Pre-emptive analgesia : effect of low dose Ketamine as pre-emptive analgesia in postoperative pain management after lower abdominal surgery

A Prospective randomized placebo-controlled study was done at Dhaka Medical College Hospital to evaluate the effects of low dose Ketamine as preemptive analgesia in post operative pain management after lower abdominal surgery. Sixty patients scheduled for elective total abdominal hysterectomy under General Anaesthesia were randomly divided into three equal groups. In Group-A, patients received 0.5 mg/kg ketamine I/V 90 seconds before incision, in Group-B, patients received the same dose after incision and in Group-C, patients were regarded as controlled, received 0.5 ml distilled water before incision. The patients were premedicated orally by giving Tab. diazepam 5mg with sips of water one hour before induction of anaesthesia. General anaesthesia was induced with thiopental sodium 3-5 mg/kg. Suxamethonium 1.5 mg/kg was given to facilitate endotracheal intubation. The neuromuscular block was continued with vecuronium. Anaesthesia was maintained with N20 (60-70%) and halothane in 02. Halothane was adjusted to maintain the MAP and heart rate within 20% of the pre-induction value. Opioids were not administered during the induction or during the operation. At the end of the anaesthesia, residual neuromuscular block was antagonized with intravenous neostigonine 0.05 mg/kg in atropine 0.02 mg/kg. In the post operative ward following parameters were recorded for 24 hours: recovery status, time of first analgesic demand, pain intensity by VAS & VRS, total opioid consumption, sedation score, haemodynamic status and, complications like nausea, vomiting, delirium and hallucination. Upon the first complaint of moderate pain (>5 on VAS), pethidine 1.5 mg/kg was administered intramuscularly & then repeated 4 hourly. If pain intensity remained >5 on VAS scale, rescue analgesic Pethidine 10 mg was administered intravenously. Time of first demand for analgesic among three groups: Gr- A( preincision): 68.4 ± 6 min; Gr-B (post-incision): 37.4 ± 3.3 min; and Gr-C (Control): 18.9 ± 2.1 min. It is statistically significant (P