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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 9  |  Issue : 4  |  Page : 157-163

To study the efficacy of intravenous infusion of magnesium sulfate in the Indian population during epidural anesthesia using 0.5% bupivacaine for postoperative pain in infra-umbilical surgery


1 Department of Anesthesia, Bangalore Medical College and Research Institute, Bengaluru, Karnataka, India
2 Department of Anaesthesia and Critical Care, Level III IFH MONUSCO, Goma, DR Congo
3 Department of Anaesthesia, Rajshekar Multispeciality Hospital, Bengaluru, Karnataka, India
4 Department of Radiodiagnosis and Imaging, Alchemist Ojas Hospital, Panchkula, Haryana, India
5 Department of Psychiatry, Level III IFH MONUSCO, Goma, DR Congo

Date of Submission28-Apr-2021
Date of Decision07-May-2021
Date of Acceptance05-Jul-2021
Date of Web Publication26-Nov-2021

Correspondence Address:
Dr. Shibu Sasidharan
Department of Anaesthesia and Critical Care, Level III UN Hospital, Goma
DR Congo
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mjhs.mjhs_32_21

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  Abstract 


Objectives: Infra-umbilical surgeries are associated with moderate-to-severe pain postoperatively. Intravenous infusion of magnesium sulfate during epidural anesthesia was given which prolonged the duration of analgesia and decreased doses of analgesics. As hardly any study has been done on the Indian population, this study evaluated the effectiveness of magnesium sulfate infusion on quality of epidural anesthesia, postoperative analgesic requirements, and incidence of nausea and vomiting in the patients undergoing any infra-umbilical surgery.
Methodology: A prospective randomized controlled double-blind study was carried out at a tertiary level hospital in India in seventy patients scheduled for infra-umbilical surgeries belonging to the American Society of Anesthesiologists I and II. Patients were randomized into two groups of 35 each. Group MG patients received MgSO4 50 mg/kg in 100 ml NS in 10 min, followed by an infusion of MgSO4 10 mg/kg/h in 100 ml NS over 1 h. Group NS received 100 ml NS in 10 min, followed by an infusion of 100 ml NS over 1 h.
Results: The onset time of sensory and motor block was similar in both the groups, but the duration of sensory and motor block and duration of analgesia was more in MG group compared to NS group. The mean sensory onset time in MG group was 9.09 ± 2.23 min and 9.34 ± 2.29 min in NS group, which was statistically insignificant (P = 0.642). The mean motor onset time in MG group was 13.35 ± 2.62 min and13.54 ± 2.60 min in NS group, which again was statistically insignificant (P = 0.763). The duration of sensory block for MG group was 424.12 ± 53.43 min and 226.57 ± 27.22 min for NS group. This was statistically significant (P ≤ 0.001). The duration of motor block for MG group was 361.62 ± 43.04 min and 208.29 ± 27.38 min for NS group. This was statistically significant (P ≤ 0.001). The duration of analgesia for MG group was 436.18 ± 53.88 min and 234.00 ± 30.31 min for NS group. This too was statistically significant (P ≤ 0.001). There were no significant differences between the study groups with respect to changes in heart rate, systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, and saturation perioperatively. There was no incidence of nausea and vomiting in both the groups.
Conclusion: Magnesium sulfate infusion improves the quality of epidural anesthesia, postoperative analgesia requirements, and nausea and vomiting in patients undergoing infra-umbilical surgery.

Keywords: Analgesia, epidural anesthesia, infra-umbilical surgeries, magnesium sulfate


How to cite this article:
Chindanand K G, Raghavendra Rao R S, Sasidharan S, Praveen Pateel G N, Manalikuzhiyil B, Dhillon HS. To study the efficacy of intravenous infusion of magnesium sulfate in the Indian population during epidural anesthesia using 0.5% bupivacaine for postoperative pain in infra-umbilical surgery. MRIMS J Health Sci 2021;9:157-63

How to cite this URL:
Chindanand K G, Raghavendra Rao R S, Sasidharan S, Praveen Pateel G N, Manalikuzhiyil B, Dhillon HS. To study the efficacy of intravenous infusion of magnesium sulfate in the Indian population during epidural anesthesia using 0.5% bupivacaine for postoperative pain in infra-umbilical surgery. MRIMS J Health Sci [serial online] 2021 [cited 2022 Jan 19];9:157-63. Available from: http://www.mrimsjournal.com/text.asp?2021/9/4/157/331241




  Introduction Top


Infra-umbilical surgeries are associated with moderate-to-severe pain postoperatively. Various adjuvants have been studied to prolong analgesia in the postoperative period.

Magnesium is the fourth most abundant cation in the body responsible for many biochemical reactions. It is also called as “nature's physiologic calcium channel blocker”.[1],[2] Magnesium is an inorganic ion that has a noncompetitive N-methyl-D-aspartate receptor antagonist property with antinociceptive effects in animals and human models.[3],[4] This antagonism reduces the induction and maintenance of central sensitization of nociceptive stimulation by altering pain processing.

Numerous clinical investigations have demonstrated that magnesium infusion during general anesthesia and spinal anesthesia reduced anesthetic requirements and postoperative analgesic consumption.[5],[6]

With this background, we hypothesized that the concomitant use of intravenous (IV) infusion of magnesium sulfate may have an effect on the block characteristics and the duration of action of epidural bupivacaine. This study is designed to evaluate and observe the effects of concomitant IV infusion of magnesium sulfate on epidural block characteristics and duration of postoperative analgesia in patients undergoing infra-umbilical surgeries under epidural block with bupivacaine.


  Methodology Top


Source of data

The study was conducted in a tertiary level hospital in south India from November 2016 to May 2018.

Type of study

Prospective study.

Study design

Randomized clinical study.

Sample size

Two groups of 35 each.

Sample size estimation was done using power and sample size calculation software version 2.1.30. Using these data and assuming a study power of 80% and probability of type I error of 5%, a sample size of 70 patients was found to be required for obtaining statistically significant mean difference of mean duration of analgesia in two groups. So assuming equal distribution of patients in both the groups, a total number of 70 patients were incorporated in the study with 35 patients in each group.

N = 2 (Zα + Zβ2/(μ1−μ2)2

N = Sample size

Zα = Level of significance

Zβ = Required power

σ = Anticipated standard deviation (SD)

μ1−μ2 = Meaningful difference between two means.

Sampling method

Randomization was done using numbers generated from www.randomisation.org.

Method of collection of data

Seventy patients aged between 18 years and 60 years of physical status American Society of Anesthesiologists (ASA) Grade 1 and ASA Grade 2 undergoing elective infra-umbilical surgeries were included in the study after ethical clearance from the college ethical committee.

Each patient was visited preoperatively and the procedure explained and written informed consent was obtained. Complete blood count, blood grouping, blood sugar, bleeding time, clotting time, blood urea, serum creatinine, serum electrolytes (sodium, potassium, and chloride), chest X-ray, and electrocardiogram (ECG) were done as institutional protocol. All patients were premedicated with tablet alprazolam 0.5 mg overnight the day before surgery.

Inclusion criteria

  1. Patients aged 18–60 years
  2. Patients posted for surgeries lasting for <3 h under epidural anesthesia
  3. Patients with ASA Grades 1 and 2.


Exclusion criteria

  1. Patients refusing to participate in the study
  2. Patients with uncontrolled hypertension, diabetes, cardiorespiratory disorders, neuropsychiatric disorders, hepatic or renal dysfunction, obesity (body mass index >30), and history of alcohol or drug abuse
  3. Patients with ASA Grade 3 or more.


Each patient was randomly allocated to one of the two groups of 35 patients each.

  • Group MG – Patients were given MgSO4 50 mg/kg in 100 ml NS in 10 min, followed by an infusion of MgSO4 10 mg/kg/h in 100 ml NS over 1 h
  • Group NS – Patients were given 100 ml NS in 10 min, followed by an infusion of 100 ml NS over 1 h.


All necessary equipments and drugs needed for the administration of general anesthesia and resuscitation were kept ready to manage failure of epidural and any complications.

Procedure

IV access to be obtained in the upper limb with an IV cannula-18G and IV fluid connected. Standard monitors, ECG, pulse oximeter, noninvasive blood pressure, and respiratory monitoring to be connected and basal parameter noted.

Patients were given MgSO4 50 mg/kg in 100 ml NS in 10 min, followed by an infusion of MgSO4 10 mg/kg/h in 100 ml (MG group) for 1 h or normal saline in the same volume and rate for 1 h was used in MG group through an infusion pump (NS group). After initiating the infusion, epidural anesthesia was given L1–L2 interspace using loss of resistance technique to air in sitting position using midline approach with 18G Tuohy's needle. Epidural catheter threaded cephalad and Inj. Two percent Ligno adrenaline 3 ml test dose was given. Patients were made to lie down in the supine posture immediately after the epidural, keeping the table flat and activated with injection bupivacaine 0.5% 12 ml. Level of sensory block by pinprick method and motor block by modified Bromage score was assessed at every 2 min following epidural injection and the time taken to achieve a complete loss of sensations up to T10 level and complete motor block was noted. Surgery began after confirming the loss of pinprick sensation over T10 level. Oxygen at 2 L/min through face mask and fluid therapy was given to all patients.

Intraoperative parameters such as systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), SpO2, and ECG were noted every 5 min till the end of surgery. Postoperatively, the parameters were noted immediately and then every 30 min till full sensory and motor recovery. Postoperative block was assessed every 15 min and time taken for regression of sensory block to the level of L1 and recovery of motor block to able to perform partial knee bend (modified Bromage score 6) was noted. Pain at rest was assessed using Visual Analog Scale every 10 min for 3 h and every 15 min for next 2 h, every 30 min for next 3 h. Rescue analgesia given when VAS score was more than 3. Period of analgesia that is, the time from epidural anesthesia to the time of first rescue analgesia required, and total requirement of analgesia in 24 h was recorded. Both the observer of the parameters and the patient were unaware to the drug injected IV and in epidural space. The collected data were statistically analyzed using Student's t-test.

Definitions of study parameters

  1. Onset of sensory blockade: It is defined as the time interval from administration of epidural anesthesia to the time of loss of pinprick sensation at T10 level is achieved
  2. Onset of motor blockade: Time required to attain modified Bromage score 1 from the time of activation of epidural
  3. Duration of sensory blockade: This was the time interval from the highest sensory level achieved to complete recovery of sensory analgesia
  4. Duration of motor blockade: Time required to regain modified Bromage score 1 from the time of activation of epidural
  5. Duration of analgesia: Defined as the time from epidural activation of drug to the time when a patient complaints of pain at the surgical site or VAS score reaches >3 and receives rescue analgesia.[7]


Statistical methods

Descriptive and inferential statistical analysis has been carried out in the present study. Results on continuous measurements were presented on mean ± SD (minimum–maximum) and results on categorical measurements were presented in number (%). Significance was assessed at 5% level of significance. The following assumptions on data were made:

  1. Dependent variables should be normally distributed
  2. Samples drawn from the population should be random
  3. Cases of the samples should be independent.


Student's t-test (two tailed, independent) has been used to find the significance of study parameters on continuous scale between two groups (inter-group analysis) on metric parameters.

Significant figures

  • + Suggestive significance (P value: 0.05 < P < 0.10)
  • Moderately significant (P value: 0.01 < P ≤ 0.05)
  • ** Strongly significant (P value: P ≤ 0.01).


Statistical software

The Statistical software, namely by IBM India Pvt Ltd and by Rick Becker and Allan Wilks of Bell Laboratories, New Jersey, USA, were used for the analysis of the data and Microsoft Word and Excel have been used to generate graphs, tables, etc.


  Results Top


The present study was conducted on 70 consenting patients aged between 18 and 60 years. Each received 30 ml of 0.5% bupivacaine via epidural anesthesia along with either magnesium sulfate infusion or normal saline infusion. Types of surgery are tabulated in [Table 1].
Table 1: Distribution of study population based on proposed surgery

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The mean duration of surgery, as shown in [Table 2], was 106.18 ± 9.62 min in group MG and 105.57 ± 9.22 minutes in group NS which was comparable with P = 0.790.
Table 2: Comparison of duration of surgery between the groups

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The mean onset time of sensory block in MG group was 9.09 ± 2.23 min and 9.34 ± 2.29 min in NS group, as shown in [Table 3]. The statistical analysis showed no significant difference between the two groups (P = 0.642).
Table 3: Onset and duration of sensory blockade (min)

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The mean duration of sensory block in magnesium sulfate group was 424.12 ± 53.43 min and 226.57 ± 27.22 min in normal saline group, as depicted in [Table 3], which shows that the duration of sensory blockade is more with MG group compared to NS group, which is statistically significant (P ≤ 0.001**).

The mean onset time of motor block in MG group, as shown in [Table 4], was 13.35 ± 2.62 min and 13.54 ± 2.60 min in NS group. No significant statistical difference was seen between the two groups (P = 0.76 3).
Table 4: Onset and duration of motor blockade (min)

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The mean duration of motor block in magnesium sulfate group was 361.62 ± 43.04 min and 208.29 ± 27.38 min in the normal saline group. Duration of motor blockade is more with MG group compared to NS group, as shown in [Table 4], which is statistically significant (P ≤ 0.001).

As shown in [Table 5], the mean duration of analgesia in magnesium sulfate group was 436.18 ± 53.88 min and 234.00 ± 30.31 min in normal saline group. Duration of analgesia was more with MG group compared to NS group, which is statistically significant (P ≤ 0.001).
Table 5: Duration of analgesia (min)

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As shown in [Figure 1] and [Figure 2], there was no statistical difference in the HR variation and MAP between the two groups (P > 0.05).
Figure 1: Comparison of heart rate (bpm) between two groups

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Figure 2: Comparison of mean arterial pressure between two groups

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There was no incidence of any adverse effect, i.e., bradycardia, hypotension, and postoperative nausea and vomiting in both the groups.


  Discussion Top


This study was conducted in our institution to evaluate and compare onset of sensory and motor block, duration of sensory and motor block, duration of analgesia, and safety profile of iv infusion of magnesium sulfate during epidural anesthesia using 0.5% bupivacaine for infra-umbilical surgeries. Sample size was calculated keeping two sided alpha error at 5% and power at 80%. A minimum of 34 patient in each group is required to detect a minimum of 2 min difference in onset of sensory block between two groups. For better validation, 35 patients were selected in each group.

In our study, we observed that onset time of sensory block in magnesium group was 9.09 ± 2.23 min and 9.34 ± 2.29 min in the normal saline group, which is statistically insignificant (P = 0.642).

The onset time of motor block in magnesium sulfate group was 13.35 ± 2.62 min and 13.54 ± 2.60 min in normal saline group, which again is statistically insignificant (P = 0.763). In our study, onset time of sensory and motor blockade in magnesium sulfate group was comparable with normal saline group.

These findings were similar to that of the findings in a study by Samir et al.[8] where there was no significant difference in the time taken for the onset of sensory blockade between the study groups.

A study conducted by Agrawal et al.[9] observed that the two groups were similar in terms of onset time of sensory and motor blockade.

Duration of sensory block

In our study, the duration of sensory block was more in magnesium sulfate group, i.e. 424.12 ± 53.43 min compared to normal saline group i.e. 226.57 ± 27.22 min.

The study carried out by Kumar et al.[10] found that the duration of sensory block was more in patients who received magnesium sulfate infusion.

Similar to our study, Samir et al.[8] also in their study observed that duration of sensory block (min) has a significant prolongation in the duration of sensory blockade as well as analgesia when magnesium sulfate was used as an adjuvant, irrespective of the route of administration.

Agrawal et al.[11] in their study, found that the duration of sensory block was longer in magnesium sulfate group compared with normal saline group.

The above observations were similar to our results which prove that magnesium sulfate infusion prolongs the duration of sensory blockade.

Duration of motor block

The duration of motor blockade, in our study, was 361.62 ± 43.04 min in magnesium sulfate group and 208.29 ± 27.38 min in normal saline group, which is statistically significant (P ≤ 0.001).

Kahraman and Eroglu[12] also had similar observation with respect to duration of motor blockade after magnesium sulfate infusion.

Shah and Dhengle[13] in their study found that infusion of magnesium sulfate prolonged the duration of motor blockade.

Duration of analgesia

In our study, the duration of sensory block was 436.18 ± 53.88 min in magnesium sulfate group and 234.00 ± 30.31 min in normal saline group, which is statistically significant (P ≤ 0.001).

Ryu et al.,[14] in their study, observed that postoperative pain scores, cumulative analgesic consumption, and shivering incidents were significantly lower in the test group compared to the control group.

Hwang et al.[15] concluded that magnesium sulfate given IV during spinal anesthesia reduced postoperative pain and analgesic consumption without complications.

Hwang et al.,[15] in their study, found that the time to first pain in MG group was little later than in the control group.

A study conducted by Tyagi et al.[16] found that postoperative pain scores were markedly lower in the magnesium group after surgery.

Our study confirms to the findings of the above studies, which have stated that the duration of sensory and motor block and duration of analgesia in patients who received magnesium sulfate infusion were more compared to the control group.

Hence, we conclude, IV infusion of magnesium sulfate during epidural anesthesia using 0.5% bupivacaine in infra-umbilical surgery increases duration of sensory and motor blockade and duration of analgesia.

Changes in the perioperative hemodynamic parameters

There were no significant differences between the study groups with respect to changes in HR, SBP, DBP, and mean arterial blood pressure perioperatively.

Adverse events

We did not observe any side effects in our study.

Limitations

  1. Serum magnesium level was not measured
  2. Awareness and sedation parameters were not included in this study.



  Conclusion Top


A prospective, randomized controlled double-blind clinical study was conducted on 70 patients of ASA Class I and II of age group between 18 and 60 years posted for infra-umbilical surgeries. They were randomized into two groups – Group MG-patients were given MgSO4 50/mg/kg in 100 ml NS in 10 min, followed by an infusion of MgSO4 10 mg/kg/h in 100 ml NS over 1 h (n = 35), and Group NS – patients were given 100 ml NS in 10 min, followed by an infusion of 100 ml NS over 1 h (n = 35).

There were no significant differences between the study groups with respect to changes in HR, SBP, DBP, and MAP perioperatively.

Onset of sensory blockade was similar in the two groups, i.e., 9.09 ± 2.23 min in magnesium sulfate group and 9.34 ± 2.29 min in normal saline group, which was statistically insignificant (P = 0.642). The duration of sensory block for bupivacaine group was more, i.e., 424.12 ± 53.43 min compared to normal saline group, i.e., 226.57 ± 27.22 min. These values are statistically significant (P ≤ 0.001**).

The onset time of motor block in magnesium sulfate was 13.35 ± 2.62 min and 13.54 ± 2.60 min in normal saline group, which again is statistically insignificant (P = 0.763). The duration of motor block for magnesium sulfate group was 361.62 ± 43.04 min and 208.29 ± 27.38 min for normal saline group. These values are statistically significant (P ≤ 0.001**).

The duration of analgesia was more in magnesium sulfate group in comparison with normal saline group, i.e., 436.18 ± 53.88 min in magnesium sulfate group and 234.00 ± 30.31 min in normal saline group. These values too are statistically significant (P ≤ 0.001**).

We did not observe any side effects and failed block in our study.

Our comparative study of the efficacy of iv infusion of magnesium sulfate during epidural anesthesia using 0.5% bupivacaine for infra-umbilical surgeries on postoperative analgesia concludes that:

  1. Onset of sensory block and motor block was similar in magnesium sulfate and normal saline group
  2. Duration of sensory blockade and motor blockade wa more in magnesium sulfate group compared to normal saline group
  3. Duration of analgesia was more in magnesium sulfate group compared to normal saline group.


In conclusion of our study, IV infusion of magnesium sulfate during epidural anesthesia using 0.5% bupivacaine for infra-umbilical surgeries has better postoperative analgesia compared to 0.5% bupivacaine alone with hemodynamic stability.

Ethical approval and consent to participate

Ethical approval and consent to participate were obtained.

Consent for publication

The authors certify that they have obtained all appropriate patient consent forms. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Availability of data and materials

Yes.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Iseri LT, French JH. Magnesium: Nature's physiologic calcium blocker. Am Heart J 1984;108:188-93.  Back to cited text no. 1
    
2.
Levine BS, Coburn JW. Magnesium, the mimic/antagonist to calcium. N Engl J Med 1984;310:1253-5.  Back to cited text no. 2
    
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Do SH. Magnesium: A versatile drug for anesthesiologists. Korean J Anesthesiol 2013;65:4-8.  Back to cited text no. 3
    
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McCarthy RJ, Kroin JS, Tuman KJ, Penn RD, Ivankovich AD. Antinociceptive potentiation and attenuation of tolerance by intrathecal co-infusion of magnesium sulfate and morphine in rats. Anesth Analg 1998;86:830-6.  Back to cited text no. 4
    
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Telci L, Esen F, Akcora D, Erden T, Canbolat AT, Akpir K. Evaluation of effects of magnesium sulphate in reducing intraoperative anaesthetic requirements. Br J Anaesth 2002;89:594-8.  Back to cited text no. 5
    
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Koinig H, Wallner T, Marhofer P, Andel H, Hörauf K, Mayer N. Magnesium Sulphate reduces intra-and postoperative analgesic requirements. Anaesth Analg 1998;87:206-10.  Back to cited text no. 6
    
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Sasidharan S, Singh V, Singh J, Madan GS, Dhillon HS, Dash PK, et al. COVID-19 ARDS: A Multispecialty Assessment of Challenges in Care, Review of Research, and Recommendations. Journal of Anaesthesiology, Clinical Pharmacology 2021;37:179.  Back to cited text no. 7
    
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Samir EM, Badawy SS, Hassan AR. Intrathecalvs intravenous magnesium as an adjuvant to bupivacaine spinal anesthesia for total hip arthroplasty. Egyp J Anaesth 2013;29:395-400.  Back to cited text no. 8
    
9.
Agrawal J, Singh K, Mittal R, Choudhary B. A randomized clinical study to evaluate the effect of intravenous magnesium sulphate for postoperative pain relief in patients undergoing lower segment caesarean section. J Evol Med Dent Sci 2015;72:12478-84.  Back to cited text no. 9
    
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Kumar M, Dayal N, Rautela RS, Sethi AK. Effect of intravenous magnesium sulphate on postoperative pain following spinal anesthesia. A randomized double blind controlled study. Middle East J Anaesthesiol 2013;22:251-6.  Back to cited text no. 10
    
11.
Agrawal A, Agrawal S, Payal YS. Effect of continuous magnesium sulfate infusion on spinal block characteristics: A prospective study. Saudi J Anaesth 2014;8:78-82.  Back to cited text no. 11
    
12.
Sasidharan S, Goyal R, Babitha M, Singh S, Dhillon H. COVID aerosol barrier intubation box-Boon or bane?. Journal of Anaesthesiology Clinical Pharmacology 2020;36:150.  Back to cited text no. 12
    
13.
Shah PN, Dhengle Y. Magnesium sulfate for postoperative analgesia after surgery under spinal anesthesia. Acta Anaesthesiol Taiwan 2016;54:62-4.  Back to cited text no. 13
    
14.
Ryu JH, Kang MH, Park KS, Do SH. Effects of magnesium sulphate on intraoperative anaesthetic requirements and postoperative analgesia in gynaecology patients receiving total intravenous anaesthesia. Br J Anaesth 2008;100:397-403.  Back to cited text no. 14
    
15.
Hwang JY, Na HS, Jeon YT, Ro YJ, Kim CS, Do SH. I.V. infusion of magnesium sulphate during spinal anaesthesia improves postoperative analgesia. Br J Anaesth 2010;104:89-93.  Back to cited text no. 15
    
16.
Tyagi V, Rajendra A, Chaturvedi S, Chaudhri RS. I. V. Infusion of magnesium sulphate during spinal anaesthesia to improve postoperative analgesia in patients undergoing lower extremity surgery. J Evol Med Dent Sci 2013;25:4587-93.  Back to cited text no. 16
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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