Year : 2016 | Volume
| Issue : 2 | Page : 187-191
Adding magnesium sulfate to bupivacaine in transversus abdominis plane block for laparoscopic cholecystectomy: A single blinded randomized controlled trial
K Al-Refaey, EM Usama, E Al-Hefnawey
Department of Anesthesia and Surgical Intensive Care, Mansoura University, Mansoura, Egypt
Department of Anesthesia and Surgical Intensive Care, Mansoura University, Mansoura
Source of Support: None, Conflict of Interest: None
|Date of Web Publication||02-Nov-2015|
Introduction and Aim: Use of transversus abdominis plane block (TAP) in the management of postoperative pain after the laparoscopic cholecystectomy (LC) has been a common anesthetic practice. This study evaluates the effect of adding magnesium sulfate to bupivacaine in TAP block in LC regarding postoperative analgesia and analgesic consumption.
Patients and Methods: Ninety patients of American Society of Anesthesiologists I and II was divided into three groups: Control group (C group, n = 30), bupivacaine group (B group, n = 30), bupivacaine magnesium group (M group, n = 30).
Results: M group showed better analgesic profile in the 1 st postoperative day in the form of lower mean visual analog scale score (2.8 ± 0.6 for C group, 2.1 ± 0.5 for B group, 2.2 ± 0.5 for M group, P < 0.001), longer duration of analgesia (7 ± 2.8 h for C group , 16 ± 2.5 h for B group, 19 ± 2.2 h for M group, P < 0.006), lower morphine consumption (2 ± 0.1 mg for C group, 0.9 ± 0.1 mg for B group, 0.5 ± 0.1 mg for M group, P < 0.011). There was a significant lower incidence of postoperative nausea and vomiting (PONV) (32% for C group, 6% B group, 7% M group, P < 0.004).
Conclusion: Adding MgSo4 as an adjuvant to bupivacaine in TAP block; during anesthesia for LC; improved postoperative analgesia in the form of increased duration, decreased analgesic requirements and PONV.
Keywords: Anesthesia, laparoscopic cholecystectomy, regional, transversus abdominis plane
|How to cite this article:|
Al-Refaey K, Usama E M, Al-Hefnawey E. Adding magnesium sulfate to bupivacaine in transversus abdominis plane block for laparoscopic cholecystectomy: A single blinded randomized controlled trial. Saudi J Anaesth 2016;10:187-91
|How to cite this URL:|
Al-Refaey K, Usama E M, Al-Hefnawey E. Adding magnesium sulfate to bupivacaine in transversus abdominis plane block for laparoscopic cholecystectomy: A single blinded randomized controlled trial. Saudi J Anaesth [serial online] 2016 [cited 2020 Feb 28];10:187-91. Available from: http://www.saudija.org/text.asp?2016/10/2/187/168821
| Introduction|| |
Laparoscopic cholecystectomy (LC) is one of the commonly performed surgical procedures that is associated with a moderate degree of postoperative pain especially on the 1 st postoperative day. , Adequate postoperative analgesia allows early patient ambulation, decreases analgesic requirements, and hospital length of stay. , Transversus abdominis plane (TAP) block is a recent analgesic technique that has proved its efficacy in perioperative pain therapy for LC. ,,
The aim of this study was to investigate the effect of adding magnesium sulfate to bupivacaine on postoperative pain scores (primary outcome), opioid consumption, and postoperative nausea and vomiting (PONV) (secondary outcomes) in the patients undergoing LC.
| Patients and Methods|| |
After the approval of Local Ethical Committee, the consent was obtained from 90 patients scheduled for LC in Gastroenterology Surgical Center, Mansoura University, Egypt. Patients were of either American Society of Anesthesiologists I and II, with age ranging from 18 to 40 years, and body mass index <35. The patients were randomized into three groups (using closed envelope technique in blocks of 18); controlled group (C group), bupivacaine group (B group), and bupivacaine magnesium group (M group).
Anesthesia induction was the same in the three groups (propofol 1-1.5 mglkg, fentanyl 1 m/kg, and atracurium 0.5 mg/kg), then sevoflorane inhalational anesthesia for maintenance in 0.4 oxygen/air mixture.
In both M group and B group, the preemptive ultrasound guided subcostal TAP block (Toshiba Xario, Japan) was performed on both sides using 20 ml volume (0.25 bupivacaine in B group or 0.25 bupivacaine plus 0.5 g of MgSo 4 in M group). Surgical sterilization started 5 min after the block and surgery started 5 min later. Hemodynamic data (heart rate [HR], mean arterial pressure [MAP]) was collected immediately after induction, at the start of surgery, and each 10 min later.
At the end of surgery, and after the closure of surgical ports, anesthesia was terminated, and extubation was done when patients fulfilled the required criteria. Postoperative hemodynamic data (HR, MAP), visual analogue scale (VAS) score, and PONV were recorded at 0, 1, 2, 6, 12, and 24 h after surgery, Ramsay sedation was recorded at 0, 1, 2, and 6 h postoperatively. Boluses of morphine (0.02 mg/kg) were given whenever postoperative VAS score ≥4 for any patient in the three studied groups.
For sample size calculation, G*Power version 184.108.40.206 was used. Mean postoperative VAS score was adopted as a primary variable and power of 80 was achieved accepting an effective size of 35%, if the total sample size of 84 was included in the study. Six cases were added to compensate for dropouts leading to a total sample size of 90 patients, 30 in each group.
Data were collected, tabulated, and statistically analyzed using SPSS program, version 16 (IBM-International Business Machines Corporation, Armonk, New York, United States). Continuous data were tested for normality and expressed in mean ± standard deviation if normally distributed, median (interquartile range) if not. Categorical data were presented as proportions. ANOVA test was used to detect the statistical significance between the studied groups considering a P < 0.05 as significant.
| Results|| |
No statistical difference was found between the three studied groups as regards age, weight, height, HR, MAP, anesthetic, or surgery duration [Table 1]. Intra-operative HR measurements, MAP showed no significant difference among the three groups, this is shown in [Table 2].
|Table 1: Patient characteristic and operative time among the 3 studied groups, data are presented as mean ± SD |
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|Table 2: Intra-operative parameters between studied groups. Data is presented as mean±SD |
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Mean VAS score was statically lower in M group (2.8 ± 0.6 for C group, 2.1 ± 0.5 for B group, and 2.2 ± 0.5 for M group, P < 0.001). Also total morphine consumption (2 ± 0.1 for C group, 0.9 ± 0.1 for B group, and 0.5 ± 0.1 for M group, P < 0.011) was lower in M group. Duration of analgesia was longer in MAG group (7 ± 2.8 for C group, 16 ± 2.5 for B group, and 19 ± 2.2 for M group, P < 0.006). There was a significant lower incidence of PONV (32% for C group, 6% B group, and 7% M group, P < 0.004) shown in [Figure 1] and [Figure 2].
|Figure 1: Postoperative analgesic profile and postoperative nausea and vomiting in the three studied groups|
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|Figure 2: Visual analog scale score in the first 24 h in the three studied groups|
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| Discussion|| |
Our study showed that using MgSo 4 as an adjuvant in TAP block in cases of LC resulted in a better analgesic profile, lower VAS score, lower analgesic consumption, and longer duration of analgesia with no recorded complications.
The use of TAP block has succeeded as an analgesic technique after LC in the last decade. ,,,, Also, adding MgSo 4 as an adjuvant to local anesthetics in regional procedures has proofed its efficacy in many clinical trials. ,,, In our study; MgSo 4 augmented the postoperative analgesic effect of TAP block. This result coincides with multiple previous studies that used intravenous (IV) MgSo 4 either IV bolus or infusion in thoracic, spine, gynecologic, neurosurgery, and abdominal surgeries. ,,,,,, Other studies used MgSo 4 as an adjuvant to various regional techniques such as brachial, intra-articular, epidural, or even intrathecal blocks where MgSo 4 had a beneficial effect on postoperative analgesia and analgesic requirements. ,,
N-methyl D-aspartate (NMDA) receptor is the major affecting site for the effects of magnesium. Magnesium is an antagonist of the NMDA receptor, acting as a noncompetitive antagonist, blocking ion channels in a voltage dependent fashion. This receptor is found in many parts of the body, including the nerve endings, and plays a well-defined role in modulating pain and a number of inflammatory responses. ,, NMDA receptor antagonists could prevent central sensitization that occurs due to the peripheral nociceptive stimulation. 
The mechanism of action by which TAP MgSo 4 potentiates the analgesic effect of local anesthetics still is not clear and may be related to systemic and or local actions. The analgesic effects of Magnesium are primarily based on antagonism of calcium influx into nerve fiber, and NMDA receptor blocking activity ,,,,, thus interfering with the release of neurotransmitter substances at synaptic junctions or may potentiate the action of local anesthetics.  Also, magnesium ions are known to elevate the firing threshold in both myelinated and unmyelinated axons. Divalent cations have been suggested to reduce the fixed negative surface charge on the outside of nerve membranes and thereby increase the trans-membranes potential (i.e., cause a hyper polarization). ,
Another suggested mechanism is systemic absorption. Serum magnesium levels are strongly associated with reduced postsynaptic activity of slow conducting unmyelinated C-fibers which are chiefly afferent fibers conveying the input signals from the periphery to central nervous system. Magnesium prevents the activation of NMDA receptors which causes calcium and sodium influx into the cell with an efflux of potassium and initiation of central sensitization and wind-up leading to the propagation of peripheral nociceptive stimulation. This antagonist prevents and abolish the hypersensitization, once it is established by blocking dorsal horn NMDA receptor activation induced by excitatory amino acid transmitters such as glutamate and aspartate. ,,,
The safety of perineural use of MgSo 4 has been an issue of debate among the multiple human and animal studies and also in many reports of inadvertent use. ,,,,,, Most neurological damage in the form of vaculation or demyelination was related to high dose and concentration of the drug, more than 15% in most reports. , In our study, we used MgSo 4 of 2.5%, which is too much far from the postulated harmful concentration.
The lower incidence of PONV in both B and M groups is related to lower pain scores, and lower opioid consumption. ,[ 30]
An area of limitation in this study was that serum Mg level had not been measured to be correlated to the efficacy of TAP block or another group receiving MgSo 4 should have been added to detect if the potentiation effect is related to a systemic or local action of MgSo 4 .
| Conclusion|| |
Adding MgSo 4 as an adjuvant to bupivacaine in TAP block; during anesthesia for LC; resulted in improved postoperative analgesia in the form of increased duration and decreased analgesic requirements and was associated with less incidence of PONV.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]