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Background and goal of the study: Clonidine is proposed in premedication to induce preoperative sedation and to decrease anaesthetic requirements [1]. This prospective study was undertaken to assess the interactions of clonidine and anaesthetics on the BIS during induction of anaesthesia and orotracheal intubation (OTI).
Materials and methods: After institutional approval and patient informed consent, 22 adult patients (ASA 1-2) scheduled for elective general surgery were randomly assigned to two groups according to the premedication. Clonidine 150 μg or placebo were administrated 2 h preoperatively. Anaesthesia was induced in the two groups with propofol at effect site concentration of 4 μg mL−1. Three minutes later remifentanil (RF) was administered at effect site concentration of 2 ng mL−1, then atracurium 0.5 mg kg−1 was injected by the isolated forearm technique. OTI was performed at 6 min, after the steady state of RF was reached. Patient movement during and after OTI was noted. The BIS, BP, HR were monitored continuously. Sedation score (0-4) was used before induction of anaesthesia. Times selected for statistical analysis were: preinduction, propofol (steady state), preOTI (before laryngoscopy), then 1, 2 and 5 min after OTI. Repeated values of ANOVA was used to analyse these data.
Results and discussion: Although clonidine did not change BIS values during general anaesthesia, we observed a higher sedation score, and a lower BIS value at the preinduction time in the clonidine group (Table). We also noted decreases in somatic and sympathetic responses to OTI in the clonidine group.
Conclusions: These results are in accordance with a subcortical action of α2-adrenergic agonists.
