European Journal of Cardiovascular Medicine

Lower limb surgeries include a broad spectrum of procedures, from minor soft tissue operations to complex orthopedic interventions like knee replacements, ankle surgeries, and foot reconstructions.1 Traditionally performed under general or neuraxial anesthesia, these procedures have increasingly incorporated regional techniques with the advent of ultrasound-guided peripheral nerve blocks.2 Notably, femoro-sciatic nerve blocks have become key for providing effective anesthesia and postoperative analgesia.3 Ultrasound guidance has greatly improved the precision, efficacy, and safety of these blocks by enabling real-time visualization of anatomical structures, needle placement, and local anesthetic spread, thereby reducing complications and enhancing success rates4

Peripheral nerve blocks offer targeted anesthesia with advantages over general anesthesia, including reduced systemic effects, better hemodynamic stability, decreased postoperative nausea and vomiting, superior pain control, and shorter hospital stays. Combined femoral and sciatic nerve blocks provide comprehensive anesthesia for most of the lower extremity, making them ideal for a wide range of lower limb surgeries.5 The femoral nerve (L2–L4) supplies the anterior thigh and medial leg via the saphenous nerve, while the sciatic nerve (L4–S3), the body’s largest peripheral nerve, innervates the posterior thigh, leg, and foot, sparing only the medial lower leg. Together, these blocks anesthetize approximately 90% of the lower limb, offering a viable alternative to neuraxial or general anesthesia.7

Ultrasound guidance has revolutionized regional anesthesia by enabling real-time visualization of neurovascular structures, improving needle placement accuracy, reducing anesthetic volumes, and minimizing complications compared to landmark- and nerve stimulation-based techniques. A meta-analysis by Salinas et al. reported a 29% increase in block success rates with ultrasound guidance. It also facilitates management of anatomical variations, particularly in the inguinal and popliteal regions, enhancing the reliability of femoro-sciatic blocks.8

The choice of local anesthetic influences block quality and duration. Levobupivacaine, favored for its safer cardiac and CNS profile, offers prolonged sensory blockade lasting 9–24 hours, though often insufficient for extended postoperative analgesia. To address this, adjuvants such as alpha-2 adrenergic agonists (clonidine, dexmedetomidine) are used to prolong block duration, improve analgesia, and lower anesthetic doses, thereby reducing toxicity risk.10 These agents act via central sympatholysis, peripheral nerve inhibition, local vasoconstriction, and anti-inflammatory effects. Clonidine, one of the earliest adjuvants studied, extends analgesia by about 2 hours but is associated with hypotension and sedation. Optimal dosing, typically between 0.5–2 μg/kg, remains under investigation to balance efficacy and side effects.11

Dexmedetomidine, a highly selective alpha-2 adrenergic agonist (selectivity ratio 1620:1 vs. 220:1 for clonidine), has gained interest as a peripheral nerve block adjuvant. Its greater alpha-2 affinity may offer improved analgesia with fewer side effects. Experimental studies indicate that dexmedetomidine prolongs sensory and motor block duration and enhances analgesia through peripheral and central mechanisms.12 Peripherally, it activates alpha-2A receptors on nerve endings, hyperpolarizing neurons via potassium channels, while alpha-2B receptor-mediated vasoconstriction slows systemic anesthetic absorption. Centrally, it modulates pain via alpha-2 receptors in the locus coeruleus and dorsal horn.13

Clinical trials support its efficacy. Esmaoglu et al. found that adding 100 μg dexmedetomidine to levobupivacaine for axillary brachial plexus block extended block duration without added side effects. Similarly, Abdallah et al. reported a 60% increase in analgesia duration when combined with bupivacaine for posterior tibial nerve block. However, a direct comparison of clonidine versus dexmedetomidine as adjuvants to levobupivacaine in femoro-sciatic nerve blocks remains limited.

Prolonged postoperative analgesia is crucial after lower limb surgeries, facilitating early mobilization, reducing thromboembolic risk, enhancing satisfaction, and preventing chronic pain, which affects 15–20% of patients after procedures like total knee arthroplasty.14 Prolonging nerve block duration using adjuvants may also reduce opioid requirements and their associated side effects.

This study aims to compare the efficacy and safety of clonidine and dexmedetomidine as adjuvants to levobupivacaine for ultrasound-guided femoro-sciatic nerve blocks in lower limb surgeries.18 Primary endpoints include duration of sensory and motor block, intraoperative anesthesia quality, postoperative pain scores, time to first analgesic request, total 24-hour analgesic use, and adverse effects (hypotension, bradycardia, sedation, respiratory depression). Secondary endpoints include patient satisfaction, ease of block performance, discharge timing, and functional recovery. This comparison seeks to inform optimal adjuvant selection in regional anesthesia protocols for improved patient outcomes.20

OBJECTIVES:

To evaluate the efficacy of FSN Block formulation Levobupivacaine 20ml + Clonidine (0.5 µg/kg) and Levobupivacaine 20 ml+ Dexmedetomidine (0.5 µg/kg), as the post operative analgesia up to 24 hours after the surgery.

SOURCE OF DATA: • Study design: “Prospective, randomized, double-blind controlled trial • Study area: Department of General Medicine, R.L. Jalappa Hospital and Research Centre, affiliated with Sri Devaraj Urs Medical College, Tamaka, Kolar. • Study period: Research study was conducted from July 2023 to December 2024. Below is the work plan”. SAMPLE SIZE CALCULATION: The sample size was calculated using Cohen's d-method with Family-Wise Error Rate (FWER). With a significance level (α) of 0.05 and power (1-β) of 0.80, the study was designed to detect a real effect between the groups. Since the study involved comparisons between two intervention groups, the FWER was adjusted to 0.025 (0.05/2). Using an effect size (d) of 0.6, which is slightly above the moderate effect size of 0.5, a sample size of 45 patients per group was determined to be adequate. This calculation was based on the method described by Suresh K.P. and Chandrasekhar S (2012) in their publication on sample size estimation and power analysis for clinical research studies in the Journal of Human Reproduction Science INCLUSION CRITERIA 1. Age 20 to 60 years Males and Females. 2. ASA 1 and 2 3. Surgery of Foot and Leg. EXCLUSION CRITERIA 1. Refusal of the patient to block. 2. “History of heart, renal, or hepatic disease. Local infection at the area where the needle for block is to go in”. 3. Patients who have brady-arrythmia or are on beta blocker therapy. 4. Younger than 20 years old. 5. American Society of Anaesthesiologists physical status IV or V SAMPLING PROCEDURE: This prospective, randomized, double-blind controlled trial was conducted at R.L. Jalappa Hospital and Research Centre, affiliated with Sri Devaraj Urs Medical College, Kolar, between May 2023 and October 2024, following Institutional Ethics Committee approval. Written informed consent was obtained from all participants. Randomization and Blinding Eligible patients were randomized into two groups using computer-generated numbers: • Group A: Ultrasound-guided femoro-sciatic nerve block with 0.125% levobupivacaine + clonidine (0.5 μg/kg). • Group B: Ultrasound-guided femoro-sciatic nerve block with 0.125% levobupivacaine + dexmedetomidine (0.5 μg/kg). Study drugs were prepared by an independent anesthesiologist in identical syringes labelled with patient IDs. Both the performing anesthesiologist and the patient were blinded to group allocation. Pre-Anesthetic Assessment All patients underwent a detailed clinical evaluation, physical examination, and routine investigations. Demographic data and ASA status were recorded. Anesthetic Technique Standard monitors (ECG, NIBP, SpO₂) were applied in the operating room. Subarachnoid block was administered for intraoperative anesthesia. At surgery completion and before spinal regression, an ultrasound-guided femoro-sciatic nerve block was performed. Femoral Nerve Block With the patient supine, a high-frequency linear transducer (8–13 MHz) was placed transversely at the inguinal crease to identify the femoral nerve lateral to the femoral artery. Following skin infiltration, a 22G, 100 mm needle was advanced in-plane, and 10 ml of study drug was injected under ultrasound guidance. Sciatic Nerve Block In the lateral position, a low-frequency curvilinear probe (2–5 MHz) identified the sciatic nerve in the subgluteal region. A 22G, 150 mm needle was advanced in-plane, and 10 ml of study drug was injected after negative aspiration. Postoperative Monitoring Patients were monitored in the PACU for heart rate, blood pressure, mean arterial pressure, SpO₂, pain (VAS score), sedation (Ramsay score), and motor block (Bromage scale) at 0, 2, 4, 8, 12, and 24 hours postoperatively. Outcomes The primary outcome was duration of postoperative analgesia (time from block to first rescue analgesia at VAS ≥ 4). Secondary outcomes included VAS scores, 24-hour analgesic consumption, and adverse effects (bradycardia, hypotension, sedation). Rescue analgesia consisted of IV tramadol 100 mg. Adverse events were managed per institutional protocol. STATISTICAL ANALYSIS Statistical analysis was performed using SPSS version 22.0 software. Continuous variables were expressed as mean ± standard deviation, and categorical variables were expressed as frequencies and percentages. The normality of data was assessed using the Kolmogorov-Smirnov test. For normally distributed data, comparisons between the groups were performed using the independent Student's t-test. For non-normally distributed data, the Mann-Whitney U test was used. Categorical variables were compared using the Chi-square test or Fisher's exact test as appropriate. A p-value < 0.05 was considered statistically significant

Table 1: Age distribution

“The mean age was 42.20 ± 12.15 years in Group A (Clonidine) and 41.49 ± 10.91 years in Group B (Dexmedetomidine). The age distribution was similar between groups (p=0.771). In Group A, 42.2% of patients were aged 20-40 years and 57.8% were 41-60 years. In Group B, 46.7% were 20-40 years and 53.3% were 41-60 years. There was no significant difference in age distribution between groups (p=0.671).

Table 2: Weight comparison

The mean weight in Group A (Clonidine) was 70.71 ± 11.57 kg, while in Group B (Dexmedetomidine) it was 71.09 ± 11.43 kg. There was no significant difference in weight between the two groups (p=0.877), indicating homogeneity in patient weight across both groups.

Table 3: comparison of different parameters

The study compared surgery duration and drug dose between the two groups. The mean surgery duration was 83.69 ± 20.32 minutes in Group A (Clonidine) and 88.67 ± 23.29 minutes in Group B (Dexmedetomidine). There was no significant difference in surgery duration between groups (p=0.283). The mean drug dose was similar between Group A (35.36 ± 5.78) and Group B (35.51 ± 5.72), with no significant difference (p=0.898).

Table 4: Gender Distribution

In Group A (Clonidine), 57.8% of patients were male and 42.2% were female. In Group B (Dexmedetomidine), 53.3% were male and 46.7% were female. The gender distribution was comparable between the two groups with no significant difference (p=0.671).

Table 5: ASA Physical Status

The American Society of Anesthesiologists (ASA) physical status classification was compared between groups. In Group A (Clonidine), 77.8% of patients were ASA I and 22.2% were ASA II. In Group B (Dexmedetomidine), 88.9% were ASA I and 11.1% were ASA II. There was no significant difference in ASA physical status between groups (p=0.157).

Table 6: Visual Analog Scale (VAS) Scores

*Statistically significant (p<0.05)

The VAS scores, measuring pain intensity, were significantly lower in Group B (Dexmedetomidine) compared to Group A (Clonidine) at all time points (0, 2, 4, 8, 12, and 24 hours post-surgery), with p<0.001 at each measurement.

At 0 hours, the mean VAS score was 6.91 ± 0.87 in Group A vs. 5.20 ± 0.89 in Group B. By 24 hours, the scores had reduced to 1.96 ± 0.85 in Group A vs. 0.49 ± 0.51 in Group B. This indicates that dexmedetomidine provided significantly better pain relief compared to clonidine throughout the 24-hour post-operative period.

The mean heart rates were comparable between Group A (Clonidine) and Group B (Dexmedetomidine) at all time points (0, 2, 4, 8, 12, and 24 hours post-surgery), with no statistically significant differences (p>0.05 at all time points).

At 0 hours, the mean heart rate was 73.73 ± 7.59 bpm in Group A vs. 75.89 ± 7.97 bpm in Group B (p=0.192). At 24 hours, the mean heart rate was 74.82 ± 7.83 bpm in Group A vs. 76.76 ± 7.73 bpm in Group B (p=0.242). This suggests that both adjuvants had similar effects on heart rate throughout the post-operative period.

Table 7: Heart Rate (beats per minute)

Table 8: Systolic Blood Pressure (mmHg)

*Statistically significant (p<0.05)

The systolic blood pressure (SBP) measurements showed significant differences between groups at 4 hours and 8 hours post-surgery. At 4 hours, Group A (Clonidine) had a mean SBP of 114.76 ± 8.24 mmHg vs. 109.58 ± 10.15 mmHg in Group B (Dexmedetomidine), p=0.009. At 8 hours, Group A had a mean SBP of 116.56 ± 8.28 mmHg vs. 112.20 ± 9.84 mmHg in Group B, p=0.026.

No significant differences were observed at 0, 2, 12, and 24 hours post-surgery. This suggests that dexmedetomidine had a more pronounced effect on lowering systolic blood pressure during the middle phase of the post-operative period.

Table 9: Diastolic Blood Pressure (mmHg)

*Statistically significant (p<0.05)

The diastolic blood pressure (DBP) measurements showed a significant difference between groups only at 12 hours post-surgery. At this time point, Group A (Clonidine) had a mean DBP of 78.60 ± 7.21 mmHg vs. 84.00 ± 0.00 mmHg in Group B (Dexmedetomidine), p<0.001.

No significant differences were observed at 0, 2, 4, 8, and 24 hours post-surgery. The fact that Group B showed no standard deviation at 12 hours (84.00 ± 0.00) suggests all patients in this group had identical measurements at this time point, which is unusual and may require further investigation.

The mean arterial pressure (MAP) showed significant differences between groups at 2, 4, 8, and 12 hours post-surgery (p<0.001 for all). Interestingly, Group B (Dexmedetomidine) had no standard deviation (fixed values) at multiple time points:

• At 2 hours: 110.00 ± 0.00 mmHg in Group B vs. 102.69 ± 6.28 mmHg in Group A
• At 4 hours: 98.00 ± 0.00 mmHg in Group B vs. 101.87 ± 6.52 mmHg in Group A
• At 8 hours: 112.00 ± 0.00 mmHg in Group B vs. 103.60 ± 6.56 mmHg in Group A
• At 12 hours: 110.00 ± 0.00 mmHg in Group B vs. 104.62 ± 6.55 mmHg in Group A

No significant differences were observed at 0 and 24 hours. The lack of standard deviation in Group B at multiple time points is unusual and may require verification of the data.

Table 10: Mean Arterial Pressure (mmHg)

*Statistically significant (p<0.05)

The oxygen saturation levels were comparable between Group A (Clonidine) and Group B (Dexmedetomidine) at all time points (0, 2, 4, 8, 12, and 24 hours post-surgery), with no statistically significant differences (p>0.05 at all time points).

Both groups maintained adequate oxygen saturation levels (above 98%) throughout the 24-hour post-operative period, indicating that neither adjuvant adversely affected respiratory function. This suggests both drugs are equally safe regarding respiratory parameters

The Bromage score, which measures the degree of motor block, showed significant differences between the groups at 2, 4, and 8 hours post-surgery (p<0.001 for all). Group B (Dexmedetomidine) consistently had lower scores compared to Group A (Clonidine), indicating less motor blockade:

• At 2 hours: 1.40 ± 0.50 in Group B vs. 1.82 ± 0.39 in Group A
• At 4 hours: 2.40 ± 0.50 in Group B vs. 2.82 ± 0.39 in Group A
• At 8 hours: 3.40 ± 0.50 in Group B vs. 3.82 ± 0.39 in Group A

By 12 and 24 hours, both groups had similar scores with no significant differences. This suggests that dexmedetomidine led to faster recovery of motor function compared to clonidine during the early and middle post-operative period.

The incidence of bradycardia was significantly higher in Group B (Dexmedetomidine) at 33.3% compared to 15.6% in Group A (Clonidine), p=0.050. Similarly, hypotension was significantly more frequent in Group B at 26.7% versus 4.4% in Group A, p=0.004.

The incidence of nausea/vomiting was similar between groups: 24.4% in Group B versus 22.2% in Group A, with no significant difference (p=0.803).

These findings suggest that while dexmedetomidine may provide better pain control, it is associated with a higher incidence of bradycardia and hypotension compared to clonidine”.

Postoperative pain management remains a significant challenge in anesthesiology despite advances in analgesic techniques. Peripheral nerve blocks, particularly for lower limb surgeries, offer effective postoperative analgesia, and the use of adjuvants to local anesthetics has gained interest for prolonging analgesia and reducing supplemental analgesic requirements. Among these, α2-adrenergic agonists such as clonidine and dexmedetomidine have shown promise when combined with local anesthetics.1 This study aimed to compare the efficacy and safety of clonidine versus dexmedetomidine as adjuvants to levobupivacaine in ultrasound-guided femoro-sciatic nerve blocks for lower limb surgeries.2 Demographic and Baseline Characteristics Both groups were comparable in terms of demographic parameters, ASA status, and operative details. The mean age was 42.20 ± 12.15 years in Group A (clonidine) and 41.49 ± 10.91 years in Group B (dexmedetomidine) (p=0.771).4 Mean weight was 70.71 ± 11.57 kg in Group A and 71.09 ± 11.43 kg in Group B (p=0.877). Gender distribution showed a slight male predominance in both groups (p=0.671). The duration of surgery and local anesthetic doses were also comparable (p=0.283 and p=0.898, respectively), ensuring homogeneity and validity in outcome comparisons. These findings align with earlier studies by Agarwal et al.43 and Das et al.,44 who reported similar demographic consistency in comparable trials. Analgesic Efficacy and Pain Scores Dexmedetomidine demonstrated superior analgesic efficacy, with consistently lower Visual Analog Scale (VAS) scores compared to clonidine at all postoperative time points (p<0.001). Mean VAS scores in the dexmedetomidine group were 1.5–2.5 points lower throughout the 24-hour period, with the most significant differences at 4 and 8 hours postoperatively (2.71 points at both intervals), coinciding with the expected decline of intraoperative analgesia.10 These results are consistent with those reported by Swami et al. and Gandhi et al., who found dexmedetomidine to provide significantly better postoperative analgesia and lower pain scores than clonidine when used in brachial plexus blocks. The enhanced analgesic effect of dexmedetomidine is attributed to its higher α2:α1 selectivity ratio (1620:1) compared to clonidine (220:1), enabling potent analgesia via α2-receptor-mediated inhibition of nociceptive transmission and reduced norepinephrine release.24 Brummett et al. further demonstrated in animal models that perineural dexmedetomidine prolongs local anesthetic-induced antinociception through α2-mediated mechanisms independent of vasoconstriction. Hemodynamic Parameters No significant differences in heart rates were observed between the clonidine and dexmedetomidine groups throughout the 24-hour period, with values remaining within acceptable clinical ranges.18 This aligns with Kathuria et al. but contrasts with Tripathi et al., likely due to differences in administration route and drug dose.14 Dexmedetomidine was associated with significantly lower systolic blood pressure at 4 and 8 hours, and higher diastolic pressure at 12 hours. Mean arterial pressure differed at multiple time points, reflecting the complex, biphasic pharmacodynamics of dexmedetomidine. These modest fluctuations were consistent with previous peripheral nerve block studies.25 Motor Block Characteristics Bromage scores were significantly higher in the clonidine group at 2, 4, and 8 hours, indicating more intense motor blockade.This contrasts with studies reporting greater motor block with dexmedetomidine in brachial plexus blocks, likely due to differences in block technique, local anesthetic, and assessment methods. Clinically, dexmedetomidine's lesser motor blockade may favor early mobilization in ERAS protocols, while clonidine may be preferable when motor block is desired postoperatively.17 Side Effects Bradycardia (33.3% vs. 15.6%, p=0.050) and hypotension (26.7% vs. 4.4%, p=0.004) were significantly more common with dexmedetomidine, consistent with prior findings. Nausea/vomiting and oxygen saturation remained comparable between groups.18 Clinical Implications Dexmedetomidine offers superior analgesia but at the expense of a higher incidence of cardiovascular side effects. Clonidine provides more profound motor blockade. Choice of adjuvant should be individualized, considering analgesic needs, motor block requirements, and patient comorbidities. Comparison with Literature Our results agree with meta-analyses demonstrating superior analgesia with dexmedetomidine but diverge on motor blockade intensity, possibly due to differences in block site and outcome measures. Limited data exist for femoro-sciatic blocks specifically, highlighting the relevance of our study.20 Strengths and Limitations Strengths include a randomized design, adequate sample size, comprehensive outcome assessment, and standardized technique. Limitations: absence of a control group, lack of opioid consumption and duration of analgesia data, 24-hour follow-up limit, and no pharmacokinetic analysis. Future Research Future studies should identify optimal dosing, explore different local anesthetic combinations, investigate mechanisms underlying sensory-motor differential effects, assess long-term outcomes including chronic pain, and evaluate cost-effectiveness. Dexmedetomidine enhances postoperative analgesia more effectively than clonidine in ultrasound-guided femoro-sciatic nerve blocks, albeit with increased bradycardia and hypotension. Clonidine induces deeper motor block. Adjuvant selection should be guided by patient profile, surgical demands, and perioperative priorities.22

In conclusion, both clonidine and dexmedetomidine are effective adjuvants to levobupivacaine in ultrasound-guided femoro-sciatic nerve blocks, but with distinct advantages and limitations. Dexmedetomidine provides superior analgesia but carries a higher risk of cardiovascular side effects, while clonidine offers more intense motor blockade with a more favorable cardiovascular profile. The choice between these adjuvants should be individualized based on patient characteristics, surgical requirements, and the specific goals of perioperative care”.

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3.           Jochum D, O’Neill T, Jabbour H, Diarra PD, Cuignet‐Pourel E, Bouaziz H. Evaluation of femoral nerve blockade following inguinal paravascular block of Winnie: are there still lessons to be learnt? Anaesthesia. 2005 Oct 19;60(10):974–7.

4.           Salinas F V., Hanson NA. Evidence-based medicine for ultrasound-guided regional anesthesia. Vol. 32, Anesthesiology Clinics. 2014.

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7.           Brummett CM, Hong EK, Janda AM, Amodeo FS, Lydic R. Perineural dexmedetomidine added to ropivacaine for sciatic nerve block in rats prolongs the duration of analgesia by blocking the hyperpolarization- activated cation current. Anesthesiology. 2011;115(4).

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16.         Basinger H, Hogg JP. Anatomy, Abdomen and Pelvis, Femoral Triangle. StatPearls. 2019.

17.         Pascarella G, Costa F, Del Buono R, Agrò F. Adductor canal and femoral triangle: Two different rooms with the same door. Vol. 13, Saudi Journal of Anaesthesia. 2019.

18.         Munirama S, McLeod G. Ultrasound-guided femoral and sciatic nerve blocks. Continuing Education in Anaesthesia, Critical Care and Pain. 2013;13(4).

19.         Chan EY, Fransen M, Parker DA, Assam PN, Chua N. Femoral nerve blocks for acute postoperative pain after knee replacement surgery. Vol. 2014, Cochrane Database of Systematic Reviews. 2014.

20.         Auroy Y, Benhamou D, Bargues L, Ecoffey C, Falissard B, Mercier F, et al. Major complications of regional anesthesia in France: The SOS Regional Anesthesia Hotline Service. Anesthesiology. 2002;97(5).

21.         Ok SH, Hong JM, Lee SH, Sohn JT. Lipid emulsion for treating local anesthetic systemic toxicity. Vol. 15, International Journal of Medical Sciences. 2018.

22.         Chandran R, Beh ZY, Tsai FC, Kuruppu SD, Lim JY. Peripheral nerve blocks for above knee amputation in high-risk patients. J Anaesthesiol Clin Pharmacol. 2018;34(4).

23.         Nwawka OK, Meyer R, Miller TT. Ultrasound-guided subgluteal sciatic nerve perineural injection: Report on safety and efficacy at a single institution. Journal of Ultrasound in Medicine. 2017;36(11).

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