local anesthesia. Preinduction monitors such as a noninvasive blood pressure monitor, ECG, and a pulse oximeter were attached. All patients were preloaded with 10 ml/kg body weight of Ringer's lactate or normal saline before induction as per protocol.
An epidural catheter was inserted under sterile aseptic conditions into the T8 -T12 level. Epidural placement of the catheter was confirmed with a test dose (3 ml of 2% lignocaine with 1 in 200 000 adrenaline) before induction of general anesthesia. The baseline heart rate (HR) and blood pressure were noted and after 3 min of the epidural test dose.
All patients received glycopyrrolate 0.2 mg, fentanyl 2 mcg/kg, and midazolam 0.4 mg/kg intravenously. Induction of anesthesia was achieved by titrated doses of propofol up to 2.5 mg/kg intravenously. Endotracheal intubation was facilitated after the administration of suxamethonium 1.5 mg/kg or vecuronium 0.1 mg/kg.
The patients in group B received an epidural infusion of 0.2% bupivacaine with fentanyl 2 mcg/ml at the rate of 6 ml/h intraoperatively and 0.1% bupivacaine with fentanyl 2 mcg/ml at 6 ml/h postoperatively.
The patients in group R received an epidural infusion of 0.2% ropivacaine with fentanyl 2 mcg/ml at the rate of 6 ml/h intraoperatively and 0.1% ropivacaine with fentanyl 2 mcg/ml 6 ml/h postoperatively.
HR, systolic, and diastolic and mean arterial pressures (MAP) were monitored every 5 min intraoperatively, but the data collected at 5, 15, 30, and 60 min after epidural insertion, followed by hourly readings until the end of surgery were only statistically analyzed. If the HR and MAP decreased by more than 20% from baseline, the infusion rate was reduced to 4 ml/h. The local anesthetic infusion was stopped at MAP less than 50 mmHg. Similarly, an increase in MAP and HR was treated with an increase in the local anesthetic infusion to 8 ml/h. Significant increases in HR and blood pressure were treated with a bolus of 8 ml of 0.2% bupivacaine with 2 mcg/ml or with 8 ml of 0.2% ropivacaine with 2 mcg/ml fentanyl according to the group. If the HR and blood pressure were not adequately controlled within 15 min of local anesthetic topup, 1 mcg/kg fentanyl bolus was used as a rescue analgesic. The total volume of local anesthetic used in each group and the total rescue analgesia were calculated in each group.
At the end of surgery, neuromuscular blockade was reversed with neostigmine 2.5 mg and glycopyrrolate 0.4 mg intravenously. Following extubation, the patients were shifted to the ICU. The epidural infusion of drugs was continued at the analgesic dose in the ICU. The HR and blood pressure were recorded on arrival in the ICU and were documented every fourth hour. For the assessment of postoperative pain, the visual analogue scale (VAS) was used, with 0 representing no pain and 10 representing the worst pain imaginable. The first postoperative VAS score was assessed when the patient was awake, and then every fourth hour for 24 h. If the VAS score was at least 5, 8 ml of 0.1% bupivacaine with 2 mcg/ml fentanyl or 8 ml 0.1% ropivacaine with 2 mcg/ml fentanyl was administered as per the patient group. Any lack of response to pain was treated with intravenous fentanyl 1 mcg/kg as a rescue analgesic. The timing, frequency, and total amount of rescue analgesia were noted.
To test the statistical significance of the difference in the variables from the preoperative to the postoperative period, a paired t-test was used. The Student t-test was used to test the statistical significance of the difference in the mean values. Appropriate adjustment was performed if the basal preoperative values were statistically different between the groups. Intraoperatively, HR and MAP were analyzed using a Paired t-test. The median and interquartile range of postoperative VAS scores were calculated and compared using the Mann-Whitney U-test. The level of significance was P value less than 0.05. Demographic data (age, weight) were compared using one-way analysis of variance and sex distribution was compared using the c2 -test.
The group comparison showed no statistically significant difference in the distribution among the two groups with respect to age, sex, weight, ASA status, and types of surgeries [Table 1]. The duration of surgery and the total volume of local anesthetic used intraoperatively were comparable between the groups, but the volume of local anesthetic used postoperatively was significantly higher in group B (155 vs. 149 ml, [Table 2].
Table 1 Comparison of demographic data and types of surgeries
Table 2 Comparison of the duration of surgery and the volume of local anesthetics used in the intraoperative and postoperative periods
Compared with the baseline, the mean HR was always lower in group B at all time intervals, except at 300, 360, 420 min intraoperatively, but there was no significant difference between the groups [Table 3]. Similarly, the postoperative HR in both groups were comparable [Table 4].
Table 3 Comparison of the mean intraoperative heart rates
Table 4 Comparison of the mean postoperative heart rates
As both intraoperative and postoperative baseline MAP in group B and group R were not comparable, percentage difference at various intervals from the baseline value was used for analysis. It was shown that both the groups had comparable MAP intraoperatively and postoperatively [Table 5] and [Table 6].
On comparing the postoperative pain scores between groups B and R, it was found that the median and interquartile range of VAS scores at different time points up 24 h were significantly higher in group B [Figure 1], [Table 7].
Figure 1: Postoperative visual analogue scale scores
Table 5 Comparison of the mean of percentage differences in intraoperative mean arterial pressure from baseline at various time intervals
Table 6 Comparison of percentage differences in the mean postoperative heart rate from baseline
Table 7 Comparison of postoperative visual analogue scale scores
Comparison of the number of epidural topups required was not statistically significant intraoperatively between groups [Table 8], but in the postoperative period, group B needed significantly more number of epidural topups (P < 0.001, [Table 9], in line with a higher VAS score in group B. A comparison of the requirement of rescue analgesia (fentanyl bolus) between the groups showed no statistical significance intraoperatively and postoperatively [Table 10]).
Table 8 Comparison of intraoperative epidural topups between groups
Table 9 Comparison of postoperative epidural topups between groups
Table 10 Comparison of the rescue analgesic (fentanyl) dose between groups
Epidural catheterization is a standard practice today for analgesia and anesthesia in major abdominal surgery [1] . Among the most commonly used pain-relieving techniques, there is evidence that the epidural local anesthetic or local anesthetic-opioid combinations are the most effective in providing pain relief after major surgical procedures [1],[2],[3],[4] .
Bupivacaine remains the most widely used long-acting local anesthetic. It is used in 0.5 and 0.75% concentrations for surgical anesthesia, but analgesic techniques can be performed with concentrations ranging from 0.125 to 0.25%. Ropivacaine is used in 0.5-1% concentrations for surgical anesthesia and 0.1-0.3% concentrations for analgesia. In an individual patient, the clinical effect of ropivacaine is difficult to separate from a similar effect from bupivacaine, although it appears to produce less motor block and has a slightly shorter duration of action than bupivacine.
Epidurally administered opioids produce segmental analgesia [5] and improve the quality and duration of sensory block produced by local anesthetics, which may explain the better pain relief compared with intravenous analgesia [6] .
We chose the bupivacaine and fentanyl combination in group B on the basis of the observations by Rimaitis et al. [7] , where they reported fewer side effects compared with a bupivacaine and morphine mixture or opioid or local anesthetic alone. Bupivacaine was used as a 0.1% solution with fentanyl 2 mcg/ml as an epidural infusion as there have been no reports of significant breakthrough pain and complications such as significant hypotension and motor block with this dose in any previous studies [7],[8],[9] .
On the basis of published data reported by Priestly et al. [10] showing adequate pain relief and minimal side effects with epidural fentanyl 2 mcg/ml along with a local anesthetic agent in patients undergoing coronary artery bypass surgery, we chose the present dose. A higher dose of fentanyl was associated with an increase in dose-dependent complications such as hypotension, pruritus, respiratory depression, and sedation.
It is a common understanding and observation that reduction in pain following postoperative anesthesia should correlate with the corresponding changes in the hemodynamic parameters. Lower, but normotensive arterial blood pressure and HR values in the epidural group might be a result of sympathetic blockade and suppressed stress response [11],[12],[13] .
The significantly higher requirement of local anesthetic in the immediate postoperative period in the bupivacaine group (P < 0.001) in our study could be because of the higher pain scores in that group. The comparable intraoperative hemodynamics with subsequent different pain scores could have been because of the fact that the intraoperative HR and blood pressure are dependent on many factors other than just adequate analgesia. Use of inhalation agents, b blockers, intravascular fluid status, body temperature, or factors that affect venous return such as the use of abdominal packs, retractors, and even the position of the patient could influence the intraoperative HR and blood pressure.
The study by Dahl et al. [4] showed that epidural 0.2% ropivacaine was almost identical to 0.2% bupivacaine with respect to the onset, quality, and duration of sensory blockade for initiation and maintenance of labor analgesia. However, the present study showed better postoperative analgesia with respect to the quality and duration of sensory blockade with epidural ropivacaine with fentanyl. The dissimilar results could be because the study populations in both studies were different and intraoperative use of intravenous opioids in our study might have influenced the postoperative pain scores.
It is concluded that ropivacaine 0.2% with fentanyl administered as an epidural infusion provides better intraoperative and postoperative analgesia with hemodynamic stability in abdominal surgery compared with bupivacaine 0.2% with fentanyl.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]
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Lakshmi K
Kumari MP
Sunil R
bupivacaine
ropivacaine
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