Tramadol 2.5 mg x kg(-1) appears to be the optimal intraoperative loading dose before patient-controlled analgesia

We previously established that a 5 mg x kg(-1) intraoperative dose can reduce the nausea/vomiting associated with tramadol patient-controlled analgesia (PCA). This study was conducted to identify the most appropriate initial dose to improve the quality of tramadol PCA.During general anesthesia, 60 patients undergoing knee arthroplasty were randomly allocated to receive 1.25 mg x kg(-1) (Group I), 2.5 mg x kg(-1) (Group II), 3.75 mg x kg(-1) (Group III), or 5 mg x kg(-1) (Group IV) tramadol. The emergence condition was recorded. The titration of additional tramadol 20 mg + metoclopramide 1 mg doses by PCA every five minutes was performed in the postanesthesia care unit (PACU) until the visual analogue scale (VAS) score wasor = 3. An investigator blinded to study group recorded the VAS and side effects every ten minutes.In the PACU, significantly more tramadol (8.4 +/- 3.1 vs 4.3 +/- 2.1, 2.5 +/- 1.8, and 0.4 +/- 0.3, P0.05), and a higher incidence (15/15 vs 5/15, 3/15, and 2/15, P0.05) of PCA use was observed in Group I compared to Groups II-IV. VAS was significantly higher in Group I than in Groups II-IV at zero and ten minutes (P0.05). Unexpected delayed emergence anesthesia (30 min) was observed in Group III (n = 1) and in Group IV (n = 2). Sedation was more important in Groups III and IV than in Groups I and II (P0.05).When considering efficacy and side-effect profile, 2.5 mg x kg(-1) of tramadol is the optimal intraoperative dose of this drug to provide effective postoperative analgesia with minimal sedation.