European Journal of Cardiovascular Medicine

The advancement of ultrasound-guided techniques has made brachial plexus block a better alternative to general anesthesia for surgeries of upper limb. It serves not only as an effective method for intraoperative anesthesia but also extends postoperative analgesia, enhances pain relief, reduces postoperative opioid consumption and avoids the adverse effects associated with general anesthesia¹. The supraclavicular approach of brachial plexus block targets the middle of the brachial plexus, where the nerves are densely packed, ensuring even distribution of the anesthetic and a rapid onset of complete anesthesia².

Ropivacaine is a pure S-enantiomer of bupivacaine, distinguished by its lower lipophilicity. This characteristic results in diminished motor blockade, as it penetrates large myelinated motor fibers less effectively. The differentiation between sensory and motor effects, along with a lower risk of neurological and cardiovascular toxicity, has contributed to the increasing use of ropivacaine in clinical practice³.

Minimal Effective Concentration 90 (MEC90) of ropivacaine is found to be 0.25% for supraclavicular brachial plexus blocks⁴. Hence in order to prevent the toxic effects of higher concentrations of ropivacaine (0.5%, 0.75%), very minimal concentration of 0.2% ropivacaine is being used in this study.

Various adjuvants like dexamethasone, opioids, clonidine, tramadol, neostigmine etc. have been used to prolong the duration of analgesia and improvise the postoperative comfort of the patient. Dexmedetomidine, a newer alpha-2 agonist has been used widely these days due to its sedative, anxiolytic and analgesic properties⁵.

Not many studies are available on dexmedetomidine as adjuvant to 0.2% ropivacaine in supraclavicular brachial plexus block. So, this study was conducted to evaluate the efficacy of dexmedetomidine as an adjuvant to 0.2% ropivacaine in supraclavicular brachial plexus block in patients undergoing elective below elbow surgeries under USG guidance.

Objectives:

1. To determine and compare the time of onset of sensory and motor blockade between the two groups.
2. To determine and compare the duration of sensory and motor blockade between the two groups.
3. To determine and compare the duration of analgesia between the two groups.
4. To determine and compare the hemodynamic variability between the two groups.
5. Intraoperative and postoperative side-effects and complications.

This randomized, prospective and double blinded study was conducted at Hassan teaching hospital after the approval of the institutional ethical committee. Informed written consent was obtained from all the 60 patients aged between 18-55 years, belonging to American society of Anesthesiologists physical status (ASA) I / II undergoing elective below elbow surgeries. Patients with history of allergy to the local anesthetics, bleeding disorders, on anticoagulant therapy, cardiac diseases and on medications like beta blockers/opioids were excluded from the study. Standard ASA fasting guidelines were followed in all of them.

Computer based random allocation of 60 patients was done into two groups:

Group RN: receiving 30 ml of ropivacaine 0.2% along with 1 ml of normal saline

Group RD: receiving 30ml of ropivacaine 0.2% along with dexmedetomodine -1 mcg/kg (made to 1 ml).

On arrival at the operation theatre, baseline heart rate, blood pressure, respiratory rate and peripheral oxygen saturation were recorded. An 18G intravenous cannula was secured and intravenous infusion of ringer lactate was started. Ultrasound guided supraclavicular brachial plexus block was performed in supine position and the study drugs were injected as mentioned earlier.

The drug solutions were made to look identical and handed over in the coded forms to the anesthesiologist who performed the block and monitored the patients throughout the study. The patient was also not aware of the drug solution that he/she received. Hence, double blinding was achieved effectively.

Then the sensory and motor block characteristics were assessed. Primary objectives were to evaluate the time for onset of sensory block, duration of sensory blockade, time of onset of motor block, duration of motor block, total duration of postoperative analgesia.

Sensory block was assessed by loss of sensation to pinprick over the desired dermatomes using a 3-points scale [7] which is as follows ⁶: 0 - Sharp pain, 1 - Dull pain (analgesia), 2 - No pain (anesthesia).Sensory onset time was defined as the time interval between the end of local anesthetic administration and establishment of score 2 on 3-point scale in all the desired dermatomes. Sensory block duration was defined as the time from injection of local anesthetic to complete recovery from cold and pain sensation in the desired dermatomes.

Motor block was assessed using Motor blockade scale⁶.  Grade 1 – ability to flex or extend the forearm, Grade 2 – ability to flex or extend only wrist or fingers, Grade 3 - ability to flex or extend only fingers, Grade 4- inability to move the forearm, wrist or fingers. Motor block onset time was defined as the time interval between the end of LA administration and complete motor block (score 2). Motor block duration was defined as the time from injection of local anesthetic study solution to complete recovery of movements of upper limb.

Total duration of analgesia was measured till the patient has VAS >3 and rescue analgesia was be given.

Secondary objectives were hemodynamic parameters and side effects. Hemodynamic parameters such as heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), oxygen saturation, and respiratory rate were monitored at every 10 min interval till 1 hour following local anesthetic injection and then every 20 min till the end of 2nd hour and thereafter every hour till the end of surgery. All side effects such as hypotension (20% reduction in relation to the baseline value), bradycardia (HR), nausea and vomiting were noted in both the groups.

Statistical Analysis:

Data was entered into Microsoft Excel data sheet and analyzed using SPSS 22 version software. Categorical data was represented in the form of frequencies and proportions. Chi-square test was the test of significance. Continuous data was represented as mean and standard deviation. Independent t test was the test of significance to identify the mean difference between the two groups. Differences were judged significant at P<0.05.

Sample size: Sample size was estimated using the findings of the study done by Marhofer D et al where the mean duration of onset of motor block in ropivacaine group was 47±3.6 and in ropivacaine and dexmedetomidine group was 21±15. Using these values at 95% confidence limit and at 1% error and 90% power, sample size of 29 was obtained in each group by using the below mentioned formula and Med calc sample size software. With 10% non-response sample size of 26+2.9~ 32, this was rounded off to 30 cases in each group.

Sixty patients were enrolled into the study based on the above-mentioned criteria and then randomly allocated into group RD and group RN. Demographic characteristics were comparable in both the groups as per Fig 1.

The onset of sensory and motor block was significantly faster in group RD than that of group RN (P<0.05) Fig 2 & 3.

The duration of sensory and motor blockade was also significantly prolonged on adding dexmedetomidine to 0.2% ropivacaine than that of using ropivacaine alone (P<0.05)

The total duration of analgesia was significantly longer in group RD than that of group RN (P<0.05).

Hemodynamic variables showed no significant differences in both the groups. No side effects were reported in the groups.

The brachial plexus block is commonly employed either alongside general anesthesia (GA) or as the primary anesthesia technique for upper limb surgeries. It offers superior analgesia while minimizing the typical side effects associated with GA, making it especially beneficial for patients with significant comorbidities7.

Bupivacaine is a commonly used local anesthetic agent due to its longer duration of action and favorable sensory-to-motor block ratio. However, its toxicity is of significant concern, particularly with larger doses and prolonged infusion for postoperative analgesia. Hence, a newer long acting amide local anesthetic, ropivacaine, was developed with better safety profile8.

Kaur et al9 compared the effects of equal volumes and concentrations of bupivacaine and ropivacaine in patients undergoing elective forearm surgeries under brachial plexus block and found that the ropivacaine is a safer alternative to bupivacaine with faster recovery of motor functions.

The clinical concentrations of ropivacaine used for brachial plexus block (BPB) typically range from 0.25% to 1%4. To prevent excessive administration of local anesthetics and ensure painless surgery, it is important to determine the minimum effective concentration (MEC 90) that achieves adequate anesthesia in 90% of patients. The minimum effective concentration (MEC 90) of ropivacaine is 0.25% according to recent studies 4,10 Fang et al4 conducted ultrasound guided supraclavicular brachial plexus block in patients undergoing arm surgeries using 0.257% of ropivacaine and found that the lower concentration of ropivacaine(0.25%) was successful in providing adequate blockade. Taha et al0 found that the perineural injection of 0.167% of ropivacaine under ultrasound guidance provided successful femoral nerve block in 90% of patients. So we conducted this study using lower concentration of ropivacaine (0.2%) in USG guided supraclavicular brachial plexus block in patients undergoing forearm surgeries. The time of onset of sensory and motor blockade were 14.60 and 4.32 minutes, respectively, while the durations of sensory and motor blockade were 331.73 and 368.93 minutes, respectively in this study. There were no changes in hemodynamic parameters or side effects when using the lower concentration (0.2%) of ropivacaine.

Various adjuvants like dexamethasone, clonidine, opioids etc are incorporated into local anesthetics (LAs) to accelerate the onset and extend the duration of the block.11 Dexmedetomidine, a newer α2 agonist with sedative, analgesic, anxiolytic, sympatholytic, and opioid-sparing properties, has become widely utilized as an adjuvant in combination with various local anesthetics for peripheral nerve blocks5   Very few studies are available on the effects of adding dexmedetomidine to lower concentration of ropivacaine(0.2%) in patients undergoing USG guided supraclavicular brachial plexus block. A study conducted by Sharma et al12 on patients undergoing elective upper limb surgeries under supraclavicular brachial plexus block showed that the patients receiving 0.5% Ropivacaine + 0.75 mcg/kg Dexmedetomidine had rapid onset of sensory and motor blockade, prolongation of duration of sensory and motor blockade and duration of analgesia postoperatively without any significant side effects than that of patients receiving 0.5% ropivacaine alone. Also Tiwari et al13 studied the effects of adding 50mcg of dexmedetomidine to 0.75% of ropivacaine in patients undergoing elective upper limb surgery under supraclavicular brachial plexus block and concluded that dexmedetomidine as an adjuvant extended the duration of analgesia and shortened the onset time of sensory and motor block. Hassan et al14 conducted a prospective observational study on patients undergoing elective arthroscopic shoulder surgeries under general anesthesia with USG guided interscalene brachial plexus block and found that adding 50mcg of dexmedetomidine to 0.2% ropivacaine hastened the onset of sensory and motor block with prolonged duration of block and no hemodynamic changes/side-effects. This study showed that the onset of sensory (3.4667 minutes) and motor (1.5500minutes) blockade were shortened and duration of sensory and motor blockade were prolonged as 514.233 minutes and 567.6667 minutes respectively. Total duration of analgesia was significantly prolonged on adding dexmedetomidine (894 minutes) without any variations in the hemodynamic parameters and side-effects.

This study demonstrates that 0.2% ropivacaine provides effective blockade for below-elbow surgeries, and the addition of dexmedetomidine significantly extends the duration of analgesia.

1. Dai W, Tang M, He K. The effect and safety of dexmedetomidine added to ropivacaine in brachial plexus block: A meta-analysis of randomized controlled trials. Medicine. 2018 Oct 1; 97(41)
2. Das B, Lakshmegowda M, Sharma M, Mitra S, Chauhan R. Supraclavicular brachial plexus block using ropivacaine alone or combined with dexmedetomidine for upper limb surgery: a prospective, randomized, double-blinded, comparative study. Revista Española de Anestesiología y Reanimación (English Edition). 2016 Mar 1; 63(3):135-40.
3. Kuthiala G, Chaudhary G. Ropivacaine: A review of its pharmacology and clinical use. Indian journal of anaesthesia. 2011 Mar 1; 55(2):104-10.
4. Fang G, Wan L, Mei W, Yu HH, Luo AL. The minimum effective concentration (MEC 90) of ropivacaine for ultrasound‐guided supraclavicular brachial plexus block. Anaesthesia. 2016 Jun; 71(6):700-5.
5. Lee S. Dexmedetomidine: present and future directions. Korean journal of anesthesiology. 2019 Aug 1; 72(4):323-30.
6. Rashmi HD, Komala HK. Effect of dexmedetomidine as an adjuvant to 0.75% ropivacaine in interscalene brachial plexus block using nerve stimulator: a prospective, randomized double-blind study. Anesthesia Essays and Researches. 2017 Jan 1; 11(1):134-9.
7. Kumar S, Palaria U, Sinha AK, Punera DC, Pandey V. Comparative evaluation of ropivacaine and ropivacaine with dexamethasone in supraclavicular brachial plexus block for postoperative analgesia. Anesthesia Essays and Researches. 2014 May 1;8(2):202-8.
8. Kaur A, Singh RB, Tripathi RK, Choubey S. Comparison between bupivacaine and ropivacaine in patients undergoing forearm surgeries under axillary brachial plexus block: a prospective randomized study. Journal of clinical and diagnostic research: JCDR. 2015 Jan;9(1):UC01.
9. Wu L, Zhang W, Zhang X, Wu Y, Qu H, Zhang D, Wei Y. Optimal concentration of ropivacaine for brachial plexus blocks in adult patients undergoing upper limb surgeries: a systematic review and meta-analysis. Frontiers in Pharmacology. 2023 Nov 16; 14: 1288697.
10. M. Taha, A. M. Abd-Elmaksoud. Ropivacaine in ultrasound-guided femoral nerve block: what is the minimal effective anaesthetic concentration (EC₉₀)? Anaesthesia 2014, 69, 678–682
11. Dai W, Tang M, He K. The effect and safety of dexmedetomidine added to ropivacaine in brachial plexus block: A meta-analysis of randomized controlled trials. Medicine. 2018 Oct 1;97(41):e12573.
12. Sharma S, Shrestha A, Koirala M. Effect of dexmedetomidine with ropivacaine in supraclavicular brachial plexus block. Kathmandu Univ Med J (KUMJ). 2019 Jul 1;17(67):178-83.
13. Prashant Tiwari, Manish Jain, Bhawana Rastogi, Salony aggarwal, Kumkum Gupta and VP Singh. A comparative clinical study of perineural administration of 0.75% ropivacaine with and without dexmedetomidinein upper limb surgery by ultrasound guided single injection supraclavicular brachial plexus block. Glob Anesth Perioper Med. 2015 Volume 1(5): 131-133
14. Aaqib Hassan, Safura Riaz, Fahim Maqbool, Akim M Shah. Perioperative hemodynamic effects of dexmedetomidine as an adjuvant to 0.2% ropivacaine in ultrasonography guided interscalene brachial plexus block for elective shoulder arthroscopic surgeries under general anaesthesia: a prospective observational study. Int J Res Med Sci. 2023 Jan;11(1):266-27.