Background: Regional anesthesia is a preferred technique for various surgical procedures due to its safety, cost-effectiveness, and superior postoperative analgesia. The addition of adjuvants to local anesthetics in epidural anesthesia can enhance block quality, prolong analgesia, and provide sedation without significant respiratory depression. Dexmedetomidine and clonidine, both α2-adrenergic agonists, have shown promise as epidural adjuvants. Aim: To evaluate and compare the efficacy of epidural clonidine and dexmedetomidine as adjuvants to bupivacaine in providing postoperative analgesia in patients undergoing abdominal and vaginal hysterectomies. Materials and Methods: A randomized, comparative clinical study was conducted on 100 patients aged 44–65 years, classified as ASA grade I and II, scheduled for hysterectomy. Patients were randomly allocated into two groups of 50 each. Group A received 17 ml of 0.5% bupivacaine with clonidine (2 µg/kg), and Group B received 17 ml of 0.5% bupivacaine with dexmedetomidine (1.5 µg/kg) via epidural route. Parameters assessed included onset time of sensory and motor block, duration of analgesia, hemodynamic changes, sedation scores, and incidence of side effects. Results: Both groups were comparable in demographic and surgical characteristics (p > 0.05). The dexmedetomidine group showed a significantly faster onset of sensory and motor block (p < 0.001) and a longer duration of analgesia (p < 0.001) compared to the clonidine group. The time to two-segment regression, sensory regression to S1, and time to first epidural top-up were significantly prolonged with dexmedetomidine. Hemodynamic parameters and sedation scores were comparable, except for a lower heart rate at 120 minutes in the dexmedetomidine group (p < 0.05). The incidence of side effects was similar in both groups and not statistically significant. Conclusion: Dexmedetomidine, when used as an epidural adjuvant to bupivacaine, provides a faster onset of block and prolonged postoperative analgesia compared to clonidine, without an increased incidence of adverse effects. It can be considered a superior alternative for enhancing perioperative analgesia in hysterectomy patients.
Regional anesthesia continues to be a highly effective, safe, and cost-efficient technique for surgical procedures. It not only provides excellent intraoperative conditions through optimal muscle relaxation but is also widely preferred for delivering superior postoperative analgesia. Among regional techniques, epidural anesthesia holds a unique advantage as it allows precise titration of anesthetic drugs to achieve the desired surgical plane and offers the flexibility of continuous postoperative pain management through catheter-based delivery.
Despite these advantages, patients often experience significant anxiety and apprehension related to surgery under regional anesthesia. The fear of being awake in the unfamiliar and dynamic environment of the operating theater, coupled with the noise from surgical equipment, contributes to their psychological discomfort. To address this limitation, various adjuvants with sedative and analgesic properties have been explored to supplement local anesthetics. Several agents, including opioids such as fentanyl and morphine, NMDA receptor antagonists like ketamine, and α2-adrenergic agonists such as clonidine and dexmedetomidine, have been studied extensively as additives in regional anesthesia techniques. Each of these adjuvants possesses distinct pharmacological profiles and varying side effect patterns but share the common benefit of enhancing analgesia and prolonging the duration of anesthesia.¹–⁸
Dexmedetomidine, a highly selective α2-adrenergic agonist, exhibits greater receptor affinity compared to clonidine. As a result, clonidine typically requires a higher dose (1.5–2 times that of dexmedetomidine) to achieve comparable clinical effects.⁹,¹⁰ Both dexmedetomidine and clonidine offer the additional benefit of producing sedation without significant respiratory depression, making them particularly attractive in regional anesthesia.
The use of these adjuvants not only augments the action of local anesthetics, thereby reducing the total anesthetic requirement, but also contributes to better hemodynamic stability and decreased oxygen demand during surgery.¹¹,¹²
In light of these advantages, the present study was undertaken to compare the efficacy of epidural clonidine and dexmedetomidine as adjuvants in providing postoperative analgesia in patients undergoing abdominal and vaginal hysterectomies. The study aimed to evaluate differences in block characteristics, duration of postoperative analgesia, hemodynamic stability, and side effect profiles between the two agents.
Aim
To evaluate and compare the efficacy of epidural clonidine and dexmedetomidine as adjuvants to bupivacaine in providing postoperative analgesia in patients undergoing abdominal and vaginal hysterectomies.
Objectives
Source of Data:
The study was conducted at the Department of Anesthesiology, Fathima Institute of Medical Sciences, Ramarajupalli, Pulivendula Road, Kadapa – 516003, Andhra Pradesh, India.
January 2023 to June
Study Period:
2025 (18 months).
Study Design:
A prospective, randomized, comparative clinical study.
Ethical Considerations:
Approval was obtained from the Institutional Ethics Committee of Fathima Institute of Medical Sciences prior to commencing the study. Written informed consent was obtained from all participants after explaining the procedure in detail.
Sample Size:
A total of 100 patients scheduled for abdominal and vaginal hysterectomies, aged between 44 and 65 years and classified as ASA physical status grade I or II, were enrolled and randomly divided into two groups of 50 each.
Inclusion Criteria:
Exclusion Criteria:
Methodology:
A thorough pre-anesthetic evaluation was conducted one day before surgery. Systemic examinations and necessary laboratory investigations were performed, and the epidural anesthesia procedure was explained to the patients. Patients were advised overnight fasting and premedicated on the day of surgery with oral ranitidine 150 mg and alprazolam 0.5 mg.
In the operating theater, all equipment was checked, and emergency drugs and resuscitation equipment were prepared. An 18G intravenous cannula was secured, and standard ASA monitoring (heart rate, blood pressure, oxygen saturation) was established. Baseline vital parameters were recorded.
The epidural space was identified at the L2-L3 interspace using an 18G Tuohy needle and the loss of resistance technique. An epidural catheter was advanced 3–4 cm into the epidural space and secured. A test dose of 3 ml of 2% lignocaine with adrenaline (1:200,000) was administered to rule out intrathecal or intravascular placement.
Patients were then positioned supine. The study drugs were administered through the epidural catheter as follows:
Patients undergoing vaginal hysterectomy were shifted to lithotomy position after 15 minutes.
Parameters Recorded:
Sensory block level was assessed using the bilateral cold swab method, and motor block was evaluated with the modified Bromage scale. The time to reach T10 sensory level, time to maximum sensory block, onset time for complete motor block (Bromage 3), duration of analgesia, and regression times were recorded. Hemodynamic parameters (heart rate, blood pressure, SpO₂) and sedation (Ramsay sedation scale) were monitored at 1, 5, 10, 20, and 30 minutes, then every 15 minutes up to 60 minutes, and every 20 minutes thereafter until 120 minutes. The need for epidural top-ups, two-segment regression time, time to Bromage 1 regression, and sensory regression to S1 were also noted. Adverse events like hypotension (systolic BP drop >20%), treated with IV ephedrine (6 mg boluses), and bradycardia (HR <50 bpm), treated with IV atropine (0.3 mg), were recorded.
Statistical Analysis:
Data were expressed as mean ± standard deviation (SD). Intergroup comparisons were performed using independent two-tailed Student’s t-test. A p-value of <0.05 was considered statistically significant.
Table 1: Comparison of baseline parameters between the two groups
Parameters |
Group A (N = 50) |
Group B (N = 50) |
T value |
P value |
Age (years) |
49.8 ± 4.6 |
50.2 ± 5.1 |
0.412 |
0.681 |
Weight (kg) |
65.1 ± 4.5 |
66.1 ± 6.5 |
1.285 |
0.202 |
Duration of surgery (min) |
114 ± 10.2 |
113 ± 9.9 |
0.137 |
0.892 |
Parameters |
Group A (N = 50) |
Group B (N = 50) |
Chi-square |
P value |
ASA grade I |
23 (46%) |
20 (40%) |
0.568 |
0.451 |
ASA grade II |
27 (54%) |
30 (60%) |
||
Abdominal hysterectomy |
26 (52%) |
25 (50%) |
0.042 |
0.838 |
Vaginal hysterectomy |
24 (48%) |
25 (50%) |
Table 2: Comparison of sensory and motor block parameters
Variables |
Group A |
Group B |
T value |
P value |
Time for onset of sensory and motor block |
||||
Time to T10 sensory level (min) |
12.9 ± 4.3 |
8.6 ± 2.2 |
5.590 |
<0.001 |
Time to maximum sensory block (min) |
19.4 ± 5.8 |
11.5 ± 2.4 |
8.090 |
<0.001 |
Onset time to Bromage 3 (min) |
24.3 ± 7.0 |
16.1 ± 3.6 |
6.880 |
<0.001 |
Mean SpO₂ (%) |
||||
Preoperative |
96.3 ± 1.4 |
95.9 ± 1.1 |
0.965 |
0.336 |
Intraoperative |
96.0 ± 0.7 |
96.1 ± 0.6 |
0.251 |
0.802 |
Postoperative block parameters |
||||
Time to 2-segment regression (min) |
307 ± 35 |
422 ± 28 |
17.560 |
<0.001 |
Time to Bromage 1 (min) |
345 ± 31 |
453 ± 30 |
17.730 |
<0.001 |
Time to sensory regression to S1 (min) |
374 ± 27 |
482 ± 27 |
19.100 |
<0.001 |
Time to epidural top-up (min) |
393 ± 25 |
501 ± 22 |
18.100 |
<0.001 |
Table 3: Highest sensory level achieved
Sensory level |
Group A |
% |
Group B |
% |
Chi-square |
P value |
T4 |
18 |
36% |
24 |
48% |
1.020 |
0.313 |
T6 |
32 |
64% |
26 |
52% |
||
Total |
50 |
100% |
50 |
100% |
Table 4: Incidence of side effects
Side effect |
Group A |
% |
Group B |
% |
Chi-square |
P value |
Nausea |
6 |
12% |
5 |
10% |
0.125 |
0.724 |
Shivering |
5 |
10% |
3 |
6% |
0.201 |
0.654 |
Dry mouth |
4 |
8% |
9 |
18% |
1.450 |
0.228 |
Hypotension |
5 |
10% |
7 |
14% |
1.550 |
0.213 |
Bradycardia |
3 |
6% |
6 |
12% |
2.880 |
0.090 |
Table 5: Comparison of hemodynamic and sedation parameters
Parameters |
Group A |
Group B |
T value |
P value |
SBP (mmHg) |
||||
Preoperative |
125.2 ± 6.1 |
126.0 ± 3.5 |
1.350 |
0.180 |
120 min |
112.2 ± 7.9 |
110.4 ± 5.0 |
1.340 |
0.185 |
DBP (mmHg) |
||||
Preoperative |
78.8 ± 5.0 |
80.3 ± 5.7 |
1.790 |
0.077 |
120 min |
68.0 ± 4.5 |
67.2 ± 2.3 |
1.160 |
0.249 |
MAP (mmHg) |
||||
Preoperative |
93.9 ± 4.2 |
95.1 ± 4.2 |
1.910 |
0.058 |
120 min |
82.2 ± 5.3 |
81.3 ± 2.1 |
1.140 |
0.257 |
HR (bpm) |
||||
Preoperative |
74.1 ± 6.1 |
72.4 ± 3.7 |
1.570 |
0.121 |
120 min |
72.4 ± 6.4 |
70.1 ± 4.6 |
2.010 |
0.046* |
RSS |
||||
Preoperative |
1.0 ± 0 |
1.0 ± 0 |
— |
— |
120 min |
3.0 ± 0 |
2.9 ± 0.2 |
1.820 |
0.071 |
*P < 0.05 (significant)
The baseline characteristics, including age, weight, duration of surgery, ASA grading, and type of surgery, were comparable between the two groups, with no statistically significant differences. The onset of sensory and motor block was significantly faster in the dexmedetomidine group compared to the clonidine group. Similarly, parameters such as time to T10 sensory level, time to maximum sensory block, and onset time to achieve Bromage 3 score were all shorter in the dexmedetomidine group (p < 0.001). Postoperative block characteristics, including time to two-segment regression, time to reach Bromage 1, time for sensory regression to S1, and time to first epidural top-up, were significantly prolonged in the dexmedetomidine group, indicating longer analgesia duration (p < 0.001).
The highest sensory level achieved was similar between both groups without significant differences.
The incidence of side effects (nausea, shivering, dry mouth, hypotension, and bradycardia) was comparable across groups, with no significant differences. Hemodynamic parameters (SBP, DBP, MAP) and Ramsay sedation scores were similar between groups both preoperatively and at 120 minutes postoperatively, except for heart rate, which was significantly lower in the dexmedetomidine group at 120 minutes (p < 0.05).
In the present study, the demographic characteristics, including mean age, weight, duration of surgery, ASA physical status, and type of surgical procedure (abdominal or vaginal hysterectomy), were comparable between the two groups. The mean age was 49.6 years in the clonidine group and 50 years in the dexmedetomidine group, with no statistically significant difference (p > 0.05). Similar age distributions have been reported by Bajwa SJ et al., underscoring the demographic consistency and generalizability of our findings.
The mean weight was also comparable between the groups (64.8 kg vs. 66.4 kg), echoing the results of Bajwa SJ et al., who highlighted that patient weight does not significantly influence the efficacy of epidural adjuvants when appropriately dosed. The mean duration of surgery in both groups was around 113 minutes, similar to Bajwa SJ et al., indicating uniformity in surgical exposure time and minimizing potential confounding effects related to surgical duration.
The distribution of ASA physical status grades was similar, ensuring that comorbid conditions did not bias the analgesic outcomes. Additionally, the proportion of patients undergoing abdominal versus vaginal hysterectomy was equal, further supporting the internal validity of the study.
One of the primary outcomes examined was the time to onset of sensory block. Our findings revealed a significantly faster onset in the dexmedetomidine group compared to the clonidine group (p < 0.05). These results align with those reported by Shaikh SI et al., who observed onset times of 8.7 minutes for dexmedetomidine and 11.23 minutes for clonidine. Saravana Babu MS et al. and Kaur S et al. also documented similar findings, attributing the rapid onset to the higher affinity of dexmedetomidine for α2-adrenergic receptors, resulting in enhanced hyperpolarization and inhibition of neuronal firing.
Similarly, the time to achieve maximum sensory block was shorter in the dexmedetomidine group. Shaikh SI et al. reported comparable results, indicating times of 12.87 minutes for dexmedetomidine and 17.13 minutes for clonidine. Saravana Babu MS et al. and Bajwa SJ et al. corroborated these findings, suggesting that dexmedetomidine’s stronger α2-agonist effect enhances the local anesthetic action, leading to a quicker and denser block.
The time to achieve complete motor blockade (Bromage score 3) was also significantly shorter with dexmedetomidine. This is consistent with findings by Bajwa SJ et al., Shaikh SI et al., and Kaur S et al., who all observed that dexmedetomidine facilitates faster and more profound motor block, which may be advantageous in surgeries requiring complete muscle relaxation.
Hemodynamic stability is an essential consideration in the perioperative period. In our study, although both groups exhibited reductions in heart rate and mean arterial pressure following epidural administration, these changes were more pronounced in the dexmedetomidine group at 120 minutes (p < 0.05). Bajwa SJ et al. similarly reported significant reductions in heart rate and mean arterial pressure, particularly with dexmedetomidine. This can be attributed to dexmedetomidine’s central sympatholytic action, resulting in decreased sympathetic outflow and enhanced vagal activity. Kaur S et al. noted transient episodes of bradycardia and hypotension in their study, which were effectively managed with atropine and ephedrine. Our study also observed such events, though the incidence was not statistically different between groups, and all episodes were managed successfully, ensuring patient safety.
The duration of postoperative analgesia is a crucial determinant of patient comfort and satisfaction. In our study, the total duration of analgesia, measured as time to regression of sensory block to the S1 dermatome, was significantly longer in the dexmedetomidine group (479.4 ± 28.74 min) compared to the clonidine group (371.4 ± 27.70 min). These findings are consistent with Saravana Babu MS et al., who reported durations of 407 ± 47.06 min for dexmedetomidine and 345 ± 35.02 min for clonidine (p < 0.0001). Kaur S et al. also reported a significantly prolonged sensory block with dexmedetomidine (535.18 ± 19.85 min) compared to plain ropivacaine (375.20 ± 15.97 min). Furthermore, Shaikh SI et al. observed that the mean time to sensory regression to S1 was longer with dexmedetomidine (314.17 ± 18.87 min) than with clonidine (298.73 ± 20.68 min, p = 0.0038). In line with these studies, our results confirm that dexmedetomidine extends analgesia duration, thereby delaying the need for rescue analgesia and reducing postoperative analgesic requirements.
Other block characteristics such as time to two-segment regression and time to regression of motor block to Bromage score 1 were also significantly prolonged in the dexmedetomidine group, indicating a more sustained block. The time to first epidural top-up was also longer in this group, reinforcing the advantage of dexmedetomidine for extended postoperative pain relief.
In terms of intraoperative analgesic efficacy, none of the patients in either group reported pain during surgery, and all procedures were completed successfully within three hours. This emphasizes the effectiveness of both clonidine and dexmedetomidine as adjuvants to bupivacaine in providing adequate intraoperative anesthesia for hysterectomies.
The choice of dexmedetomidine as a preferred adjuvant is further supported by its favorable profile in prolonging postoperative analgesia while providing a faster onset. However, it is important to note that a slightly higher dose (1.5 µg/kg) was used in our study to achieve these effects in hysterectomy patients, whereas lower doses (1 µg/kg) have been effective in lower limb surgeries, as reported by Kaur S et al. and Bajwa SJ et al.
Regarding side effects, the incidence of nausea, shivering, dry mouth, hypotension, and bradycardia was similar between the two groups and did not reach statistical significance (p > 0.05). These findings align with previous studies by Bajwa SJ et al. and Shaikh SI et al., suggesting that both adjuvants are generally safe and well-tolerated when appropriately monitored.
In conclusion, our study supports the use of dexmedetomidine as a superior epidural adjuvant to clonidine, given its advantages of faster onset, longer duration of sensory and motor blockade, and extended postoperative analgesia, without an increased risk of adverse effects. This makes it a valuable option for enhancing perioperative analgesic management in patients undergoing major gynecological surgeries.
The present study demonstrated that dexmedetomidine, when used as an epidural adjuvant to bupivacaine, provides significant advantages over clonidine in patients undergoing abdominal and vaginal hysterectomies. Dexmedetomidine resulted in a faster onset of sensory and motor blockade, a longer duration of postoperative analgesia, and a prolonged regression time of both sensory and motor blocks.
Although heart rate reduction was more pronounced in the dexmedetomidine group, overall hemodynamic stability and the incidence of side effects were comparable between the two groups and remained within safe clinical limits.
Based on these findings, dexmedetomidine at a dose of 1.5 µg/kg appears to be a superior epidural adjuvant to clonidine, offering enhanced intraoperative anesthesia and extended postoperative pain relief without increasing the risk of adverse effects. Thus, it can be recommended as an effective and safe alternative for improving perioperative analgesic management in major gynecological surgeries.