The prospective study on the effect of a preemptive long-term postoperative administration of a low-dose ketamine on the incidence of chronic post-mastectomy pain
Abstract
N-methyl D-aspartate receptor is involved both in postoperative central sensitization and development of chronic postoperative pain. Ketamine - an antagonist is used both for potentiation of postoperative analgesia and treatment of chronic pain.
There is little information concerning the long-term effect of peri-operative administration of ketamine on chronic pain. We have proposed a study to confirm a hypothesis, that a preemptive and long-term postoperative administration of a low-dose ketamine suppresses the incidence of chronic post-operative pain.
Material and Method: after an institutional ethic committee approval and written consent, 100 patients elicited for total or partial mastectomy were randomly divided into control (C) and ketamine (K) groups. Group K were blindly administered after induction of anesthesia 48 hours' continuous infusion of ketamine 1.0 mg.kg-1.day-1, group C were administered normal saline.
General anesthesia, surgery and post-operative regimen were standard and equal in both groups. Six months after surgery the patients were sent a questionnaire concerning the incidence and characteristics of chronic pain.
Results: there was no difference in demography, type of surgery, postoperative course and postoperative pain intensity between groups. We have gained 40 questionnaires from group C and 46 from group K (response rate was 86 per cent).
The incidence of chronic pain was in C vs. K (per cent) 14 (35) vs. 14 (30), out of them the pain was permanent in 5 (36) vs. 2 (14) and more intense than mild in 9 (64) vs. 5 (35) respondents.
Because of the sample size, the results were not significant (p=0.15 and 0.2 resp.). Conclusion: low-dose ketamine administered for 48 hours after mastectomy exhibits trend to suppress the incidence of permanent and moderate and severe post-mastectomy chronic pain.