Effect of Added Alpha 2 Agonists with Local Anaesthetic in Infraclavicular Brachial Plexus Block: A Comparative Study between Dexmedetomidine and Clonidine.

BACKGROUND: Many adjuvant drugs are added with local anesthetics to increase the quality of regional blocks. AIM: To compare the effects of dexmedetomidine and clonidine added to bupivacaine in infraclavicular brachial plexus block in prolonging the duration of analgesia in patients undergoing orthopedic surgery of forearm or hand and also to compare the duration of sensory and motor block, sedation, and hemodynamic changes like bradycardia and hypotension in two groups. SETTINGS AND
DESIGN: This was an observational study conducted in a tertiary care hospital.
MATERIALS AND METHODS: A study was conducted among 60 patients admitted for elective upper limb surgeries under ultrasound-guided infraclavicular block. Patients who received bupivacaine 0.5% (20 mL) + Clonidine 1 μg.kg-1 were classified as Group A and those received bupivacaine 0.5% (20 mL) + dexmedetomidine 1 μg.kg-1 were classified as Group B. STATISTICAL ANALYSIS: Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) software version 25.
RESULTS: Duration of analgesia was significantly higher in Group B as compared to Group A (mean + standard deviation = 764 ± 17.573 min vs. 526 ± 9.958 min, respectively, P = 0.001). The mean time for onset of a sensory block as well as motor block was significantly less in Group B when compared to Group A (P = 0.001). The mean duration of both sensory block and motor block was higher in Group B as compared to Group A (P = 0.001).
CONCLUSIONS: The dexmedetomidine group (Group B) provides a quicker and prolonged analgesic action without major adverse effects. Copyright:

INTRODUCTION

Managing pain after upper limb procedures is a great challenge to the anesthesiologist. To improve analgesia and facilitate mobilization, regional anesthesia can be made of use. Regional anesthesia reduces the incidence of perioperative complications such as deep vein thrombosis, pulmonary embolism, blood loss, respiratory complications, and death.[1] Regional anesthesia also leads to reduction in stress response, systemic analgesic requirements, opioid-related side effects, and development of chronic pain. Mixing local anesthetic with adjuvant drugs is an attempt to prolong analgesia from nerve blocks. The objective of this study is to compare clonidine and dexmedetomidine in peripheral nerve blocks in terms of duration of motor and sensory blockade and postoperative analgesia and hemodynamic changes and sedation.

MATERIALS AND METHODS

An observational study was done among, those coming for orthopedic surgeries of forearm or hand for 1 year starting from October 2014 at a tertiary care hospital. The study protocol was approved by the Institutional Review Board (IEC-SGMC 12/111/03/2014). The study was done as per International Conference on Harmonization– Good Clinical Practice, Declaration of Helsinki (1964), and other regulatory guidelines. Only patients belonging to the American Society of Anesthesiologists (ASA) class I and II undergoing elective operative procedure for upper limb surgeries were included. A total of 60 patients were studied. Informed consent was taken from patients after explaining the details of the study. Patients with a history of bleeding disorders, localized infection at the site of block, those with documented neuromuscular disorders, and those with known allergy to local anesthetic drugs were excluded. Weight, basal heart rate, and blood pressure were measured during preoperative assessment of the patient. All the patients received brachial plexus block through ultrasound-guided infraclavicular approach. After sterile preparation and development of skin wheal with plain Lignocaine, ultrasound-guided infraclavicular nerve block was given after negative aspiration for blood by an experienced anesthesiologist. In this study, we compared two α agonists (clonidine and dexmedetomidine) as adjuvant to bupivacaine in infraclavicular brachial plexus block. The aim of the study was to compare the onset and duration of sensory and motor blockade with clonidine and dexmedetomidine and to compare the intraoperative and postoperative hemodynamic stability with these adjuvants. One group (Group A) received bupivacaine 0.5% (20 mL) + clonidine 1 μg.kg−1 and the other group (Group B) received bupivacaine 0.5% (20 mL) + dexmedetomidine 1 μg.kg−1. The duration of analgesia, onset, and duration of sensory block, onset and duration of motor block, heart rate, blood pressure, oxygen saturation, and sedation were recorded at the 1st min and at 5, 10, 30, 60,120, 180, 240, 360, and 480 min after completion of injection. Intraoperative monitoring included ECG, pulse oximetry, noninvasive blood pressure monitoring. Motor and sensory block of radial, median, ulnar and musculocutaneous nerves were determined at 1st min and then at 5, 10, 30, 60, 120, 180, 240, 360, and 480 min after completion of injection. Sensory block was determined by the pinprick test. Patients were requested to compare the pinprick (26 gauge needle) sensation on the test arm to that in contralateral arm as reference. A score of 0 indicates no sensation and a score of 100 indicates full sensation. Sensory block onset is defined as reduction in sensibility to 30% or less.

Duration of the sensory blockade is defined as the time interval between injection and complete recovery of sensation. Patients were asked to note the complete recovery of sensation, which will then be verified by the anesthetist. Motor block was determined by a modified British Medical Research Council rating scale ranging from 5 (normal power) to 0 (complete paralysis). Motor block onset is defined as a reduction in power to 3 or less. Postoperative pain was assessed using Visual analogue scale (VAS). (VAS 0 = no pain, 10 = worst pain imaginable). Analgesia duration was measured by the time of injection to the first demand of analgesic. Sedation score ranges from 1 (alert) to 4 (asleep, not arousable by verbal contact). The highest sedation score in first 2 h after injection were taken as the sedation score of the patient for statistical purposes. The occurrence of hypotension (fall of mean blood pressure by >30% of baseline) anytime during the monitored period was defined as the presence of hypotension. Bradycardia (<45 beats/min) was monitored. Analgesic effect was measured by the time of injection to the first demand of analgesic.

Statistical analysis

Numerical data were expressed as mean along with standard deviation (SD) or and categorical data were presented in percentage. Chi-square test was used to analyze the baseline characteristics like age and gender distribution of both groups. The duration of analgesia, onset, and duration of both sensory and motor block were compared using the Student's t-test. P < 0.05 was considered to be statistically significant. Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) for Windows User (version 21; IBM, Armonk, NY, USA).

RESULTS

A total of 30 patients were studied in each group. Both the groups were comparable with respect to age and gender. The mean age and SD of Group A and Group B were 47.4 ± 14.2 and 48.3 ± 13.1 years, respectively. 60% of Group A and 53.3% of Group B were males as compared to females 40% and 46.7%, respectively. The mean weight and SD of Group A and Group B were 70.97 ± 9.04 and 71.47 ± 7.54 kg, respectively. The ASA physical status scores were compared among two groups. Thirteen (43.3%) patients in Group A were of ASA Class I and 17 (56.7%) patients were ASA Class II. 12 (40%) patients in Group B were of ASA Class I and 18 (60%) patients were class ASA II. Chi-square analysis showed no significant difference among the two groups. As shown in Table 1, the two study groups were comparable in terms of patient characteristics such as age and gender. The two groups showed a significant difference for the duration of analgesia, onset, and duration of sensory as well as motor block [Table 2]. Sedation was found to be significantly lower in the dexmedetomidine [Figure 1]. There was no significant difference in the hemodynamic stability of both the groups [Table 3]. In our study, no adverse effects like hypotension or bradycardia were noted.

Table 1

Comparison of demographic data among Group A and Group B

	Group A, (n=30), n (%)	Group B, (n=30), n (%)	df	P†
Gender
Male	18 (60)	16 (53.3)	1	0.602
Female	12 (40)	14 (46.7)
Age (years), mean±SD	47.4±14.28	48.33±13.15	58	0.793
ASA physical status
I	13 (43.3)	12 (40)	1	0.793
II	17 (56.7)	18 (60)

†Intergroup comparison done using the student’s t-test for numerical data and Chi-square for categorical data. P<0.05 was taken as statistically significant. Data expressed as mean±SD or number of cases (%). df=Degree of freedom, ASA=American Society of Anaesthesiologists, SD=Standard deviation

Table 2

Comparison of group based on duration of analgesia, onset of sensory and motor block, duration of sensory and motor block (n=30)

	Group	Mean±SD	t	df	P	95% CI
Duration of analgesia	Group A	526.7±9.958	64.684	58	0.001	−245.915-−231.152
	Group B	764.6±17.573
Onset of sensory block	Group A	18±0.83	20.56	58	0.001	4.935-5.999
	Group B	12.53±1.196
Onset of motor block	Group A	19.4±0.77	15.038	58	0.001	3.901-5.099
	Group B	14.9±1.447
Duration of sensory block	Group A	477.3±9.956	58.08	58	0.001	−270.409-−252.391
	Group B	738.7±22.551
Duration of motor block	Group A	422.5±9.054	59.267	58	0.001	−250.621-−234.245
	Group B	664.93±20.494

Comparison of two groups were done using Student’s t test. Data presented as mean±SD. P value <0.05 is considered as significant. SD=Standard deviation, df=Degree of freedom, CI=Confidence interval

Figure 1

Comparison of groups based on sedation

Table 3

Comparison of group based on systolic and diastolic blood pressure and heart rate

	Mean±SD		t	df	P	95% CI
	Group A	Group B
Baseline
SBP	122.27±4.246	125.2±1.961	0.864	58	0.391	−9.732.3.865
DBP	78.67±0.148	81.33±.763	0.860	58	0.390	−7.567.2.233
HR	75.53±.249	74.93±.903	0.306	58	0.761	−3.331.4.531
1 min
SBP	122.4±4.426	125.4±1.863	0.88	58	0.383	−9.826.3.826
DBP	78.0±0.192	81.13±.72	0.953	58	0.345	−7.236.2.569
HR	75.7±.317	74.93±.254	0.397	58	0.693	−3.233.4.833
5 min						−8.602.4.068
SBP	122.33±3.534	124.6±0.82	0.716	58	0.477	−8.602.4.068
DBP	78.93±9.047	81.6±7.937	1.214	58	0.23	−7.065-1.732
HR	75.63±7.898	75.63±7.165	0.001	58	1.000	−3.897-3.897
10 min
SBP	121.86±13.695	125.53±10.44	0.996	58	0.323	−9.429-3.162
DBP	77.66±9.308	81.33±7.849	1.649	58	0.104	−8.116-0.783
HR	75.87±7.234	74.83±7.297	0.551	58	0.584	−2.722-4.788
30 min
SBP	122.26±13.276	124.53±10.66	0.72	58	0.474	−8.119-0.786
DBP	78.53±9.825	80.866±7.977	1.01	58	0.317	−6.963-2.296
HR	75.4±7.3	74.93±7.839	0.239	58	0.812	−3.448, 4.381
60 min
SBP	122.13±13.276	124.46±11.81	0.719	58	0.475	−8.827-4.161
DBP	78.266±9.723	81.066±7.856	1.227	58	0.225	−7.369-1.769
HR	75.4±7.736	75.27±7.23	0.310	58	0.757	−3.270-4.470
120 min
SBP	122.33±13.936	124.06±11.796	0.56	58	0.605	−8.406-4.940
DBP	77.933±9.804	80.9±8.035	1.282	58	0.205	−7.600-1.666
HR	74.87±7.838	75.2±7.039	0.173	58	0.863	−4.183-3.517
180 min
SBP	122.46±13.753	124.66±11.865	0.663	58	0.51	−8.838-4.438
DBP	78.733±9.53	81.4±8.536	1.141	58	0.258	−7.343-2.010
HR	75.77±7.592	75.73±7.196	0.017	58	0.986	−3.790-3.856
240 min
SBP	122.00±14.706	124.0±10.967	0.597	58	0.553	−8.705-4.705
DBP	78.0±9.57	81.73±8.098	1.631	58	0.108	−8.315-0.848
HR	75.4±7.668	75.73±7.234	0.069	58	0.493	−8.059-3.926
360 min
SBP	121.8±13.81	124.66±11.281	0.881	58	0.382	−9.384-3.650
DBP	78.33±9.426	81.466±9.03	1.314	58	0.194	−7.905-1.639
HR	76.17±7.135	75.07±6.823	0.610	58	0.544	−2.508-4.708
480 min
SBP	121.93±14.34	124.6±11.40	0.797	58	0.429	−9.362-4.029
DBP	77.733±9.391	81.8±8.45	1.762	58	0.083	−8.686-0.552
HR	75.67±7.63	75.13±7.31	0.276	58	0533	−3.328-4.395

Comparison of two groups were done using Student’s t test. Data presented as mean±SD. P value <0.05 is considered as significant. SD=Standard deviation, df=Degree of freedom, CI =Confidence interval, DBP=Diastolic blood pressure, SBP=Systolic blood pressure, HR=Heart rate

DISCUSSION

The brachial plexus block for upper limb surgery has proved to be an effective method of regional anesthesia. Various approaches have been described like supraclavicular, interscalene, infraclavicular, and axillary, but all of these are associated with some technical difficulties like inadequate blocks and some complications.

Postoperative analgesia, defined as the time until first analgesic request, was significantly longer in the bupivacaine–dexmedetomidine group (764.6 ± 17.5 min) while in bupivacaine–clonidine group it was 526.7 ± 9.9 min showing a mean prolongation of 237 min. A study done by Swami et al., Harshavardhana, Ammar and Mahmoud and Gandhi et al. showed significant prolongation in the duration of postoperative analgesia when dexmedetomidine was used as an adjuvant to local anesthetic.[2345]

In this study, the onset of motor block was shortened by an average of 4.5 min in dexmedetomidine group when compared to clonidine group. This has statistical significance as analyzed by t-test. A study by Swami et al. showed that onset of motor block was faster with clonidine group (3.87 ± 1.78) when compared with the dexmedetomidine group (4.65 ± 2.46) and was found that it was not a significant difference.[2]

In this study, the onset of sensory block was shortened by an average of 5.47 min in dexmedetomidine group when compared to clonidine group. This has statistical significance as analyzed by t-test. Study by Swami et al.[2] showed that onset of sensory block was faster with dexmedetomidine (1.77 ± 1.28) than Clonidine group (2.33 ± 1.21) min. But this was not statistically significant. A study done by Harshavardhana also showed that onset of sensory block was faster with dexmedetomidine (2.59 ± 2.2) than clonidine group (3.26 ± 1.4) min. which was also statistically significant.[3]

Jinjil et al. compared dexmedetomidine and clonidine as adjuvant to 0.25% ropivacaine in ultrasonography-guided supraclavicular block and found that onset of sensory block was 9.7 ± 1.5 min, dexmedetomidine group and in clonidine group, it was 12.9 ± 1.4 min. The onset of motor block in dexmedetomidine group was 15.7 ± 1.5 and in clonidine group, it was 20.4 ± 1.8 min. The onset for sensory and motor block in dexmedetomidine group was significantly faster.[6]

Dar et al. evaluated the effect of adding dexmedetomidine to ropivacaine for axillary brachial plexus blockade in 80 patients scheduled for elective forearm and hand surgeries. Sensory and motor block onset times were shorter when dexmedetomidine was added.[7]

The mean duration of sensory block in the bupivacaine-clonidine group was 477.3 ± 9.9 min while in bupivacaine–dexmedetomidine group was 738.7 ± 22.5 min. This shows a significant prolongation of the duration of the sensory block in the dexmedetomidine group by about 261 min. Duration of sensory block was 212.90 ± 24.8 min in clonidine group as compared with 413.97 ± 87.31 min in dexmedetomidine group in the study done by Swami et al.[2]

The mean duration of motor block in Group A (Clonidine) was 422.5 ± 9.05 min while in Group B (dexmedetomidine) it was 664.93 ± 20.4 min. This denotes a mean difference of 242 min and was statistically significant. Duration of motor block was 292.67 ± 59.13 min in clonidine group as compared with 472.24 ± 90.06 min in dexmedetomidine group in the study done by Swami et al. which was statistically significant.[2]

In the randomised control trial done by Esmaoglu et al. 60 patients were assigned to receive either 40 ml of 0.5% levobupivacaine with 1 ml dexmedetomidine or 40 ml of 0.5% levobupivacaine with 1 ml of saline and found that sensory and motor onset time was significantly faster in the study group compared to control group.[8]

Agarwal et al. compared the effects of adding dexmedetomidine to bupivacaine in supraclavicular brachial plexus block and they concluded that dexmedetomidine added as an adjuvant to bupivacaine for supraclavicular brachial plexus block significantly prolongs the duration of sensory and motor blocks and duration of analgesia.[9]

Biswas et al. evaluated the effect of combining dexmedetomidine with levobupivacine with respect to duration of motor and sensory block and duration of analgesia, in supraclavicular block. They found sensory and motor block durations were longer when dexmedetomidine was added as an adjuvant. The duration of analgesia was also significantly longer with the addition of dexmedetomidine.[10]

Danelli et al. evaluated the effects of adding 50 μg clonidine to 150 mg ropivacaine for superficial cervical plexus block in patients undergoing elective carotid endarterectomy. They opined that adding 50 μg clonidine to 150 mg ropivacaine for superficial cervical plexus block shortened the onset time and improved the quality of surgical anesthesia.[11]

McCartney et al. reviewed studies (1385 patients) using clonidine as an adjuvant to local anesthetics for a variety of peripheral nerve blocks. They concluded that clonidine was beneficial only when added to intermediate-acting local anesthetics.[12] These studies showed that dexmedetomidine and clonidine when studied independently with local anesthetics as an adjuvant had a faster onset of sensory and motor blockade with prolonged duration of sensory and motor blockade with increased duration of analgesia.

The result of our study shows that all patients in both groups were comparable with respect to demographic profile. The onset of sensory and motor blockade was faster in Group B (dexmedetomidine) which was statistically significant. Duration of sensory and motor blockade was more in Group B (dexmedetomidine) which was also statistically significant. The duration of analgesia was more in Group B, also statistically significant. These results show that dexmedetomidine has faster onset of sensory and motor blockade, prolonged duration of sensory and motor blockade, and also increased duration of analgesia.

Dexmedetomidine acts in a manner similar to clonidine. Dexmedetomidine, due to its high selectivity to α2 receptor with α2:α1 binding selectivity ratio of 1620:1 as compared to220:1 for clonidine, reduces the unwanted side effects of α1 receptors. The patients who received Dexmedetomidine were comfortable throughout the surgery with arousable sedative effects.[13]

We conclude that in infraclavicular brachial plexus block addition of dexmedetomidine as an adjuvant to 0.25% Bupivacaine shortens the sensory and motor block onset time, prolongs both sensory and motor block duration and is not associated with any major side-effect. The added advantage of conscious sedation and hemodynamic stability makes it a potential adjuvant for nerve blocks. Thus it can be concluded that dexmedetomidine is a better adjuvant than Clonidine in infraclavicular brachial plexus block.

CONCLUSIONS

In infraclavicular brachial plexus block addition of dexmedetomidine as an adjuvant to 0.25% Bupivacaine shortens the sensory and motor block onset time, prolongs both sensory and motor block duration and is not associated with any major side-effect. The added advantage of conscious sedation and hemodynamic stability makes it a potential adjuvant for nerve blocks. Thus, it can be concluded that dexmedetomidine is a better adjuvant than Clonidine in infraclavicular brachial plexus block.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.