Comparison of morphine and ropivacaine following knee arthroscopy

Abstract

Purpose: The purpose of this study was to compare the effectiveness of ropivacaine, a new local amidic anesthetic, compared with morphine as an intra-articular drug in controlling pain in patients after arthroscopic knee surgery.

Type of study: Randomized trial.

Methods: We enrolled 90 patients scheduled to undergo elective knee arthroscopy. Patients were homogenous regarding demographic data and ASA physical status. Procedures included were diagnostic arthroscopies, lateral and medial meniscectomies, meniscal repair, and removal of loose bodies. All cases were treated by the same surgeon, under general anesthesia, using the same procedure. Patients were randomly divided into 3 groups. The first group received ropivacaine 75 mg in 20 mL of saline solution, the second group received 2 mg morphine in 20 mL of saline solution, and the third group received 20 mL of saline solution. No other oral or injectable analgesic administration was allowed. A blind observer assessed the patients' postoperative pain using a 10-cm visual analogue scale (VAS), ranging from no pain (0) to unbearable pain (10). Scores were taken at 0, 1, 4, 6, 12, and 24 hours after drug injection. VAS scores were analyzed using analysis of variance; significance was set at P <.005.

Results: None of the patients treated with ropivacaine or morphine needed administration of any other oral or injectable analgesic. No adverse reaction was noted in ropivacaine group. VAS score analysis in the first 4 postoperative hours showed greater effectiveness for ropivacaine versus morphine or placebo with highly significant results (P <.001). In the first 24 postoperative hours, the ropivacaine group versus the morphine group showed no significant differences (P =.207).

Conclusions: Although its cost is very high compared with morphine, ropivacaine is a safe, site-specific, and long lasting anesthetic drug with an earlier onset than morphine and almost the same duration, covering the whole postoperative period (24 hours).