[Comparison of premedication with clonidine and midazolam combined with TCI for orthopaedic shoulder surgery]

The most frequently used drugs for premedication are benzodiazepines and alpha (2)-adrenoceptor agonists. In this study we examined midazolam and clonidine for premedication in combination with target controlled infusion anaesthesia (TCI) in patients undergoing orthopaedic shoulder surgery and analysed the effects on the peri- and postoperative course.

Forty-five Patients (ASA I-III) were included in this prospective randomized, double blind study. Sixty minutes prior to anaesthetic induction the patients received clonidine in a dosage of 2 microg x kg(-1) (group ND) or 5 microg x kg(-1) (group HD) or 0.1 mg x kg(-1) midazolam (group midazolam) per orally. Anaesthesia was performed as TCI with propofol (plasma concentration 2.0-4.0 microg x ml(-1)) und remifentanil (plasma concentration 0.2-0.4 microg x ml(-1) x min(-1)). 15 minutes before the operation was finished, all patients received a bolus dose of 0.1 mg x kg(-1) piritramid i.v., followed by administration of piritramid via a PCA pump (patient controlled analgesia) for a duration of 24 hours. During the time of the operation the influence of premedication on the anaesthetic course was determined by vital parameters and ranking scales. For statistic evaluation we used the Kruskal-Wallis test, ANOVA with Tukey as post hoc test and the test named after Fisher (p < 0.05).

The effects of premedication on haemodynamic parameters and ranking scales for sedation as well as anaesthetic requirements were comparable in all three groups. In the postoperative period the incidence of postoperative nausea and vomiting (PONV) (ND: n = 8, HD: n = 2, midazolam: n = 6) and the use of pritramid were lower in the clonidine HD group (HD: 38.7 +/- 30.7 mg, ND: 51.7 +/- 25.1 mg, midazolam: 45.1 +/- 30.4 mg) than in the other groups.

Premedication with the alpha(2)-adrenoceptor agonist clonidine is as good as with benzodiazepines in combination with TCI. Because of the lower incidence of PONV and the need of piritramid in the postoperative period patients premedicated with 5 microg x kg(-1) clonidine may benefit from this premedication.