A comparative study of intrathecal ketamine as an additive to 0.5% hyperbaric bupivacaine for intrathecal anaesthesia

Background: Spinal anaesthesia with bupivacaine for lower limb and lower abdominal surgeries is limited by the fixed duration of action and cannot be prolonged except with usage of spinal catheters which increase the chance of infection and occurrence of haemodynamic instability when used in high doses. To minimize the instability in haemodynamics, several neuraxial adjuvants have been used. Methods: We carried out a prospective randomized double-blind study in 60 patients posted for lower abdominal and lower limb surgeries. Patients were divided into two groups of 30 each. Both groups received 3 mL of intrathecal hyperbaric 0.5% bupivacaine. In addition, ketamine group (Gr K) received ketamine 0.1mg/kg body weight intathecal (made to total volume of 0.5 mL); saline group (Gr S) received equal volumes of 0.9% normal saline intrathecally. The onset and duration of sensory and motor blockade and intraoperative haemodynamics were studied. Results: Addition of ketamine in comparison to saline administration produced significantly earlier onset (5.2±1Vs. 3.4±1; p=0.000), prolonged duration of sensory block (129.7±14.9 Vs. 111.3±11; p=0.000) and long duration of postoperative analgesia (150.8±11.7Vs. 127.8±12.8; p=0.000). Conclusion: Addition of ketamine to intrathecal hyperbaric bupivacaine provides better intraoperative spinal block characteristics, stable haemodynamics and longer duration of postoperative analgesia.