Effects of Intravenous Small Dose Ketamine and Midazolam on Postoperative Pain Following Knee Arthroscopy

Background:   The aim of this randomized, double blind, controlled study was to assess the effect of intravenous coadministration of small dose midazolam with ketamine on postoperative pain and spinal block level.
Methods:   Sixty patients undergoing arthroscopic knee surgery under spinal anesthesia were randomized into three groups: Group I (saline control); group II (ketamine 0.15 mg/kg i.v.); and group III (ketamine 0.15 mg/kg +  midazolam 0.01 mg/kg i.v.). Sedation scores, visual analogue scores, time to first postoperative analgesic, total meperidine consumption, patient satisfaction, sensory and motor block levels, and two segments regression times were assessed.
Results:   Sedation scores were significantly lower in group I when compared with groups II and III at 1, 3, 5, and 10 minutes after administration of the spinal anesthetic ( P  = 0.001). Sensory block was significantly higher in group III ( P  = 0.001) in comparison with group II. Two segment regression time was significantly longer in group II than group I, whereas no difference was found between groups II and III. Total meperidine consumption was significantly higher in group I ( P  = 0,001). Patient satisfaction was significantly higher in group III compared with group I ( P  = 0.001), but no difference was found between groups II and III ( P  = 0.3).
Conclusion:   Ketamine improved the postoperative pain patient satisfaction, increased the maximal sensory level, and was associated with lower sedation scores in the first 15 minutes after administration. Group I was also associated with decreased total meperidine consumption and delayed the time to first recue analgesic administration. Coadministration of ketamine and midazolam did not provide any further benefit over ketamine alone.