Effective perioperative pain control is an essential component of contemporary anaesthetic practice, as inadequate analgesia may delay recovery, limit early mobilization, increase postoperative morbidity, and negatively affect patient satisfaction.[1] Although opioids continue to play an important role in perioperative analgesic regimens, their use is frequently associated with undesirable effects, including nausea, vomiting, respiratory depression, pruritus, sedation, and delayed recovery.[2] This has led to increasing emphasis on multimodal analgesic strategies incorporating regional anaesthesia techniques to achieve effective pain relief while minimizing opioid-related complications.

Peripheral nerve blocks (PNBs) provide selective interruption of nociceptive pathways and have become an integral component of multimodal analgesia. They offer superior postoperative pain control, reduced systemic analgesic requirements, decreased opioid consumption, and enhanced functional recovery.[3] The advent of ultrasound-guided techniques has further improved the safety and reliability of PNBs by enabling real-time visualization of neural structures, precise needle placement, improved block success, and reduction in procedure-related complications.

Brachial plexus blockade remains a widely utilized regional anaesthetic technique for upper limb surgeries, providing effective surgical anaesthesia and postoperative analgesia.[4] Among the various approaches, ultrasound-guided supraclavicular brachial plexus block provides a rapid, dense, and predictable block due to the compact arrangement of neural structures at this level. However, the analgesic duration achieved with local anaesthetic agents alone is often limited and may not provide adequate coverage for prolonged postoperative pain.[5] Consequently, several pharmacological adjuvants have been investigated to enhance block characteristics and extend analgesic duration. Various agents, including opioids, α2-adrenergic agonists, corticosteroids, magnesium sulphate, and vasoconstrictors, have been evaluated as additives to local anaesthetics. Among these, dexamethasone and dexmedetomidine have emerged as promising agents due to their ability to prolong sensory and motor blockade and reduce postoperative analgesic requirements.[6]

Dexamethasone, a potent synthetic glucocorticoid, exerts analgesic effects through inhibition of inflammatory mediator release, modulation of nociceptive signalling, suppression of C-fibre activity, and reduction of local inflammatory response.[7] Intravenous administration of dexamethasone has gained popularity due to its simple route of delivery, avoidance of concerns related to perineural steroid administration, and additional benefits such as antiemetic and anti-inflammatory effects.[8]

Dexmedetomidine, a highly selective α2-adrenergic receptor agonist, has also demonstrated significant potential as an adjuvant in regional anaesthesia. Its analgesic properties are mediated through central and peripheral α2 receptor activation, inhibition of nociceptive transmission, attenuation of sympathetic activity, and enhancement of local anaesthetic effects.[9,10] Previous studies have reported that dexmedetomidine may improve block onset characteristics, prolong sensory and motor blockade, and reduce opioid consumption. However, its clinical application may be limited by adverse effects such as bradycardia, hypotension, and sedation.[11]

Although both intravenous dexamethasone and dexmedetomidine have shown beneficial effects in enhancing peripheral nerve block efficacy, variations exist regarding their relative effectiveness, duration of analgesia, haemodynamic stability, and safety profile.[12] A direct comparison between these agents is clinically relevant to identify the optimal adjuvant that provides prolonged analgesia with minimal adverse effects.

Therefore, the present prospective randomized double-blind study was conducted to compare intravenous dexmedetomidine versus dexamethasone as adjuvants to ultrasound-guided peripheral nerve blocks in patients undergoing upper limb surgeries, with evaluation of block characteristics, postoperative analgesic requirements, and perioperative outcome.

Study Design and Study Setting The present study was designed as a prospective, randomized, double-blind comparative clinical trial to evaluate and compare the efficacy, duration of analgesia, and safety profile of intravenous dexmedetomidine versus intravenous dexamethasone as adjuvants to ultrasound-guided peripheral nerve blocks in patients undergoing upper limb surgeries. The study was conducted in the Department of Anaesthesiology over a period of 18 months. Study Population The study included adult patients scheduled for elective upper limb surgical procedures requiring ultrasound-guided supraclavicular brachial plexus block as the primary anaesthetic technique. A total of 100 patients fulfilling the predefined inclusion criteria were enrolled and randomly allocated into two groups of 50 patients each. Group DEX (Dexmedetomidine Group) (n=50) Patients received intravenous dexmedetomidine as an adjuvant along with the standard local anaesthetic regimen for ultrasound-guided peripheral nerve block. Group DXM (Dexamethasone Group) (n=50) Patients received intravenous dexamethasone as an adjuvant along with the same local anaesthetic regimen for ultrasound-guided peripheral nerve block. Randomization and Blinding Patients were randomly assigned to either study group using a computer-generated randomization sequence. Allocation concealment was ensured using sequentially numbered, sealed, opaque envelopes. The study medications were prepared by an independent anaesthesiologist who was not involved in patient management, block assessment, or outcome evaluation. Both the patients and the investigator responsible for recording perioperative parameters were blinded to the group allocation, ensuring a double-blind study design. Inclusion Criteria Patients fulfilling the following criteria were included: • Patients aged 18–60 years. • Patients belonging to ASA physical status I and II. • Patients undergoing elective upper limb surgeries under ultrasound-guided supraclavicular brachial plexus block. • Patients willing to participate and provide written informed consent. • Surgical duration expected to be less than 3 hours. Exclusion Criteria Patients were excluded if they had: • Refusal to participate in the study. • Known allergy or hypersensitivity to dexmedetomidine, dexamethasone, or local anaesthetic agents. • Significant cardiovascular, respiratory, hepatic, or renal dysfunction. • Coagulation abnormalities or bleeding disorders. • Pre-existing neurological deficits involving the operative limb. • Local infection at the proposed block site. • Pregnancy or lactation. • Chronic opioid use or long-term analgesic therapy. • Contraindications to regional anaesthesia. Preoperative Assessment All patients underwent detailed preoperative evaluation, including medical history, systemic examination, airway assessment, and review of relevant laboratory investigations. Baseline parameters including heart rate, blood pressure, respiratory rate, oxygen saturation, and electrocardiogram findings were documented. Patients were kept fasting according to standard fasting guidelines. Intravenous access was established, and standard monitoring with electrocardiography, non-invasive blood pressure monitoring, and pulse oximetry was initiated before performing the nerve block. Anaesthetic Technique After transfer to the operating room, standard monitoring was applied, and baseline heart rate, mean arterial pressure, oxygen saturation, and respiratory rate were recorded. All patients received oxygen supplementation through a face mask. Minimal sedation was administered when required, ensuring patient cooperation and maintenance of spontaneous respiration during block performance. Ultrasound-Guided Supraclavicular Brachial Plexus Block Technique Patients were positioned supine with the head turned opposite to the side of surgery. Under strict aseptic precautions, a high-frequency linear ultrasound probe was placed in the supraclavicular region to identify the brachial plexus elements located lateral and superior to the subclavian artery. A sterile needle was advanced under real-time ultrasound guidance using an in-plane technique. Following negative aspiration, the local anaesthetic solution containing the assigned study adjuvant was injected incrementally around the brachial plexus sheath. The adequacy of block was assessed clinically by evaluating sensory and motor blockade in the distribution of the brachial plexus. Study Drug Administration Patients received one of the following intravenous adjuvants according to group allocation: Group DEX (n=50) Patients received intravenous dexmedetomidine as an adjuvant according to the predefined study protocol. Group DXM (n=50) Patients received intravenous dexamethasone as an adjuvant according to the predefined study protocol. Both groups received an identical local anaesthetic regimen for ultrasound-guided supraclavicular brachial plexus block. Assessment of Block Characteristics Sensory Block Assessment Sensory blockade was assessed using cold sensation and pinprick testing in the distribution of the brachial plexus nerves. • Sensory block onset time was defined as the interval between completion of local anaesthetic injection and achievement of complete sensory blockade. • Duration of sensory block was defined as the time from onset of complete sensory blockade until complete return of sensory function. Motor Block Assessment Motor blockade was assessed using standard motor grading of upper limb movements. • Motor block onset time was defined as the time required to achieve complete motor blockade following local anaesthetic injection. • Duration of motor block was calculated from achievement of complete motor blockade until complete recovery of motor function. Assessment of Postoperative Analgesia Postoperative pain assessment was performed using the Visual Analogue Scale (VAS), where 0 indicated no pain and 10 indicated the worst imaginable pain. The following parameters were recorded: • Duration of postoperative analgesia. • Time to first rescue analgesic requirement. • Total analgesic consumption during the first 24 hours. • Number of rescue analgesic doses required. • Rescue analgesia was administered when the VAS score crossed the predefined threshold. Haemodynamic and Safety Monitoring Patients were monitored intraoperatively and postoperatively for: • Heart rate variations. • Mean arterial pressure changes. • Oxygen saturation. • Sedation level. • Bradycardia. • Hypotension. • Nausea and vomiting. • Other adverse effects related to study medications. • Any complications were documented and managed according to standard clinical protocols. Outcome Measures Primary Outcome • Comparison of duration of postoperative analgesia between intravenous dexmedetomidine and dexamethasone groups. Secondary Outcomes • Sensory block onset time. • Motor block onset time. • Duration of sensory blockade. • Duration of motor blockade. • Time to first rescue analgesic requirement. • Total 24-hour analgesic consumption. • Haemodynamic variations. • Incidence of adverse effects. Statistical Analysis Data were collected, coded, and analysed using SPSS version 21.0 statistical software. Continuous variables were expressed as mean ± standard deviation or median (interquartile range) based on data distribution. Categorical variables were presented as frequency and percentage. Comparison between the two groups was performed using the independent sample t-test or Mann–Whitney U test for continuous variables, and Chi-square test or Fisher’s exact test for categorical variables. Normality of distribution was assessed before applying statistical tests. A p-value <0.05 was considered statistically significant.

A total of 100 patients undergoing elective upper limb surgeries under ultrasound-guided supraclavicular brachial plexus block were included in the study and randomly allocated into two groups of 50 patients each. The demographic and baseline characteristics were comparable between the groups. The mean age was 38.6 ± 10.2 years in the Group DEX and 39.1 ± 9.8 years in the Group DXM (p=0.81). Distribution of patients across different age categories, gender, body weight, ASA physical status, and duration of surgery showed no statistically significant difference between the two groups, indicating adequate baseline comparability (Table 1).

The comparison of block characteristics demonstrated significant differences between the two groups. Patients receiving dexmedetomidine showed a faster onset of sensory and motor blockade compared with dexamethasone. The mean sensory block onset time was 8.4 ± 2.1 minutes in Group DEX compared with 10.1 ± 2.4 minutes in Group DXM (p<0.001). Similarly, motor block onset was significantly earlier in the dexmedetomidine group (10.6 ± 2.8 vs 12.3 ± 3.1 minutes; p=0.004). The duration of sensory blockade (13.8 ± 2.6 vs 11.9 ± 2.3 hours; p<0.001) and motor blockade (11.9 ± 2.4 vs 10.2 ± 2.1 hours; p<0.001) were significantly prolonged in the dexmedetomidine group. Time to achieve complete surgical anaesthesia was also shorter with dexmedetomidine (18.2 ± 4.5 vs 20.4 ± 4.8 minutes; p=0.021) (Table 2; Figure 1).

Postoperative analgesic outcomes showed significant superiority of dexmedetomidine over dexamethasone. The duration of analgesia was significantly longer in Group DEX (15.6 ± 3.2 hours) compared with Group DXM (13.4 ± 2.8 hours; p<0.001). Similarly, the time to first rescue analgesic requirement was prolonged in the dexmedetomidine group (16.1 ± 3.4 vs 13.9 ± 3.0 hours; p=0.001). Total analgesic consumption during the first 24 hours was significantly lower among patients receiving dexmedetomidine (78.6 ± 28.4 mg vs 104.2 ± 32.6 mg tramadol equivalent; p<0.001). The number of rescue analgesic doses was also significantly reduced in Group DEX (1.2 ± 0.5 vs 1.8 ± 0.7; p<0.001). Fewer patients in the dexmedetomidine group required rescue analgesia within the first 12 hours (16.0% vs 42.0%; p=0.006) (Table 3).

Postoperative pain assessment using the Visual Analogue Scale (VAS) revealed comparable pain scores during the immediate postoperative period. However, from 4 hours onwards, patients in the dexmedetomidine group demonstrated significantly lower pain scores compared with the dexamethasone group. At 4 hours, VAS scores were 1.8 ± 1.0 versus 2.3 ± 1.1 (p=0.021), while at 6 hours they were 2.4 ± 1.2 versus 3.1 ± 1.3 (p=0.006). A significant difference persisted at 12 hours (3.2 ± 1.4 vs 4.1 ± 1.5; p=0.003). At 24 hours, the difference was not statistically significant (4.1 ± 1.3 vs 4.6 ± 1.5; p=0.08) (Table 4; Figure 2).

Haemodynamic assessment demonstrated comparable baseline parameters between the groups. Baseline heart rate and mean arterial pressure were similar in both groups (p>0.05). However, intraoperative heart rate was significantly lower in the dexmedetomidine group (72.6 ± 8.8 vs 79.4 ± 9.2 beats/min; p<0.001). Similarly, intraoperative mean arterial pressure was lower in Group DEX (84.6 ± 7.9 vs 89.2 ± 8.1 mmHg; p=0.005). Oxygen saturation remained comparable between groups throughout the perioperative period (Table 5).

Evaluation of adverse effects demonstrated that dexmedetomidine was associated with a higher incidence of bradycardia compared with dexamethasone (14.0% vs 2.0%; p=0.028). Hypotension was observed more frequently in the dexmedetomidine group, although the difference was not statistically significant (12.0% vs 4.0%; p=0.14). Sedation scores ≥3 were higher with dexmedetomidine (18.0% vs 6.0%; p=0.06), while nausea and vomiting rates were comparable between groups (8.0% vs 10.0%; p=0.73). No respiratory complications were observed in either group. Overall patient satisfaction was high in both groups, with slightly higher satisfaction in the dexmedetomidine group (92.0% vs 84.0%; p=0.24) (Table 6; Figure 3).

Overall, intravenous dexmedetomidine provided faster block onset, prolonged sensory and motor blockade, extended postoperative analgesia, reduced analgesic consumption, and improved pain control compared with dexamethasone, although it was associated with a higher incidence of haemodynamic adverse effects such as bradycardia.

Table 1: Demographic and Baseline Characteristics of Study Participants (n=100)

Table 2: Comparison of Block Characteristics Between Dexmedetomidine and Dexamethasone Groups (n=100)

Figure 1 Comparison of Block Characteristics Between Dexmedetomidine and Dexamethasone Groups (n=100)

Table 3: Comparison of Postoperative Analgesic Outcomes Between Study Groups (n=100)

Table 4: Postoperative Pain Scores (VAS) at Different Time Intervals Between Study Groups (n=100)

Figure 2 Postoperative Pain Scores (VAS) at Different Time Intervals Between Study Groups (n=100)

Table 5: Haemodynamic Parameters Between Dexmedetomidine and Dexamethasone Groups (n=100)

Table 6: Incidence of Adverse Effects and Recovery Parameters Between Study Groups (n=100)

Figure 3 Incidence of Adverse Effects and Recovery Parameters Between Study Groups (n=100)

The present prospective randomized double-blind comparative study evaluated the efficacy and safety of intravenous dexmedetomidine versus dexamethasone as adjuvants to ultrasound-guided supraclavicular brachial plexus block in 100 patients undergoing upper limb surgeries. Patients were randomly allocated into two groups of 50 each. Dexmedetomidine demonstrated superior block characteristics by providing faster onset of sensory and motor blockade, prolonged duration of block, extended postoperative analgesia, reduced rescue analgesic requirement, and improved postoperative pain control compared with dexamethasone. However, dexmedetomidine was associated with a higher incidence of bradycardia and sedation. Baseline demographic and clinical parameters, including age, gender, body weight, ASA grade, and duration of surgery, were comparable between groups, indicating effective randomization and minimizing confounding effects (Table 1). Similar baseline comparability was reported by Nagaraju et al. (2023)[13] in patients receiving dexmedetomidine and dexamethasone as adjuvants for supraclavicular brachial plexus block. Dexmedetomidine significantly improved block performance, with faster sensory (8.4 ± 2.1 vs 10.1 ± 2.4 minutes; p<0.001) and motor block onset (10.6 ± 2.8 vs 12.3 ± 3.1 minutes; p=0.004), prolonged sensory (13.8 ± 2.6 vs 11.9 ± 2.3 hours; p<0.001) and motor blockade duration (11.9 ± 2.4 vs 10.2 ± 2.1 hours; p<0.001), and shorter time to achieve complete surgical anaesthesia (18.2 ± 4.5 vs 20.4 ± 4.8 minutes; p=0.021) (Table 2). These effects may be attributed to peripheral α2-adrenergic receptor activation by dexmedetomidine, resulting in neuronal hyperpolarization and inhibition of nociceptive transmission. Similar findings were reported by Nagaraju et al. (2023)[13] and Mangal et al. (2018)[14], whereas Venkatraman et al. (2021)[15] reported longer analgesic duration with dexamethasone, highlighting the influence of dosage, drug concentration, and block technique. Postoperative analgesic outcomes were significantly better with dexmedetomidine. The duration of analgesia (15.6 ± 3.2 vs 13.4 ± 2.8 hours; p<0.001), time to first rescue analgesia (16.1 ± 3.4 vs 13.9 ± 3.0 hours; p=0.001), and total 24-hour analgesic consumption (78.6 ± 28.4 vs 104.2 ± 32.6 mg; p<0.001) were significantly improved in the dexmedetomidine group (Table 3). Similar opioid-sparing effects were observed by Das et al. (2014)[16] and Ping et al. (2017)[17]. VAS pain scores were comparable during the immediate postoperative period; however, dexmedetomidine provided significantly lower pain scores at 4, 6, and 12 hours (Table 4). At 24 hours, the difference was not statistically significant, likely due to regression of block effects and increasing inflammatory pain. Haemodynamic parameters remained clinically stable in both groups; however, dexmedetomidine produced significantly lower intraoperative heart rate and mean arterial pressure (Table 5), consistent with its central sympatholytic action. Safety analysis revealed significantly higher bradycardia with dexmedetomidine (14.0% vs 2.0%; p=0.028), while sedation and hypotension were more frequent but statistically insignificant (Table 6). Similar adverse effects have been reported by Mangal et al. (2018)[14] and Nagaraju et al. (2023)[13]. Overall, intravenous dexmedetomidine was found to be a more effective adjuvant than dexamethasone for enhancing the quality and duration of ultrasound-guided supraclavicular brachial plexus block. Although associated with increased haemodynamic effects, these were manageable with appropriate monitoring, making dexmedetomidine a valuable option for improving perioperative analgesia in upper limb surgeries.

Intravenous dexmedetomidine as an adjuvant to ultrasound-guided peripheral nerve blocks provided superior block characteristics compared with dexamethasone, with faster onset and prolonged sensory and motor blockade. It significantly extended postoperative analgesia duration, delayed the need for rescue analgesia, and reduced 24-hour analgesic consumption. Dexmedetomidine also resulted in better postoperative pain control during the intermediate recovery period. However, its use was associated with a higher incidence of bradycardia and sedation, requiring careful monitoring. Overall, dexmedetomidine appears to be an effective adjuvant for improving analgesic outcomes in upper limb surgeries under regional anaesthesia.

LIMITATIONS

The study was conducted at a single centre with a relatively limited sample size, which may restrict the generalizability of the findings. The follow-up period was limited to the immediate postoperative period, preventing assessment of long-term outcomes. Variations in surgical procedures and individual patient responses may have influenced analgesic requirements. Further multicentric studies with larger sample sizes are required to confirm these findings.

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