Abstract: AIM: To study the dose-response relationshiPofPainful sensibility andPostoperative intravenousPCA(Patients controlled analgesia)individualized with tramadol.METHODS: The 128 cases ofPatients(ASA I-III)with highPainful sensibility and thelowPainful sensibility were screened out through aPainful reactiondependent manner.The high-sensibility cases were divided into four groups:standard-dose grouP(HSDG)(tramadol 8.4 mg·kg^-1·24 h^-1)and other three increased dose groups(increased by 10 %,20 %,and 30 %,respectively,based on the standard dose,n =16),and thelow-sensibility cases were also divided into 4 groups:standard-dose grouP(lSDG)(tramadol 8.4 mg·kg^-1·24h^-1)and other three decreased dose groups(decreased by 10 %,20 %,and 30 %,respectively).The effects of analgesia,the satisfactory degree and the adverse effects were evaluated duringPostoperative intravenousPCA.RESULTS: The analgesia effects inlSDG was significantly better than that in HSDG(P<0.05).For cases with the high sensibility,the effects of analgesia in the increased dose groups(20 % and 30 %)were markedly better than that in HSDG(P<0.01),but for cases with thelow sensibility,the analgesia effects in decreased dose groups(30 %)decreased(P<0.05)in comparison withlSDG.The adverse effects,such as sweat,changed with the doses of tramadol increasing or decreasing.CONCLUSION: Painful sensibility influences the effects of tramadol intravenousPCA.For thePatients with high sensibility,tramadol dose increased by 20 % based on 8.4mg·kg^-1·24 h^-1can obtain the best effect,but forlow sensibility,the dose should decreased by 10 %.

Key words: pharmacodynamics, painful sensibility, individual difference, tramadol, PCA, intravenous, postoperative