Background: This study was designed to evaluate the role of intraperitoneal S (+) ketamine in peripheral NMDA receptors blockade, and whether it reduces the postoperative analgesic requirements after bariatric surgery in morbidly obese patients in comparison with intraperitoneal lidocaine.
Patients and Methods: The study included 45 patients, and a standardized general anesthetic technique including fentanyl, propofol, isoflurane, and vecuronium for muscle relaxation were used. At the end of surgery, patients were divided into three groups ,15 patients each, S (+) Ketamine 0.5 mg /kg diluted in 50 ml saline was injected intra peritoneally in (ketamine group), 50 ml of 1% lidocaine in saline was injected intra peritoneally in (lidocaine group), 50 ml of normal saline was injected intra peritoneally in (saline group). Parameters were evaluated time of first request of analgesia in minutes, postoperative shoulder pain and arm pain for 24 hours(VAS score), and the amount of post operative mepridine (mg) consumed in 0-6.6-12,12-18,18-24, hours after extubation.
Results: Times of the first request of postoperative analgesia were 60(10), 50(5), 20(5) minutes, in Intra peritoneal S Ketamine group, Intra peritoneal lidocaine group, and Intra peritoneal Saline group respectively. It was statistically longer in Ketamine group and Lidocaine group than Saline group, with statistically longer duration in Ketamine group than Lidocaine group.
However the amount of mepridine was statistically higher in Lidocaine group and Saline group than in Ketamine group, at 6, 8,12,18,24 hours postoperatively, it was statistically higher in Saline group than in Lidocaine group.
Both the incidence postoperative shoulder pain, and the visual analogue score were significantly higher in Lidocaine group and Saline group than in Ketamine group, but it was statistically higher in Saline group than in Lidocaine group.
Conclusion: Peripheral (peritoneal) NMDA receptors blockade by S (+) Ketamine was involved in reduction of postoperative pain, and analgesic requirement following bariatric surgery.