|Year : 2020 | Volume
| Issue : 2 | Page : 121-128
Efficacy of dexmedetomidine used as an adjuvant to 0.5% ropivacaine in ultrasound-guided supraclavicular brachial plexus block for upper limb surgeries
Kavita Jain, Surendra Kumar Sethi, Vikas Gupta, Deepak Kumar Garg
Department of Anaesthesiology, J.L.N. Medical College, Ajmer, Rajasthan, India
|Date of Submission||02-Sep-2019|
|Date of Acceptance||12-Feb-2020|
|Date of Web Publication||19-Sep-2020|
Dr. Surendra Kumar Sethi
Flat No. 202, Shiva Enclave, Civil Lines, Ajmer, Rajasthan
Source of Support: None, Conflict of Interest: None
Background: Supraclavicular brachial plexus block (SCBPB) has gained popularity with the addition of various adjuncts to local anesthetics. This study aimed to evaluate the efficacy of dexmedetomidine as an adjuvant to 0.5% ropivacaine in ultrasound-guided (USG) SCBPB.
Materials and Methods: One hundred patients of either sex, belonging to the American Society of Anesthesiologists physical status I or II, aged between 15 and 65 years and scheduled for elective upper arm surgery under USG SCBPB were enrolled. Patients were randomly allocated into two groups (n = 50). Both groups received 16 ml (120 mg) 0.75% ropivacaine with 1 μg/kg dexmedetomidine diluted in 8 ml normal saline (NS) (Group Ropivacaine Dexmedetomidine [RD]) or with 8 ml NS only (Group R). The primary outcome measure was the duration of analgesia, whereas secondary outcome measures were onset and duration of sensory and motor block, quality of anesthesia, sedation score, hemodynamic changes, and side effects. Statistical analysis was performed using unpaired Student's t-test or nonparametric Mann–Whitney test and Chi-square test.
Results: The duration of analgesia was significantly prolonged in Group RD (730.70 ± 51.62 min) compared to Group R (388.30 ± 41.66 min), (P < 0.0001). The onset time of sensory and motor block was significantly shorter in Group RD in comparison to Group R (P < 0.001). The duration of sensory and motor block was significantly prolonged in Group RD compared to Group R, (P < 0.0001). The quality of anesthesia was significantly better in Group RD (P < 0.05). Sedation scores were significantly higher in Group RD (P < 0.05). No significant hemodynamic changes and side effects were observed in both groups (P > 0.05).
Conclusion: Dexmedetomidine provides the prolonged duration of analgesia along with faster onset as well as prolonged duration of both sensory and motor block without any significant hemodynamic changes and side effects.
Keywords: Dexmedetomidine, ropivacaine, supraclavicular brachial plexus block, ultrasound
|How to cite this article:|
Jain K, Sethi SK, Gupta V, Garg DK. Efficacy of dexmedetomidine used as an adjuvant to 0.5% ropivacaine in ultrasound-guided supraclavicular brachial plexus block for upper limb surgeries. Indian Anaesth Forum 2020;21:121-8
|How to cite this URL:|
Jain K, Sethi SK, Gupta V, Garg DK. Efficacy of dexmedetomidine used as an adjuvant to 0.5% ropivacaine in ultrasound-guided supraclavicular brachial plexus block for upper limb surgeries. Indian Anaesth Forum [serial online] 2020 [cited 2020 Oct 25];21:121-8. Available from: http://www.theiaforum.org/text.asp?2020/21/2/121/295387
| Introduction|| |
Upper limb orthopedic surgeries can be performed under both regional anesthesia (RA) and general anesthesia (GA). RA has an added advantage of postoperative analgesia. It provides ideal operating conditions with adequate relaxation of muscles of the upper limb, stable intraoperative hemodynamics, and postoperative period free from nausea, vomiting, central nervous system depression, and pain. Avoidance of GA and resultant complications itself is the greatest advantage of RA. Nowadays, upper limb surgeries are preferably done under peripheral nerve blocks.,
The supraclavicular brachial plexus block (SCBPB) is a safe alternative to GA using advanced techniques like ultrasound, newer local anesthetics (LAs) and newer adjuvants for successful conduct and improved efficacy of block. The classical approach using paresthesia technique and peripheral nerve stimulator techniques are blind procedures and associated with higher failure and complication rates.,,, Ultrasound-guided (USG) SCBPB is quick to perform, offers improved safety, fewer respiratory complications and accuracy in identifying the position of the structures and nerves to be blocked.,
Various LAs used previously have short duration of sensory and motor block and short duration of analgesia. Bupivacaine being most potent is used frequently, but it has high cardiac toxicity potential. Ropivacaine, a long acting amide is a newer drug with a safer cardiac profile. Due to its unique pharmacological properties and fewer side effects, it is now preferred by anesthesiologists for peripheral nerve blocks. In recent years, the addition of various adjuncts to LA solution has been acclaimed to increase the efficacy and duration of block while minimizing the systemic adverse effects as it reduces the total dose of LA used. Dexmedetomidine, an α2-adrenoceptor agonist, has become well known as an adjuvant to LA. It prolongs the postoperative analgesia, provides better hemodynamic stability and has minimal side effects, thus preferred over other adjuvants.
In this study, we have compared the effect of 1 μg/kg dexmedetomidine and placebo given perineurally as an adjuvant to 0.75% ropivacaine (final concentration achieved is 0.5%) in USG-guided SCBPB. The primary outcome measure was the duration of analgesia, whereas secondary outcome measures were time of onset and duration of sensory and motor blocks, sedation score, quality of anesthesia, hemodynamic changes, and side effects.
| Materials and Methods|| |
After approval from the institutional ethical committee (No. 2370/Acad-III/MCA/2016 Dt. 18/12/2018) and CTRI registration (CTRI/2019/01/017309), this prospective, randomized, double-blind, comparative study was conducted on 100 patients of either sex, belonging to the American Society of Anesthesiologists (ASA) physical status I or II aged between 15 and 65 years and scheduled for various elective upper limb surgeries under USG SCBPB. Patients who did not give consent, had chronic pain or on long-term analgesics, allergic to any of the study drugs, had history of significant respiratory, cardiac, hepatic, renal, neurological, psychiatric, neuromuscular disease, bleeding or thyroid disorder, had any preexisting neurological deficit with local pathology at the site of injection, pregnant or lactating mothers were excluded from this study.
The patients were randomly allocated into two groups by chit in box method. Patients in Group R (n = 50) received 0.75% isobaric ropivacaine 16 ml (120 mg) diluted with 8 ml normal saline (NS), whereas Group RD (n = 50) received 0.75% isobaric ropivacaine 16 ml (120 mg) with dexmedetomidine (1 μg/kg) prepared in 8 ml NS (total volume-24 ml and final concentration of the solution-0.5%) using USG SCBPB [Figure 1]. To maintain blinding, the anesthesiologists who prepared the study drug, performed the procedure and monitored the patients as well as the patient and surgeon, all were unaware of group allocation.
All patients underwent a thorough preanesthetic evaluation before surgery including history, physical examination, and routine investigations. Written informed consent was obtained from all patients after explaining the anesthetic technique, use of ultrasound machine and merits or demerits of the procedure. All patients were kept nil per oral at least 8 h before surgery. After the arrival of the patient in the operating room, an intravenous (IV) line was secured using 18G IV cannula, and the ringer's lactate solution was started. Patients were not given any premedication. After reassuring the patient, standard ASA monitoring was applied, including noninvasive blood pressure (NIBP), pulse oximetry (SpO2), and electrocardiogram (ECG). The baseline values of heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), respiratory rate (RR), SpO2, and sedation score were recorded.
Under strict aseptic precautions and after local infiltration of 2 ml (2%) lidocaine, brachial plexus was located using USG (SonoSite M-Turbo) FUJIFILM Sonosite Inc. 21919 30th drive SE Bothell, WA 98021, USA) with high frequency 13-6 MHz Linear probe HFL 38x (placed superior and parallel to clavicle), and then 24 ml of drug solution was injected within the nerve sheath using needle (22G, 5 cm long) after negative blood aspiration. A brief massage was performed for 1 min at the injection site to facilitate even drug distribution. The patient was evaluated for the onset of sensory and motor block every 2 min for the first 30 min after the injection of the study drug. The sensory block was assessed by pinprick with 25G hypodermic needle and graded as Grade 0-sharp pain on pinprick (normal sensation), Grade 1-loss of the sensation of pinprick (analgesia), Grade 2-loss of the sensation of touch (anesthesia). The onset of sensory block was defined as the time interval between the end of total LA administration and disappearance of sharp pain by pinprick test (Grade 1 sensory block) in skin dermatome C4-T2 and duration of sensory block was defined as the time taken from the administration of LA to the return of touch sensation (complete recovery of anesthesia) in the territories of all nerves.
Motor block was evaluated by thumb abduction (radial nerve), thumb adduction (ulnar nerve), thumb opposition (median nerve), and flexion at the elbow (musculocutaneous nerve) and graded as Grade 0-normal motor function, Grade 1-reduced motor strength but able to move fingers (paresis), and Grade 2-complete motor block (paralysis). The onset of motor block was defined as the time interval between the LA administration and the grade 1 motor block (paresis). The duration of motor block was defined as the time interval between the LA administration and the recovery of the complete motor function of the hand and forearm (return to Grade 0 motor block). The grade of sensory and motor block was also checked soon after completion of surgery. The highest grade of sensory and motor block achieved was also recorded. The time of the start of surgery (incision) and completion of surgery (skin closure), i.e., duration of surgery, was noted. Blood loss was assessed and managed accordingly with fluids. Failure of block/inadequate block defined as block Grade < 1 for both sensory and motor block even after 30 min of LA administration. Such cases were managed by providing GA and were excluded from the study.
At the end of the operation, quality of anesthesia was graded by the anesthesiologist as-Excellent (4): No complaint from the patient, Good (3): Minor complaint with no need for supplemental analgesics, Moderate (2): Complaint that required supplemental analgesics and Unsuccessful (1): Patient required GA. A five-point sedation scale was used; 1: Awake and alert; 2: Sedated, responding to verbal commands; 3: Sedated, responding to the mild physical stimulus; 4: Sedated; responding to moderate or severe physical stimulus and 5: Not arousable.
HR, SBP, DBP, MAP, RR, SpO2, and sedation scores were noted every 5 min for the first 30 min and thereafter every 15 min till the completion of surgery. Postoperative HR, SBP, DBP, MAP, RR, sedation score, sensory and motor block grades were recorded at various time intervals-0 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 18 h, and 24 h. Pain was assessed using visual analog scale (VAS) graded from 1 (no pain) to 10 (worst imaginable pain). The rescue analgesic (diclofenac sodium 75 mg I.M.,) was given at VAS ≥4 and the time was noted. The duration of analgesia was defined as the time from the commencement of block to the time when the patient first demanded rescue analgesia or VAS ≥4. All patients were monitored for adverse perioperative events such as hypotension, bradycardia, nausea or vomiting, respiratory depression, dryness of mouth, pneumothorax, hematoma, LA toxicity, and post block neuropathy.
The sample size calculation was based on the previous study. The sample size was estimated using duration of analgesia among two groups as the main primary outcome measure. To calculate the required sample size for comparison of two independent means, the required inputs are Type I error (alpha), Type II error (beta), the hypothesized difference and standard deviations (SDs) in the first and second samples. Using table of trade-offs for any combination of sample size and power, a sample size of 40 in each group has the 80% power and 95% confidence interval to detect a difference between means of 4.08 and SD of 6.5 min with a significance level (alpha) of 0.05 (two-tailed). Hence, a sample size of 50 in each group was used in this study. The statistical analysis was carried out by the Chi-square test for nominal categorical data such as gender and ordinal categorical data, whereas unpaired Student's t-test/nonparametric Mann–Whitney test was used for intergroup comparison. Values are presented as Mean ± SD, median (interquartile range), or number (%). Raw data were entered into a Microsoft Excel spreadsheet analyzed using standard SPSS statistical software version 18.0 (SPSS Inc., Chicago, IL, USA). P < 0.05 was considered statistically significant.
| Results|| |
One hundred and eighteen patients were enrolled in our study. Eighteen patients were excluded from the study as 15 patients did not meet the inclusion criteria and three patients had other reasons. Hence, a total of 100 patients were randomly divided into two groups of 50 patients each. None of the patients were lost to follow-up [Figure 1]. The demographic data including age, sex, height, weight, ASA physical status classification, and duration of surgery were comparable between two groups; [Table 1].
|Table 1: Comparison of demographic data and duration of surgery in two groups|
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The mean duration of analgesia in Group R and RD was 388.30 ± 41.66 min and 730.70 ± 51.62 min, respectively. The mean duration of analgesia was prolonged in Group RD as compared to Group R and this difference was statistically significant; (P <0.0001) [Table 2].
The mean onset time of sensory blockade for Group R and RD was 9.34 ± 1.17 min and 5.58 ± 1.18 min, respectively. The onset of sensory block in Group RD was significantly faster as compared to Group R (P <0.0001). Similarly, the mean onset time of motor blockade for Group R and RD were 19.34 ± 1.92 and 16.32 ± 2.36 min, respectively. The onset of the motor blockade in Group RD was significantly faster as compared to Group R; (P <0.0001) [Table 2].
The mean duration of sensory block in Group R and RD was 339.30 ± 39.45 min and 676.40 ± 45.40 min, respectively. The mean duration of sensory block was prolonged in Group RD as compared to Group R, and this difference was statistically significant; (P <0.0001). The mean duration of motor block in Group R and RD was 278.50 ± 29.70 min and 582.60 ± 43.19 min, respectively, and the mean duration of motor block was also significantly prolonged in Group RD as compared to Group R; (P <0.0001).
The grade of quality of anesthesia (Median [interquartile range (IQR)]) was significantly better in Group RD 4 (4-4) when compared to Group R 4 (3–4); (P <0.001) [Table 3]. The sedation score (Median [IQR]) was recorded at predefined time intervals during both the intraoperative and postoperative periods. The sedation score in Group RD was significantly higher during a time interval from 10 min intraoperatively to 2 h postoperatively as compared to Group R which had a mean sedation score of one throughout this period. The difference in sedation score was statistically highly significant (P <0.0001) with a maximum sedation score being 3 (3-3) in Group RD at 25 and 30 min intraoperatively; [Figure 2].
|Table 3: Comparison of grade of quality of anesthesia in both groups (median [interquartile range])|
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|Figure 2: Comparison of sedation scores in two groups (Median [interquartile range]). *Sedation score expressed as Median (interquartile range) - Interquartile range.*Group R: Ropivacaine; Group RD: Ropivacaine + dexmedetomidine|
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The mean HR was lower in Group RD as compared to Group R during a time interval of 5 min to 75 min and the difference was statistically significant (P <0.001). Similarly, the mean SBP and MAP were also significantly lower in Group RD when compared to Group R from 20 min to 75 min intraoperatively; (P <0.05). However, the mean DBP remained comparable at all-time intervals in both groups; (P > 0.05). Similar trends were noted for both RR and SpO2 and they remained comparable at all-time intervals in both groups; (P > 0.05) [Figure 3].
|Figure 3: Comparison of various hemodynamic parameters in two groups. *Group R: Ropivacaine; Group RD: Ropivacaine+Dexmedetomidine*HR: Heart rate; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; MAP: Mean arterial pressure |
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No significant adverse effects or complications were observed in any of the group during both intraoperative and postoperative period except three patients in Group RD who had bradycardia intraoperatively but was managed by awakening the patient with the gentle tap (arousable sedation) and no pharmacotherapy was given.
| Discussion|| |
The present study aimed to evaluate the effect of adding dexmedetomidine to isobaric ropivacaine 0.75% (final concentration achieved was 0.5%)) in USG-guided SCBPB. We have used 24 ml of study drug (0.5% ropivacaine with or without dexmedetomidine 1 μg/kg) and found satisfactory results regarding the efficacy of block and duration of analgesia in comparison with a similar study done by Das et al. who had used 30 ml of 0.5% ropivacaine with or without 100 μg dexmedetomidine. The rationale for choosing 0.5% concentration of ropivacaine was supported by Klein et al. who found that increasing the concentration of ropivacaine had no benefit in improving the onset and duration of the block while simultaneously reducing the risk associated with a higher total dose of local anesthetic. O'Donnell and Iohom and Eichenberger et al. found that needle placement and visualization of the spread of the injected LA under USG guidance reduced the amount of LA needed for successful peripheral nerve block. We have used lower dose of ropivacaine (120 mg) in comparison to other studies done by Das et al. and Tiwari et al. who had used comparatively higher doses of ropivacaine (150 mg) in their studies, thereby reducing the risk of LA systemic toxicity.
In our study, the mean duration of analgesia was significantly prolonged in Group RD (730.70 ± 51.62 min) as compared to Group R (388.30 ± 41.66 min). This result was further supported by similar results of previous studies done by Das et al. (846.67 ± 102.09 min), Gurajala et al., (960 min), Kathuria et al. (967.55 ± 310.50 min), and Tiwari et al. (1209.90 ± 107.536 min), who reported a significant prolongation of the duration of analgesia with dexmedetomidine. The significant prolongation of the duration of analgesia in the study done by Tiwari et al. might be due to the higher concentration of ropivacaine (0.75%) used in their study. Various mechanisms have been proposed for the analgesic effect of dexmedetomidine. Ishii et al. conducted a study to evaluate the action of dexmedetomidine on the neurons in the substantia gelatinosa of the rat spinal cord and concluded that the analgesic effect of dexmedetomidine is mediated through stimulation of α2C and α2A receptors in the dorsal horn which leads to suppression of pain transmission by reducing the release of pro-nociceptive transmitters like substance P and glutamate, and hyperpolarization of interneurons. However, Kathuria et al. in their study concluded that the central effects of dexmedetomidine also seem to play some role in the prolongation of sensory and motor block duration. Brummett et al. also described the prolongation of analgesic effect due to blocking the hyperpolarization-activated current.
The mean onset time of sensory block was significantly shorter in dexmedetomidine group (5.58 ± 1.18 min) when compared to the group with ropivacaine alone (9.34 ± 1.17 min). The mean onset of sensory block was found to be even earlier than the studies done by Das et al. (14.71 ± 3.70 min) and Gurajala et al.(24 min) probably due to different definition of onset of sensory block taken in our study as the loss of pinprick sensation (Grade 1) rather than loss of touch sensation (Grade 2). The mean duration of sensory block was significantly prolonged in the dexmedetomidine group (676.40 ± 45.40 min) when compared to group with ropivacaine alone (339.30 ± 39.45 min). Similar results were observed in previous studies done by Kathuria et al., Gurajala et al., Das et al., Tiwari et al., and Marhofer et al. who reported a significant prolongation of sensory blockade in dexmedetomidine group that might be due to prolonged hyperpolarization of unmyelinated C fibers (sensory) and to a lesser extent the A fibers (motor).
In our study, the mean onset time of motor block (16.32 ± 2.36 min in Group RD vs. 19.34 ± 1.92 min in Group R) was significantly shortened in the dexmedetomidine group. Similar results were reported by Das et al. (19.96 ± 1.28) and Kathuria et al.(18.75 ± 6.37 min) who used higher doses of ropivacaine (150 mg) in their studies; however, Tiwari et al. found earlier onset of motor block (11.62 ± 3.395 min) though they had also used higher dose of ropivacaine (150 mg) in their study. In contrast to the study done by Gurajala et al., the onset time of motor block was shorter in our study which might be due to the definition of the onset of motor block used in our study as paresis (Grade 1) while it was taken as complete paralysis (Grade 2) in the previous study. The mean duration of motor block (582.60 ± 43.19 min in Group RD versus 278.50 ± 29.70 min in Group R) was significantly prolonged in the dexmedetomidine group. Similar findings were noted with dexmedetomidine in studies done by Das et al. (624.2 ± 200.9 min), Gurajala et al. and Kathuria et al.
The quality of anesthesia score was significantly better in the dexmedetomidine group in accordance with the previous study done by Kathuria et al. This depicted the improved quality of anesthesia from good to excellent in most of the patients and favors the use of dexmedetomidine. The median sedation score in Group RD was significantly higher (P <0.0001) from 10 min intraoperatively to 2 h postoperatively as compared to Group R. Intraoperatively, the maximum median sedation score recorded was found to be 3 (3-3) in Group RD at 30 min. The patients had conscious sedation and remained arousable throughout the intraoperative and postoperative periods. The sedation score was assessed by Das et al., Kathuria et al., and Culebras et al. in their studies. Our results were further supported by the studies done by Ebert et al. and Hsu et al. It has been hypothesized that dexmedetomidine produces the sedative effect by its action on alpha 2 receptors in the locus coeruleus and analgesia by its action on alpha 2 receptors within the locus coeruleus and the spinal cord.
In a meta-analysis done by Abdallah and Brull it has been showed that dexmedetomidine is a potential LA adjuvant which prolonged the duration of LAs. However, they recommended some more studies to establish the safety of dexmedetomidine when used as a perineural adjunct to LAs especially when the drug is used off-label. Similarly, Dai et al. also conducted a meta-analysis in which they investigated the efficacy and safety of dexmedetomidine added to ropivacaine in brachial plexus blocks. They showed that dexmedetomidine prolonged the duration of sensory and motor block along with the duration of analgesia. They also recommended further research studies to find more effective and safer doses of dexmedetomidine. In a recent study by Chinnappa et al., they showed that dexmedetomidine used as an adjuvant to perineural ropivacaine in SCBPB is effective in providing prolonged duration of sensory and motor block with the duration of analgesia. Our study results are in concordance with the results of these meta-analyses done. There is insufficient safety data available for using perineural dexmedetomidine so the safety of perineural dexmedetomidine needs to be established by further research studies.
As far as hemodynamic parameters are concerned, the mean HR was significantly (P <0.001) decreased in Group RD when compared to Group R during the time interval of 5–120 min. The decrease in HR was more during 5–75 min intraoperatively and can be correlated with higher sedation scores in that period. Despite of lower HRs in Group RD, only three patients had bradycardia (HR < 50 beats/min) that was managed without any pharmacological intervention. Intraoperatively, the mean SBP, DBP, and MAP were significantly (P <0.001) decreased in Group RD when compared to Group R, but no significant hypotension was recorded in both groups. Similar trends of hemodynamic parameters were found in studies done by Tiwari et al. and Gurjala et al. No other significant hemodynamic changes or any other complication occurred in both groups.
As with all studies, this study has its drawbacks. The major limitation of this study is that there was a lack of control group with IV administration of dexmedetomidine to compare it with the perineural route. It does not make any hypothesis regarding the mechanism of action of dexmedetomidine. No recommendations were made for its use in age < 15 years and > 65 years. The number of rescue analgesics consumed postoperatively in 24 h was not calculated. No premedication was used, so co-operation of the patient was needed and anxiety remained an objective issue in few patients, especially in the control group. It was difficult to perform block in obese patients even under ultrasound guidance. Although the results of our study are consistent with previous studies, but none of the studies establish its safety data as a perineural adjunct. They recommended that it can be used safely as an adjunct to local anesthetics, but the available evidence is insufficient regarding the safety profile of dexmedetomidine used as an adjuvant to perineural ropivacaine so further research needs to be conducted to establish its safety profile.
| Conclusion|| |
Hence, we conclude that addition of 1 μg/kg dexmedetomidine to 0.5% isobaric ropivacaine in SCBPB resulted in prolonged duration of analgesia along with the faster onset of both sensory and motor block, longer duration of sensory and motor blockade, better quality of anesthesia, and hemodynamic stability without any undue sedation or side effects. Thus, dexmedetomidine can be considered as an effective adjuvant to ropivacaine in SCBPB for upper limb orthopedic surgeries.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]