[Intra-articular ketamine after arthroscopic knee surgery. Optimisation of postoperative analgesia].

BACKGROUND: Surgery of the knee can be very painful and sufficient postoperative pain treatment is often problematic. To optimize postoperative analgesia, application of local analgesics has been suggested. In the present study it was investigated whether intra-articular administration of ketamine reduces the level of pain after arthroscopic knee surgery.

MATERIAL AND METHODS: A total of 68 patients undergoing arthroscopic knee surgery were randomized into 4 groups. At the end of surgery the following pharmaceuticals were administered: 10 ml 0.25% bupivacaine intra-articular (i.a.), 0.25 mg S-(+)-ketamine/kg body weight to 10 ml in 0.9% NaCl i.a., 0.25 mg S-(+)-ketamine/kg body weight intravenous (i.v.), and 10 ml 0.9% NaCl i.a. as placebo. Postoperative pain therapy was performed as i.v. patient controlled analgesia (PCA) with piritramide. Postoperative opioid consumption and pain intensity were assessed as the main criteria in the postoperative course.

RESULTS: All 4 groups were comparable with respect to biometrical data. The scores of the visual analogue scale (VAS) showed a significantly (p<0.05) lower pain intensity in patients treated with ketamine i.a. or i.v. compared to the other groups. Shortly after surgery the highest reduction of pain was detected in the i.a. ketamine group compared to i.a. bupivacaine or placebo administration. The postoperative opioid consumption was always lowest in the i.a. ketamine group. A significant difference in piritramide consumption (p<0.05) was demonstrated in the first 20 min after operation in the i.a. ketamine group compared to the i.a. administration of placebo and bupivacaine.

CONCLUSIONS: The i.a. application of ketamine after arthroscopic knee surgery leads to a significant decrease of postoperative analgesic demand and decreases patients' subjective level of pain compared to i.a. application of bupivacaine or placebo. Likewise, the i.v. application of ketamine is similarly effective but the effect is of shorter duration.