|Year : 2021 | Volume
| Issue : 1 | Page : 53-59
Comparative evaluation of clonidine and dexamethasone as adjuvants to ropivacaine for ultrasound-guided transversus abdominis plane block
Hemlata, Rajesh Kumar Singh, Reetu Verma, Dinesh Singh, Ajay Kumar Chaudhary, Brij Bihari Kushwaha
Department of Anaesthesiology and Critical Care, King George's Medical University, Lucknow, Uttar Pradesh, India
|Date of Submission||08-Jul-2020|
|Date of Decision||08-Aug-2020|
|Date of Acceptance||26-Sep-2020|
|Date of Web Publication||22-Feb-2021|
Department of Anaesthesiology and Critical Care, King George's Medical University, Lucknow - 226 003, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Aim: This study aims to study the effect of addition of clonidine and dexamethasone to ropivacaine for ultrasound-guided TAP block in patients undergoing abdominal surgeries. We primarily compared the quality and duration of postoperative analgesia.
Materials and Methods: This randomized double-blind study was done after taking approval from Institutional Ethical Committee and written informed consent from all the patients. Sixty patients undergoing abdominal surgery under general anesthesia were enrolled in the study and randomly divided into two groups: Group-RC (n = 30) and Group-RD (n = 30). Patients in both the groups were given bilateral ultrasound-guided TAP block at the end of surgery. Patients in Group-RC received 20 ml ropivacaine 0.2% with 75 μg clonidine on each side and patients in Group-RD received 20 ml ropivacaine 0.2% with 4 mg dexamethasone on each side.
Results: Visual analogue scale score for pain was significantly less in Group-RC as compared to Group-RD at all-time intervals (P <.05). Duration of pain relief in Group-RC was significantly greater than in Group-RD (16.50 ± 6.68 vs. 9.67 ± 6.46 h; P = 0.001). Requirement of rescue analgesia was also significantly less in Group-RC as compared to Group-RD (80% vs. 90%; P = 0.014). Except for a higher incidence of nausea in Group-RC, there was no other significant difference in the incidence of complications between the two groups.
Conclusion: Addition of Clonidine (75 μg) to ropivacaine for ultrasound-guided TAP block provides better and prolonged postoperative analgesia as compared to addition of dexamethasone (4 mg) without any significant side-effects.
Keywords: Abdominal surgery, general anesthesia, postoperative analgesia, transversus abdominis plane block, visual analogue scale
|How to cite this article:|
Hemlata, Singh RK, Verma R, Singh D, Chaudhary AK, Kushwaha BB. Comparative evaluation of clonidine and dexamethasone as adjuvants to ropivacaine for ultrasound-guided transversus abdominis plane block. Indian Anaesth Forum 2021;22:53-9
|How to cite this URL:|
Hemlata, Singh RK, Verma R, Singh D, Chaudhary AK, Kushwaha BB. Comparative evaluation of clonidine and dexamethasone as adjuvants to ropivacaine for ultrasound-guided transversus abdominis plane block. Indian Anaesth Forum [serial online] 2021 [cited 2021 May 9];22:53-9. Available from: http://www.theiaforum.org/text.asp?2021/22/1/53/309740
| Introduction|| |
Patients undergoing abdominal surgeries experience significant amount of postoperative pain. Multimodal analgesia technique is utilized for the management of pain observed in the postoperative period. Traditional pain management with opioids increases the incidence of side effects such as postoperative nausea and vomiting, constipation, urinary retention, and excessive sedation resulting in respiratory depression.. Precaution should also be taken with use of nonsteroidal anti-inflammatory drugs (NSAIDs) due to possible adverse effects in elderly patients, patients with renal, cardiac, hematopoietic and liver failure, and in patients with previous history of gastrointestinal bleeding.
Transversus abdominis plane (TAP) block is an effective alternative method of postoperative analgesia for abdominal surgeries. It provides enhanced pain control by blocking the sensory nerves supplying the anterior abdominal wall by injecting local anesthetics (LAs) in a plane between the abdominal muscles. With the help of an ultrasound or anatomical landmark, the neurovascular plane of the anterior abdominal wall (where the nerves from T6 to L1 are located) is identified and LA is injected.
Currently, TAP block is used for the management of pain in the postoperative period after various surgical procedures, namely open/laparoscopic appendectomy, caesarean section, total abdominal hysterectomy, laparoscopic cholecystectomy, open prostatectomy, renal transplantation, and abdominoplasty among others.,, One major limitation of TAP block is that its duration is limited to the duration of effect of the administered LA. Many adjuvant medications have been added to LA to prolong the effect of TAP block. Dexamethasone and Clonidine are amongst such drugs used with ropivacaine and studies have shown proven efficacy of both of these in prolongation of the LA effect. However, we have not come across any study comparing efficacy of these drugs as adjuvants to ropivacaine in TAP block.
Aims and objectives
This study was undertaken to study the effects of clonidine and dexamethasone as adjuvants to ropivacaine for TAP block in patients undergoing abdominal surgeries. Primary objective was to compare the quality and duration of postoperative analgesia. Secondary objectives were to compare the total dose of rescue analgesics required in 24 h and to study the adverse effects if any.
| Materials and Methods|| |
This randomized double-blind study was conducted at our institute over a period of 1 year (October 2018–September 2019) after approval from Institutional Ethical Committee (338/Ethics/18 dated 06/10/2018) and CTRI registration (REF/2019/06/026710). Written informed consent was obtained from all the patients. Sixty patients of either sex aged 18–60 years undergoing abdominal surgery and belonging to American Society of Anesthesiologists (ASA) physical Status I and II were enrolled in this study. Patients with known allergy to LA agents, who received any NSAIDs or opiates 48 h prior to surgery, and with any mental conditions were excluded from the surgery. These patients were randomly allocated to one of the two equal groups with the help of a computer-generated table of random numbers. The study drugs were prepared by a separate anesthesiologist who was not involved in patient management or data collection and data was recorded by another observer who was unaware of group allocation.
All the patients enrolled in the study underwent abdominal surgery under general anesthesia. Patients were admitted 1 day prior to the scheduled surgery. After examination, they were explained about the procedure and written informed consent was taken. No hypnotic was given prior to surgery. On the day of surgery, peripheral IV lines were placed, monitors were attached and baseline parameters (heart rate [HR], blood pressure, oxygen saturation, and electrocardiography) recorded. After preoxygenation for 3 min, anesthesia was induced according to a standard anesthetic protocol using midazolam 0.05 mg/kg, fentanyl 2 mcg/kg and propofol 1.5–2 mg/kg. Tracheal intubation was facilitated by the administration of vecuronium 0.1 mg/kg. Anesthesia was maintained with O2 and nitrous oxide in the ratio of 40:60, inhalational agent and intermittent doses of vecuronium bromide 0.02 mg/kg every 20–25 min. After 30 min of surgery, each patient received 1 g paracetamol infused over 15 min intravenously. The surgical technique was identical in the two groups. During surgery, Ringer lactate solution was administered in maintenance dose. At the end of surgery, patients were given bilateral ultrasound-guided TAP block using 20 ml of study drug on each side as per group allocation.
- Group-RC (n = 30): received 20 ml of ropivacaine 0.2% with 75 μg clonidine on each side
- Group-RD (n = 30): received 20 ml of ropivacaine 0.2% with 4 mg dexamethasone on each side.
Postoperative pain was evaluated using visual analog scale (VAS) score for pain scoring just after extubation, at 1 h, 3 h, 6 h, 12 h, and 24 h postoperatively and recorded. Injection paracetamol 1 g IV was given whenever VAS score was ≥ 4. Time to the first dose of rescue analgesia requirement and total number of doses of rescue analgesia required in first 24 h postoperatively were also noted. Time to the first rescue analgesia given was considered as duration of analgesia.
The statistical analysis was done using SPSS (Statistical Package for Social Sciences) Version 21.0 Statistical Analysis Software (Chicago, USA). The values were represented in number (%) and mean ± standard deviation (SD). To test the significance of two means the Student's t-test was used. To compare the change in a parameter at two different time intervals, paired t-test was used. Other tests used were Chi-square test and Mann–Whitney U-test.
Sample size calculation
Sample size was determined on the basis of variation in VAS score using the formula
Where d = M1 − M2
SD = 0.9
Zα = 1.96, Zβ = 1.64 for 90% power.
The sample size came out to be n = 30 in each group.
| Results|| |
A total of 60 patients were included in the study, 30 patients in each group. Patients in Group-RC were given TAP block with ropivacaine and clonidine and patients in Group-RD were given TAP block with ropivacaine and dexamethasone.
Patients of both the groups were comparable in terms of demographic variables namely age, weight, height, body mass index, gender, and ASA grade [Table 1]. All the baseline hemodynamic variables (HR, systolic blood pressure, diastolic blood pressure, mean arterial pressure [MAP], and oxygen saturation) were comparable between the groups [Table 2].
VAS score for pain in patients of Group-RC was found to be lower than that of the patients in Group-RD at all time intervals and the difference was statistically significant at 1 h, 3 h and 6 h time intervals [Table 3].
|Table 3: Comparison of visual analogue scale scores at different time intervals|
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Of 60 patients enrolled in the study, nine patients (15%) did not require any rescue analgesia over the period of observation of 24 h, 32 patients (53.3%) required single dose of rescue analgesia, 14 (23.3%) required two doses whereas five patients (8.3%) required three doses of rescue analgesia. All the five patients who required three doses of rescue analgesia belonged to Group RD. In Group RC, 24 patients (80%) required rescue analgesia as compared to 27 patients (90%) in group RD. The difference was found to be statistically significant [Table 4].
The mean duration of analgesia, i.e., time to requirement of 1st dose of rescue analgesia was more in Group-RC as compared to Group-RD (16.50 ± 6.68 vs. 9.67 ± 6.46 h) and the difference was statistically significant (P = 0.001) [Table 5]. Patients of group RC had higher rate of complications as compared to group RD but the difference between the groups was not statistically significant except for the incidence of nausea [Table 6].
|Table 5: Comparison of time to first dose of rescue analgesia (h) (n=51)|
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Mean HR of patients of Group-RC was found to be higher as compared to Group-RD at all the periods of observations. However, the difference was not found to be statistically significant except at time interval just after extubation [Figure 1]. The mean HR of both the groups remained within normal limits. MAP of patients of Group RD was found to be higher than the patients of Group RC at all periods of time and the difference was statistically significant just before TAP block, just after TAP block, at 1 h, 3 h and 24 h [Figure 2]. However, the values were within normal limits at all time intervals.
|Figure 2: Comparison of mean arterial pressure at different time intervals|
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| Discussion|| |
There is an increasing trend in the use of TAP block for postoperative pain relief as a part of multimodal analgesia. TAP block reduces postoperative pain scores, decreases opioid consumption, allows for early ambulation and discharge from hospital after various abdominal surgeries.
Bupivacaine and ropivacaine are the LAs commonly used for TAP block. Ropivacaine was chosen as the LA for this study, as it can provide prolonged postoperative analgesia with a greater margin of safety for cardiotoxicity and neurotoxicity. Ropivacaine 0.2% was used as it is generally accepted as the optimal concentration required for postoperative analgesia in different regional anesthesia techniques.
One major limitation of TAP block is its duration which is limited to the duration of effect of the administered LAs. Both clonidine and dexamethasone are adjuvants known to improve the duration and efficacy of ropivacaine when used for peripheral nerve blocks. Clonidine is one of the frequently used adjuvants to LAs. It is an α-2 agonist and has anti-hypertensive effect. α-2 receptors are present in large number in the central nervous system which is responsible for clonidine's effect on centrally mediated sedation and analgesia. Peripheral action of clonidine is less obvious as α-2 receptors are not present on axons of normal peripheral nerves. One mechanism can be that Clonidine blocks conduction of C and A-delta fibers and increases conduction of potassium in in vitro neurons causing conduction block. Second, due to the local vasoconstriction caused by clonidine, the vascular uptake of LA from around the neurons is reduced.
Although it is widely believed that clonidine improves quality and duration of LA block when used as an adjuvant for peripheral nerve blocks, the benefits are less clear. Murphy et al. did an analysis of randomized trials that used a variety of adjuvants like clonidine when added to LAs for brachial plexus block. In the data from six trials (349 patients), it was concluded that clonidine in dose up to 150 mcg prolongs postoperative analgesia and has minimal side-effects. McCartney et al. did a review of clonidine used as an adjuvant to LA in 27 studies (1385 patients) and concluded that clonidine prolongs postoperative analgesia when used with intermediate acting LAs but not with long acting LAs. A meta-analysis of 20 randomized control trials done by Pöpping et al. found that clonidine is a useful adjuvant to LAs for peripheral nerve block. The duration of postoperative analgesia which is defined as time till first analgesic request was increased by clonidine by 2 h. In a study done by Singh et al., addition of clonidine to bupivacaine in single shot TAP block for caesarean section reduced the requirement of postoperative rescue analgesia and prolonged analgesia by 10–12 h. In a study done by Hutschala et al., it was found that addition of clonidine to bupivacaine plus epinephrine prolongs and enhances brachial plexus blockade. Casati et al., in their study found that addition of 1 μg/kg of clonidine to 0.75% ropivacaine increases the time of analgesia in lower limb surgery.
Dexamethasone is also known to improve the analgesic efficacy of LA used for peripheral nerve blocks. The mechanism of analgesia induced by corticosteroids can be due to their anti-inflammatory or immuno-suppressive properties or mainly due to their direct effect on nerve membrane. Perineural vasoconstriction induced by corticosteroids via specific glucocorticoid receptors and modulation of the effects of potassium channels on the cells leads to slower absorption of LA resulting in their prolonged action.,, Various studies have been done previously which show increase in postoperative analgesia with dexamethasone added to ropivacaine and other LA. Kartalov et al. studied the adjuvant effect of 4 mg dexamethasone with 0.5% ropivacaine in unilateral inguinal hernia repair in 90 patients divided randomly in three groups of 30 patients each. They demonstrated a decrease in postoperative pain score and 24-h reduction of morphine consumption with the addition of dexamethasone. Kim et al., in their study, found that the number of subjects who were pain-free during the 48 h postoperative period in children undergoing orchiopexy was significantly greater (P = 0.001) in group receiving dexamethasone 0.1 mg/kg as an adjunct to 1.5 ml/kg of 0.15% ropivacaine (19 of 38;50%) than in group receiving only ropivacaine (4 of 37;10.8%) for caudal analgesia. Sharma et al. had also done a prospective, double blind controlled trial to study the effect of addition of dexamethasone to ropivacaine on postoperative analgesia in ultrasonography-guided TAP block for inguinal hernia repair. It was concluded that addition of dexamethasone to ropivacaine in ultrasound-guided TAP block significantly reduces postoperative pain and prolongs the duration of postoperative analgesia, thereby reducing analgesic consumption.
Although there are previous studies which have been done to compare the efficacy of clonidine and dexamethasone as adjuvants to bupivacaine for TAP block and also there are previous studies comparing addition of these two drugs to ropivacaine in blocks other than TAP blocks, however we have not come across any study comparing efficacy of these two drugs as adjuvants to ropivacaine for TAP block., This study was done to compare the efficacy of clonidine and dexamethasone added to ropivacaine for TAP block. We used 0.2% ropivacaine along with 75 μg of clonidine in Group-RC and 0.2% ropivacaine with 4 mg dexamethasone in Group-RD. Dose of clonidine (75 μg) was based on the study done by Ali et al. in which they used 75 μg of clonidine as an adjuvant to 0.50% ropivacaine for supraclavicular brachial plexus block for upper limb surgeries and found that clonidine provides better postoperative analgesia without significant side-effects. Dose of dexamethasone in our study was based on the study done by Kartalov et al. who used 4 mg dexamethasone as an adjuvant to 0.5% ropivacaine in TAP block for unilateral inguinal hernia repair and found better postoperative pain relief with the combination.
In our study, the addition of clonidine as an adjuvant to ropivacaine provided significantly better postoperative analgesia and for a longer time as compared to addition of dexamethasone to ropivacaine. VAS scores in Group-RC was less as compared to Group-RD at all time intervals in our study. Overall requirement of rescue analgesia was also significantly less in group-RC than in Group-RD. Further, the duration of analgesia (mean time to requirement of 1st dose of rescue analgesia) was 6.83 h longer in the group-RC than in group-RD (16.50 ± 6.68 vs. 9.67 ± 6.46 h) and this difference was significant (P = 0.001).
There are previous studies comparing addition of these two drugs to ropivacaine in blocks other than TAP blocks. Nasir et al. had done a study to evaluate the efficacy of adding dexamethasone, clonidine, or combination of both as adjuvant to ropivacaine on duration of ultrasound guided supraclavicular brachial plexus block for postoperative analgesia. They concluded that clonidine, but not dexamethasone, prolongs the duration of ropivacaine induced supraclavicular brachial plexus nerve block. This finding is somewhat similar to our study in which we found more prolonged postoperative analgesia with clonidine than dexamethasone when added to ropivacaine in TAP block.
However, the findings of our study are not in agreement with that of the study done by Raghukumar and Majigoudar. They had done the study in 60 patients undergoing LSCS receiving USG guided TAP block, divided randomly in three groups of 20 patients each. They found that the pain scores were similar in the two groups (bupivacaine plus clonidine and bupivacaine plus dexamethasone as compared to plain bupivacaine) at different time intervals up to 12 h and also requirement of 1st dose of rescue analgesia was comparable in the two groups, both requiring 1st dose of rescue analgesia in the first 2 h. This difference may be due to the use of lower dose of clonidine (50 μg) in their study as compared to our study (75 μg). Moreover, they had compared these two drugs as adjuvant to bupivacaine rather than Ropivacaine which is longer acting. Similarly, Yadhuraj et al. had undertaken a study to compare the analgesic efficacy of dexamethasone 8 mg and clonidine 1 μ/kg added to 0.5% bupivacaine for supraclavicular brachial plexus block using USG technique and concluded that dexamethasone is a better adjuvant compared to clonidine.
Clonidine is associated with some systemic side-effects such as bradycardia, hypotension, and sedation at higher doses but we did not encounter it in our study as we used a low dose of clonidine in our study (75 μg on either side). Kanazi et al., studied the effect of low dose clonidine on bupivacaine spinal anesthesia and found prolonged duration of motor and sensory block with preserved hemodynamic stability. Baj et al. used 60 μg clonidine as an adjuvant with 0.75% ropivacaine in supraclavicular brachial plexus block and found prolonged analgesia without any significant hypotension or bradycardia. Similarly, all the patients in our study were hemodynamically stable throughout the study and there were no significant changes in HR and blood pressure requiring any intervention at any point of time. Patients in Group RC showed higher rate of complications as compared to those of Group RD such as nausea (30% vs. 6.7%), vomiting (13.3% vs. 6.7%), and respiratory depression (3.3% vs. 0%) but the difference between the rates of complication was not statistically significant except for nausea.
This was a single-centric study with relatively less number of patients. Larger multi-centric studies are needed in future to reveal significant between-group differences in clinical efficacy data and detect uncommon adverse effects. Lack of a control group was another limiting factor in our study. The use of VAS score for assessing pain was also a limitation of our study as it is a subjective test for evaluating outcome and is subject to bias.
| Conclusion|| |
From our study, we concluded that both clonidine and dexamethasone may be considered as safe and effective adjuvants to ropivacaine for ultrasound-guided TAP block, clonidine being much more beneficial. Addition of Clonidine (75 μg) provided better and prolonged postoperative analgesia as compared to addition of dexamethasone (4 mg).
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]