The effect of different doses of intra-articular ketamine on postoperative analgesia in diagnostic arthroscopic knee surgery

Arthroscopic knee surgery is a painful operation and control of its pain causes earlier recovery of the patients. Therefore, the reduction of the post-operative pain is very important. The aim of this study was to evaluate the analgesic effect of intra-articular ketamine injection after knee arthroscopy. In a double blind randomized study, 75 patients with age ranging of 18-60 years who were candidate for elective arthroscopy were chosen and the same anesthetic method was used for all of them. Based on the injected anesthetic drug, they were divided into five equal groups, A-E. Group A received both intra-articular ketamine (0.5 mg/kg) and intravenous placebo. Group B received intra-articular ketamine (0.75 mg/kg) and intravenous placebo. Group C received intravenous ketamine (0.5 mg/kg) and intra-articular placebo. Group D received intravenous ketamine (0.75 mg/kg) and intra-articular placebo. Group E received intravenous and intra-articular placebo. After the operation, if necessary, intra-veouns morphine (0.05 mg/kg) was given for pain relief. Using visual analogue scale (VAS 1 to 10), the pain was evaluated at 4, 8 and 24 hours after the operation. The time of first rescue analgesic request, and the total dose of morphine used was recorded. Statistical analysis was carried out by using SPSS software. The results of this study showed that there was no significant difference in the cases of age, sex, weight and duration of operation among 5 groups studied. Also, the total amount of opioid or the time beginning of analgesic request was not statistically different among the groups during 24 hours observation. Based on our results, intra-articular ketamine injection did not reduce postoperative pain after diagnostic knee arthroscopy and had no sparing effect on total opioid consumption and first postoperative analgesic request.