The use of midazolam and small-dose ketamine for sedation and analgesia during local anesthesia.

Abstract

Small-dose ketamine in combination with sedative drugs has increasingly been used for sedation and analgesia in local anesthesia. We compared the clinical efficacy of midazolam with two different ketamine infusion regimens during plastic surgery under local anesthesia. Sixty patients undergoing plastic surgery procedures with local anesthesia were randomly assigned to two groups of 30 patients each in a double-blinded fashion. All patients received a bolus of 0.05 mg/kg midazolam, followed by a stepwise infusion: 1.67 microg x kg(-1) x min(-1) for the first 30 min, then reduced to 1.33 microg x kg(-1) x min(-1) for 90 min and subsequently to 1 microg x kg(-1) x min(-1). Two minutes before the infiltration of local anesthetic solution, a bolus of ketamine 0.3 mg/kg IV was administered, followed by a stepwise infusion of ketamine: Group A, 16.67 microg x kg(-1) x min(-1) for 30 min, 13.3 microg x kg(-1) x min(-1) for 90 min, and subsequently 10 microg x kg(-1) x min(-1); Group B, 8.33 microg x kg(-1) x min(-1) for 30 min, 6.67 microg x kg(-1) x min(-1) for 90 min, and then 5 microg x kg(-1) x min(-1). The level of sedation was evaluated by using the modified Observer's Assessment of Alertness/Sedation scale. We observed the effects of the two ketamine infusion regimens on sedation levels, respiratory and cardiovascular variables, and perioperative side effects. In both groups, midazolam and ketamine produced adequate sedation (with Observer's Assessment of Alertness/Sedation scores of 2-4) without significant respiratory and cardiovascular depression during surgery. However, there were fewer disruptive movements and there was less postoperative vomiting in Group B (P < 0.01). In conclusion, ketamine and midazolam provided satisfactory intraoperative sedation, analgesia, and amnesia in both groups. However, side effects associated with ketamine occurred less often in the smaller-dose ketamine group. Sedation and analgesia are often provided during local anesthesia. This study demonstrates that a small-dose ketamine infusion in combination with midazolam provided satisfactory intraoperative sedation, analgesia, and amnesia in healthy plastic-surgery patients when it was used to supplement local anesthesia.