Regional anesthesia techniques have evolved significantly over recent decades, offering important alternatives to general anesthesia for upper limb surgeries. Brachial plexus blockade has emerged as a particularly effective approach, providing superior pain control, reduced opioid consumption, and improved patient satisfaction [1]. The supraclavicular approach to the brachial plexus targets the second division of the plexus where the trunks are compactly arranged, allowing for consistent and reliable anesthesia of the entire upper extremity distal to the shoulder [2].

Ultrasound guidance has revolutionized the practice of supraclavicular blocks by enabling real-time visualization of neural structures, facilitating precise needle placement, and reducing the risk of complications such as pneumothorax and vascular puncture [3]. The combination of lignocaine with adrenaline and bupivacaine provides both rapid onset (from lignocaine) and prolonged duration (from bupivacaine), but the analgesic duration is often insufficient to cover the entire postoperative pain period, particularly following orthopedic procedures.

Among the numerous adjuvants explored to prolong analgesia, dexmedetomidine, a highly selective α2-adrenergic agonist, has demonstrated efficacy through mechanisms including local vasoconstriction and decreased nodal action potential propagation [4]. Dexamethasone, a potent synthetic glucocorticoid, has similarly extended block duration through reduction of local inflammation and inhibition of ectopic neural discharge [5].

While both agents have individually shown efficacy as adjuvants to local anesthetic combinations, direct comparative studies between dexmedetomidine and dexamethasone are limited, with inconsistent findings regarding onset time, block duration, and adverse effects [6].

Therefore, this study aims to compare the efficacy of dexmedetomidine (1μg/kg) versus dexamethasone (4mg) as adjuvants to lignocaine with adrenaline and bupivacaine combination in ultrasound-guided supraclavicular brachial plexus block for patients undergoing forearm surgeries. The primary objective is to evaluate the comparative effect on duration of postoperative analgesia, with secondary objectives including assessment of block characteristics, postoperative pain intensity, analgesic requirements, and adverse effects.

This prospective comparative study was conducted at A.C.S medical college and hospital, Chennai, between January 2024 to August 2024 after obtaining approval from the Institutional Ethics Committee. Written informed consent was obtained from all participants in their vernacular language. The sample size was calculated using the formula n = 4PQ/E², where P = prevalence (85%, based on institutional patient flow), Q = non-prevalence (15%), and E = relative allowable error (10% of P = 8.5). The calculated minimum sample size was 72 patients.

Seventy-two patients between 18-60 years of age, ASA physical status I-II, scheduled for elective forearm surgeries were enrolled. Exclusion criteria included patient refusal, local skin infections, bleeding disorders, history of allergy to study medications, neurological or psychiatric disorders, severe systemic diseases, and pregnancy. Patients were randomized into two equal groups using computer-generated random numbers and allocation concealment was maintained using sequentially numbered, opaque, sealed envelopes. Group A (n=36) received 12.5ml of 2% lignocaine with adrenaline (1:200,000) + 12.5ml of 0.5% bupivacaine with dexmedetomidine 1μg/kg, while Group B (n=36) received 12.5ml of 2% lignocaine with adrenaline (1:200,000) + 12.5ml of 0.5% bupivacaine with dexamethasone 4mg. Study medications were prepared by an anesthesiologist not involved in block performance or data collection.

Pre-anesthetic evaluation included detailed history, physical examination, airway assessment, and standard laboratory investigations. Standard monitoring was established with electrocardiogram, non-invasive blood pressure, and pulse oximetry. An 18-gauge intravenous cannula was secured and Ringer's lactate infusion was initiated at 100ml/hour. The patient was positioned supine with the head turned 30° contralaterally. Following aseptic precautions, the supraclavicular area was scanned using a SonoSite M-Turbo ultrasound machine with a high-frequency linear transducer (6-13 MHz).

The subclavian artery and brachial plexus were identified, and a 22G, 50mm echogenic needle was advanced in-plane under continuous ultrasonographic visualization. After negative aspiration, the study drug mixture was injected incrementally with proper spread around the brachial plexus confirmed sonographically. All blocks were performed by the same experienced anesthesiologist to ensure technical consistency.

Block characteristics were assessed by a blinded investigator every 3 minutes for 45 minutes. Sensory block was evaluated using pinprick sensation (Hollmen scale: Grade I-normal sensation to Grade IV-no sensation) in the distributions of median, ulnar, radial, and musculocutaneous nerves. Motor block was assessed using the Modified Bromage Scale (Grade 0-normal motor function to Grade 2-complete motor block). Onset of sensory and motor blocks was defined as the time to achieve at least Grade II sensory block and Grade 1 motor block, respectively. Duration was defined as the time from onset until complete recovery.

Intraoperative monitoring included continuous electrocardiogram, non-invasive blood pressure, heart rate, oxygen saturation, and respiratory rate, recorded at baseline and at 5, 10, 15, 30, and 45 minutes after block placement. Postoperatively, pain was assessed using the Numerical Rating Scale (0-10) at 2, 3, 6, 12, and 24 hours. Injection diclofenac sodium 75mg intramuscularly was administered as rescue analgesia when NRS score was ≥4. Duration of analgesia was defined as the time from sensory block onset to first analgesic request. Patients were monitored for adverse effects including bradycardia, hypotension, nausea, vomiting, Horner's syndrome, and pneumothorax.

Data analysis was performed using SPSS version 29.02. Continuous variables were presented as mean±SD and analyzed using independent samples t-test or Mann-Whitney U test based on data distribution. Categorical variables were expressed as frequencies and percentages and compared using Chi-square or Fisher's exact test. A p-value <0.05 was considered statistically significant. The primary outcome measure was duration of analgesia, with secondary outcomes including block characteristics, pain scores, analgesic consumption, and adverse effects.

In this prospective comparative study, 72 patients undergoing elective forearm surgeries under ultrasound-guided supraclavicular brachial plexus block were divided into two equal groups: Group A (n=36) received 12.5ml of 2% lignocaine with adrenaline (1:200,000) + 12.5ml of 0.5% bupivacaine with dexmedetomidine (1µg/kg), while Group B (n=36) received 12.5ml of 2% lignocaine with adrenaline (1:200,000) + 12.5ml of 0.5% bupivacaine with dexamethasone (4mg).

Demographic and Baseline Characteristics

Analysis of demographic data revealed comparable patient profiles between the two groups with no statistically significant differences in age, gender, weight, ASA physical status, or type of surgery (Table 1). The majority of patients were male (63.89%) and belonged to the 18-30 years age group (36.11%), consistent with the epidemiological pattern of forearm injuries. The distribution of surgical procedures was similar between groups (p=0.987), with radius fracture fixation being the most common procedure overall (40.28%).

Table 1: Demographic characteristics and type of surgery

Values expressed as mean ± SD or number (percentage). Statistical tests used: Unpaired t-test for continuous variables, Chi-square test for categorical variables. p < 0.05 considered statistically significant.

Baseline vital parameters were comparable between the groups, establishing a homogeneous study population and eliminating potential confounding variables.

Block Characteristics

Analysis of block characteristics revealed significant differences between the two groups (Table 2). Group A (Dexmedetomidine) demonstrated significantly faster onset of both sensory and motor blockade compared to Group B (Dexamethasone) (p<0.001). The mean onset time for sensory block in Group A was 8.72 ± 1.86 minutes versus 11.44 ± 2.08 minutes in Group B. Similarly, motor block onset was faster in Group A (12.14 ± 2.22 minutes) compared to Group B (15.36 ± 2.48 minutes).

The duration of sensory block, motor block, and analgesia was also significantly prolonged in Group A compared to Group B (p<0.001 for all parameters). Patients receiving dexmedetomidine experienced approximately 2 hours longer sensory blockade (13.68 ± 1.92 vs. 11.86 ± 1.74 hours) and motor blockade (11.94 ± 1.68 vs. 10.26 ± 1.52 hours), with an extended analgesic duration of approximately 2 hours (16.42 ± 2.18 vs. 14.28 ± 1.96 hours).

Table 2: Block characteristics and duration of analgesia

Values expressed as mean ± SD. Statistical test used: Unpaired t-test. p < 0.05 considered statistically significant.

Pain Assessment and Analgesic Requirements

Analysis of postoperative pain scores revealed no significant differences between the groups at 2, 3, and 6 hours. However, at 12 and 24 hours, Group A demonstrated significantly lower pain scores compared to Group B (p=0.001 and p<0.001, respectively) (Table 3). Total analgesic consumption (diclofenac) in the first 24 hours was significantly lower in Group A (82.64 ± 24.86 mg) compared to Group B (112.38 ± 30.42 mg) (p<0.001), representing a 26.5% reduction in analgesic requirement.

Table 3: Postoperative pain scores and analgesic consumption

Values expressed as mean ± SD. Statistical test used: Unpaired t-test. p < 0.05 considered statistically significant.

Hemodynamic Parameters and Adverse Effects

Analysis of hemodynamic parameters revealed significant differences between the groups, particularly from 5 minutes onward (Table 4). Group A demonstrated significantly lower heart rates and blood pressure values compared to Group B, which can be attributed to the sympatholytic effect of dexmedetomidine.

Table 4: Hemodynamic parameters at different time intervals

Values expressed as mean ± SD. Statistical test used: Unpaired t-test. p < 0.05 considered statistically significant.

The overall incidence of adverse effects was significantly higher in Group A (25.00%) compared to Group B (5.56%) (p=0.024) (Table 5). Bradycardia was the most common adverse effect in Group A (11.11%), followed by hypotension (8.33%), Horner's syndrome (2.78%), and nausea/vomiting (2.78%). In Group B, only nausea/vomiting was observed (5.56%). All adverse effects were transient and managed effectively without serious complications.

Table 5: Adverse effects in both groups

Values expressed as number (percentage). Statistical tests used: Fisher's exact test for individual adverse effects, Chi-square test for total adverse effects. p < 0.05 considered statistically significant.

Overall, both dexmedetomidine and dexamethasone as adjuvants to the combination of lignocaine with adrenaline and bupivacaine provided effective analgesia in supraclavicular brachial plexus block. However, dexmedetomidine demonstrated superior efficacy with faster onset of sensory and motor blockade, prolonged duration of sensory and motor block, extended duration of analgesia, lower pain scores at 12 and 24 hours, and reduced analgesic requirements compared to dexamethasone. These advantages were associated with a higher incidence of hemodynamic alterations and bradycardia in the dexmedetomidine group, though all adverse effects were transient and manageable.

This prospective comparative study demonstrated that dexmedetomidine as an adjuvant to lignocaine with adrenaline and bupivacaine combination provides significantly faster onset and longer duration of supraclavicular brachial plexus block compared to dexamethasone. The 2.72-minute faster sensory onset and 3.22-minute faster motor onset with dexmedetomidine represent clinically meaningful differences that can enhance operating room efficiency.

Our findings align with Das et al, who reported similar acceleration in block onset with dexmedetomidine [8]. The mechanism involves peripheral α2-adrenoceptor-mediated vasoconstriction reducing systemic absorption and prolonging local anesthetic retention at the target site, as described by Brummett et al [9]. Additionally, dexmedetomidine directly inhibits nerve conduction through modulation of hyperpolarization-activated cation currents.

The prolonged duration of blockade with dexmedetomidine (13.68±1.92 vs. 11.86±1.74 hours for sensory block) corroborates findings from Abdallah et al's systematic review, which documented 4-6 hours extension compared to local anesthetic combinations alone[10].This prolongation results from α2-adrenoceptor activation on peripheral nerves, decreasing norepinephrine release and enhancing sodium channel inhibition.

The superior analgesic profile of dexmedetomidine (16.42±2.18 vs. 14.28±1.96 hours) correlates with El-Boghdadly et al's meta-analysis[11]. The 26.5% reduction in analgesic consumption aligns with current opioid-sparing strategies and may facilitate enhanced recovery protocols, as similarly reported by Bharti et al[14].

Dexamethasone demonstrated moderate efficacy consistent with Choi et al's meta-analysis when added to local anesthetic combinations[12]. Its mechanism differs fundamentally, involving anti-inflammatory effects and membrane stabilization that require more time for expression, explaining the slower onset compared to dexmedetomidine's immediate ion channel modulation [13].

Hemodynamic effects revealed important safety considerations. Dexmedetomidine caused bradycardia in 11.11% of patients, similar to Marhofer et al's findings [15, 16]. While manageable with standard interventions, this necessitates careful patient selection. Conversely, dexamethasone exhibited hemodynamic stability, consistent with Pehora et al's review,[17] making it potentially safer for patients with cardiovascular concerns.

The combination approach using lignocaine with adrenaline and bupivacaine provides the advantage of rapid onset from lignocaine while maintaining prolonged duration from bupivacaine. The addition of adjuvants further enhances these characteristics, with dexmedetomidine showing superior performance in most parameters evaluated.

Study limitations include fixed dosing and 24-hour follow-up period. Future research should explore dose-optimization, adjuvant combinations, and evaluation in specific populations. Economic analyses would provide valuable data for resource-limited settings.

Overall, while both adjuvants effectively prolong supraclavicular block when added to lignocaine-bupivacaine combination, dexmedetomidine offers superior block characteristics at the cost of increased hemodynamic effects, necessitating individualized selection based on patient factors and clinical requirements.

Both dexmedetomidine and dexamethasone are effective adjuvants to lignocaine with adrenaline and bupivacaine combination in supraclavicular block for forearm surgeries. Dexmedetomidine provides faster onset, longer duration of block and analgesia, and reduced analgesic requirements compared to dexamethasone, albeit with higher incidence of bradycardia. The choice between these adjuvants should be individualized based on patient factors and clinical requirements.

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