Introduction

To date, results of studies evaluating the efficacy of opioids and local anesthetic combinations in the brachial plexus are inconclusive ₁,₂,₃,₄ . However, over the past 20 years, several studies have suggested that the addition of certain opiates to the local anesthetic used for brachial block may provide effective, long-lasting postoperative analgesia ₃,₄ . Some studies indicated that the agonist-antagonist, buprenorphine, added to bupivacaine provided a longer period of postoperative analgesia than the traditional opiates. This practice can be of particular benefit to patients undergoing ambulatory upper extremity surgery by providing prolonged analgesia after discharge from the hospital. ₅,₆,₇,₈ We conducted a prospective double blind study to evaluate the effect of mixing buprenorphine with bupivacaine used for perivascular brachial plexus block. The observations were made for the effect of buprenorphine on the onset of block, quality and duration of postoperative analgesia and associated side effects.

Patients and Methods

After approval of the ethical committee, forty healthy consenting adult patients scheduled for upper extremity surgery were enrolled in the study. Premedication was provided by tab. Alprazolam 0.5 mg orally 1 hr. before surgery. Anesthesia was given by a subclavian perivascular brachial plexus block. Patients were assigned randomly to either of two groups based on the agents used for the blocks. Group-I (control group) (n=20) patients received 30 ml 0.3% bupivacaine+ 1 ml saline and intramuscular 1ml drug(3 µgkg ^-1 buprenorphine + saline to make volume= 1 ml). Group-II (study group) (n=20) patients received 30 ml 0.3% bupivacaine+ 1 ml study drug (3 µgkg ^-1 bupivacaine + saline to make volume= 1 ml ) and 1 ml of intramuscular injection of saline. The study was kept double-blind by having 1 anesthesiologist prepare the solutions, a second anesthesiologist performs the blocks, and third anesthesiologists monitor the anesthesia and analgesia thereafter, up to and including the time of the first request for an analgesic medication. The data were reported as means (+/- SD), and differences between groups were determined using repeated measures of analysis of variance (ANOVA) and followed by T test for comparison by using ‘AcaStat' statistical computer software, P value of < 0.05 was considered to be statistically significant.

Technique: After sterile preparation of the region the 22G, 4 cm needle was inserted through the skin wheel and above the palpating finger immediately lateral to the subclavian artery. Needle was directed 45 degree dorso-laterally parallel to the scalene muscles and toward the elbow of the patient. There was a click once the sheath pierced and entered. The patient felt paresthesias of the hand and fingers once the tip of the needle crossed the perineural sheath. Drug was injected after repeated aspiration to avoid inadvertent vascular entry. After injection, the sensory block tested by sensations to pin prick. Motor block was evaluated by thumb movements e.g. abduction (Radial nerve), adduction (Ulnar Nerve), opposition (Median nerve). Musculocutaneous nerve block assessed by flexion of elbow and supination-pronation of forearm. Hollmen scale was used to assess both sensory and motor blockade. The eight nerves were evaluated for sensory function and four nerves studied for motor blockade. Evaluation was carried out for every minute after completion of the injection and the time of onset was noted for both sensory and motor blockade. Onset of block was defined as minimum of grade 2 in Hollmen scale. Block was considered complete when sensory and motor scores were grade 3 in Hollmen scale. Duration of sensory blockade was considered as the time interval between the local anaesthetic injection and the onset of pain in the postoperative period. The duration of motor blockade was considered as the time interval between injection of local anaesthetic and recovery of muscle power. When separate nerve blocks or supplementation with IV analgesia or general anaesthesia was required due to inadequate/ failed block were not included in study. Intra-operative and postoperative complications were recorded. All patients were monitored with continuous Pulse, ECG, SpO2 and NIBP every 5 minutes intra-operatively and continuous SpO2 and one hourly Pulse and NIBP post-operatively. Postoperative analgesia was provided by Injection Diclophenac sodium 75 mg IM on demand. Injection Ondansetron 4 mg IV was given for PONV.

Hollmen scale

Observations

Figure 1

Table 1: Demographic profile

Figure 2

Table 2: Type of Surgery

Table 3: Comparison between Group-I, and Group-II for onset time, time taken for complete block, duration of sensory and motor block

Figure 3

Figure 4

Table 4: Intensity of Block (Hollmen's Scale):

Figure 5

Table 5: Complications and Side effects

Results

In Group-I the onset time for motor block was 4.05±0.944 min. and sensory block was 6.65± 1.182 min. Group-II the onset time for motor block was 3.75±1.208 min. and sensory block was 4.25±1.25 min. This difference was not significant (p<0.404) for sensory and (p<0.152) for motor block. There was no significant deference in to achieve complete motor block 17.05± 2.633 min. in Group-I and, 19.2± 3.53 min. in Group-II (p<0.105). The complete sensory block took significantly longer time in Group-I 22.4± 3.8 min. than Group-II 20.5±2.5 min. (p<0.037).

The mean duration of satisfactory analgesia was 331.2± 33.54 minutes in Group-I and 680.6±86.27 minutes in Group-II the difference in duration between two groups was significant (p<0.0001). The mean duration of motor block was not significant, 300.9±26.1 minutes in Group-I and 329.2± 28.4 minutes in Group-II (p<0.352). Intensity of motor block (number of cases in different grade) were comparable (P<0.322), but there was significant difference in quality of sensory block (P<0.05).

Two patients had arterial puncture ( one in each group), needle was repositioned and block was completed. Both the blocks were effective. Inadquate block occurred in 3 patients ( one in Group-I and two in Group-II) required injection ketamine 25mg increments (50-100mg), one of such patient was given ulner block with 5 ml 0.25% bupivacaine posted for ORIF fracture both bone left forearm.Complete Failed block occurred in one patient of Group-I, conventional GA with relaxant was given due to required difficult surgical position ( # both bones and olecranon ORIF through posterior approach). Nausea and vomiting occurred in 4 patients( two patients of each group) managed with one Intravenous dose of Injection Ondansetron 4 mg. Horner's syndrome was seen in 5 patients ( 2 in Group-I and 3 in Group-II) without any sequelae. No patient develop any serious complications due to block procedure (pneumothorax, large hematoma or prolonged nerve palsy) or buprenorphine (respiratory depression) etc. There was no signifant difference in complications between two Groups.

Discussion

This prospective, randomized, double blind study was done in 40 patients scheduled for upper limb surgery under subclavian perivascular brachial block (Winnies' approach) ₁₀ with similar surgical and demographical profile (Table 1& 2). We have used the Intramuscular buprenorphine in control group so that the systemic analgesic effect of buprenorphine can be differentiated from its peripheral action. ₅,₇

Results of this study show that addition of 3 µgkg ^-1 buprenorphine to 0.3% bupivacaine mixture for perivascular brachial block in upper limb orthopedic surgery improves the quality of sensory block and lengthens the duration of analgesia without affecting the duration of motor block.

Buprenorphine-local anesthetic perivascular brachial plexus block provided postoperative analgesia lasting 3 times longer than local anesthetic block alone and twice as long as buprenorphine given by IM injection plus only local anesthetic block have been reported. This supports the concept of peripherally mediated opioid analgesia by Buprenorphine. ₅ The addition of buprenorphine to the local anesthetic used for brachial plexus block in the present study provided a 2-fold increase in the duration of postoperative analgesia, with complete analgesia persisting 5-7 hours beyond the duration provided by the local anesthetic alone in most of the patients. This practice can be of particular benefit to patients undergoing ambulatory upper extremity surgery by providing prolonged analgesia after discharge from the hospital ₇ . In our study the mean duration of satisfactory analgesia with buprenorphine was 680.6 minutes is simillar as reported in other studies (14-34 hrs.). ₅,₆,₇

Ortells Polo et al ₁₁ in their study of modified supraclavicular perivascular block recorded an onset time of 4.9+ 0.2 minutes and the time for motor paralysis at 15.2+ 6.9 minutes. This study support our data i.e. in Group-I the onset time for motor block was 4.05±0.944 min. and sensory block was 6.65± 1.182 min. Group-II the onset time for motor block was 3.75±1.208 min. and sensory block was 4.25±1.25 min.

In our study, we noticed that buprenorphine does not affect the onset of sensory or motor block; rather the complete sensory effect was delayed significantly than control group. Nishikawa K et al have shown that addition of fentanyl to lidocaine causes an improved success rate of sensory blockade but a delayed onset of analgesia due to decreased pH of the mixture. ₁₂ In our study the onset of motor block was significantly faster than sensory block in both the groups (Group-I and Group-II), this can be explained by ‘core and mantle' concept of Winnie et al, 1977. ₁₃

Opioids have long been thought to act exclusively within the central nervous system. An increasing number of studies recently reported the existence of opioid receptors outside the central nervous system and therefore suggested that opioids are also able to produce analgesic effects in the periphery. ₁₄ Experimental studies have shown that opioids could produce two types of effect on neuronal excitability. The first one is a local anesthetic action on the nerve fiber with a diminution of sodium and potassium conductance. The second is due to a linkage of the opioid with a receptor on the internal face of the membrane. Opioids could also migrate to the posterior horn of the spinal cord after linkage with axonal receptors. These findings expand the gate control theory of pain and suggest new approaches such as the development of peripherally acting opioid analgesics without central side-effects. ₁₅ No serious complications related to block technique or addition of buprenorphine were observed in present study (Table 5).

Clinical studies have proved that opioid injection in the brachial plexus produce a prolonged analgesia in the postoperative period. The more liposoluble opioids like fentanyl and buprenorphine are the more effective ₁₆ . Our study and other studies ₅,₆,₇,₈ have shown that addition of buprenorphine to local anaesthetic increase the postoperative analgesia to a great extent, however the controversy still exist. Trials of a higher quality are needed to provide a definitive answer. ₁₇

Conclusion

We conclude that the addition 3 µgkg ^-1 buprenorphine to 0.3% bupivacaine mixture for perivascular brachial block in upper limb orthopedic surgery does not effect the onset time for motor as well as sensory block. It delays in completion of sensory effect. It improves the quality of sensory block and lengthens the duration of analgesia without affecting the duration of motor block.