[Preventive pain therapy. Preventive tramadol infusion versus bolus application in the early postoperative phase].

Even today, adequate postoperative analgesia is still a great problem. Based on positive results of former studies using a continuous infusion of tramadol for postoperative pain relief, we aimed to improve this regimen. In order to investigate the effectiveness of preventive analgesia, one group of patients was given 100 mg tramadol (Tramal) at the time of extubation, followed by a maintenance infusion. The other group was treated with single boluses of tramadol on demand, thus representing common pain treatment. METHODS. 112 patients undergoing abdominal surgery were chosen at random for this double-blind study. Half of them (preventive group) received an injection of 100 mg tramadol at the time of extubation; the others (on-demand group) were given a placebo instead. A continuous infusion of 500 ml NaCl 0.9% (administered with 30 ml/h) followed, either containing 200 mg tramadol (preventive group) or a placebo (on-demand group) and was maintained until the end of the study. At the first expression of pain, patients in the preventive group received 50 mg tramadol (representing the first subsequent injection) whereas patients of the on-demand group were given 100 mg tramadol as a loading dose. For further treatment of pain, the members of both groups received 50 mg tramadol when necessary. The level of pain was assessed by means of VAS (visual analogue scale) every hour and additionally at first expression of pain, and finally by VRS (verbal rating scale) after eight hours at the end of the study. RESULTS. 112 patients were chosen at random. 18 had to be excluded--two treatment failures, twelve violations of the study protocol and four patients of the on-demand group, who did not ask for treatment for pain and therefore did not receive any tramadol. Hence only 94 patients could be statistically evaluated. 50% of the remaining 48 patients in the preventive group needed none or only one subsequent injection of tramadol, the other 50% needed two or more subsequent injections. However the patients in the on-demand group, now 46, split up into 71.7% who where administered up to one subsequent injection and 28.3% who received more than one subsequent injection. The number of patients who asked for treatment for pain twice or more during the study period totalled 50% in the preventive group and 58.7% in the on-demand group. The average interval between extubation and first expression of pain was 106.3 +/- 84.2 min in the preventive group, and 75.0 +/- 22.7 min in the on-demand group. The intensity of pain evaluated by VAS as that time was comparable: 55.6 +/- 22.7 (preventive) versus (63.4 +/- 18.3 (on demand). The pain relief obtained, shown by the VAS-differences between the first expression of pain and following assessment, came up to 27.7 +/- 22.9 in the preventive group and 30.3 +/- 23.4 in the on-demand group within a period of 46.2 +/- 17.2 min (preventive) and 43.7 +/- 17.2 min (on-demand). Retrograde assessment of pain (VRS) showed that 85.5% of the preventive group found pain relief excellent or good and 78.3% of the on-demand group were of the same opinion. Total consumption of tramadol totalled 281.4 +/- 53.6 mg in the preventive group in comparison with 150.0 +/- 53.7 mg in the on-demand group. CONCLUSIONS. Only 28.3% of patients of the on-demand group received more than one subsequent injection of tramadol in comparison with 50% of the preventive group--an unexpected result. However, it has to be considered that the injection of tramadol given at the first expression of pain in the preventive group was counted as the first subsequent injection already. The patients in the preventive group asked, on average, 30 min later for treatment for pain. The subsequent pain relief in both groups was comparable, although the amount of tramadol administered at that time was higher in the on demand group than in the preventive group (100 mg versus 50 mg+ amount given by infusion). These facts show the efficacy of the preventive infus