Ketamine for preemptive analgesia in major gynaecologic surgery

Background: It has been suggested that the prolonged pain and hyperalgesia occurring after an injury is due to central sensitization in the spinal cord. N- methyl D- Aspirate (NMDA) receptors are activated by glutamate and aspartate and have been implicated in the wind-up phenomenon of central sensitization. Ketamine blocks the NMDA receptor sites and has been suggested to provide preemptive analgesia. This study was designed to assess the pre -emptive analgesic effect of ketamine in Nigerians. Method: Two groups of twenty patients scheduled for intra-abdominal gynecological operation were randomly assigned to receive either 0.5mg/kg ketamine pre-incision or post incision. They all had standard general anaesthesia with pentazocine for intra-operative analgesia. Post-operatively, the time to first request for analgesic (TFA) and pain intensity, using the visual analogue scale (VAS) at that time were noted. Pain intensity was also scored at 4, 8, 12 and 24 hours. Adverse reactions and patient satisfaction were recorded. Results: The TFA for the pre-incision group was significantly longer than the post-incision group. The pain intensity scores at the periods measured were not significantly different in both groups. Conclusion: It is concluded that at 0.5mg/kg body weight, ketamine prolongs the TFA but a sustained preemptive effect of ketamine could not be demonstrated. Nig J Surg Res 2003; 5: 7 – 11) Key words: Preemptive analgesia, ketamin