AUTHORS: Ravindra V. Prasad, M.D.; Frederick B. Payne, M.D.

AFFILIATION: Department of Anesthesiology, University of North Carolina School of Medicine, Chapel Hill, NC  27599

INTRODUCTION:  Ketamine is a useful drug in anesthetic practice in that it produces sedation, amnesia, and profound analgesia.  Its use in ambulatory surgery has been limited because of the potential for postoperative hallucinations, dissociative reactions, and delayed recovery.  Recent studies have demonstrated that the coadministration of propofol and ketamine prevents ketamine induced psychic disturbances.1  The purpose of this study was to compare the efficacy and side effects of propofol in combination with ketamine to propofol alone for intravenous sedation during laparoscopic tubal ligation.

METHOD:  This study was approved by the Committee on the Protection of Human Subjects of UNC School of Medicine.  Medical records of 48 consecutive patients undergoing laparoscopic tubal ligation under local anesthesia with sedation were reviewed. Data collected included demographic variables, hemodynamic variables, anesthetic agents used, recovery times, and presence of side effects.  Subjects were divided into two groups according to the primary anesthetic agents used for sedation.  Subjects in group P received propofol as the primary sedative agent (n=21) while subjects in group KP received propofol in combination with ketamine (n=27).  Ketamine was mixed with propofol to achieve a final concentration of 1 mg/ml of ketamine.  Differences between groups were analyzed using students t-test and chi-square analysis where appropriate.  P values <0.05 were considered statistically significant.

RESULTS:  There were no differences in baseline demographic or hemodynamic variables, or intraoperative midazolam or fentanyl dosing between the groups.  Patients in group KP received a lower dose of intraoperative propofol by bolus injection (228 µg/kg vs. 435 µg/kg; p=0.03).  More patients in group P required supplementation with N2O than in group KP (5 [24%] vs. 0 [0%]; p=0.03).  Two patients in group P required intubation compared to 0 in group KP.  Intraoperative hemodynamic variables were the same between groups except (1) minimum systolic blood pressure was higher in group KP compared to group P (118 mmHg vs. 109 mmHg), and (2) peak systolic blood pressure was 20% greater than baseline more frequently in group P (6 [29%] vs. 1 [4%], p=0.04).  There were no differences in surgery times, recover times, PARS scores, postoperative nausea or vomiting requiring treatment, or the need for supplemental analgesics in the PACU.  No psychic disturbances were identified in either group.

DISCUSSION:  Ketamine in combination with propofol provided satisfactory sedation for outpatient laparoscopic tubal ligation.  Compared to sedation with propofol alone, the combination of propofol and ketamine reduced propofol requirements as well as the need for supplementation with nitrous oxide.  The use of ketamine in combination with propofol did not alter the incidence of adverse effects compared to propofol alone.  Prospective studies are needed to confirm the efficacy and safety of ketamine with propofol in ambulatory surgery.

REFERENCES:  1.  Anaesthetist.  1991 pp. 199-204.