European Journal of Cardiovascular Medicine

Brachial plexus block is most common peripheral nerve block technique for upper limb surgeries. It produces rapid and reliable anaesthesia for upper limb surgeries from injection of local anaesthetic. Advantages includes postoperative pain relief and short recovery time. It can be used in full stomach patients. Regional anaesthesia avoids risks and adverse effects of general anaesthesia which includes postoperative nausea, vomiting, atelectasis and deep vein thrombosis.¹ It produces better preservation of mental function in elderly patients, intact pharyngeal and laryngeal reflexes, thus reduces the chance of aspiration and stress response to anaesthesia. ²

Local anaesthetics used in nerve blocks provides postoperative pain relief by blockade of dorsal horn signal transmission.³ Local anaesthetics are commonly used in anaesthetic practice, but limited duration of action of local anaesthetic drugs is a concern for anaesthetists.⁴ Variety of adjuvants like opioids (Fentanyl, Tramadol, Butorphanol, Buprenorphine, Morphine), Alpha-2 agonists (Dexmedetomidine, Clonidine), Dexamethasone, Neostigmine etc., have been used in clinical practice to fasten the time of onset and to prolong the duration of analgesic effect of nerve blocks.

Magnesium sulphate is a noncompetitive N- methyl- D- aspartate (NMDA) receptor antagonist in the central as well as peripheral nervous system. The NMDA receptor contains binding sites for antagonists like magnesium. Magnesium sulphate potentiates the effect of local anaesthetic drugs and hence, used as an adjuvant in peripheral nerve block. Many clinical studies demonstrates that administration of magnesium during general anaesthesia reduced the intra-operative anaesthetic and post-operative analgesic requirement.⁵ Present study was aimed to know the efficacy of magnesium sulphate as an adjuvant to Ropivacaine in interscalene brachial plexus block using peripheral nerve stimulator.

Present study was hospital based, randomized, double blinded, clinical trial conducted in department of anaesthesiology, in teriatry care hospital. Study was approved by institutional ethical committee.

Inclusion criteria

• Patients of age group 18-55 years, ASA grade I and II, posted for above elbow surgeries e., Humerus fracture patients posted for Nailing, Plating or K-wire, under peripheral nerve stimulator guided interscalene brachial plexus block Willing to participate in present study

Exclusion criteria

• Patient's
• Known allergy to local
• Infection at local
• Patient with ASA grade > II
• Bleeding disorders or patient on anticoagulant
• Hepatic/Renal
• Respiratory
• History of cardiovascular

Preanaesthetic evaluation carried out on the day prior to surgery for all patients. Detailed general and systemic examination done along with airway. Consent for participation in study was taken from patients after explaining the procedure to be performed and reassured them to alleviate anxieties.

All patients underwent investigations such as Hemoglobin, Total leucocyte count, Differential leucocyte count, Bleeding time, Clotting time, Serum urea, Serum creatinine, Serum bilirubin, Blood sugar level and Blood group, HIV, HbsAg, Urine - Routine and microscopy, ECG and Chest x-ray PA view. All patients were kept NBM or nil per oral for 8 hours prior to surgery.

Intravenous line secured in the contralateral upper limb with 20G intravenous cannula under aseptic technique. Premedication with injection Ondansetron 4mg by intravenous route.

Patients were randomly allocated to Group A and B with 40patients in each group.

Group A- Total 25ml of Injection Ropivacaine 0.5% (5mg/ml) with Normal saline.

Group B – Total 25ml of Injection Ropivacaine 0.5% (5mg/ml) with 0.3ml Magnesium sulphate (150mg).

Standard multipara monitors like ECG, Pulse oximeter, Non-invasive blood pressure (NIBP) was connected and monitored in all patients. Data recorded every 3mins for 1^st 15mins, 5mins for next 15mins and every 30mins after completion of surgery till complete recovery of blockade.

Interscalene block was performed in all patients with the peripheral nerve stimulator connected to 3.5-cm, 22-gauge, short-bevel insulated stimulating needle by modified Winnie’s approach. After eliciting motor response, 25ml of 0.5% ropivacaine with normal saline was given in Group A & 25ml of 0.5% ropivacaine with 150 mg (0.3 ml) of Magnesium sulphate in group B, in the increments of 5 ml after fixing the stimulating needle, aspirating in between to avoid inadvertent intrathecal or intravascular injection.

Hemodynamic parameters such as HR, SBP, DBP and SpO2 were monitored at every 3 min interval till 15min of LA injection and then every 5 min till 30 min and thereafter every 30 min till the end of surgery and postoperatively till complete recovery from block. Adverse events such as hypotension (20% decrease in relation to the baseline value), bradycardia (HR < 60 bpm), hypoxemia (Spo < 90%) and perioperative nausea and vomiting were recorded.

Data was collected and compiled using Microsoft Excel,  analysed using SPSS 23.0 version. Frequency, percentage, means and standard deviations (SD) was calculated for the continuous variables, while ratios and proportions were calculated for the categorical variables. Difference of proportions between qualitative variables were tested using chi- square test or Fisher exact test as applicable. P value less than 0.5 was considered as statistically significant.

The study included 80 patients between the age group of 18-55years posted for upper limb surgeries under peripheral nerve stimulator guided interscalene brachial plexus block. Mean age, gender, mean height, mean weight & ASA grade were comparable in both groups & difference was not statistically significant.

Table 1- General characteristics

There was no statistically significant difference in heart rate between two groups except at 3mins and 1hr where it was significantly reduced in Group A than Group B.

Table no. 2 - Comparison of mean Heart rate of patients in two groups

There was no statistically significant difference observed in the systolic blood pressure of patients between two groups except at 2hrs, 2.5hrs and 3hrs where SBP was significantly reduced in Group A as compared to Group B.

Table no.3 - Comparison of mean Systolic Blood Pressure of patients in two groups

There was no statistically significant difference observed in the diastolic blood pressure of patients between two groups except at 2.5hrs and 3hrs where DBP was significantly reduced in Group A as compared to Group B. 

Table no. 4 - Comparison of mean Diastolic Blood Pressure of patients in two groups

No significant difference was observed in duration of the surgery in both groups (p=0.385).

Mean onset time of sensory blockade was earlier in group A (7.95 ± 1.154 min) as compared to group B (8.63 ± 0.740 min), difference was statistically significant. Mean onset time of motor blockade was earlier in group A (11.88 ± 1.381 min)) as compared to group B (14.40 ± 1.081min), difference was statistically significant.

Mean duration of sensory blockade was less in group A (310.8 ± 44.82 min) as compared to group B (486 ± 26.46 min), difference was statistically significant. Mean duration of motor blockade was less in group A (265.8 ± 30.06 min) as compared to group B (369 ± 28.98 min), difference was statistically significant.

The mean VAS score of Group A at 12hours is 3.95 ± 0.136 and group B is 2.00 ± 0.000, which was statistically significant. Mean VAS score of Group A at 24hours is 4.95 ± 0.316 and group B is 3.00 ± 0.000, which was statistically significant.

In Group A, mean duration of postoperative analgesia was 345 ± 57.24 min i.e., 5.75± 0.954 hours and in Group B it was 457.8 ± 35.16 min i.e., 7.63 ± 0.586 hours.

Table 5- Anaesthesia Characteristics

In Group A, 1 patient required 1 Rescue analgesic dose whereas in group B, 31 patients required 1 dose. Two Rescue analgesic doses was required for 27 patients in group A and only 7 patients in group B. Three Rescue analgesic dose was required for 12 patients in group A and only 2 patients in group B. The difference was statistically significant (P value  <0.001).

Table no.6 Rescue analgesic doses required by patients in two groups

Rescue analgesic time was < 6hrs in 11 patients in Group A and none in group B, While, rescue analgesic time was 6-12 hrs. in 29 Patients in group A and in 7 cases of group B. Whereas, it was >12 hrs. in 33 cases of group B out of which 2 cases required more than 24 hrs. Thus, it is evident that group B provides good analgesia for >6 hrs. The difference was statistically significant (P value <0.001)

Table no .7- Comparison of rescue analgesic Time between two groups

In group A none of the patients had intraoperative complications whereas, two patients in group B suffered from vomiting, which was statistically significant (P value <0.001)

Table no.8- Comparison of intraoperative complications between two groups

Regional anaesthesia enable patient to be conscious and avoids any airway manipulation, lesser interference with vital signs and few side effects.¹ These made regional anaesthesia the choice especially for the patients with comorbidities. Various adjuvants have been used to increase the efficacy of peripheral nerve blocks. In our study, Ropivacaine was used with magnesium sulphate as adjuvant for interscalene brachial plexus block using peripheral nerve stimulator.

Interscalene block is administered at the level of roots of the brachial plexus. As a result of this block, a prompt onset of anaesthesia is achieved. Local anaesthetics alone for block provides good operative conditions but have shorter duration of postoperative analgesia, hence adjuvants are used.

Ropivacaine was chosen for the study because of its better sensory to motor block profile and lesser cardiotoxicity compared to bupivacaine, which was in accordance with study done by Hofmann et al.,⁶ and Raeder et al.,⁷

Magnesium sulphate in general has analgesic, antihypertensive, anaesthetic sparing effects when used in systemic route.⁸ Magnesium sulphate has been used as an adjuvant in various dose with local anaesthetics under neuraxial anaesthesia. Mixing magnesium sulphate as adjuvant with local anaesthetics during peripheral nerve and nerve plexus blockade has recently been practiced by anaesthesiologist. ^9,10 The dose of 150 mg Magnesium was based on the previous studies done by Mukherjee et al.,⁴ who used 150 mg of MgSO4 with ropivacaine in supraclavicular brachial plexus block.

In our study it was concluded that on addition of magnesium to ropivacaine, the onset of sensory blockade was delayed significantly. This was comparable to the study done by Mukherjee et al.,⁴ whose time of onset of sensory block was 15.91 ± 1.60 min Vs 16.27 ± 3.07 min and Gupta et al.,¹¹ whose time of onset of sensory block was 16.63 + 2.79 min Vs 17.33 + 2.25 min who also had delayed onset but both studies it was not of statistical significance.

In our study it was concluded that on addition of magnesium to ropivacaine, the onset of motor blockade was delayed significantly. This was comparable to the study done by Mukherjee et al.,⁴ whose time of onset of motor block was 17.80 ± 7.6 min Vs 19.2 ± 6.2 min and Gupta et al.,¹¹ whose time of onset of motor block was 18.63 + 2.79 min Vs 19.76 + 2.18 min.

In our study it was concluded that addition of magnesium to ropivacaine, prolongs the duration of sensory blockade significantly. This was comparable to the study done by Mukherjee et al.,⁴ whose duration of sensory block was 289.67 ± 62.50 min Vs 456.21 ± 97.99 min (P value 0.001) and Verma et al.,¹² whose duration of sensory block was also prolonged significantly.

The mean duration of motor blockade was 265.8 ± 30.06 min in Group A and 369 ± 28.98 min in Group B. P value between Groups A and B is 0.001 which is statistically significant. Thus, from our study it was concluded that addition of magnesium to ropivacaine, prolongs the duration of motor blockade significantly. This was comparable to the study done by Mukherjee et al.,⁴ whose duration of motor block was 242.16 ± 23.86 min Vs 366.62 ± 24.42 min (P value 0.012) and Verma et al.,¹² whose duration of motor block was also prolonged significantly.

VAS Score was calculated for first 24 hours postoperatively. Mean VAS score at 12hours in Group A was 3.95±0.316 and 2.00±0.000 in Group B (P <0.001); at 24hours was 4.95± 0.316 in Group A and 3.00±0.000 in Group B (P <0.001), which was statistically significant.  It is comparable to the study done by Gupta et al.,¹¹ in which the VAS Score was significant at 6th and 12th hours.

The mean duration of postoperative analgesia in Group A was 345 ± 57.24 min and 457.8 ± 35.16 min in Group B. P value between Groups A and B is 0.001 which is statistically significant. Thus, it was strongly concluded that magnesium prolongs the duration of postoperative analgesia when added to the local anaesthetic. This is similar to the studies  conducted by Gupta et al.,¹¹ in which time to first rescue analgesic prolonged from 377.67 + 73.31 min to 491 + 100.22 min and similar to Mukherjee et al3 whose post op analgesia increased from 379.79 ± 145.52 min to461.71 ± 152.57 min and similar to the studies of Verma et al.,¹²

The mean number of rescue analgesics in Group A was 2.28±0.506 and Group B was 1.28±0.554, which is statistically significant. Thus, it is inferred that addition of magnesium to ropivacaine significantly reduced the number of rescue analgesics postoperatively. This is in accordance to the study done by Mukherjee et al.,⁴ ELShamaa et al.,¹³ also concluded that much less amount i.e., 35.6 mg vs. 113.6 mg of diclofenac sodium was administered as rescue analgesic in bupivacaine plus magnesium group than in control group.

The possible side effects include Nausea, Vomiting and Hypotension. Two patients in group B suffered from vomiting which was managed with iv fluids and IV ondansetron 4 mg. Choi et al.,¹⁴ also found similar side effects (nausea, vomiting, dizziness), but the difference between magnesium and normal saline group was also not significant (P = 0.62).

Addition of 150 mg magnesium sulphate to 0.5% ropivacaine in interscalene brachial plexus block significantly prolongs the duration of sensory and motor blockade and significantly reduces the requirement of rescue analgesic in postoperative period but delays the onset time of sensory and motor blockade.

Conflict of Interest: None to declare

Source of funding: Nil

1. Brown DL, Birdenbaugh DL, Cousins MJ, Bridenburgh PO. The upper extremity. 3rd ed. Chapter 10. In: Neural blockade; 1998. pp. 345-6.
2. Damien B, Murhy, Collin JL, Cartney VWS. Novel analgesic adjuvants for brachial plexus block: a systemic review. Anesth Analg. 2000;90:1122-8.
3. Babu Narendra MC, Sreeraghu GM, Sreeharsha S, Chandra DP, Dhingra U. A comparative study of bupivacaine 0.5% and ropivacaine 0.5% for supraclavicular brachial plexus block (perivascular approach). J Evol Med Dent Sci. 2014;3(43):10722-32.
4. Mukherjee K, Das A, Basunia SR, Dutta S, Mandal P, Mukherjee A. Evaluation of magnesium as an adjuvant in ropivacaine-induced supraclavicular brachial plexus block: a prospective, double- blinded randomized controlled study. J Res Pharm Pract. 2014;3:123-9.
5. Apan A, Buyukkocak U, Ozcan S, Sari F, Basar H. Postoperative magnesium sulphate infusion reduces analgesic requirements in spinal anaesthesia. Eur J Anaesthesiol. 2004;21(10):766-9.
6. Hofmann KF, Herbrich C, Seebauer A, Schwender D, Peter K. Ropivacaine 7.5 mg/mL versus bupivacaine 5 mg/mL for interscalene brachial plexus block: a comparative study. Anaesth Intensive Care. 2002;30(3):435-52.
7. Raeder JC, Drosdahl S, Klaastad O, Kvalsvik O, Isaksen B, Stromskag KE, et al. Axillary brachial plexus block with ropivacaine 7.5 mg/mL: a comparative study with bupivacaine 5 mg/mL. Acta Anaesthesiol Scand. 1999;43:794-8.
8. Christopher L, Lionel D, Martin Magnesium as an adjuvant to postoperative analgesia: a systematic review of randomized trials. Anesth Analg. 2007;104:1532-9.
9. Riveron P, Lemus G, Velasco B, Ruiz V. Clinical comparison of bupivacaine and ropivacaine for neurostimulation-guided brachial plexus block by axillary approach. Rev Mex Anestesiol. 2009;32:7-13.
10. Susanne H, Marianne E, Schonherr S, De Hert M, Markus WH. Magnesium—essentials for anesthesiologists. Anesthesiology. 2011;114:971-93.
11. Gupta D, Mangal V, Sharma G, Kulsheshta A, Kalra P. Efficacy of magnesium sulfate as an adjuvant to ropivacaine 0.4% for supraclavicular brachial plexus block in patients undergoing upper limb surgery. J Recent Adv Pain. 2017;3(2):85-9.
12. Verma V, Rana S, Chaudhary SK, Singh J, Verma RK, Sood S. A dose finding randomized controlled trial of magnesium sulphate as an adjuvant in ultrasound guided supraclavicular brachial plexus block. Indian J Anaesth. 2017;61:250-5.
13. ElShamaa HA, Ibrahim M, Eldesuky HI. Magnesium sulfate in femoral nerve block: does postoperative analgesia differ? A comparative study. Egypt J Anaesth. 2014;30:169-73.
14. Choi IG, Choi YS, Kim YH, Min JH, Chae YK, Lee YK, et al. The effects of postoperative brachial plexus block using MgSO4 on the postoperative pain after upper extremity surgery. Korean J Pain. 2011;24:158-63.