Postoperative analgesia by intraarticular clonidine and neostigmine in patients undergoing knee arthroscopy

Clonidine and neostigmine have a central mechanism of analgesic action and are synergistic when given intrathecally. Both drugs also have a peripheral analgesic effect. The purpose of this study was to compare the analgesic effect of intraarticular clonidine and neostigmine, used separately and in combination, in patients undergoing knee arthroscopy.

Eighty-four American Society of Anesthesiologists (ASA) I and II patients scheduled for meniscus repair under arthroscopy were allocated randomly in 6 groups to receive in a double-blind manner at the end of surgery 150 microg of intraarticular clonidine with subcutaneous saline, 500 microg of intraarticular neostigmine with subcutaneous saline, an intraarticular combination of 150 microg of clonidine and 500 microg of neostigmine with subcutaneous saline, 150 microg of intraarticular clonidine with 500 microg of subcutaneous neostigmine, 500 microg of intraarticular neostigmine with 150 microg of subcutaneous clonidine, or intraarticular and subcutaneous isotonic saline. Postoperative pain scores were measured on a visual analog scale (VAS) at rest and on mobilization. Paracetamol (1 g) was given as a rescue medication when pain score was greater than 40.

VAS scores at rest and on mobilization were lower in the first 5 groups compared with the intraarticular saline group (P <.05), but no significant difference was documented between the treated groups. The time to the first paracetamol administration was shorter in the saline group compared with the other groups, and the paracetamol demand was also higher in this group. Forty-five percent of the patients who had received clonidine had at least 1 episode of hypotension versus 4% of those who did not (P <.01). The incidence of bradycardia was 20% and 0%, respectively (P =.01). The incidence of nausea was not statistically different in patients who did and did not receive neostigmine (43% v. 36%, respectively).

Intraarticular administration of 150 microg of clonidine, 500 microg of neostigmine, or both produce postoperative analgesia, and the combination is not more effective.