[Premedication in maxillofacial surgery under total intravenous anesthesia . Effects of clonidine compared to midazolam on the perioperative course].

OBJECTIVE: The effects of the currently favoured preanaesthetic drugs (benzodiazepines, alpha 2-adrenoceptor agonists) on the perioperative course are inadequately investigated for new ways of performing anaesthesia with recently introduced drugs (e.g. remifentanil). Therefore clonidine and midazolam were used for premedication in maxillo-facial surgery under total intravenous anesthesia, and the perioperative courses were analyzed.

METHODS: Thirty patients (ASA 1-2) were included in the present doubleblinded, prospective study. 60-90 minutes preoperatively these patients got an oral premedication with 5 micrograms kg-1 clonidine or 100 micrograms kg-1 midazolam. For anaesthesia a standardized procedure with propofol, remifentanil and rocuronium was performed. After induction of anaesthesia the infusion of remifentanil was regulated by using spectral edge frequency (target-SEF90, 10-13 Hz). The efficiency of the premedication as well as the emergence and recovery were assessed by using established standardized tests. The perioperative stress response was assessed by recording the effects on haemodynamic parameters (NIBP. heart rate. Holter-ECG).

RESULTS: Referring to the effects of premedication (sedation, anxiety) there were no differences between the groups. The clonidine group required a lower remifentanil rate in keeping a steady-target-SEF90 (-24%). The time until emergence and recovery was not significantly different. Even the occurrence of PONV, VAS or the postoperative analgetic requirement did not differ between the two groups. However, the incidence of postoperative shivering was significantly higher in the midazolam group. Intraoperatively the values of MAP were quite equal between the groups. However, heart rate was significantly lower in the clonidine group. Postoperatively both MAP as well as heart rate were lower in the clonidine group. Furthermore, in the midazolam group there was a significantly higher cumulative duration of tachycardia (heart rate > 100 min-1; following descripted as medium with 25% and 75%-percentage; clonidine: 29/0/563 sec.: midazolam: 1058/232/3171 sec.).

CONCLUSION: After remifentanil supplemented anesthesia there is, especially in the postoperative period, a benefit in using clonidine compared to the premedication with midazolam.