[The effect of blood conservation techniques on the plasma concentration and elimination of midazolam in patients undergoing hip joint surgery].

OBJECTIVE

The question was to evaluate whether haemodilution or intraoperative autotransfusion have an influence on plasma levels and clearance of midazolam.

DESIGN

The study was designed as a prospective evaluation of patients with total hip joint replacement. The patients received neuroleptanalgesia supplemented with enflurane. After induction of anaesthesia with midazolam (0.1 mg/kg body weight) haemodilution procedure was started. During surgery a cell saver was used for blood salvage. In the recovery room drainage blood was also being processed by a cell saver.

PATIENTS

The study includes 10 patients belonging to ASA-group II with an average weight of 79.4 kg (53-100 kg), at an average age of 57.9 years (44-68 years).

MEASUREMENTS AND MAIN RESULTS

Midazolam was measured in patient blood and in autologous blood units by gas chromatography. 151 micrograms of midazolam, i.e. 1.8% of the initial dose was retransfused in hemodilution blood. By processing of blood in the cell saver, 99.5% of the amount of midazolam found in the sample unit was eliminated. The maximum quantity was 5.5 micrograms in the washed autologous red cell concentrate.

CONCLUSION

Considering the analytic limit of 2 micrograms/l of midazolam in plasma, retransfusion of autologous blood cannot influence the plasma concentration of midazolam. Therefore, there is no risk of re-sedation in retransfusing autologous blood postoperatively.