European Journal of Cardiovascular Medicine

The novice application of ultra-sound for regional nerve block is exciting modern anaesthetist for frequent use of regional anaesthesia for upper limb surgeries. Brachial plexus blockade by an axillary approach is amenable to the use of ultrasound guidance. Ultrasonography allows real-time visualization of neural structures and visualization of optimal spread of drug solution. When compared with other methods of nerve localization, sonography decreases failure rate, procedure time, onset time for blockade. The use of ultrasound for peripheral nerve blockade demonstrates decreased procedure related complications such as unintentional vascular punctures and nerve injury.¹

Classically axillary brachial plexus block techniques relying on surface anatomical landmarks require large volumes of local anaesthesics, generally 40 ml or greater, predispose the patients for local anaesthesia systemic complications.

The recent literature search had suggested that lower volumes of local anaesthetic can yield successful axillary plexus blockade and interscalene brachial plexus block. With smaller volumes of local anaesthetic observed to be clinically effective, the tradition of using large volumes of local anaesthetic for axillary blocks, may be unwarranted.^2,3

Recent clinical studies support using a low volume of local anaesthetic for brachial plexus blockade, there is paucity of outcome data from randomized trials. The primary objective of this study was to evaluate two different volumes of local anaesthetic for axillary brachial plexus blockade.

The prospective, randomized, double blinded study was conducted in the Department of Anaesthesiology and Critical Care, Pt. B. D. Sharma PGIMS, Rohtak(October 2022 – March 2024). Patients of either gender, aged 18 to 65 years, ASA grade I - III who were scheduled to undergo elective below mid-arm surgeries   were included in the study. Patients with known coagulopathy or on anticoagulant therapy,  Infection and burns at the injection site, Allergy to local anaesthetics, Diabetes mellitus, neuropathy, patients receiving opioids for chronic pain therapy, Inability to give informed consent, Patients with psychiatric illness, Pregnant and lactating females were excluded from the study.

The patients  were divided into one of the two groups of 25 each using computer generated randomization number table. In both groups, USG guided perivascular axillary brachial plexus block was performed with Group-1(25): 20ml of 0.5% bupivacaine and Group-2(25): 30ml of 0.5% bupivacaine. Group assignment was revealed only to the anaesthesiologist performing the block. Patient, surgeons, clinical research assistant and resident collecting the data were all blinded to the technique used.

 Patients scheduled for elective upper limb surgery were enrolled at the time of pre-anaesthetic consultation. Detailed clinical history was taken and patients were examined thoroughly. Routine blood and radiological investigations as required were obtained. Informed and written consent was obtained from each patient after explaining the procedure in detail.  All the patients were kept nil per mouth 6 hours before surgery. All patients were advised on premedication with tablet alprazolam (0.25 mg) orally at night before surgery to relieve the anxiety. On the day of surgery, in the operation theater, all the patients were monitored with the pulse oximeter, noninvasive blood pressure cuff, and electrocardiography. An intravenous line was secured with 18 or 20-gauge cannula. Premedication with intravenous midazolam (1-3 mg as per requirement) was given.  

 Patients were positioned supine with the arm abducted to 90° and elbow flexed to 90°, with dorsum of the hand resting on pillow. All blocks were performed with a Sonosite M-Turbo ultrasound machine using high frequency linear probe. Ultrasound probe was applied in a sterile fashion in the axilla. Short axis view of axillary artery with optimal pressure to avoid collapse of axillary vein was used to visualize the neurovascular bundle. After obtaining a satisfactory image, a skin wheal was raised lateral to axillary artery with 2ml of 1% lignocaine. In both the groups, out of plane technique for needle pathway was used, in which only tip of the needle was visible. All injections were given after confirming negative aspiration and no paresthesia. Needle entry point was just lateral to axillary artery in an antero-posterior direction, perpendicular to ultrasound beam. The needle tip was localized with help of test dose of saline (0.5-1ml). After ensuring optimal spread of saline, few ml of drug was injected there, then needle was advanced further to reach for posterior regions of artery and 7ml of drug was injected and the remaining drug was injected after withdrawing the needle anteriorly. In both the groups, the musculocutaneous nerve was localized as an oval shaped structure within the Coracobrachialis muscle a few centimeters away from axilla and was anaesthetized with 4ml of drug. Oxygen inhalation was given to the patient by face mask at 4-6 liters per minute. Routine vitals were recorded and then surgery was commenced. After the completion of surgery tourniquet time and duration of surgery were noted. After surgery patients were shifted to post anaesthesia care unit. VAS score was recorded at 0, 30 minutes, 1 hr, 6 hrs, 12 hrs, and 24 hrs. If VAS >4 or patient complaining of pain, injection Paracetamol 1gm IV was given. Patient will be re-assessed after 30 minutes if VAS score >4 then inj. Diclofenac 75mg was given as rescue analgesic.

 Following parameters were observed:

 1.Demographic parameters: Age, gender, weight, height, BMI, surgical site and duration of surgery.

2.Block characteristics:  Success of block, Onset of block, Duration of block. Number of cutaneous needle insertion.

3.Assessment of sensory and motor blockade: Onset time of sensory and motor blockade in the cutaneous territories of terminal branches of brachial plexus were assessed every 5 minutes until 30 minutes from the end of LA injection. Sensory blockade was assessed by pin prick test. For the radial nerve sensations were checked at dorsum of hand, for the median nerve medial aspect of forearm, for the ulnar nerve palmar and dorsal aspects of the medial 1.5 digits and adjacent palm, for the musculocutaneous nerve lateral aspect of forearm. Sensory blockade was graded according to a 3-point scale: 0= normal sensation (no block), 1= analgesia (touch but no pain; partial block), 2= anaesthesia (no touch, no pain sensation; complete block). Motor blockade was evaluated for the musculocutaneous nerve using active elbow flexion, for the radial nerve by active elbow and wrist extension, for the median nerve by thumb and second digit pinch, and for the ulnar nerve by thumb and fifth digit pinch. Motor blockade was scored on a 3-point scale: 0= normal strength (no block), 1= paresis, and 2= paralysis, no movement (complete motor block).53 The maximal score was 16. Patients were considered ready for surgery when anaesthetic block achieve for all nerves (8/8 sensory score), regardless of the score for motor blockade. Surgical anaesthesia was considered a success when other than two doses of supplemental analgesia, patient didn’t require supplementation with sedative or conversion to general anaesthesia during surgery.

4. Assessment of pain and patient satisfaction: Patient were asked about the procedural pain using a 10-point visual analogue scale (0= no pain, 10= worst imaginable pain) and their satisfaction using a similar visual analogue scale (0= not satisfied, 10= totally satisfied) twice – immediately after the procedure and after the end of the surgery in the recovery room.

5. Demand Time of first rescue analgesia was recorded.

6. Procedural complications: the following side effects and complications were noted. a. Vascular puncture, b. Paresthesia, c. Intravascular injection of drug, d. Systemic toxicity of local anaesthetics, e. Nerve injuries.

7.Total analgesic requirement in first 24 hours was recorded. Rescue analgesia: In case of patient complaining mild pain, intravenous injection of fentanyl (1mcg/kg) was used as rescue analgesic. Equal dose of fentanyl was repeated after 10 minutes if needed. If pain persists, procedure was abandoned considering as failure and was managed further by the attending anaesthesiologist.

 Statistical analysis:

The data was coded and entered into Microsoft Excel spreadsheet. Analysis was done using IBM SPSS (SPSS Inc., IBM Corporation, NY, USA) Statistics Version 25 for Windows software program. Descriptive statistics included computation of percentages, means and standard deviations. The data were checked for normality before statistical analysis using Kolmogorov Simonov test. The Mann–Whitney U‑test (for quantitative data to compare two independent observations) was applied. The chi square test was used for qualitative data comparison of all clinical indicators. Level of significance was set at P≤0.05

Figure-1: showing number of needle passes.

Onset of block at various time periods of median , radial, ulnar, musculocutaneous nerves.

                                       Figure-2: Sensory block onset of median nerve

figure-3: Sensory block onset of radial nerve

 figure-4: Sensory block onset of ulnar nerve

figure-5: Sensory block onset of musculocutaneous nerve                                               

Figure-6: Motor block onset  of median nerve

Figure-7: Motor block onset of radial nerve

figure-8: Motor block onset of ulnar nerve

Figure-9: Motor block onset of musculocutaneous nerve

Figure-10: Composite sensory blockade at different time

figure-11 Composite motor blockade at different time intervals

Figure-12: Complete blockade at different time intervals

Figure-13: Number of patients achieving composite sensory blockade 8/8 at different time-points

Figure-14: Number of patients achieving composite motor blockade 8/8

Figure-15: Number of patients achieving Composite blockade 8/8.

Figure-16: showing patient satisfaction.

Figure-17: showing Time for 1^strescue analgesic(in mins).

Figure-18: Duration of block in hours.

Figure 19 : Showing analgesic requirement in first 24hours (Diclofenac 75mg)

  RESULTS:

 Patients in all groups were comparable with respect to mean age, weight, height, BMI  sex, ASA- grading. The surgical site, duration of surgery, tourniquet time and tourniquet pressure were comparable between the two groups (p>0.05).

 The mean number of needle passes in group 1 was 2.6±0.5 and in group 2 was 2.56±0.507(figure-1). The number of needle passes for block was statistically similar between the two groups (p>0.05). The onset time in group 1 was 20.00±3.37 minutes and in group 2 was 19.38±3.70 minutes(p>0.05). The success rate in group 1 was 92% and in group 2 was 96%. The success rate was comparable between the two groups with (p value 0.55).   

The duration of block (mean ± SD) in group 1 was 9.056±0.79 hours and in group 2 was 15.20±0.94 hours (figure-18). Our two groups significantly differed statistically in terms of duration of block (p=0.001). The duration of block was longer in 30ml group as compared to 20ml group.   

Complete blockade between the two groups was statistically significant at 5 minutes and the median complete blockade score of 16/16 achieved at 20 minutes in both the groups (figure-12). So, there was early initiation of complete blockade in the group 2. 72% patients in group 1 and 68% in group 2 achieved complete blockade score of 16/16 at 30 minutes. The two groups compared in terms of procedural pain after block and after surgery on VAS scale(p=0.32).The mean VAS score observed in group 1 and group 2 after block was 3.92±0.640 and 4.12±0.781 respectively. Both the groups were statistically comparable. The mean VAS score observed in group 1 and group 2 after surgery was 0.60±0.5 and 0.64±0.569 respectively. Both the groups were statistically comparable. The two groups compared in terms of patient satisfaction after block and after surgery on VAS scale. The mean VAS score observed in group 1 and group 2 after block was 5.84±0.987 and 6.16±0.898 respectively. Both the groups were statistically comparable. The mean VAS score observed in group 1 and group 2 after surgery was 8.88±0.781 and 8.92±0.702 respectively. Both the groups were statistically comparable and equally satisfied.   Three patients had unintentional vascular puncture in group 1 and one in group 2.  In group 1, one patient received double dose of fentanyl, two patients received single dose of fentanyl and twenty patients didn’t received any supplemental fentanyl. In group 2, two patients received single dose of fentanyl and twenty-two patients didn’t received supplemental fentanyl. There was no statistically significant difference in terms of Intraoperative fentanyl supplementation, with p value of 0.6.  In group 1, one dose of diclofenac was required by two patients, two doses of diclofenac were required by seventeen patients, three doses of diclofenac were required by four patients and two patients were not followed up for 24 hours. In group 2, one dose of diclofenac was required by twenty patients, two doses of diclofenac were required by four patients and one patient was not followed up for 24 hours.

In our study we found that the onset time and total anaesthesia related time was statistically similar between the two groups (p>0.05). The success rate in group 1 was 92% and in group 2  it was 96%. The success rate was comparable between the two groups with p value 0.55. we observed that our two groups differed statistically significantly in terms of duration of block (p=0.001). The duration of block was longer in 30ml group as compared to 20ml group. Although duration of block was adequate for anaesthesia during operative period and also good analgesia was obtained during postoperative period with 20 ml bupivacaine (0.5% group 1).

 In our study, we calculated the total number of needle insertion. Our both groups were statistically similar in terms of needle passes (p=0.77). The mean number of needle passes in group 1 was 2.6±0.5 and in group 2 was 2.56±0.507. Both the groups were statistically comparable. Vastrad et al⁴ observed mean number of needle passes (2.30±0.5) in perivascular group similar to our study.

 In our study, onset time was defined as the time interval between the end of total local anaesthetic administration and complete sensory blockade. Complete sensory blockade was defined by the anaesthetic block (score 2) on all four nerve distributions (composite sensory score of 8/8).  In our study, the mean onset time in group 1 was 20.0±3.37 minutes and in group 2 was 19.38±3.70 minutes. The onset time ranged from 15-25 minutes in both the groups. Our two groups were found statistically comparable in terms of mean onset time (p=0.54). We observed in our study that there is no effect of local anaesthetic volume on mean onset time. Ronakh  et al⁵ observed onset time similar to our study. In contrast to our study, Badole et al⁶, kaur et al⁷, observed shorter onset time because they considered sensory onset when there was a dull sensation to pinprick along the distribution of any of the individual nerve and also because of difference in technique (firm digital pressure with gauze piece for 5 minutes to assist in proximal spread of drug solution. Abdelhady et al⁸  observed sensory onset time shorter than our study, this difference can be because of difference in technique (they used in-plane technique). Nalini et al⁹ observed onset time less than our study, this difference can be because of mixing lignocaine with adrenaline in bupivacaine and also the difference in the definition of onset time.

 In our study, we considered successful block when patients didn’t require sedative drug or conversion to general anaesthesia other than two supplemental doses of fentanyl (one dose=1mcg/kg). The success rate was 92% (23 patients) in group 1 and 96% (24 patients) in group 2. Our two groups were found statistically similar in terms of success rate (p=0.55). Serradell et al¹⁰ and Ronakh et al⁵ reported success rate similar to our study and not found any significant difference in terms of success rate in different volume groups. 

The primary objective of our study was to compare the duration of block between the two groups. The duration of block was defined as pain complaint by the patient and assessment with VAS score of 4 any time post procedure and first rescue analgesic with injection diclofenac 75 mg intravenously was given to the patient. In our study, the mean duration of block (hours) was 9.056±0.79 in group 1 and 15.20±0.94 in group 2. The two groups were found to be statistically different in terms of duration of block (p=0.001). Ronakh et al, Badole et al also observed prolonged duration of block similar to our study with 20 ml of drug. Fenten et al found prolonged duration of block with higher volume/ higer dose(300mg vs 450 mg mepivacaine) of drug similar to our study and also we did not studied different volume with similar dose. They observed that changes in volumes between 20 ml of 1.5% mepivacaine or 30 ml of 1% mepivacaine with same dose of LA (300 mg mepivacaine) didn’t have a significant difference in the duration of blockade, but increasing the dose 30 ml of 1.5% mepivacaine (450 mg mepivacaine) resulted in significant prolongation of duration of blockade.

 In contrast to our study,  Kaur et al⁷ (30ml 0.5% bupivacaine) observed duration of analgesia/sensory block (8.32±0.99) less than our study, this could be because of difference in the technique, they used transarterial blind approach, needle placement may be less accurate and may not be as optimal as that is possible with use of ultrasound. Moreover, ultrasound allows observation of real-time spread of local anaesthetic around nerves and needle position can be optimized further. Abdelhady et al⁸ (30ml 0.5% bupivacaine) observed duration of first rescue analgesia (608.68±21.74 minutes) shorter than our study, this is attributed to the fact that patients involved in their study were medically different from our study (their patients had ESRD and history of diabetes).  

 Sensory blockade was assessed by pin prick test. For the radial nerve sensations were checked at dorsum of hand, for the median nerve medial aspect of forearm, for the ulnar nerve palmar and dorsal aspects of the medial 1.5 digits and adjacent palm, for the musculocutaneous nerve lateral aspect of forearm. Sensory blockade was graded according to a 3-point scale: 0=normal sensation (no block), 1=analgesia (touch but no pain; partial block), 2= anesthesia (no touch, no pain sensation; complete block). Motor blockade was evaluated for the musculocutaneous nerve using active elbow flexion, for the radial nerve by active elbow and wrist extension, for the median nerve by thumb and second digit pinch, and for the ulnar nerve by thumb and fifth digit pinch. Motor blockade was scored on a 3-point scale: 0= normal strength (no block), 1= paresis, and 2= paralysis, no movement (complete motor block). The maximal score was 16. Patients were considered ready for surgery when anaesthetic block achieve for all nerves (8/8 sensory score), regardless of the score for motor blockade. Block was considered successful when patients didn’t require sedative drug or conversion to general anaesthesia other than two supplemental doses of fentanyl (one dose=1mcg/kg). The median sensory blockade score of 2 for median nerve was achieved at 15 minutes in both the groups and the two groups were statistically comparable at all timepoints and with respect to change of sensory blockade over time. The median sensory blockade score for radial nerve between the two groups was statistically significant at 5 and 15 minutes. The median score of 2 was achieved earlier in group 2 at 15 minutes as compared to group 1 at 20 minutes The median sensory blockade score of 2 for ulnar nerve was achieved at 15 minutes in both the groups and the two groups were statistically comparable at all timepoints and with respect to change of sensory blockade over time. The median sensory blockade score for musculocutaneous nerve between the two groups was statistically significant at 15 minutes. The median score of 2 was achieved earlier in group 2 at 15 minutes as compared to group 1 at 20 minutes. The median motor blockade score of 2 for median nerve was achieved at 15 minutes in both the groups and the two groups were statistically comparable at all timepoints and with respect to change of sensory blockade over time. The median motor blockade score for radial nerve between the two groups was statistically significant at 5 and 15 minutes. The median score of 2 was achieved earlier in group 2 at 15 minutes as compared to group 1 at 20 minutes. The median motor blockade score of 2 for ulnar nerve was achieved at 15 minutes in both the groups and the two groups were statistically comparable at all timepoints and with respect to change of sensory blockade over time. The median motor blockade score for musculocutaneous nerve between the two groups was statistically significant at 15 minutes. The median score of 2 was achieved earlier in group 2 at 15 minutes as compared to group 1 at 20 minutes. In terms of median composite sensory blockade, the two groups were comparable at all observed time-points and in both the groups median composite sensory blockade score of 8 was achieved at 20 minutes. Number of patients achieving score of 8/8 were significantly more in group 2 as compared to group 1 at 15 minutes (32% vs 20%; p=0.03). 72% of the patients achieved score of 8/8 at 20 minutes and 92% at 30 minutes, 2 (8%) patients couldn’t achieve a score of 8/8 in group 1. 76% of the patients achieved score of 8/8 at 20 minutes and 96% at 30 minutes, 1 (4%) patients couldn’t achieve a score of 8/8 in group 2. Kaur et al⁷ observed 88% of the patients achieved full composite sensory blockade score at 15 minutes which was earlier than our study, this is attributed to the difference in the technique (firm digital pressure with gauze piece at the site of block for 5 minutes assist in proximal spread of the anaesthetic solution). Composite motor blockade between the two groups was statistically significant at 5 minutes and the median motor composite blockade score of 8/8 achieved at 20 minutes in both the groups. So, there was early initiation of motor blockade in the group 2. 72% patients in group 1 and 68% in group 2 achieved composite motor blockade score of 8/8 at 30 minutes. Although the motor blockade of 8/8 was not achieved in 7 patients in group 1 and 8 patients in group 2, patients were deemed fit for surgery when composite sensory blockade score 8/8. So, surgery was commenced in these patients. Complete blockade between the two groups was statistically significant at 5 minutes and the median complete blockade score of 16/16 achieved at 20 minutes in both the groups. So, there was early initiation of complete blockade in the group 2. 72% patients in group 1 and 68% in group 2 achieved complete blockade score of 16/16 at 30 minutes.

Patients were asked about the procedural pain using a 10-point visual analogue scale (0= no pain, 10=worst imaginable pain) after block and after surgery. In our study, mean VAS score of procedural pain after block in group 1 was 3.92±0.640 and in group 2 was 4.12±0.781. Both the groups were statistically comparable with p=0.32. Tran et al¹¹ reported a mean block related pain score of 1.7 (2.4) for PV technique, while that reported by Bernucci et al¹²  was 2.9 (2.8). In our study, though we used midazolam injection and local anaesthetic Infiltration in and around skin puncture site before performing block procedure, we avoided using fentanyl as premedication. But in these studies, author used midazolam and fentanyl injection (0.6mcg/kg) as premedication before performing procedure which might have caused less pain during procedure. After surgery mean VAS score for pain was 0.60±0.5 in group 1 and 0.64±0.569 in group 2. Both the groups were statistically comparable with p=0.79. Thus we can say that both the volumes were equally effective in providing intra-operative analgesia. This can be attributed to the fact that in both the groups success rate was comparable and duration of blockade in both the groups exceeded the duration of surgery, hence patients didn’t feel intra-operative pain.

 Patients were asked about their satisfaction using 10-point visual analogue scale (0=no satisfaction, 10= totally satisfied) after block and after surgery. In our study, mean VAS score of patient satisfaction after block in group 1 was 5.84±0.987 and in group 2 was 6.16±0.898. Both the groups were statistically comparable with p=0.253. After surgery mean VAS score for patient satisfaction was 8.88±0.781 in group 1 and 8.92±0.702 in group 2. Both the groups were statistically comparable with p=0.85. Fenten et al¹³, reported no statistically significant difference in terms of patient satisfaction between three different volume groups (Group A- 20 ml of 1.5% mepivacaine, Group B- 30 ml of 1% mepivacaine and Group C- 30 ml of 1.5% mepivacaine).

 Every regional block has the risk of some adverse events. In our study, we considered major adverse events can be vascular puncture, paresthesia, intravascular injection of drug, systemic toxicity of LA and nerve injuries. We encountered, three patients out of twenty-five in group 1 had unintentional vascular puncture and one patient out of twenty-five in group 2. On analyzing, it was observed that there was no statistically significant difference between the two groups in terms of procedural complications. We attributed this to the fact that vascular puncture during block depends on expertise of the person performing block not on volume of local anaesthetic. Serradell et al ¹⁰, reported more number of vascular puncture compared to our study, but also not found any significant difference between the three groups (36 ml vs 28ml vs 20ml) in terms of procedural complications. Ronakh et al, reported no procedure related complications in their study.

 Total analgesic requirement in first 24 hours: Total analgesic requirement in first 24 hours after surgery was recorded in both the groups. In group 1, one dose of Diclofenac was required by two patients, two doses by seventeen and three doses by four patients. In group 2, one dose of Diclofenac was required by twenty patients and 2 doses by four patients. We observed statistically significant difference in two groups in terms of analgesic requirement in first 24 hours (p=0.001). This difference was attributed to the fact that, in group 1 the mean duration of block (9.056±0.79 hours) was shorter as compared to the group 2 (15.20±0.94 hours), so group 1 required more number of analgesic doses as compared to group 2. After thorough search of literature related to axillary brachial plexus block, we couldn’t any study recording total analgesic requirement in 24 hours.

 Limitations: 1. Imaging and needling time was not observed separately in the overall block performance time. The relative position of the individual cords with the axillary artery differs anatomically in different patients. This may lead to extended imaging time to locate the nerves accurately and thus increasing the overall performance time (imaging + needling time) in patients with similar needling time. 2. Our results are specific to the study drug that is 0.5% bupivacaine and may not relate to other local anaesthetic agents with slower or fast onset of action. 3. We only compared 20 vs 30ml 0.5% bupivacaine and didn’t find the least volume required to provide effective anaesthesia in ultrasound guided axillary brachial plexus block.

In conclusion low volume (20ml) of 0.5% bupivacaine is equally efficacious compared to the conventional volume (30ml) with respect to the onset time of sensory blockade and success rate of the ultrasound guided axillary brachial plexus block. However the duration of the block was significantly more in 30ml group as compared to the 20ml group. The dose of the rescue analgesia required in post-operative period was also significantly less in the 30ml group. The procedural pain and patient satisfaction (after block and surgery) was comparable between the two groups. The procedural complications were also comparable. However, further multi-centric studies with larger sample size and wider group range with graded low volume are required to find out the least effective volume that would be sufficient for upper limb surgeries using ultrasound guided axillary brachial plexus block

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