|Year : 2017 | Volume
| Issue : 1 | Page : 28-34
Dexmedetomidine in supraclavicular block: Effects on quality of block and analgesia
Vivek S Palsule1, Avani P Shah1, Hitendra H Kanzariya2
1 Department of Anesthesia, Choithram Hospital and Research Center, Indore, Madhya Pradesh, India
2 Department of Anesthesia, PramukhSwami Medical College, Karamsad, Gujarat, India
|Date of Web Publication||5-May-2017|
Avani P Shah
5/A, Everest Park Society, Opp. Matangi Flate, Gordhanwadi Tekra, Kankaria, Ahmedabad - 380 028, Gujarat
Source of Support: None, Conflict of Interest: None
Context and Objectives: Upper limb surgeries are most commonly performed under brachial plexus block (BPB). A variety of adjuvants have been used to enhance the effect of local anesthetics in peripheral nerve block. We evaluated the effect of dexmedetomidine as an adjuvant to 0.25% bupivacaine in supraclavicular block (SCB) in terms of onset and duration of sensory and motor block, analgesia, and quality of block. Subjects and Methods: Sixty American Society of Anesthesiologists physical status I and II patients undergoing upper limb surgery, in which SCB was used, were enrolled. Patients were assigned to one of the following groups alternatively: Group C received BPB with bupivacaine 0.25% (34 ml) + normal saline 1 ml. Group D received BPB with bupivacaine 0.25% (34 ml) + dexmedetomidine 1 μg/kg. Onset and duration of sensory and motor block, duration of analgesia, sedation score, and hemodynamic parameters were studied in both the groups. Results: There were no significant differences in patient and surgery characteristics between two groups. In Group D, shorter time to onset of sensory block (09.8 vs. 15.3 min, P = 0.006) and longer duration (691.3 vs. 395.6 min, P = 0.006) was observed. Onset time to achieve motor block (11.8 vs. 17.3 min, P = 0.009) was also short and duration was longer (637 vs. 367.6 min, P< 0.001) in Group D. Duration of analgesia (735.6 vs. 423.6 min, P< 0.001) was higher as compared to control group. Conclusions: Adding dexmedetomidine to bupivacaine during supraclavicular BPB shortens sensory and motor block onset time, increases the sensory and motor block duration, and prolongs the duration of postoperative analgesia without any significant side effect.
Keywords: Analgesia, bupivacaine, dexmedetomidine, supraclavicular block
|How to cite this article:|
Palsule VS, Shah AP, Kanzariya HH. Dexmedetomidine in supraclavicular block: Effects on quality of block and analgesia. Indian J Pain 2017;31:28-34
| Introduction|| |
Upper limb surgeries are mostly performed under brachial plexus block (BPB) which avoids the unwanted effects of anesthetic drugs, stress of laryngoscopy and tracheal intubation, and also extend analgesia in the postoperative period without any systemic side effects such as nausea, vomiting, and respiratory depression. Supraclavicular approach for BPB gives the most effective block for all portion of upper extremity.,,
A variety of adjuvants have been studied for BPB including opioid and nonopioid agents., Alpha-2 adrenergic receptor agonists have been the focus of interest for their sedative, analgesic, perioperative sympatholytic, and cardiovascular stabilizing effects with reduced anesthetic requirements.,, Dexmedetomidine, an imidazole compound, dextroisomer of medetomidine, displays specific and selective α2-adrenoceptor agonist. Dexmedetomidine may act on supraspinal (locus coeruleus) or spinal level or peripheral α2-adrenoreceptor to reduce nociceptive transmission, leading to analgesia. In various animal studies, dexmedetomidine has been reported to enhance sensory and motor block along with increased duration of analgesia.,,, However, there remains limited knowledge on the analgesic efficacy and clinical utility of adding dexmedetomidine to local anesthetics during peripheral nerve block in humans.,
In our study, we evaluated the effect of dexmedetomidine as an adjuvant to 0.25% bupivacaine in supraclavicular block (SCB) in terms of onset and duration of sensory and motor block, postoperative analgesia, and quality of block.
| Subjects and Methods|| |
Sixty American Society of Anesthesiologists Physical Status I and II patients aging 18–60 years undergoing upper limb surgery were included in the prospective randomized controlled study after obtaining Ethical Committee clearance and informed consent. Sample size calculation was based on previous studies. Keeping the power at 80% and confidence interval at 95%, to detect at least 15% difference in duration of analgesia, the minimum sample size required was 16 patients in each group. However, we included thirty patients in each group for better validation of results.
Patients with cardiorespiratory and renal or hepatic failure; receiving adrenoreceptor agonist or antagonist treatment; and pregnant women were excluded from the study.
All the patients underwent thorough preanesthetic evaluation and basic laboratory investigations, and the anesthetic procedure to be carried out was explained. They were educated regarding the visual analog scale (VAS). All the patients were kept nil orally (nil by mouth) for 6 h.
Methodology of study
Patient grouping and drug dosing
Patients were assigned to one of the following two groups alternatively. Group C received block with bupivacaine 0.25% (34 ml) + normal saline 1 ml whereas Group D received block with bupivacaine 0.25% (34 ml) + dexmedetomidine 1 μg/kg.
In the operation theater, baseline heart rate (HR), blood pressure (BP), respiratory rate (RR), and oxygen saturation (SpO2) were recorded. An intravenous (IV) line was secured in the unaffected limb and IV fluid was started. No premedication was given. With patient placed in supine position, the head was turned away 45° from the side to be blocked and the arm adducted with hand extended toward the ipsilateral knee. A small roll of towel placed between the shoulder blades to make the plexus taut. The point of entry was the lateral border of anterior scalene muscle, approximately 1.5–2 cm posterior to the midpoint of clavicle. After antiseptic painting and draping, a skin wheal was raised with local anesthetic (2 ml of 2% lignocaine).
Neural localization was achieved using a nerve locator connected to a 22-gauge, 50 mm long stimulating needle (Stimuplex, Braun, Germany). The stimulator was adjusted to 1 mA, 2 Hz, 0.1 ms parameters at the beginning of the procedure. The location end point was a distal motor response with lower than 0.5 mA. After localization, 35 ml of a drug solution as mentioned above was injected. During injection, negative aspiration was performed every 3 ml to avoid intravascular injection. A 3 min massage was performed to facilitate an even drug distribution.
Sensory block was assessed by the pinprick method. It was graded as grade 0: sharp pin felt; Grade 1: analgesia, dull sensation felt; and Grade 2: anesthesia, no sensation felt. Motor block was assessed with modified Bromage scale for upper extremities on a three-point scale: 0 = normal motor function, 1 = ability to flex and extend wrist and fingers, 2 = ability to flex and extend only fingers, 3 = complete motor block with the inability to move elbow, wrist, and finger. Sensory and motor block were assessed at each minute after completion of drug injection for first 30 min and thereafter every 30 min till complete recovery.
The time between the end of the drug injection and a dull sensation to pinprick along the distribution of any of nerves - median, ulnar, radial, or musculocutaneous was considered as onset time of sensory block, and the time between the end of the drug injection and Grade 1 motor block was considered as onset time for motor block. The duration of sensory block was the time interval between the onset time of sensory block and the complete resolution of anesthesia on all nerves, and the duration of motor block was the time interval between the onset time of motor block and the recovery of complete motor function of that limb.
The block was considered incomplete when any of the segments supplied by median, radial, ulnar, and musculocutaneous nerve was not having analgesia even after 30 min of drug injection. These patients were supplemented with IV fentanyl (1 μg/kg) and midazolam (0.02 mg/kg). When more than one nerve remains unaffected, it was considered a failed block. In this case, general anesthesia was given, and those cases with failed block were excluded from analysis.
Patients were monitored for hemodynamic variables such as HR, BP, RR, and SpO2. Sedation of patient was assessed by the Ramsay Sedation Scale. The intensity of pain was assessed using VAS score. Duration of analgesia was considered till the recorded score of >5.
At the end of the procedure, quality of operative conditions was assessed according to the following numeric scale: grade 1: (Excellent) no complaint from patient; Grade 2: (Good) minor complaint with no need for the supplemental analgesics; and Grade 3: (Poor) complaint that required supplemental analgesia.
Assessment of blood loss was done and fluid was administered as per the loss. Duration of surgery was noted.
All patients were observed for any side effects or complications in the intra and postoperative periods such as anaphylaxis, urticaria, nausea, vomiting, dryness of mouth, thirst, agitation, fever, headache, anxiety, circumoral numbness, hyperacusis, tinnitus, visual disturbance, convulsion, respiratory depression, pneumothorax, vascular puncture, hematoma, local anesthetic toxicity, phrenic nerve block and diaphragmatic paralysis, and postblock neuropathy and any hemodynamic instability.
Statistical analysis was done using unpaired t-test for finding the statistical difference between the means of quantitative data and two sample t-test for proportion. P value was calculated. P<0.05 was considered statistically significant, whereas P > 0.05 was considered as not significant. Statistical package SPSS Version 20.0 (Armonk, NY: IBM Corp) was used for the analysis of data.
| Results|| |
Both groups were comparable in terms of demographic data and surgical characteristic as shown in [Table 1]. The baseline hemodynamic parameters were comparable in both groups. HR pattern of both groups shows a significant difference from 5 to 480 min of the after giving block [Figure 1]. Comparison of systolic BP (SBP) and mean arterial pressure (MAP) between two groups shows a significant difference between 10 and 360 min. Low BP did not require any intervention with lowest mean SBP being 111 mmHg at 60th and 90th min and lowest mean MAP 80 mmHg at 90th min in Group D [Figure 2]. The compared diastolic BP between two groups shows significant difference between 10 min and 480 min with lowest mean DBP 64.6 mmHg at 90th min in Group D. Mean RR remained significantly lower in dexmedetomidine group compared to control group till 600 min with lowest mean RR being 10.6/min at 90th min in Group D. At 60, 90, and 120 min, SpO2 was found lower (99.3, 98.9, and 99.17) in Group D compared to Group C (P < 0.05). However, no patient required oxygen supplementation in dexmedetomidine group. After 15 min, sedation score was significantly higher in dexmedetomidine group as compared to control group up to 480 min.
A significant reduction in onset time of sensory and motor block and increase in duration of sensory, motor block, and duration of analgesia was found in dexmedetomidine group as compared to control group [Figure 3],[Figure 4] and [Table 2].
|Table 2: Sensory and motor block onset time, block and analgesia duration in both groups|
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In our study, Grade 1 block was achieved in 46% of patients in Group D and 23% of patients in Group C which was statistically not significant (P = 0.109). Grade 2 block was achieved in 27% of patients in either group and Grade 3 block was achieved in 43% of patients in Group D and 34% in Group C. This difference was statistically not significant.
| Discussion|| |
We evaluated the effect of adding dexmedetomidine as an adjuvant to 0.25% bupivacaine in SCB for the patients undergoing upper limb surgeries and found a decrease in onset time of sensory and motor block and increase in duration of sensory, motor block, and duration of postoperative analgesia without any adverse effect in dexmedetomidine group.
Carlo et al. found that subclavian perivascular approach consistently provides an effective block for the upper limb. At the site of injection, the plexus is reduced to its smallest components, and the sheath is reduced to its smallest volume, which explains the success (98.8%) obtained with it. They demonstrated highly successful and safe nerve stimulator technique. Brown  also found that SCB provides anesthesia of the entire upper limb in the most consistent, time efficient manner.
To date, there has been an increasing use of adjuncts (e.g., opioids and α2-adrenoreceptor agonists) to local anesthetics to improve the block quality.,
Various animal studies have been conducted using intrathecal dexmedetomidine at a dose range of 2.5–100 μg without any neurological deficit.,,,, In human beings, studies using epidural and intrathecal dexmedetomidine have been conducted without any report of neurological deficit ,, and found early onset and prolonged duration of analgesia with dexmedetomidine.,,
A study by Brummett et al. showed that dexmedetomidine enhances duration of bupivacaine anesthesia and analgesia of sciatic nerve block in rats without any damage to the nerve. The histopathological evaluation of these nerve axons and myelin was normal in both control and dexmedetomidine + bupivacaine groups. However, all studies carried out so far to prove the peripheral action of α2- agonists were animal studies.,, There are very few human studies., A study by Obayah et al. added dexmedetomidine to bupivacaine during placement of a greater palatine nerve block for cleft palate repair. The addition of dexmedetomidine to bupivacaine provided lower pain scores and prolonged analgesia (approximately 50%) with no negative effect on hemodynamics when compared with bupivacaine alone.
The dose selection was based on previous studies where dexmedetomidine 1 μg/kg and clonidine 1 μg/kg were used in Bier's block as an adjuvant to lignocaine  and in SCB as an adjuvant to 0.25% bupivacaine.
The concentration of bupivacaine that we chose for our study was lower than the usual. Studies finding minimum effective concentration (MEC90) of bupivacaine for BPB have reported that 0.25% concentration is also adequate and safer. As dexmedetomidine has peripheral action, it was used with a lesser concentration of local anesthetic (0.25%). This in turn may be beneficial in high-risk patients.
In our study, patient populations were comparable in both the groups [Table 1]. We found that using dexmedetomidine as an adjuvant to 0.25% bupivacaine in SCB had a significant influence on the onset of sensory and motor block [Table 2] and [Figure 3]. Esmaoglu et al. also found that sensory and motor block time were significantly shorter in dexmedetomidine group than in the control group (P < 0.05) in axillary plexus block using levobupivacaine. Similarly, Ammar and Mahmoud  used dexmedetomidine as an adjuvant to bupivacaine for ultrasound-guided infraclavicular block and found onset of sensory and motor block was significantly faster in dexmedetomidine group than in control group (P = 0.003). While Swami et al. also observed that onset of sensory and motor block was faster in dexmedetomidine group compared to clonidine group, but the difference was not statistically significant (P = 0.083). On the contrary, Gandhi et al. found onset of both sensory and motor block in control group was faster compared to dexmedetomidine (P < 0.0001).
We found the duration of sensory and motor block was significantly higher in dexmedetomidine group. The concern of prolongation of motor block was minimal patient discomfort on movement in the postoperative period. Our results were comparable with the results of other studies [Table 2] and [Figure 4]. Gandhi et al. in their study reported that duration of sensory and motor block was longer with dexmedetomidine than in control (P < 0.001). Similarly, Swami et al. in their study observed that the mean duration of sensory and motor block was longer in dexmedetomidine group compared to clonidine group (P = 0.001). Esmaoglu et al. in their study also found that the mean duration of sensory and motor block in dexmedetomidine group was longer than control group (P < 0.01). Similarly, Ammar and Mahmoud  also found longer duration of sensory and motor block in dexmedetomidine group (P = 0.002).
We found significantly increased duration of analgesia was found in dexmedetomidine group. A similar result was obtained in the previous study done by Gandhi et al. who observed that the duration of analgesia in dexmedetomidine Group D was 732.4 ± 95.1 min, compared to control group was 194.8 ± 60.4 min (P < 0.000). There was also significant (P = 0.001) increase in duration of analgesia in dexmedetomidine group as compared with clonidine in a comparative study done by Swami et al. Similarly, Esmaoglu et al. also reported that the duration of analgesia was significantly (P < 0.05) longer in dexmedetomidine group.
We observed that 15 min onward throughout the intraoperative and postoperative period sedation score was significantly higher till 480 min in dexmedetomidine group, with a maximum mean sedation score of 2.9 at 60 min. This can be explained on the basis that some amount of systemic absorption of drug could be present. Saadawy et al. added dexmedetomidine (1 μg/kg) to bupivacaine for caudal anesthesia in pediatrics and found improved sleep quality with no adverse clinically relevant side effects. Rancourt et al. observed a sedative effect with the use of perineural dexmedetomidine in posterior tibial nerve block. Most volunteers in the dexmedetomidine group lost at least one point on the sedation score, mostly between 60 and 120 min after the injection. This is through inhibition of the locus coeruleus, which disinhibits ventrolateral preoptic nucleus firing and mimics nonrapid eye movement sleep.
We observed that after giving block, HR starts falling in dexmedetomidine group. Throughout intraoperative and postoperative period, HR remained significantly lower in dexmedetomidine group till 480 min, but none of the patients required intervention for that. The lower HR in dexmedetomidine group could be explained due to decreased sympathetic outflow and circulating level of catecholamine caused by dexmedetomidine. Similarly, significantly lower HR was observed at 60, 90, and 120 min but not <60 beats/min in dexmedetomidine group as compared with clonidine (P < 0.001) by Swami et al. Similar lower HR was found in dexmedetomidine group by Esmaoglu et al., whereas Gandhi et al. observed that vital parameters such as mean HR, SBP, RR, and SpO2 were similar in both the groups.
In our study, SBP, DBP, and MAP did not differ significantly till 10 min in both groups, and after that, they remained significantly on lower side in dexmedetomidine group till 180, 480, and 360 min, respectively. However, there was no need of vasopressor. Swami et al. found that SBP and DBP were significantly lower than baseline from 30 to 120 min in dexmedetomidine group as compared with clonidine group (P < 0.001), but no treatment was required for this fall in BP. Esmaoglu et al. also observed that SBP levels at 10, 15, 30, 45, 60, 90, and 120 min and DBP levels at 60, 90, and 120 min were significantly lower in dexmedetomidine group (P < 0.05). Kaygusuz et al. also reported that except at 5 min, intraoperative MAP and HR values were significantly lower in dexmedetomidine group (P < 0.01). Postoperative MAP and HR values at 10 and 30 min and 1 and 2 h were lower in dexmedetomidine group (P < 0.01). However, no patient experienced an episode of hypotension, bradycardia, or hypoxemia that required treatment.
We found 46% of the patients in Group D achieved block who did not require sedation, analgesia, or counseling as opposed to 23% in Group C (P = 0.109). Swami et al. achieved the same quality of block in 80% of the patients in dexmedetomidine group as compared to 40% in clonidine group (P < 0.05). Memis et al. also showed that addition of dexmedetomidine to lignocaine for IV regional anesthesia improves both the quality of anesthesia as well as intraoperative and postoperative analgesia. This improved quality of block might be the result of various mechanisms of nerve conduction block such as hyperpolarization, decreased compound action potential (CAP), and inhibition of voltage gate of sodium pump.
No side effect was reported in both the groups in our study and also in the study by Swami et al., Esmaoglu et al., and by Kaygusuz et al., whereas Ammar and Mahmoud  observed nausea-vomiting, pruritus, and dizziness in 7, 2, and 4 patients, respectively, in control group compared to 4, 0, and 1 patients in dexmedetomidine group, but P > 0.05.
The major limitations of our study are that we did not use ultrasound; this could have helped us to lower dosages and volumes of local anesthetics. We were also unable to identify an ideal scale for assessment of quality of block. While the higher cost of dexmedetomidine can be suggested as a reason for the preference for not using it, the increased requirement of supplementary analgesia and sedation without dexmedetomidine may balance this. We admit that further studies to determine the cost-effectiveness of the drug are necessary. The beneficial effects of dexmedetomidine are explained by systemic absorption of the injected medication and by including a third control group (perineural bupivacaine + IV systemic dexmedetomidine) into the design of the study may help to address this issue. The dose used for the block was empirically chosen according to previous studies. To our knowledge, a dose-response study has not been performed to evaluate the effect of lower or higher doses.
| Conclusion|| |
The emphasis of this study was to assess the clinical utility of adding dexmedetomidine to local anesthetics for SCB. The lack of significant side effects such as respiratory depression and hemodynamic stability make dexmedetomidine an attractive choice as an adjuvant for SCB. However, further trials to determine the exact dose and effect of neurotoxicity on the human nerve are required.
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Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]
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