Comparison of Effect of Magnesium Sulphate and Preservative-Free Ketamine as an Adjunct to Epidural Bupivacaine for Postoperative Analgesia in Abdominal Hysterectomy

Abstract

BACKGROUND Neuraxial blocks are the most common method of anaesthesia in abdominal hysterectomies and epidural technique has been used widely to provide both anaesthesia and postoperative analgesia. It has become a common practice to use polypharmacy approach for treatment of intra and postoperative pain, because no drug has yet been identified that specifically inhibit nociception without side effects. The aim of the study is to compare the effects of magnesium sulphate versus preservative-free ketamine as an adjunct to epidural bupivacaine for postoperative analgesia in abdominal hysterectomy. MATERIALS AND METHODS After obtaining informed consent, the patients were divided into 3 groups of 40 each to receive 20 mL 0.5% bupivacaine (group B), 19 mL 0.5% bupivacaine + 50 mg magnesium sulphate (group BM), 19 mL 0.5% bupivacaine + 50 mg preservative-free ketamine (group BK). Epidural catheter was inserted at L1-L2 space using standard technique. Correct placement was confirmed by a test dose of 2% lignocaine + adrenaline 1 in 2 lakhs. Postoperative analgesia were assessed by VAS score and 0.125% bupivacaine infusion and 1 g paracetamol IV infusion was given as rescue analgesics when VAS ≥4. Onset duration, motor block and side effects were also monitored. RESULTS Mean time of duration of onset in group B, BM, BK were 20, 14, 18 minutes, respectively. Mean time for rescue analgesia were 180, 240 and 480 minutes in group 1, 2 and 3, respectively. These differences were statistically significant. The side effects noticed in each group were not statistically significant. CONCLUSION The onset of effect is faster when magnesium sulphate were added as an adjunct to bupivacaine as compared to preservativefree ketamine. The postoperative analgesia is found to be more with preservative-free ketamine as compared to magnesium sulphate without any significant side effects.