Background: The antihypertensive drug clonidine is a centrally acting alpha2 agonist useful as a premedicant because of its sedative, anxiolytic, and analgesic properties. We examined the effect of clonidine given as an oral preanesthetic medication in producing a bloodless surgical field in patients undergoing middle ear microsurgery. We also evaluated whether the administration of clonidine would alter the reflex cardiovascular response to laryngoscopy and endotracheal intubation, anesthetic requirement, postoperative pain intensity and consumption of analgesics, and pre- and postoperative sedation and anxiety.
Methods: A prospective, randomized, double-blind clinical trial was performed in 40 patients scheduled for elective middle ear surgery under general anesthesia. Twenty-one patients received clonidine (300 microg p.o.) 90 min prior to arrival at the operating theater and 19 received placebo (control group). The hemodynamic endpoint of the anesthetic management was maintenance of hypotension for producing a bloodless surgical field. The desired control of the cardiovascular system was attained with isoflurane (inspired concentration increments of 0.25 vol% up to a maximum of 1.5 vol%)+/-fentanyl (bolus of 1 microg. kg-1)+/-urapidil (bolus of 0.3 mg. kg-1) as needed. Intraoperative bleeding was assessed on a four-point scale from 0=no bleeding to 3=abundant bleeding.
Results: There was less bleeding in the clonidine group (mean+/-SEM) than in the control group (0.75+/-0.3 vs 1.1+/-0.4, P<0.05). Patients given clonidine required a mean inspired isoflurane concentration of 0.63+/-0.1 vol% as compared with 1.01+/-0.2 vol% in controls (P<0.05). Fentanyl requirements were also significantly lower (57.10 vs 79.42 microg. kg-1, P<0.05). Four clonidine-treated patients required urapidil to achieve satisfactory hypotension as compared with 11 controls (P<0.05). Clonidine attenuated the associated cardiovascular response following laryngoscopy and intubation, and was more effective than placebo in achieving a satisfactory preoperative sedation and decreasing intensity of postoperative pain. Preoperative anxiety and incidence of adverse events was similar in both groups.
Conclusion: Premedication with clonidine reduced bleeding in middle ear microsurgery, attenuated hyperdynamic response to tracheal intubation, and reduced isoflurane, fentanyl, and urapidil requirements for controlled hypotension.