The effects of clonidine on intraocular pressure and perioperative cardiovascular variables were studied by a randomized double blind design in 80 elderly patients (ASA physical status I-III) scheduled for elective ophthalmic surgery under general anesthesia (GA) and local anesthesia (LA). Group 1 (n = 40), the control group, received diazepam po (0.1 mg·kg-1) 90-120 min prior to arrival to the operating room. Group 2 (n = 40) received clonidine po approximately 5 μg·kg-1 po at the same time. Each group was divided into subgroups of 20 patients each to be managed with GA (GA subset) or LA (LA subset). Ninety to 120 minutes after the premedication, a large decrease in IOP from 20 ± 3 to 12 ± 3 mmHg (P < 0.01) and a small but significant reduction of both systolic and diastolic BP and HR were observed in patients receiving clonidine, while no changes occurred in controls. In the patients managed with GA, clonidine effectively prevented IOP rise and attenuated the associated cardiovascular response (P < 0.01) following laryngoscopy and tracheal intubation, and significantly reduced intraoperative cardiovascular lability and anesthetic requirement for isoflurane (P < 0.05) and for fentanyl (P < .001). In patients managed with LA, intraoperative systolic (P < 0.01) and diastolic BP and HR variability (P < 0.05) were significantly lower in patients receiving clonidine as compared to controls. Intraoperatively, a significantly higher incidence of hypertension (P < 0.01) and tachycardia (P < 0.05) were respectively observed in the LA subset and GA subset of the controls when contrasted with the corresponding subset of those receiving clonidine. Moreover, clonidine was more effective than diazepam as a premedication; in fact, satisfactory intraoperative sedation and cardiovascular stability were observed in 85% of the patients who received clonidine, and in 50% of those patients who did not receive clonidine (P < 0.01). Thus, clonidine may represent a useful adjunct in the management of the aged patient in the setting of ophthalmic surgery.
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine