[Preoperative clonidine comedication within the scope of balanced inhalation anesthesia with sevoflurane in oral surgery procedures].
Both clonidine and sevoflurane are interesting drugs for anaesthesia in maxillo-facial surgery. The present study was performed to discover how far it is possible to combine the benefits of sevoflurane (fast modulation of depth of anaesthesia, rapid emergence and recovery) and clonidine (reduction of perioperative stress response, prophylaxis of postoperative shivering, analgetic, antiemetic and anaesthetic-saving effect) without compromising the pharmacokinetic of sevoflurane. Twenty-eight patients were included in the present double-blinded prospective study. These patients were randomly treated with an infusion of 4 micrograms kg-1 clonidine (group 1) or a placebo (group 2) preoperatively. For anaesthesia a standardized procedure with fentanyl, propofol, rocuronium, N2O/O2/sevoflurane and an antiemetic prophylaxis with DHB was performed. The depth of anaesthesia was controlled by using spectral edge frequency (target--SEF90 = 10 Hz). Perioperative stress response was assessed by noting the effects on haemodynamic parameters (MAP, heart rate), and emergence and recovery were assessed by using established standardized tests. We confirmed the anaesthetic-saving property of clonidine only for fentanyl (-20%). On the other hand, there was no difference in MAC-sevoflurane values between the groups in keeping a steady target--SEF90 (1.62 +/- 0.26 versus 1.65 +/- 0.24 vol.%). The time until emergence and recovery was not significantly different. Even the occurrence of PONV, the VAS level or the postoperative analgesic requirement did not differ in the two groups. However, the incidence of postoperative shivering was significantly higher in the placebo group. The stress response to intubation or extubation was lower in the clonidine group. The haemodynamic parameters in the clonidine group were intraoperatively always below the baseline, in some cases by more than 20%, making therapy for hypotension or bradycardia frequently necessary. Postoperatively, the majority of the patients showed similar changes in these parameters, but did not reach the 20% mark. Preoperative clonidine comedication seems to complicate the management of anaesthesia. On the other hand, it is beneficial during the early postoperative period (e.g. stability in haemodynamics, prophylaxis of shivering) without compromising emergence and recovery. Our results show that therapy with clonidine should be better placed at the end of anaesthesia.