[Intravenous clonidine in the induced arterial hypotension technique for tympanoplasty]

Induced arterial hypotension is an effective technique to decrease surgical bleeding. Clonidine is an a2-agonist with central action which was proven to be safe in anesthesia. This study aimed at evaluating the efficacy of intravenous clonidine as the primary drug for induced arterial hypotension.

Participated in this prospective double-blind study 36 patients of both genders, physical status ASA I and II, who were randomly distributed in three groups of 12 patients receiving the following preanesthetic medication 15 minutes before anesthetic induction: 3 microg.kg-1 clonidine (C3), 5 microg.kg-1 clonidine (C5) or 0.9% saline solution (Control). Anesthesia was maintained with isoflurane in a maximum concentration of 2%. BP and HR were recorded before, 1 and 5 minutes after induction and at every 5 minutes of anesthesia. Patients receiving 2% isoflurane for more than 15 minutes and not presenting SBP below 80 mmHg were administered sodium nitroprusside to induce arterial hypotension.

Sodium nitroprusside was needed in three C3 group patients (25%), one C5 group patient (8%) and eight control group patients (66%). Total nitroprusside dose to induce arterial hypotension in the control group was higher as compared to groups C3 and C5 (p < 0.01). The incidence of complications was similar among groups.

Intravenous clonidine may lead to induced hypotension during tympanoplasties under balanced anesthesia with isoflurane concentration limited to 2%. In the conditions of this study, clonidine has not affected anesthetic quality and emergence time.