KETAMINE ENHANCES LOCAL-ANESTHETIC AND ANALGESIC EFFECTS OF BUPIVACAINE BY PERIPHERAL MECHANISM - A STUDY IN POSTOPERATIVE-PATIENTS

Patients with unilateral (n = 14) and bilateral (n = 4) herniorrhaphy participated in this study, With bilateral herniorrhaphy, at the end o f the surgery, the wound was infiltrated with a solution of bupivacain e 0.5% and ketamine 0.3% on one side and a solution of bupivacaine 0.5 % only, on the other. With unilateral herniorrhaphy, the patients were randomly assigned to one of two groups (n = 7). One group at the end of the surgery received the infiltration with a solution of bupivacain e 0.5% and ketamine 0.3%, the other group received the infiltration wi th a solution of bupivacaine 0.5% only. The duration of the local anes thetic (response to a von Frey filament) and postoperative analgesic ( time to mild spontaneous pain) effects of the infiltrations, as well a s wound pain threshold 24 h after surgery (pressure algometry), were d etermined. In patient with unilateral herniorrhaphy, the addition of k etamine for wound infiltration enhanced the duration of infiltration a nesthesia (206 +/- 76 versus 343 +/- 108 min, P < 0.02) and analgesia (240 +/- 45 versus 420 +/- 151 min, P < 0.03). Similar enhancement of the local anesthetic effect was observed in patients with bilateral he miorrhaphy. The increase in pain threshold to pressure on the wound wi th the addition of ketamine was evident in bilateral herniorrhaphy pat ients and also with a combination of bilateral and unilateral results (1.39 +/- 0.40 versus 2.35 +/- 0.92 kg, P < 0.02). In the group of fiv e volunteers, the subcutaneous infiltration with 0.3% ketamine produce d a local anesthetic effect lasting only 10-20 min. The results indica te that ketamine acting via a peripheral mechanism can profoundly enha nce anesthetic and analgesic actions of a local anesthetic administere d for infiltration anesthesia.