Ravi Vasupalli1, Prakash T. S. N2

The concept of preemptive analgesia was introduced by C. J. Woolf et al demonstrating that a post-injury hypersensitivity
results via a central mechanism. The effect of magnesium on perioperative analgesic requirements was first evaluated by
Koinig and his colleagues in patients with identical levels of surgical stimulation. Magnesium Sulphate is an antagonist of Nmethyl-
D-aspartate (NMDA) receptors and its associated channels and regulation of calcium influx into the cell. Magnesium
causes modulation of acute pain reducing postsurgical pain intensity and dosage of analgesics. Seyhan et al have reported
that magnesium sulphate boluses were effective for postoperative pain relief after gynaecological surgery. Fucs-Budder et al,
Kussman B et al used continuous infusion (15 mg/kg/hr.) in addition to initial bolus (50 mg/kg) of magnesium sulphate in
their studies, which caused bradycardia and delayed extubation time, which can be attributed to the infusion of Iva Bacak
Kochman et al studied effect of low dose MgSO4 (7.5 mg/kg) as analgesic agent after induction in patients undergoing
laparoscopic cholecystectomy. This bolus dose of MgSO4 given for control of sympathetic response during intubation also
reduced early postoperative pain. Study conducted by O Mentes et al on postoperative analgesic efficacy of single dose
MgSO4 (50 mg/kg) after laparoscopic cholecystectomy measured significantly less VAS scores. On this background, our study
was done to evaluate the postoperative analgesic efficacy of single dose of magnesium sulphate (50 mg/kg) as preemptive
analgesic and measured after laparoscopic cholecystectomy. In addition to VAS scores, total tramadol consumption and time
for first rescue analgesia, postoperative haemodynamic parameters and side effects if any were evaluated.
After obtaining Institutional Ethical committee clearance and written informed consent from the patients, a randomised
prospective study was conducted at King George Hospital, Vishakhapatnam. Randomisation done based on envelope method.
Study period was between November 2013 to September 2015. Study contain Sixty patients with ASA Grade I and Grade II
of both sexes undergoing laparoscopic cholecystectomy were included in study and divided in two equal groups (n=30 in
each group). Patients in magnesium group (group MS) received I.V. MgSO4 50 mg/kg in 100 mL of 0.9% normal saline
during preinduction time and patients in the control group (group NS) received 100 mL of 0.9% normal saline.
Descriptive statistics was done for all data and suitable statistical tests of comparison were done. These included the mean
and Standard Deviation (SD) for quantitative variables. Data was also analysed by Student’s “t” unpaired test. Significance
limit for all was set at P <0.05.
Statistically significant reduction of pain scores in early postoperative period was observed. Significant reduction of
postoperative analgesic requirement during the first postoperative day was noted. Intraoperatively, there was significant
reduction in mean heart rate as well as mean arterial pressure with MS group when compared to NS group. Less
postoperative shivering and PONV observed in MS group. Severe bradycardia and/or hypotension did not occur during or
after surgical procedure in any of study patient.
The present study evaluated preemptive analgesic efficacy of magnesium sulphate on pain relief after laparoscopic
cholecystectomy. It was concluded that magnesium sulphate at a dose of 50 mg/kg as a preemptive analgesic is safe. It has
good postoperative synergistic effect with analgesics and reduces the postoperative tramadol consumption compared to
normal saline group.