Procedure

The Interscalene groove was located by sliding the fingers laterally from under the sternocleidomastoid muscle. The index and middle finger of the left hand remain in the groove, and a small skin wheal is made over the groove and between these fingers. The block needle was then inserted perpendicularly to all planes and slightly caudal. The needle was advanced through the sheath, at which time a fascial "pop" may be felt. As one of the roots of the plexus is neared, the muscles supplied by that root will be stimulated to contract. Usually a current of 1-1.5 mA is adequate to start searching. Once an appropriate muscle contraction is seen, the current is decreased slowly to determine the threshold (the lowest current at which stimulation still occurs). The closer the needle is to a nerve, the lower the threshold will be. Some practitioners generally search for a current of less than 0.5 mA. If the threshold current obtained is higher than desired, the needle is repositioned. Once the desired response is found, the needle is stabilized and 30 mL of local anesthetic is injected. As with all nerve blocks, injection should be slow, in increments and with frequent aspiration. If the threshold current is 0.2 mA or less, if injection pressure is high, or if the patient has a paresthesia during needle placement or injection, the needle is pulled back slightly because of concern of intraneural placement. An acceptable motor response would be one involving the deltoid muscle or any muscle in the arm or hand. If the needle is placed lateral and posterior to the middle scalene, it is possible to stimulate the accessory, dorsal scapular, and long thoracic nerves, which results in stimulation of the trapezius, rhomboids, and serratus anterior muscles, respectively. If the needle is placed between the anterior scalene and the sternocleidomastoid muscle (ie, too anterior), the phrenic nerve is frequently stimulated, causing contraction of the diaphragm (ie, hiccupping). Thus, these undesired twitches can help guide the practitioner in repositioning of the needle.

Assessment of sensory block

Sensory block was assessed with pin prick method assessment of sensory block was done at interval of 1 minute in random sequence in the dermatomal areas corresponding to median nerve, radial nerve, musculocutaneous nerve and ulnar nerve after completion of drug injection and compared with the opposite limb. Sensory block was evaluated with Hollmen score.

Assessment of motor block

It was carried out by the same observer at each minute till complete motor blockade as occurred after drug injection. Onset of motor blockade is considered when there is Grade 1 motor blockade. Complete motor blockade was considered when there is Grade 2 motor blockade. Motor blockade was determined according to a Modified Bromage scale for upper extremities on a 3-point scale.

Statistical analysis

The independent samples t-test procedure compares means for two groups of cases. SPSS for windows (version 21.0, SPSS Inc., Chicago, IL, USA) was employed for data analysis. P < 0.05 was considered as significant.

 

Table 1: Type and Distribution of various surgeries in Group A and Group B

The two groups were well matched with respect to type of surgical procedures. Two groups were comparable and no statistical significance found (P value >0.05).

 

Table 2: Comparison of Onset of sensory block (in minutes) in Group A and Group B

	Group A Mean±SD	Group B Mean±SD	P value
Onset of sensory block	15.025±1.52	2.7±0.85	<0.0001
Duration of sensory block	225.5±19.07	440.25±55.21	<0.0001
Onset of motor block	20.075±1.40	5.425±0.95	<0.0001
Duration of motor block	188.7±20.52	400±61.81	<0.0001
Duration of analgesia	275.75±24.27	688.75±33.219	<0.0001

There was significant difference between mean onset of sensory block (in minutes) in group A and Group B. Onset of sensory was faster in Group B (2.70.85min) compared to Group A (15.0251.52min). Independent two sample T-test was applied. The difference was statistically extremely significant (P value=0.0001). There was significant difference between mean time of onset of motor blockade Group A and Group B. Time of onset of motor blockade was faster in Group B (5.4250.95min) as compared to Group A (20.0751.40min). Independent two sample T-test was applied.
The difference was statistically significant (P value= <0.0001). Duration of motor block was longer in Group B (40061.81min) and Group A (188.720.52min). There was significant difference between Mean Duration of motor block (in minutes) in group A and Group B. Independent two sample T-test was applied.
The difference was statistically significant (P value=<0.0001).The duration of sensory Block was longer in Group B (440.2555.21min) as compared to Group A (225.519.07min). There was significant difference between mean duration of sensory block (in minutes) in group A and Group B. Independent two sample T-test was applied.
The difference was statistically significant (P value=<0.0001). The duration of analgesia was longer in Group B (688.7533.219 min) as compared to Group A (275.7524.27min). Independent two sample T-test was applied.
The difference is statistically significant (P value=<0.0001).

Table 3: Comparison of Quality of Block in Group A and Group B

Table 3 shows that Grade 3 block was achieved by 26% in Group A and 6% in Group B. Grade 4 block was achieved by 85% in Group B and by 35% in group A patients. Quality of block was better in Group B as compared to Group A. Z test was applied
The difference was statistically significant. (p value<0.0001). No side effects and complications were seen during the first 24 hrs in the post-operative period in both the groups.

DISCUSSION
With the advancement in the field of regional anaesthesia and better understanding of applied anatomy, peripheral nerve blocks are becoming more and more popular with each day ahead. Brachial plexus blocks are easy and relatively safe procedures and achieve ideal operating conditions by producing complete muscle relaxation, pain relief, maintaining stable intra- operative hemodynamic. The acceptance of regional nerve block technique has been limited by two major factors inherent to local anaesthetic agents available for use namely slow onset of action and short duration of action. In our study, mean onset of sensory block was faster in group B (2.70.85 min) as compared to Group A (15.0251.52min) and mean onset of motor block was also earlier in Group B (5.42±1min) as compared to Group A (20.075±1.403min). These results were similar to the results obtained in studies conducted by Swami SS et al5 and Harshavardhana HS.6 In the study conducted by Swami SS et al5 and Harshavardhana HS,6 where dexmedetomidine (1μg/kg) was added to 35ml 0.25% Bupivacaine and Clonidine was added to Ropivacaine (0.5%), respectively in supraclavicular block found onset of sensory block in Dexmedetomidine group (1.77±1.28 min) was faster as compared to Clonidine group (2.33±1.21 min). Another study, Yu-Nan Lin et al7 compared the effect of adding Dexmedetomidine (1μg/kg) and Clonidine (1μg/kg) to 38ml 0.25% bupivacaine in cervical plexus block. They found that onset of sensory block was faster in Dexmedetomidine group (1.70±1.28 min) as compared to clonidine group (2.33±1.21 min). Dose of Dexmedetomidine (1μg/kg) and concentration (0.25%) of Bupivacaine in these studies were exactly the same as used in our study. In study of, Harshavardhana HS6 compared the effect of adding Dexmedetomidine (1μg/kg) and Clonidine (1μg/kg) to 29ml 0.5% ropivacaine in supraclavicular block. Onset of sensory and motor block was faster in Dexmedetomidine group (2.59±2.2 min and 4.12±1.6 min respectively) as compared to clonidine group (3.26±1.4 min 5.36±3.2 min respectively). Here dose of Dexmedetomidine (1μg/kg) used was same as in our study and local anaesthetic agent used (ropivacaine) is almost as potent as bupivacaine in brachial plexus block. In our study, mean duration of sensory block was longer in Group B (400±61.81min) as compared to Group A (188.7±20.52min) and mean duration of motor block was also longer in Group B (440.25±55.21 min) as compared to Group A (225.5±19.07min). Our result was similar to the studies conducted by Gandhi R et al,8 Swami SS et al,5 and El-Boghdadly K, Brull R.9 Swami SS et al5 in their study compared the effect of adding Dexmedetomidine (1μg/kg) and Clonidine (1μg/kg) to 35ml 0.25% bupivacaine in supraclavicular block and found that duration of motor and sensory block were longer in Dexmedetomidine group (413.97±87.31min and 472.24±90.06 min respectively) as compared to Clonidine group (227±48. min and 292.67±59.13 respectively). Agrawal S et al10 in their study compared the effect of mixing Dexmedetomidine (100μg) to 30ml of 0.325% bupivacaine in supraclavicular block and found that duration of sensory and motor blockade were longer in Dexmedetomidine group (755.6±126.8 min and 702±111.6 min respectively) as compared to duration of sensory and motor blockade in control group (234.8±47.9 min and 208±22.7 min respectively). El-Boghdadly K, Brull R9 compared the effect of dexmedetomidine with clonidine as perineural adjuncts to single-injection supraclavicular block. In this study, compared with clonidine, Dexmedetomidine prolonged the duration of sensory and motor block and also prolonged the duration of analgesia. Dexmedetomidine also hastened the onset of sensory block. In our study, mean duration of analgesia was longer in Group B (688.75±33.219min) as compared to Group A (275.75±24.27 min). Our result was similar to the studies conducted by Gandhi R et al,8 Swami SS et al,5 Hussain N11 and Ammar et al.12 They found that duration of sensory and motor block were longer in Dexmedetomidine group (732.4±48.9min and 660.2±60.4min respectively) as compared to the duration of sensory and motor block in control group (146.5±36.4 min and 100.7±48.3 min respectively). Gandhi R et al8 stated that duration of analgesia in Dexmedetomidine group (732.4±95.1 min) was longer when compared to control group (194.8±60.4min). Swami SS et al5 in their study showed that duration of analgesia in Dexmedetomidine group (456.21±9.7min) was longer than clonidine group (289.67±62.5min). Hussain N et al11 compared the ability of dexmedetomidine to prolong the duration and hasten the onset of motor and sensory blockade when used as an adjuvant to local anesthesia for brachial plexus blockade versus using local anesthesia alone (control). In this study, dexmedtomidine group had significant prolongation of duration of analgesia by 289.31 minutes (95% CI, 185.97-392.64 minutes; I =99%; P <0.00001) than the control group which used local anaesthetic alone. Ammar AS et al12 conducted a study to test the efficacy of adding Dexmedetomidine to bupivacaine during placement of ultrasound guide Infraclavicular brachial plexus blockade. In this study, duration of analgesia was 403 compared to 233 min in the control group. In our study quality of block was better in Dexmedetomidine group as compared to control (Bupivacaine) group. 85% patients in group B had grade IV quality of block when compared to Group A where only 35% of patients had grade IV quality of block. Swami SS et al5 also reported the better quality of block in Dexmedetomidine group (grade IV quality in 80% patients) compared to clonidine group (grade IV quality in 40% patients). Memis et al3 in their study showed that addition of dexmedetomidine to lignocaine for intravenous regional anaesthesia improves the quality of anaesthesia. This improved quality of block is due to hyperpolarisation, decreased compound action potential and inhibition of voltage gate of sodium pump.

CONCLUSION
In conclusion, Dexmedetomidine at the dose of 1 mcg/kg body weight added as an adjuvant to 0.25% bupivacaine in Interscalene brachial plexus block in upper limb surgeries is highly effective in prolongation of sensory and motor blockade and provides better postoperative analgesia. So, the patient remains comfortable in the post-operative period with considerable therapeutic benefit and without any potential side effects.

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