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Table of Contents
ORIGINAL ARTICLE
Year : 2020  |  Volume : 4  |  Issue : 4  |  Page : 156-160

Analgesic effect of magnesium sulfate as an adjuvant to ropivacaine in pectoral nerve block


1 Department of Anaesthesia, GGS Medical College and Hospital, Faridkot, Punjab, India
2 Department of Surgery, GGS Medical College and Hospital, Faridkot, Punjab, India

Date of Submission05-Jun-2020
Date of Decision27-Jun-2020
Date of Acceptance27-Jun-2020
Date of Web Publication05-Oct-2020

Correspondence Address:
Dr. Haramritpal Kaur
Department of Anaesthesia, GGS Medical College and Hospital, Faridkot, Punjab
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/BJOA.BJOA_104_20

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  Abstract 


Background: Pectoral nerve (Pecs) block is an effective component of multimodal analgesia regimens for breast surgeries. It has been used as a supplement to general anesthesia for intraoperative and postoperative analgesia. In the present study, we aimed to evaluate and compare the analgesic effect of magnesium sulfate 150 mg as an adjuvant to 0.25% ropivacaine in pecs block. Patients and Methods: A total of 60 American Society of Anaesthesiologists Grades I and II female patients with age between 18 and 65 years were enrolled in this study. Group A received ultrasound (US)-guided Pecs block with 40 ml volume containing 30 ml of 0.25% ropivacaine with 10 ml of normal saline as a placebo. Group B received US-guided Pecs block with 40 ml volume containing 30 ml of 0.25% ropivacaine and 150 mg of magnesium sulfate diluted to 10 ml of normal saline. Postoperative pain was assessed using the visual analog scale. Duration of analgesia and total analgesic consumption was noted in 24 h. Student's t-test, Mann–Whitney U–test, and Chi-square test were used for the statistical analysis. Results: The mean duration of analgesia was prolonged in Group B as compared to Group A (493.17 ± 12.54 min vs. 307.70 ± 22.37 min). Total analgesic consumption in the first 24 h postoperatively was also statistically lower in Group B as compared to Group A (132.50 ± 32.26 vs. 167 ± 32.26 mg in Group A) (P ≤ 0.001). Hemodynamics were comparable. Conclusion: The addition of 150 mg magnesium sulfate as adjuvant to 0.25% ropivacaine for Pecs block increases the duration of analgesia and significantly reduces the amount of analgesic requirement.

Keywords: Anaesthetic adjuvants, magnesium sulphate, pain management, pectoral nerve block, ropivacaine


How to cite this article:
Kaur H, Jhand HK, Baghla N, Chaudhry D, Singh A, Kaur R. Analgesic effect of magnesium sulfate as an adjuvant to ropivacaine in pectoral nerve block. Bali J Anaesthesiol 2020;4:156-60

How to cite this URL:
Kaur H, Jhand HK, Baghla N, Chaudhry D, Singh A, Kaur R. Analgesic effect of magnesium sulfate as an adjuvant to ropivacaine in pectoral nerve block. Bali J Anaesthesiol [serial online] 2020 [cited 2020 Nov 26];4:156-60. Available from: https://www.bjoaonline.com/text.asp?2020/4/4/156/299866




  Introduction Top


Pain is an unpleasant emotional and sensory experience which is associated with actual or potential tissue damage.[1] Acute postoperative pain is quite debilitating to the patient. Effective pain management is an essential component of the postoperative care of a surgical patient as adequate pain relief can lead to patient comfort, early mobilization, faster recovery, reduced risk of cardiac and pulmonary complications, less incidence of deep-vein thrombosis, and reduced cost of care. Inadequately controlled pain can result in increased morbidity like chronic pain and even mortality.[2],[3]

Patients undergoing breast surgery often experience intense pain. To manage postoperative pain effectively, various approaches have been adopted like regional anesthesia, opioid, and nonopioid analgesics.[4],[5]

Regional anesthesia is an art which provides site-specific anesthesia and analgesia. The pectoral nerve (Pecs) block is an interfascial plane block.[6] It causes decreased postoperative nausea and vomiting, improved patient outcome, and decreased duration of the postanesthesia care unit (PACU) stay.[7] Regional anesthesia with local anesthetics helps in alleviating postoperative pain. However, the duration of the block can limit its utilization, and hence, there is a constant need or desire to increase the duration of analgesia without compromising patient safety. This can be achieved by the use of perineural catheters, which is costly, time-consuming, and can lead to complications such as infection and catheter migration. It also needs more vigilant postoperative care.

Another technique practised to prolong the duration of nerve blocks is the use of different adjuvants. Magnesium has long been used in anesthesia practice for its analgesic, antihypertensive, and anesthetic sparing effects.[8] Current interest in magnesium in anesthesia practice makes us think that it might be effective in prolonging the duration of Pecs block as it has been shown to be effective in other blocks.[9],[10] The present study was planned to evaluate the analgesic effect of magnesium sulfate as an adjuvant to ropivacaine in the Pecs block.


  Patients and Methods Top


This is a prospective, randomized, controlled, double-blind study, with the approval of the institutional ethics committee and registered with the Clinical Trial Registry India (CTRI) under registration number CTRI/2018/07/014747. We studied 60 female patients of the American Society of Anesthesiologists' (ASA) Grades I and II, aged between 18 and 65 years scheduled for modified radical mastectomy under general anesthesia (GA) from April 2018 to March 2019. All participants provided written informed consent to be included in the study.

Patients were randomly allocated into two study groups of thirty patients, each using computer generated randomization. Labeled syringes were used for blinding. Group A (n = 30) received US-guided Pecs block with 40 ml volume containing 30 ml of 0.25% ropivacaine and 10 ml of normal saline as placebo. Group B (n = 30) received ultrasound (US)-guided Pecs block with 40 ml volume containing 30 ml of 0.25% ropivacaine and 150 mg of magnesium sulfate diluted to 10 ml of normal saline.

Patients with any contraindication to regional anesthesia or history of anaphylaxis to local anesthetics, pregnant or lactating patients were excluded from the study. During the preanesthetic visit, the procedure of block and Visual Analog Scale (VAS) was explained, and written informed consent was obtained.

In the operation theater, standard ASA monitors were attached and baseline parameters were recorded. After securing 18G intravenous cannula in the nonoperated side, the infusion of the crystalloid solution was started. GA was induced with morphine 0.1 mg/kg, propofol 2 mg/kg, and tracheal intubation was facilitated with vecuronium 0.1 mg/kg. Anesthesia was maintained with isoflurane 0.2%–1% and oxygen to nitrous oxide ratio of 50:50.

Pecs block was performed by senior anesthesiologist with the patient in supine position after intubation, with the ipsilateral upper limb in abduction position using US (Esaote MyLabOne Model 8100), the linear probe of high frequency (6–13 MHz) after sheathing. Vital parameters, that is, systolic blood pressure, diastolic blood pressure, mean arterial pressure (MAP), arterial saturation (SpO2), respiratory rate, and heart rate (HR) were recorded at 5 min interval to the end of surgery and postoperatively hourly for first 12 h, followed by six-hourly monitoring for first 24 h.

Adverse events such as hypotension (fall in mean arterial pressure of>20% of baseline values) and bradycardia (pulse rate of ≤50/min) were noted. Residual neuromuscular block was adequately reversed using glycopyrrolate 0.02 mg/kg, and neostigmine 0.05 mg/kg and the patient was subsequently extubated.

On arrival in the PACU, the pain was assessed using VAS (0–10) and was labeled as 0 h. VAS was then hourly till 12 h, then at 18 h and at 24 h postoperatively. Any patient showing VAS >3 was given analgesia in the form of injection diclofenac 75 mg. If the patient still had VAS >3, the second rescue analgesic drug injection tramadol 50 mg was given. Total analgesic given and the total number of rescue doses given during the first 24 h of postoperative period were recorded. The total duration of analgesia was noted in the two study groups postoperatively. It was taken from the time of completion of injection to the request of first rescue analgesia. Patient satisfaction score (PSS) was measured with a five-point numerical scale at the end of 24 h as 1-very satisfied, 2-satisfied, 3-undecided, 4-dissatisfied, and 5-very dissatisfied.

The sample size was estimated using pain scores as the primary variable. Assuming a standard deviation of 10 mm, the minimum needed sample size to detect a difference of 10 mm on the VAS of 10 cm, with Type 1 error of 0.05 and power of 80%, was 54. Hence, each group required at least 27 patients. Sixty patients were taken in the present study to account for any dropouts.

After completion of the study, the data were compiled, tabulated, and statistically analyzed using SPSS (Statistical Package for the Social Science) 21 version (SPSS 21 Inc., Chicago, IL, USA) statistical program for Microsoft Windows. Mean and standard deviation were used to represent the average and typical spread of values of variables. Student t-test and Mann–Whitney U-test were used for parametric and nonparametric data, respectively. Chi-square test was applied for comparing categorical data. A probability value (P value) of < 0.05 was considered statistically significant and < 0.001 as highly significant.


  Results Top


A total of 60 female patients were enrolled in the study. The demographic variables that are age, weight, height, body mass index, and ASA grade were similar in both the groups (P > 0.05) [Table 1].
Table 1: Demographic variables

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Duration of analgesia was more in Group B (ropivacaine plus magnesium group) than Group A (ropivacaine group), being 493.17 ± 12.54 min and 307.70 ± 22.37 min respectively [Table 2]. The total analgesic required was also less in Group B as compared to Group A, being 132.50 ± 32.26 mg and 167 ± 32.26 mg, respectively. Both results were statistically highly significant between the groups (P < 0.001). The number of rescue analgesics was also less in Group B as compared to Group A.
Table 2: Analgesic properties of both groups

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[Table 3] shows VAS scores in both groups. In the immediate postoperative period, it was <3 in both groups. VAS scores remained persistently less than three for initial 3 h in Group A and 6 h in Group B, which correlate well with the duration of analgesia. In the present study, 50% of patients of Group A and 53.3% of patients of Group B were very satisfied with anesthesia [Table 4]. There was no significant difference in PSS between the two groups (P > 0.05). [Figure 1] and [Figure 2] show intraoperative mean HR and MAP at various time points in both the groups, which were comparable.
Table 3: Visual analogue scale scores in both the groups at different time intervals

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Table 4: Patient satisfaction score between study groupsTable 4: Patient satisfaction score between study groups

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Figure 1: Intraoperative heart rate trends between two study groups

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Figure 2: Intraoperative mean arterial pressure trends between two study groups

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  Discussion Top


Postoperative pain, along with nausea, vomiting, and drowsiness is one of the most common causes of delayed patient discharge. To control this postoperative pain effectively, multimodal techniques are recommended.

Pecs block is a superficial thoracic wall block. It can be used as a part of multimodal analgesia regimen in patients undergoing modified radical mastectomy. It is a safe and inexpensive technique with the advantages of providing ideal operating conditions and effective postoperative analgesia. US guided pectoral block allows better visualization of underlying structures, movement of the needle, and direct spread of local anesthetic, thereby making procedure safe and effective, especially in patients with anatomical variations.[11]

Magnesium sulfate has been used in various peripheral nerve blocks along with local anesthetics with considerable success. The main site of action of magnesium sulfate is N-methyl D-aspartate (NMDA) receptor and associated calcium channels. NMDA receptors are present in different parts of the body, including nerve endings, and play a significant role in pain modulation and various inflammatory responses. It is a noncompetent antagonist at the NMDA receptor, which blocks ion channels in a voltage-dependent fashion. Hence, effects of magnesium sulfate in peripheral nerve blocks could be explained by the prevention of central sensitization that occurs due to peripheral nociceptive stimulation.[12],[13]

Another theory for the action of magnesium sulfate is surface charge theory. The modulation of external magnesium concentration bathing a nerve bundle can enhance the peripheral nerve block caused by local anesthetic as well as the high concentration of magnesium attracted by negative charges of outer membrane surface effected Na + channel gating that causes hyperpolarization and hence inhibition of nerve conduction.[14],[15]

In the present study, we added 150 mg of magnesium sulfate to ropivacaine 0.25% and evaluated the patients postoperatively for their VAS scores, total duration of analgesia of pec block, total analgesic consumption postoperatively and total number of rescue analgesics given postoperatively.

We found that the duration of analgesia was significantly prolonged in Group B (ropivacaine plus magnesium group) as compared to Group A (ropivacaine group), [Table 2] being 493.17 ± 12.54 min and 307.70 ± 22.37 min, respectively (P < 0.001). The mean of total analgesia required was less in Group B than Group A [Table 2], being 132.50 ± 32.26 mg and 167 ± 32.26 mg, respectively (P < 0.001). The number of rescue analgesics was also less in Group B, as compared to Group A, [Table 2], (P < 0.001).

VAS scores in both the groups in the immediate postoperative period were <3. VAS scores remained persistently less than three for the initial 3 h in Group A and 6 h in Group B [Table 3]. VAS scores significantly differ between two groups at certain time intervals from 3 h onward, and at most of the intervals, they were statistically significantly lower in Group B as compared to Group A [Table 3].

Hence, the results of the present study showed that magnesium sulfate when added to 0.25% ropivacaine in pec blocks, add on to the efficacy of ropivacaine 0.25%. Although the effect of magnesium sulfate in other blocks is supported by other studies the data regarding its use in pec block in literature is still in paucity.

A study was conducted by Rana et al., where they studied the efficacy of 150 mg of magnesium sulfate when added to 18 ml of 0.25% bupivacaine in US guided transversus abdominis plane block in patients of total abdominal hysterectomy under subarachnoid block. It was found that the duration of analgesia was prolonged in the magnesium group (968 ± 161.06 min) than in the control group (397.67 ± 92.84 min), which was statistically highly significant (P ≤ 0.001). They also found that the number of rescue analgesics required was more in the control group than in the magnesium group. The extended duration of analgesia in their study as compared to the results of the present study could be due to the added effect of the subarachnoid block in the patients.[16]

Another study was conducted by Muthiah et al., where 150 mg of magnesium sulfate was added as an adjuvant to 30 ml of 0.25% bupivacaine in 3-in-1 nerve block for arthroscopic anterior cruciate ligament repair. It was concluded that the duration of analgesia was prolonged in the magnesium group (789 ± 436 min) as compared to bupivacaine only group (466 ± 290 min), which was statistically significant (P < 0.05).[17]

The results of the present study were similar to the study done by Elyazed and Mogahed., who studied the effect of adding 150 mg of magnesium sulfate and 100 mcg of dexmedetomidine to 35 ml of 0.5% ropivacaine in US guided infraclavicular brachial plexus block. The mean duration of analgesia with ropivacaine was 403.26 ± 53.48 min, with magnesium sulfate was 598.71 ± 51.54 min, and with dexmedetomidine was 684.14 ± 51.57 min (P < 0.001). VAS was also lower in magnesium sulfate and dexmedetomidine groups than in the ropivacaine group postoperatively.[18]

The observations of the present study also correlate well with the study conducted by Al-Refaey et al., who studied the effect of adding 500 mg of magnesium sulfate to 20 ml of 0.25% bupivacaine in transversus abdominis plane block and found that mean duration of analgesia was longer in magnesium group (19 ± 2.2 h) as compared to other groups (P < 0.05). The mean VAS score was also statically lower in the magnesium group as compared to other groups (P < 0.001).[19]

In the present study, 50% of patients of Group A and 53.3% of patients of Group B were very satisfied with anesthesia (PSS = 1). About 50% of patients of Group A and 46.7% of patients of Group B were satisfied with anesthesia (PSS = 2) [Table 4]. There was no significant difference in PSS in the two groups (P > 0.05), this correlates with optimum pain control in both the groups, so both the groups were equally satisfied.

There was no statistically significant difference between the two groups regarding the hemodynamic parameters at all the time intervals [Figure 1] and [Figure 2]. There were no significant side effects or complications between the two groups. It was found that hemodynamic stability was maintained in patients of both groups. Magnesium sulfate, when used even in dosages of 500 mg added to 0.25% bupivacaine in transversus abdominis plane block, has shown that there was no significant difference between the groups in regards to intraoperative HR and MAP.[19]

Magnesium sulfate when given intravenously, can lead to various adverse effects such as hypotension, bradycardia, abnormal rhythms, temporary flushing of face and neck, drowsiness, weak reflexes, excessive sweating, paralysis of skeletal muscles, etc., However, it has been seen that magnesium sulfate when used in various doses in different nerve blocks as an adjuvant to local anesthetics does not lead to any complication or adverse effect.[17],[19],[20]

This study is just a small attempt to show the efficacy of magnesium sulfate as an adjuvant to ropivacaine in pecs block. Larger series needs to be done with different dosages of magnesium sulfate to find the optimal dose that most effectively prolongs postoperative analgesia. We could not evaluate the effect of Pecs bock with or without magnesium sulfate on chronic postsurgical pain, metastasis, or recurrence of carcinoma breast, which needed the long-term follow-up of patients in outdoor clinics. Hence, this study opens the way for large multicentric trials with extensive and prolonged follow-up to prove the efficacy of magnesium sulfate as an adjuvant in Pec blocks.


  Conclusion Top


From the present study, we conclude that the addition of 150 mg of magnesium sulfate as an adjuvant to 0.25% ropivacaine in comparison to 0.25% ropivacaine alone in Pec block, prolongs the duration of analgesia, significantly reduces the amount of analgesic requirement in first 24 h postoperatively with persistently lower VAS scores and also lesser number of rescue analgesics. This can contribute significantly to better patient comfort and safety.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Karthik GS, Sudheer R, Rangalakshmi S, Priyanka NP, Prajwal BV. Magnesium sulphate as an adjuvant to ropivacaine in ultrasound guided supraclavicular brachial plexus block: A comparative prospective randomized controlled study. Indian J Anaesth Analg 2018;5:1093-100.  Back to cited text no. 9
    
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Verma V, Rana S, Chaudhary SK, Singh J, Verma RK, Sood S. A dose-finding randomised controlled trial of magnesium sulphate as an adjuvant in ultrasound-guided supraclavicular brachial plexus block. Indian J Anaesth 2017;61:250-5.  Back to cited text no. 10
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Buvanendran A, Kroin JS. Useful adjuvants for postoperative pain management. Best Pract Res Clin Anaesthesiol 2007;21:31-49.  Back to cited text no. 13
    
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Lee AR, Yi HW, Chung IS, Ko JS, Ahn HJ, Gwak MS, et al. Magnesium added to bupivacaine prolongs the duration of analgesia after interscalene nerve block. Can J Anaesth 2012;59:21-7.  Back to cited text no. 14
    
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Rana S, Verma RK, Singh J, Chaudhary SK, Chandel A. Magnesium sulphate as an adjuvant to bupivacaine in ultrasound-guided transversus abdominis plane block in patients scheduled for total abdominal hysterectomy under subarachnoid block. Indian J Anaesth 2016;60:174-9.  Back to cited text no. 16
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Muthiah T, Arora MK, Trikha A, Sunder RA, Prasad G, Singh PM. Efficacy of magnesium as an adjuvant to bupivacaine in 3-in-1 nerve block for arthroscopic anterior cruciate ligament repair. Indian J Anaesth 2016;60:491-5.  Back to cited text no. 17
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