Evaluating the effect of adding Magnesium sulfate to intrathecal lidocaine on duration of postoperative analgesia in lower limb orthopedic surgeries

Aims and Due to the nature of the orthopaedic surgery, affecting bone and joint, it is associated with a high rate of postoperative pain. Using intravenous, intramuscular, intrathecal and epidural opioids are methods for postoperative pain control for which the side effects are numerous. However, Intrathecal administration of magnesium with blocking NMDA receptors reduces postoperative pain without increasing side effects. The aim of this study was to investigate the effect of adding magnesium sulfate to Intrathecal lidocaine- epinephrine mixture on duration of postoperative analgesia in lower limb orthopaedic surgeries. This double blind study was performed on patients who were candidate for lower extremity orthopaedic surgeries. For this purpose, 156 patients were randomly divided into two groups. One group received magnesium sulfate with lidocaine – epinephrine mixture and other group received the same drugs with distilled water as placebo. The duration of postoperative pain was determined according to patient's request for analgesics. Patient's pain degree was evaluated according to visual analogue score (VAS), and Pethedine consumption was also calculated. Data were analyzed by SPSS software. Mean age of our patients in magnesium and control groups were 34.5 ±7.5 and 31.9±8.1 years old, respectively. The Mean (±SD) of postoperative analgesia duration in the magnesium group was 143.7±29.7min and it was 100.9±18.1 min in the control group, which shows a significant difference between two groups (p <0. 000). Patients’ pain score according to VAS in magnesium group was 3.9±o.36 and it was 5.65±0.35 in the control one. This was also significantly different between the two groups (p=0.000). Also mean Pethedine consumption was 15±6.24 mg and 33±6.27mg in the magnesium and control groups, which was again statistically significant (p=0.000). Magnesium sulfate combined with lidocaine produces a reduction in postoperative pain in comparison with lidocaine alone.