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| ORIGINAL ARTICLE |
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| Year : 2022 | Volume
: 9
| Issue : 1 | Page : 42-48 |
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A comparative study of the effects of dexmedetomidine added as an adjuvant to bupivacaine, levobupivacaine, and ropivacaine in the brachial plexus blocks: A prospective randomized triple-blind study
Ramanareddy Venkata Moolagani, Ashalatha Annabhaktula, Padmavathi Vigrahala, Prasanna Eswari Pilla
Department of Anaesthesiology, Gayatri Vidya Parishad Institute of Health Care and Medical Technology, Visakhapatnam, Andhra Pradesh, India
| Date of Submission | 29-Jan-2022 |
| Date of Decision | 26-Apr-2022 |
| Date of Acceptance | 07-May-2022 |
| Date of Web Publication | 14-Jun-2022 |
Correspondence Address:
Dr. Prasanna Eswari Pilla
Department of Anaesthesiology, Gayatri Vidya Parishad Institute of Health Care and Medical Technology, Marikavalasa, Visakhapatnam, Andhra Pradesh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/ijamr.ijamr_24_22
Context: Bupivacaine is the most common local anesthetic agent used for brachial plexus blocks (BB). Due to the adverse effects noted with bupivacaine, safer alternative agents such as levobupivacaine and ropivacaine are being used now. Aims: Although several studies exist comparing pairs of anesthetic agents, few studies have compared all three agents using dexmedetomidine (DMT) as an adjuvant. To bridge this knowledge gap, we undertook the present study. Settings and Design: This was a prospective, randomized, placebo-controlled, triple-blind comparative study. Materials and Methods: Eighty patients were randomly allocated to four study groups: group B, given bupivacaine alone, and groups BD, LD, and RD, given twenty-five ml of 0.5% bupivacaine, 0.5% levobupivacaine, and 0.75% ropivacaine, respectively, along with DMT 0.5 μg/kg body weight. Onset of the sensory and motor blocks; duration of the sensory block,motor block and analgesia of the block were compared between the groups. Statistical Analysis Used: Differences between the groups were analyzed using one-way analysis of variance and Tukey's honestly significant difference -β post hoc test for parametric data, and for nonparametric data, Chi-square test and Fisher's exact test were used. Results: The durations of analgesia observed were 7 ± 0.7, 13.4 ± 0.6, 12.7 ± 1.0, and 12.5 ± 0.6 h in groups B, BD, LD, and RD, respectively; these differences were statistically significant (F = 294.825, P < 0.001). Post hoc tests revealed a statistically significant difference between Group B and all the other groups, between the BD and LD groups, and between BD and RD groups. The times to onset of sensory blocks observed were 11.3 ± 11.3, 7.6 ± 0.8, 8.1 ± 0.8, and 8.4 ± 0.8 min in groups B, BD, LD, and RD, respectively, while the times to onset of motor blocks observed were 17.1 ± 1.5, 11.0 ± 0.9, 10.3 ± 1.0, and 10.2 ± 0.7 min in groups B, BD, LD, and RD, respectively. Conclusions: DMT added as an adjuvant to bupivacaine, levobupivacaine, and ropivacaine resulted in a statistically significant enhancement of the duration of analgesia. Keywords: Brachial plexus block, bupivacaine, dexmedetomidine, levobupivacaine, ropivacaine
How to cite this article:
Moolagani RV, Annabhaktula A, Vigrahala P, Pilla PE. A comparative study of the effects of dexmedetomidine added as an adjuvant to bupivacaine, levobupivacaine, and ropivacaine in the brachial plexus blocks: A prospective randomized triple-blind study. Int J Adv Med Health Res 2022;9:42-8 |
How to cite this URL:
Moolagani RV, Annabhaktula A, Vigrahala P, Pilla PE. A comparative study of the effects of dexmedetomidine added as an adjuvant to bupivacaine, levobupivacaine, and ropivacaine in the brachial plexus blocks: A prospective randomized triple-blind study. Int J Adv Med Health Res [serial online] 2022 [cited 2023 Mar 29];9:42-8. Available from: https://www.ijamhrjournal.org/text.asp?2022/9/1/42/347469 |
| Introduction | |  |
For surgeries on the upper limb, brachial block (BB) is more advantageous than general anesthesia (GA) as it provides ideal conditions for the surgery and satisfactory analgesia extending to the postoperative period. Ultrasound-guided BBs offer the advantages of proper nerve localization, optimal needle placement, and a higher rate of success of the block.[1],[2] Till a few years back, bupivacaine was the most commonly used local anesthetic agent for BB as it provided a dense motor and sensory block of long duration. However, recently, there are several case reports of occurrence of central nervous system and cardiovascular system toxicity following inadvertent intravascular injection of bupivacaine. Because of these reasons, several safer alternative anesthetic agents such as ropivacaine and levobupivacaine are being used now.[3] Ropivacaine has comparable efficacy with bupivacaine and is reported to be safer with lesser adverse effects on the neurological and cardiovascular systems.[4] Resuscitation of cardiac toxicity resulting from ropivacaine results in more successful revivals than with bupivacaine.[5] Compared to ropivacaine, levobupivacaine is reported to provide a longer duration of analgesia, a favorable clinical profile, and lesser cardiotoxicity.[6]
Several adjuvants, such as dexmedetomidine (DMT), clonidine, and fentanyl, are used in combination with local anesthetic agents to enhance the characteristics of the block. In this context, DMT, an alpha-2-adrenergic receptor agonist, has emerged as the most popular adjuvant based on evidence that addition of DMT to local anesthetics prolongs the duration of analgesia and sensory and motor blocks, besides reducing the time of onset of sensory and motor blocks. Further, it is also reported to provide stable hemodynamics, sedative, analgesic, and sympatholytic effects without causing any respiratory depression.[7] The analgesic effect of DMT is mediated through stimulation of the α2C and α2A receptors in the dorsal horn, thereby directly suppressing the pain transmission by reducing the release of pronociceptive transmitters, substance P, glutamate, and hyperpolarization of interneurons.[8],[9] DMT is being safely used as an adjuvant for local anesthetics in subarachnoid blocks for operations of the lower limb and lower abdominal surgeries.[10] Although several studies exist comparing block characteristics of different pairs of the three local anesthetic agents bupivacaine, levobupivacaine, and ropivacaine, few have compared all the three agents together using adjuvant DMT. To bridge this knowledge gap, we undertook the present study to compare the characteristics of the BB obtained using equipotent doses of bupivacaine, levobupivacaine, and ropivacaine, along with adjuvant DMT against a control group of 0.5% bupivacaine without adjuvant DMT. We also wanted to evaluate the effect of DMT on the block characteristics of the three anesthetic agents. We added DMT at a dose of 0.5 μg/kg body weight to the local anesthetic agents, based on the findings of several case studies, which indicated that this dose of DMT produced an optimum effect on block characteristics with stable hemodynamic effects.[11]
| Materials and Methods | | |
We obtained approval for our study from our institutional ethical committee vide letter RC. No: GVPIHCMT/IEC/20201208/02 and got it registered with the clinical trial registry of India (CTRI/2020/12/030150). Eighty patients belonging to either sex and aged between 18 and 80 years, with weight ranging from 50 kg to 80 kg, and with American Society of Anesthesiologists (ASA) physical status Grade I and II, and attending our medical college hospital (Gayatri Institute of Health Care and Medical Technology, Visakhapatnam) for surgeries of the upper limb, were enrolled in this study undertaken between January 2021 and November 2021. Written informed consent was obtained from all the participants.
Exclusion criteria for our study were patients with known allergies to study drugs, patients not willing for local anesthetic block, patients suffering from neurological disorders of the upper limb, psychiatric disorders, mental retardation, coagulation, or bleeding abnormalities, pregnant women and lactating mothers, patients on negative chronotropic agents, those with severe respiratory disease, and those having an infection at the site of the block. Patients were randomly allocated to four study groups of 20 each (n = 20) using computer-generated random number sequence: group B, Group BD, Group LD, and Group RD. Serially numbered sealed opaque envelopes were used to effect allocation concealment. The anesthetic drug mixture for the BB was prepared by an anesthesiologist who was not associated with patient assessment during the intraoperative or postoperative period.
Patients in Group BD, group LD, and Group RD were given 25 ml of 0.5% bupivacaine, 0.5% levobupivacaine, and 0.75% ropivacaine, respectively. DMT 0.5 μg/kg body weight was added as an adjuvant and the total injected volume was made up to 30 ml by adding normal saline. Patients in Group B, who served as the control arm for our study, were given 25 ml of 0.5% bupivacaine and the total injected volume was made up to 30 ml by adding normal saline. The difference in the duration of analgesia was the primary outcome variable studied, while secondary outcome variables studied were differences in the time to onset of the motor and sensory blocks, the duration of the motor and sensory blocks, changes in pulse rate (PR), mean arterial pressure (MAP), respiratory rate (RR), peripheral oxygen saturation (SPO2), the total dose of rescue analgesics administered during the 1st 24 h of the postoperative period, surgeon assessment scores, patient satisfaction scores, and Ramsay sedation scores. Before posting for surgery, all patients were examined in the preanesthetic clinic by a thorough history taking and physical examination, and all the required investigations were carried out. In the preanesthetic clinic, detailed procedure of BB, methods of examination regarding the evaluation of the motor and sensory blocks, and assessment of pain on a verbal numerical rating scale (VNRS) were explained to the patients (VNRS scale: 0 = no pain and 10 = worst pain imaginable).[12]
All participants were advised to follow standard fasting guidelines before the surgery; no premedication containing sedatives was advised as it may confound observed sedation levels. Patients were kept supine on the operation table and a peripheral intravenous (IV) access was secured with an 18G IV cannula. PR, MAP, RR, electrocardiogram (ECG), saturation of peripheral oxygen (SpO2) were monitored. For all participants, the same anesthesiologist gave the BB using the same method of supraclavicular approach.
BBs were administered keeping the patients in a supine position with the head turned away from the side to be blocked while the arm to be anesthetized was kept in an adducted position. Under strict aseptic conditions, the block was performed using BPL Alpinion Ultrasound color Doppler, E CUBE 8 of Health line Medisystems, with a high-frequency linear probe of 3–12 MHz. The transducer was placed in the supraclavicular fossa behind the middle third of the clavicle and the total volume of 30 ml of the anesthetic agent was injected in 5 ml incremental doses after ensuring a negative aspiration for blood. Necessary support, through IV fluids and blood transfusions, was administered as required to maintain stable hemodynamic parameters.
The onset of the sensory block was assessed by testing for pain sensation with a pinprick method at every 2 min intervals for the initial 30 min after the administration of the block using a 27-G needle in the dermatomal areas innervated by the median, radial, ulnar, and musculocutaneous nerves. The times of the onset of sensory and motor blocks were defined as the times elapsed between the completion of the BB administration and the onset of complete sensory and motor blocks, respectively. Durations of sensory block and motor block were defined as the times elapsed between the onset of the sensory and motor blocks and the complete recovery of sensory and motor blocks, respectively, in all the nerve territories of the brachial plexus; this was assessed at every 15 min intervals subsequent to the initial 30 min period after the spinal block till complete motor and sensory recovery. The degree of the motor block was graded on a three-point modified Bromage scale for the upper limbs by testing for the ability of flexion at the elbow, wrist, and fingers against gravity.[13]
When any of the segments supplied by the median, radial, ulnar, and musculocutaneous nerves did not have sensory or motor block even after 30 min of the drug injection, the block was considered incomplete and GA was administered to complete the surgery; such cases were excluded from the study. When patients complained of pain of Grade 3 intensity on VNRS, injection diclofenac 1 mg/kg body weight was given intravenously as rescue analgesia and this time of administration of rescue analgesia was noted. The period between the onset of the sensory block and the time of administration of the first rescue analgesic medicine was considered as the total duration of analgesia.
Hemodynamic parameters of PR, MAP, RR, SPO2, sedation levels, and ECG were recorded at 5 min before the BB and subsequently at every 15 min intervals till complete recovery of the motor and sensory blocks. Sedation levels in the intraoperative and postoperative periods were assessed by the Ramsay sedation scale (RSS).[14] Adverse events observed during the study period such as nausea, vomiting, lower SPO2 levels, hypotension, bradycardia, shivering, allergic reactions, dryness of the mouth, and other complications were noted for statistical analysis. At the end of the surgery, surgeons and patients were enquired regarding their satisfaction level about the anesthetic procedure on a 3-point verbal assessment score.[15] Both in the case of patients and the surgeons, a score of two or three was considered as satisfactory and a score of one as an unsatisfactory satisfaction level.
Power analysis and sample size calculation were based on a population pooled variance of 2 h with respect to the duration of analgesia noted from the results of previous studies.
To detect a clinically significant difference in the duration of analgesia of 1 h between the groups and to obtain a power of the study of 80% with an alpha error of 5%, we need a sample size of 16. We included 20 patients in each group to compensate for any incomplete blocks and attrition due to patients leaving in the middle of the study.
Continuous data were expressed as mean ± standard deviation (SD) and discrete data as numbers and percentages. Microsoft Excel 2013 was utilized for compiling the data. The differences between the groups regarding the parametric continuous data were analyzed using analysis of variance test and the post hoc Tukey's (honestly significant difference) beta test was used for pairwise comparisons. For analyzing discrete data, the Chi-square test or Fisher's exact test was used as applicable. Statistical analysis was carried out using Microsoft Excel 2013 and IBM SPSS Statistics for Windows, version 22 (IBM Corp., Armonk, N.Y., USA). P ≤ 0.05 was considered statistically significant.
| Results | | |
Sample disposition is shown in the flowchart [Figure 1]. Eighty participants completed the study. Demographic features such as age, sex, body weight, height, ASA grades, and the side of the limb operated were comparable in all the four groups [Table 1]. | Table 1: Demographic characteristics of the patients across the groups (n=20 each)
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 | Figure 1: Flowchart showing participants progress through the study phases
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The durations of analgesia observed between the groups were analyzed and the test results revealed a significant difference (F = 294.825, P < 0.001) [Table 2]. Pair-wise comparisons revealed that the duration of sensory analgesia of Group BD was more than that of Groups LD, RD, and B [Table 2]. This showed that the addition of DMT as an adjuvant to bupivacaine, levobupivacaine, and ropivacaine resulted in a statistically significant enhancement of the duration of analgesia, which was more with bupivacaine than with other two agents. Pair-wise comparison revealed a statistically significant difference in analgesic effects between B and BD, B and LD, B and RD, BD and LD, and BD and RD; however, differences between the groups LD and RD were not statistically significant. Patients of Groups BD, LD, and RD consumed significantly less amount of analgesic medicines in the first 24 h postoperative period compared to those in Group B [Table 2], clearly demonstrating the fact that the addition of DMT to the three local anesthetic agents had enhanced the effect of analgesia. | Table 2: Characteristics of brachial plexus block between the groups (n=20 each)
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The times elapsed for the onset and duration of both the sensory and motor blocks are shown in [Table 2]; the times for onset of both sensory and motor blocks were decreased and the durations of both sensory and motor blocks were increased in patients of Groups BD, LD, and RD, in comparison to those in Group B.
The hemodynamic and other vital parameters such as PR, MAP, SPO2, RR, and ECG noted prior to administering the block were comparable in all groups. Fluctuations observed at 15-min intervals during the administration of the block and during intraoperative and postoperative periods were comparable and within the clinically acceptable range in all the groups. The changes noted in PR, MAP, and RSS are shown in [Figure 2], [Figure 3], [Figure 4], respectively. There were no instances of lower SPO2 levels or lower RR requiring active intervention. Few cases of bradycardia, hypotension, dryness of the mouth, nausea, and vomiting were noted in all four groups as shown in [Table 3], but there was no statistically significant difference in the rates of these side effects between the groups. The number, type, and duration of surgeries across groups are shown in [Table 4]. | Figure 3: Mean arterial pressure changes following administration of study drugs
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 | Figure 4: Ramsay sedation scores at different time intervals during surgery
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 | Table 3: Comparison of side effects and patient and surgeon satisfaction scores between the groups (n=20 each)
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 | Table 4: Number, type, and duration of surgeries across the groups (n=20 each)
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Statistical analysis of patient satisfaction levels with anesthetic technique revealed that patients of groups BD, LD, and RD had greater satisfaction levels in comparison [Table 3]. Analysis of the surgeon satisfaction levels with the anesthetic technique revealed that the surgeons operating on the patients of groups BD, LD, and RD had greater satisfaction levels compared to those of Group B [Table 3]. We did not encounter any failed block or patchy block in our study and no patient required supplemental analgesia or GA to complete the surgery.
| Discussion | | |
Ultrasound-guided BBs are advantageous for proper nerve localization and optimal needle placement with lesser discomfort to the patient, faster onset times, reduction of accidental vascular punctures, and a higher rate of success of the block with a lower volume of the local anesthetic compared to the blind techniques.[16] Bupivacaine is a widely used local anesthetic agent in regional anesthesia and is available as a racemic mixture (50:50) of two enantiomers: levobupivacaine and dextrobupivacaine. In the recent past, severe central nervous system and cardiovascular adverse reactions were reported after inadvertent intravascular injection of the racemic mixture of bupivacaine. The levorotatory isomers were shown to have a safer profile with less cardiac and neurotoxic adverse effects than bupivacaine and hence the pure levorotatory enantiomers ropivacaine and levobupivacaine were introduced into the clinical practice.
Local anesthetics interrupt the transmission of the action potential of excitable membranes by binding to specific receptors in the Na+ channels. Large volumes of local anesthetics required to produce desirable effects may result in systemic side effects.[17] Several adjuvants have been added to increase the duration of analgesia and reduce the total dose of local anesthetics used thereby minimizing the risk of local anesthetic toxicity. Recently, DMT has emerged as the most popular adjuvant for local anesthetics. It is a pharmacologically active d-isomer of medetomidine and is a highly specific and selective α2 adrenoceptor agonist with an α2:α1 binding selectivity ratio of 1620:1 as compared to 220:1 for clonidine. DMT has been successfully used in IV regional anesthesia and brachial plexus blocks (BBs).[18] Agarwal et al.[19] reported that DMT used as an adjuvant to bupivacaine in supraclavicular BBs had significantly shortened the onset time and prolonged the duration of sensory and motor blocks. Biswas et al.[20] studied the effect of adding DMT as an adjuvant to levobupivacaine and reported that it significantly shortened the onset time and prolonged the duration of the sensory and motor blocks.
Several clinical trials have established the fact that the administration of DMT as an adjuvant to local anesthetics in neuraxial and peripheral nerve blocks prolonged the duration of sensory and motor blocks.[21] These improved block characteristics are believed to be mediated through activation of alpha-2A adrenoceptors (α2-AR).They reduce the release of peripheral norepinephrine by stimulation of prejunctional inhibitory α2-AR and inhibit central neural transmission in the dorsal horn by presynaptic and postsynaptic mechanisms. They also have direct sympatholytic effects on spinal preganglionic sympathetic neurons. Centrally, α2 agonists produce analgesia and sedation by inhibiting the release of substance P in the nociceptive pathway at the level of the dorsal root neuron and by activatingα2-AR in the locus coeruleus.[22],[23]
To our knowledge, no prior study has compared the characteristics of BB with the three local anesthetic agents, i.e., bupivacaine, levobupivacaine, and ropivacaine in a single study employing DMT as an adjuvant. In our study, significant prolongation of the duration of the sensory and motor blocks and the duration of analgesia was observed in all three groups with DMT in comparison with the control group.
Comparing 29 ml of 0.5% levobupivacaine plus 50 μg of DMT against the same volume but 100 μg of DMT, Nallam et al. concluded that 50 μg of DMT had produced optimal results, whereas 100 μg of DMT group had a higher incidence of bradycardia. These findings are concurrent with what we observed in regard to block characteristics and complications except for the onset of sensory and motor blocks, which was longer in the prior study. However, it must be noted that we used a lesser volume of levobupivacaine. The earlier onset times noted in our study could be because we used ultrasound-guided blocks as opposed to the nerve stimulation technique used by Nallam et al. earlier.[24]
Chinnappa et al.,[25] using 30 mL 0.5% ropivacaine with 1 μg/kg of DMT as an adjuvant, reported similar times for onset of sensory and motor blocks as in the present study. Occurrences of bradycardia and hypotension were higher in their study; this may be due to the lower dose of DMT used in our study. This finding supports our assumption that 0.5 μg/kg of DMT provides optimal block features with minimal hemodynamic fluctuations.
In a study using ultrasound guided block, investigators[26] reported that with 20 ml of 0.75% ropivacaine plus DMT 1 μg/kg, the sensory and motor block durations were similar to what we found. Notably, we employed a lesser dose of 0.5 μg/kg DMT and this dose appears to be the optimal dose to be used. Similarly, Meena et al.,[27] using 0.5% bupivacaine with DMT 1 μg/kg, in supraclavicular BB by a nerve stimulation technique, reported similar outcomes measures as we found except for duration of analgesia, which was longer in the present study. This difference could be a function of variations in block technique.
Limitations of our study include a small sample size and that the findings are from a single center. Further multicentric studies on larger samples are required to confirm our observations.
| Conclusions | | |
DMT used as an adjuvant, at a dose of 0.5 μg/kg body weight, to 25 ml of 0.5% bupivacaine or 0.5% levobupivacaine, or 0.75% ropivacaine prolonged the duration of analgesia and sensory and motor blocks and also produced faster onset of sensory and motor blocks with stable hemodynamic profile and attainment of satisfactory sedation levels with minimal complications.
Financial support and sponsorship
The study was financially supported by Gayatri Vidya Parishad Institute of Health Care and Medical Technology, Marikavalasa, Visakhapatnam, Andhra Pradesh, India.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]
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